Support streaming zipformer CTC (#496)

* Support streaming zipformer CTC * test online zipformer2 CTC * Update doc of sherpa-onnx.cc * Add Python APIs for streaming zipformer2 ctc * Add Python API examples for streaming zipformer2 ctc * Swift API for streaming zipformer2 CTC * NodeJS API for streaming zipformer2 CTC * Kotlin API for streaming zipformer2 CTC * Golang API for streaming zipformer2 CTC * C# API for streaming zipformer2 CTC * Release v1.9.6
2026-01-09 07:41:06 +08:00 · 2023-12-22 13:46:33 +08:00 · 2023-12-22 13:46:33 +08:00 · e475e750ac
commit e475e750ac
parent 7634f5f034
70 changed files with 1517 additions and 211 deletions
--- a/.github/scripts/test-nodejs-npm.sh
+++ b/.github/scripts/test-nodejs-npm.sh
@ -51,6 +51,13 @@ rm sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20.tar.bz2
 node ./test-online-transducer.js
 rm -rf sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20

+curl -LS -O https://github.com/k2-fsa/sherpa-onnx/releases/download/asr-models/sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13.tar.bz2
+tar xvf sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13.tar.bz2
+rm sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13.tar.bz2
+
+node ./test-online-zipformer2-ctc.js
+rm -rf sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13
+
 # offline tts

 curl -LS -O https://github.com/k2-fsa/sherpa-onnx/releases/download/tts-models/vits-piper-en_US-amy-low.tar.bz2
--- a/.github/scripts/test-online-ctc.sh
+++ b/.github/scripts/test-online-ctc.sh
@ -13,6 +13,37 @@ echo "PATH: $PATH"

 which $EXE

+log "------------------------------------------------------------"
+log "Run streaming Zipformer2 CTC                                "
+log "------------------------------------------------------------"
+
+url=https://github.com/k2-fsa/sherpa-onnx/releases/download/asr-models/sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13.tar.bz2
+repo=$(basename -s .tar.bz2 $url)
+curl -SL -O $url
+tar xvf $repo.tar.bz2
+rm $repo.tar.bz2
+
+log "test fp32"
+
+time $EXE \
+  --debug=1 \
+  --zipformer2-ctc-model=$repo/ctc-epoch-20-avg-1-chunk-16-left-128.onnx \
+  --tokens=$repo/tokens.txt \
+  $repo/test_wavs/DEV_T0000000000.wav \
+  $repo/test_wavs/DEV_T0000000001.wav \
+  $repo/test_wavs/DEV_T0000000002.wav
+
+log "test int8"
+
+time $EXE \
+  --debug=1 \
+  --zipformer2-ctc-model=$repo/ctc-epoch-20-avg-1-chunk-16-left-128.int8.onnx \
+  --tokens=$repo/tokens.txt \
+  $repo/test_wavs/DEV_T0000000000.wav \
+  $repo/test_wavs/DEV_T0000000001.wav \
+  $repo/test_wavs/DEV_T0000000002.wav
+
+
 log "------------------------------------------------------------"
 log "Run streaming Conformer CTC from WeNet"
 log "------------------------------------------------------------"
--- a/.github/scripts/test-python.sh
+++ b/.github/scripts/test-python.sh
@ -8,6 +8,27 @@ log() {
  echo -e "$(date '+%Y-%m-%d %H:%M:%S') (${fname}:${BASH_LINENO[0]}:${FUNCNAME[1]}) $*"
 }

+mkdir -p /tmp/icefall-models
+dir=/tmp/icefall-models
+
+pushd $dir
+wget -qq https://github.com/k2-fsa/sherpa-onnx/releases/download/asr-models/sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13.tar.bz2
+tar xvf sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13.tar.bz2
+rm sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13.tar.bz2
+popd
+repo=$dir/sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13
+
+python3 ./python-api-examples/online-decode-files.py \
+  --tokens=$repo/tokens.txt \
+  --zipformer2-ctc=$repo/ctc-epoch-20-avg-1-chunk-16-left-128.onnx \
+  $repo/test_wavs/DEV_T0000000000.wav \
+  $repo/test_wavs/DEV_T0000000001.wav \
+  $repo/test_wavs/DEV_T0000000002.wav
+
+python3 sherpa-onnx/python/tests/test_offline_recognizer.py --verbose
+
+rm -rf $dir/sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13
+
 wenet_models=(
 sherpa-onnx-zh-wenet-aishell
 sherpa-onnx-zh-wenet-aishell2
@ -17,8 +38,6 @@ sherpa-onnx-en-wenet-librispeech
 sherpa-onnx-en-wenet-gigaspeech
 )

-mkdir -p /tmp/icefall-models
-dir=/tmp/icefall-models

 for name in ${wenet_models[@]}; do
  repo_url=https://huggingface.co/csukuangfj/$name
--- a/.github/scripts/test-swift.sh
+++ b/.github/scripts/test-swift.sh
@ -21,6 +21,9 @@ cat /Users/fangjun/Desktop/Obama.srt
 ./run-tts.sh
 ls -lh

+./run-decode-file.sh
+rm decode-file
+sed -i.bak  '20d' ./decode-file.swift
 ./run-decode-file.sh

 ./run-decode-file-non-streaming.sh
--- a/.github/workflows/export-wenet-to-onnx.yaml
+++ b/.github/workflows/export-wenet-to-onnx.yaml
@ -22,7 +22,7 @@ jobs:
      - uses: actions/checkout@v4

      - name: Setup Python ${{ matrix.python-version }}
-        uses: actions/setup-python@v2
+        uses: actions/setup-python@v4
        with:
          python-version: ${{ matrix.python-version }}

--- a/.github/workflows/export-wespeaker-to-onnx.yaml
+++ b/.github/workflows/export-wespeaker-to-onnx.yaml
@ -22,7 +22,7 @@ jobs:
      - uses: actions/checkout@v4

      - name: Setup Python ${{ matrix.python-version }}
-        uses: actions/setup-python@v2
+        uses: actions/setup-python@v4
        with:
          python-version: ${{ matrix.python-version }}

--- a/.github/workflows/export-whisper-to-onnx.yaml
+++ b/.github/workflows/export-whisper-to-onnx.yaml
@ -24,7 +24,7 @@ jobs:
      - uses: actions/checkout@v4

      - name: Setup Python ${{ matrix.python-version }}
-        uses: actions/setup-python@v2
+        uses: actions/setup-python@v4
        with:
          python-version: ${{ matrix.python-version }}

--- a/.github/workflows/linux.yaml
+++ b/.github/workflows/linux.yaml
@ -107,6 +107,14 @@ jobs:
          name: release-static
          path: build/bin/*

+      - name: Test online CTC
+        shell: bash
+        run: |
+          export PATH=$PWD/build/bin:$PATH
+          export EXE=sherpa-onnx
+
+          .github/scripts/test-online-ctc.sh
+
      - name: Test offline Whisper
        shell: bash
        run: |
@ -117,14 +125,6 @@ jobs:

          .github/scripts/test-offline-whisper.sh

-      - name: Test online CTC
-        shell: bash
-        run: |
-          export PATH=$PWD/build/bin:$PATH
-          export EXE=sherpa-onnx
-
-          .github/scripts/test-online-ctc.sh
-
      - name: Test offline CTC
        shell: bash
        run: |
--- a/.github/workflows/npm.yaml
+++ b/.github/workflows/npm.yaml
@ -25,7 +25,7 @@ jobs:
          fetch-depth: 0

      - name: Setup Python ${{ matrix.python-version }}
-        uses: actions/setup-python@v2
+        uses: actions/setup-python@v4
        with:
          python-version: ${{ matrix.python-version }}

--- a/.github/workflows/run-python-test.yaml
+++ b/.github/workflows/run-python-test.yaml
@ -55,7 +55,7 @@ jobs:
          key: ${{ matrix.os }}-python-${{ matrix.python-version }}

      - name: Setup Python
-        uses: actions/setup-python@v2
+        uses: actions/setup-python@v4
        with:
          python-version: ${{ matrix.python-version }}

--- a/.github/workflows/style_check.yaml
+++ b/.github/workflows/style_check.yaml
@ -49,7 +49,7 @@ jobs:
          fetch-depth: 0

      - name: Setup Python ${{ matrix.python-version }}
-        uses: actions/setup-python@v1
+        uses: actions/setup-python@v4
        with:
          python-version: ${{ matrix.python-version }}

--- a/.github/workflows/test-build-wheel.yaml
+++ b/.github/workflows/test-build-wheel.yaml
@ -29,7 +29,7 @@ jobs:
          fetch-depth: 0

      - name: Setup Python ${{ matrix.python-version }}
-        uses: actions/setup-python@v2
+        uses: actions/setup-python@v4
        with:
          python-version: ${{ matrix.python-version }}

--- a/.github/workflows/test-dot-net.yaml
+++ b/.github/workflows/test-dot-net.yaml
@ -61,7 +61,7 @@ jobs:
    strategy:
      fail-fast: false
      matrix:
-        os: [ubuntu-latest, macos-latest]
+        os: [ubuntu-latest, macos-latest] #, windows-latest]
        python-version: ["3.8"]

    steps:
@ -70,7 +70,7 @@ jobs:
          fetch-depth: 0

      - name: Setup Python ${{ matrix.python-version }}
-        uses: actions/setup-python@v2
+        uses: actions/setup-python@v4
        with:
          python-version: ${{ matrix.python-version }}

@ -143,6 +143,7 @@ jobs:
          cd dotnet-examples/

          cd online-decode-files
+          ./run-zipformer2-ctc.sh
          ./run-transducer.sh
          ./run-paraformer.sh

--- a/.github/workflows/test-go.yaml
+++ b/.github/workflows/test-go.yaml
@ -53,7 +53,7 @@ jobs:
          mkdir build
          cd build
          cmake -DCMAKE_C_COMPILER_LAUNCHER=ccache -DCMAKE_CXX_COMPILER_LAUNCHER=ccache -DBUILD_SHARED_LIBS=ON -DSHERPA_ONNX_ENABLE_PORTAUDIO=OFF -DSHERPA_ONNX_ENABLE_WEBSOCKET=OFF ..
-          make -j
+          make -j1
          cp -v _deps/onnxruntime-src/lib/libonnxruntime*dylib ./lib/

          cd ../scripts/go/_internal/
@ -153,6 +153,14 @@ jobs:

          git lfs install

+          echo "Test zipformer2 CTC"
+          wget -qq https://github.com/k2-fsa/sherpa-onnx/releases/download/asr-models/sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13.tar.bz2
+          tar xvf sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13.tar.bz2
+          rm sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13.tar.bz2
+
+          ./run-zipformer2-ctc.sh
+          rm -rf sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13
+
          echo "Test transducer"
          git clone https://huggingface.co/csukuangfj/sherpa-onnx-streaming-zipformer-en-2023-06-26
          ./run-transducer.sh
--- a/.github/workflows/test-nodejs-npm.yaml
+++ b/.github/workflows/test-nodejs-npm.yaml
@ -34,7 +34,7 @@ jobs:
          fetch-depth: 0

      - name: Setup Python ${{ matrix.python-version }}
-        uses: actions/setup-python@v2
+        uses: actions/setup-python@v4
        with:
          python-version: ${{ matrix.python-version }}

--- a/.github/workflows/test-nodejs.yaml
+++ b/.github/workflows/test-nodejs.yaml
@ -52,7 +52,7 @@ jobs:
          ls -lh install/lib

      - name: Setup Python ${{ matrix.python-version }}
-        uses: actions/setup-python@v2
+        uses: actions/setup-python@v4
        with:
          python-version: ${{ matrix.python-version }}

--- a/.github/workflows/test-pip-install.yaml
+++ b/.github/workflows/test-pip-install.yaml
@ -40,7 +40,7 @@ jobs:
          fetch-depth: 0

      - name: Setup Python ${{ matrix.python-version }}
-        uses: actions/setup-python@v2
+        uses: actions/setup-python@v4
        with:
          python-version: ${{ matrix.python-version }}

--- a/.github/workflows/test-python-offline-websocket-server.yaml
+++ b/.github/workflows/test-python-offline-websocket-server.yaml
@ -38,7 +38,7 @@ jobs:
          key: ${{ matrix.os }}-python-${{ matrix.python-version }}

      - name: Setup Python ${{ matrix.python-version }}
-        uses: actions/setup-python@v2
+        uses: actions/setup-python@v4
        with:
          python-version: ${{ matrix.python-version }}

--- a/.github/workflows/test-python-online-websocket-server.yaml
+++ b/.github/workflows/test-python-online-websocket-server.yaml
@ -25,7 +25,7 @@ jobs:
      matrix:
        os: [ubuntu-latest, windows-latest, macos-latest]
        python-version: ["3.7", "3.8", "3.9", "3.10", "3.11"]
-        model_type: ["transducer", "paraformer"]
+        model_type: ["transducer", "paraformer", "zipformer2-ctc"]

    steps:
      - uses: actions/checkout@v4
@ -38,7 +38,7 @@ jobs:
          key: ${{ matrix.os }}-python-${{ matrix.python-version }}

      - name: Setup Python ${{ matrix.python-version }}
-        uses: actions/setup-python@v2
+        uses: actions/setup-python@v4
        with:
          python-version: ${{ matrix.python-version }}

@ -57,6 +57,26 @@ jobs:
          python3 -m pip install --no-deps --verbose .
          python3 -m pip install websockets

+      - name: Start server for zipformer2 CTC models
+        if: matrix.model_type == 'zipformer2-ctc'
+        shell: bash
+        run: |
+          curl -O -L https://github.com/k2-fsa/sherpa-onnx/releases/download/asr-models/sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13.tar.bz2
+          tar xvf sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13.tar.bz2
+          rm sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13.tar.bz2
+
+          python3 ./python-api-examples/streaming_server.py \
+            --zipformer2-ctc ./sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13/ctc-epoch-20-avg-1-chunk-16-left-128.onnx \
+            --tokens=./sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13/tokens.txt &
+          echo "sleep 10 seconds to wait the server start"
+          sleep 10
+
+      - name: Start client for zipformer2 CTC models
+        if: matrix.model_type == 'zipformer2-ctc'
+        shell: bash
+        run: |
+          python3 ./python-api-examples/online-websocket-client-decode-file.py \
+            ./sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13/test_wavs/DEV_T0000000000.wav

      - name: Start server for transducer models
        if: matrix.model_type == 'transducer'
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@ -1,7 +1,7 @@
 cmake_minimum_required(VERSION 3.13 FATAL_ERROR)
 project(sherpa-onnx)

-set(SHERPA_ONNX_VERSION "1.9.4")
+set(SHERPA_ONNX_VERSION "1.9.6")

 # Disable warning about
 #
--- a/android/SherpaOnnx/app/src/main/java/com/k2fsa/sherpa/onnx/SherpaOnnx.kt
+++ b/android/SherpaOnnx/app/src/main/java/com/k2fsa/sherpa/onnx/SherpaOnnx.kt
@ -26,9 +26,14 @@ data class OnlineParaformerModelConfig(
    var decoder: String = "",
 )

+data class OnlineZipformer2CtcModelConfig(
+    var model: String = "",
+)
+
 data class OnlineModelConfig(
    var transducer: OnlineTransducerModelConfig = OnlineTransducerModelConfig(),
    var paraformer: OnlineParaformerModelConfig = OnlineParaformerModelConfig(),
+    var zipformer2Ctc: OnlineZipformer2CtcModelConfig = OnlineZipformer2CtcModelConfig(),
    var tokens: String,
    var numThreads: Int = 1,
    var debug: Boolean = false,
--- a/dotnet-examples/.gitignore
+++ b/dotnet-examples/.gitignore
@ -1,2 +1,3 @@
 bin
 obj
+!*.sh
--- a/dotnet-examples/online-decode-files/Program.cs
+++ b/dotnet-examples/online-decode-files/Program.cs
@ -38,6 +38,9 @@ class OnlineDecodeFiles
    [Option("paraformer-decoder", Required = false, HelpText = "Path to paraformer decoder.onnx")]
    public string ParaformerDecoder { get; set; }

+    [Option("zipformer2-ctc", Required = false, HelpText = "Path to zipformer2 CTC onnx model")]
+    public string Zipformer2Ctc { get; set; }
+
    [Option("num-threads", Required = false, Default = 1, HelpText = "Number of threads for computation")]
    public int NumThreads { get; set; }

@ -107,7 +110,19 @@ dotnet run \
  --files ./sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20/test_wavs/0.wav \
  ./sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20/test_wavs/1.wav

-(2) Streaming Paraformer models
+(2) Streaming Zipformer2 Ctc models
+
+dotnet run -c Release \
+  --tokens ./sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13/tokens.txt \
+  --zipformer2-ctc ./sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13/ctc-epoch-20-avg-1-chunk-16-left-128.onnx \
+  --files ./sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13/test_wavs/DEV_T0000000000.wav \
+  ./sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13/test_wavs/DEV_T0000000001.wav \
+  ./sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13/test_wavs/DEV_T0000000002.wav \
+  ./sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13/test_wavs/TEST_MEETING_T0000000113.wav \
+  ./sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13/test_wavs/TEST_MEETING_T0000000219.wav \
+  ./sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13/test_wavs/TEST_MEETING_T0000000351.wav
+
+(3) Streaming Paraformer models
 dotnet run \
  --tokens=./sherpa-onnx-streaming-paraformer-bilingual-zh-en/tokens.txt \
  --paraformer-encoder=./sherpa-onnx-streaming-paraformer-bilingual-zh-en/encoder.int8.onnx \
@ -121,6 +136,7 @@ dotnet run \
 Please refer to
 https://k2-fsa.github.io/sherpa/onnx/pretrained_models/online-transducer/index.html
 https://k2-fsa.github.io/sherpa/onnx/pretrained_models/online-paraformer/index.html
+https://k2-fsa.github.io/sherpa/onnx/pretrained_models/online-ctc/index.html
 to download pre-trained streaming models.
 ";

@ -150,6 +166,8 @@ to download pre-trained streaming models.
    config.ModelConfig.Paraformer.Encoder = options.ParaformerEncoder;
    config.ModelConfig.Paraformer.Decoder = options.ParaformerDecoder;

+    config.ModelConfig.Zipformer2Ctc.Model = options.Zipformer2Ctc;
+
    config.ModelConfig.Tokens = options.Tokens;
    config.ModelConfig.Provider = options.Provider;
    config.ModelConfig.NumThreads = options.NumThreads;
--- a/dotnet-examples/online-decode-files/run-zipformer2-ctc.sh
+++ b/dotnet-examples/online-decode-files/run-zipformer2-ctc.sh
@ -0,0 +1,21 @@
+#!/usr/bin/env bash
+
+# Please refer to
+# https://k2-fsa.github.io/sherpa/onnx/pretrained_models/online-ctc/zipformer-ctc-models.html#sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13-chinese
+# to download the model files
+
+if [ ! -d ./sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13 ]; then
+  curl -SL -O https://github.com/k2-fsa/sherpa-onnx/releases/download/asr-models/sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13.tar.bz2
+  tar xvf sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13.tar.bz2
+  rm sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13.tar.bz2
+fi
+
+dotnet run -c Release \
+  --tokens ./sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13/tokens.txt \
+  --zipformer2-ctc ./sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13/ctc-epoch-20-avg-1-chunk-16-left-128.onnx \
+  --files ./sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13/test_wavs/DEV_T0000000000.wav \
+  ./sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13/test_wavs/DEV_T0000000001.wav \
+  ./sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13/test_wavs/DEV_T0000000002.wav \
+  ./sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13/test_wavs/TEST_MEETING_T0000000113.wav \
+  ./sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13/test_wavs/TEST_MEETING_T0000000219.wav \
+  ./sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13/test_wavs/TEST_MEETING_T0000000351.wav
--- a/go-api-examples/.gitignore
+++ b/go-api-examples/.gitignore
@ -0,0 +1 @@
+!*.sh
--- a/go-api-examples/streaming-decode-files/main.go
+++ b/go-api-examples/streaming-decode-files/main.go
@ -22,6 +22,7 @@ func main() {
 	flag.StringVar(&config.ModelConfig.Transducer.Joiner, "joiner", "", "Path to the transducer joiner model")
 	flag.StringVar(&config.ModelConfig.Paraformer.Encoder, "paraformer-encoder", "", "Path to the paraformer encoder model")
 	flag.StringVar(&config.ModelConfig.Paraformer.Decoder, "paraformer-decoder", "", "Path to the paraformer decoder model")
+	flag.StringVar(&config.ModelConfig.Zipformer2Ctc.Model, "zipformer2-ctc", "", "Path to the zipformer2 CTC model")
 	flag.StringVar(&config.ModelConfig.Tokens, "tokens", "", "Path to the tokens file")
 	flag.IntVar(&config.ModelConfig.NumThreads, "num-threads", 1, "Number of threads for computing")
 	flag.IntVar(&config.ModelConfig.Debug, "debug", 0, "Whether to show debug message")
--- a/go-api-examples/streaming-decode-files/run-zipformer2-ctc.sh
+++ b/go-api-examples/streaming-decode-files/run-zipformer2-ctc.sh
@ -0,0 +1,13 @@
+#!/usr/bin/env bash
+
+# Please refer to
+# https://k2-fsa.github.io/sherpa/onnx/pretrained_models/online-ctc/zipformer-ctc-models.html#sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13-chinese
+# to download the model
+# before you run this script.
+#
+# You can switch to a different online model if you need
+
+./streaming-decode-files \
+  --zipformer2-ctc ./sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13/ctc-epoch-20-avg-1-chunk-16-left-128.onnx \
+  --tokens ./sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13/tokens.txt \
+  ./sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13/test_wavs/DEV_T0000000000.wav
--- a/kotlin-api-examples/Main.kt
+++ b/kotlin-api-examples/Main.kt
@ -8,7 +8,8 @@ fun callback(samples: FloatArray): Unit {

 fun main() {
  testTts()
-  testAsr()
+  testAsr("transducer")
+  testAsr("zipformer2-ctc")
 }

 fun testTts() {
@ -30,25 +31,43 @@ fun testTts() {
  audio.save(filename="test-en.wav")
 }

-fun testAsr() {
+fun testAsr(type: String) {
    var featConfig = FeatureConfig(
        sampleRate = 16000,
        featureDim = 80,
    )

-    // please refer to
-    // https://k2-fsa.github.io/sherpa/onnx/pretrained_models/index.html
-    // to dowload pre-trained models
-    var modelConfig = OnlineModelConfig(
-        transducer = OnlineTransducerModelConfig(
-            encoder = "./sherpa-onnx-streaming-zipformer-en-2023-02-21/encoder-epoch-99-avg-1.onnx",
-            decoder = "./sherpa-onnx-streaming-zipformer-en-2023-02-21/decoder-epoch-99-avg-1.onnx",
-            joiner = "./sherpa-onnx-streaming-zipformer-en-2023-02-21/joiner-epoch-99-avg-1.onnx",
-        ),
-        tokens = "./sherpa-onnx-streaming-zipformer-en-2023-02-21/tokens.txt",
-        numThreads = 1,
-        debug = false,
-    )
+    var waveFilename: String
+    var modelConfig: OnlineModelConfig = when (type) {
+      "transducer" -> {
+        waveFilename = "./sherpa-onnx-streaming-zipformer-en-2023-02-21/test_wavs/0.wav"
+        // please refer to
+        // https://k2-fsa.github.io/sherpa/onnx/pretrained_models/index.html
+        // to dowload pre-trained models
+        OnlineModelConfig(
+            transducer = OnlineTransducerModelConfig(
+                encoder = "./sherpa-onnx-streaming-zipformer-en-2023-02-21/encoder-epoch-99-avg-1.onnx",
+                decoder = "./sherpa-onnx-streaming-zipformer-en-2023-02-21/decoder-epoch-99-avg-1.onnx",
+                joiner = "./sherpa-onnx-streaming-zipformer-en-2023-02-21/joiner-epoch-99-avg-1.onnx",
+            ),
+            tokens = "./sherpa-onnx-streaming-zipformer-en-2023-02-21/tokens.txt",
+            numThreads = 1,
+            debug = false,
+        )
+      }
+      "zipformer2-ctc" -> {
+        waveFilename = "./sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13/test_wavs/DEV_T0000000000.wav"
+        OnlineModelConfig(
+            zipformer2Ctc = OnlineZipformer2CtcModelConfig(
+                model = "./sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13/ctc-epoch-20-avg-1-chunk-16-left-128.onnx",
+            ),
+            tokens = "./sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13/tokens.txt",
+            numThreads = 1,
+            debug = false,
+        )
+      }
+      else -> throw IllegalArgumentException(type)
+    }

    var endpointConfig = EndpointConfig()

@ -69,7 +88,7 @@ fun testAsr() {
    )

    var objArray = WaveReader.readWaveFromFile(
-        filename = "./sherpa-onnx-streaming-zipformer-en-2023-02-21/test_wavs/0.wav",
+        filename = waveFilename,
    )
    var samples: FloatArray = objArray[0] as FloatArray
    var sampleRate: Int = objArray[1] as Int
--- a/kotlin-api-examples/run.sh
+++ b/kotlin-api-examples/run.sh
@ -34,6 +34,12 @@ if [ ! -f ./sherpa-onnx-streaming-zipformer-en-2023-02-21/tokens.txt ]; then
  git clone https://huggingface.co/csukuangfj/sherpa-onnx-streaming-zipformer-en-2023-02-21
 fi

+if [ ! -d ./sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13 ]; then
+  wget -q https://github.com/k2-fsa/sherpa-onnx/releases/download/asr-models/sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13.tar.bz2
+  tar xvf sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13.tar.bz2
+  rm sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13.tar.bz2
+fi
+
 if [ ! -f ./vits-piper-en_US-amy-low/en_US-amy-low.onnx ]; then
  wget -q https://github.com/k2-fsa/sherpa-onnx/releases/download/tts-models/vits-piper-en_US-amy-low.tar.bz2
  tar xf vits-piper-en_US-amy-low.tar.bz2
--- a/nodejs-examples/README.md
+++ b/nodejs-examples/README.md
@ -85,7 +85,7 @@ npm install wav naudiodon2
 how to decode a file with a NeMo CTC model. In the code we use
 [stt_en_conformer_ctc_small](https://k2-fsa.github.io/sherpa/onnx/pretrained_models/offline-ctc/nemo/english.html#stt-en-conformer-ctc-small).

-You can use the following command run it:
+You can use the following command to run it:

 ```bash
 wget -q https://github.com/k2-fsa/sherpa-onnx/releases/download/asr-models/sherpa-onnx-nemo-ctc-en-conformer-small.tar.bz2
@ -99,7 +99,7 @@ node ./test-offline-nemo-ctc.js
 how to decode a file with a non-streaming Paraformer model. In the code we use
 [sherpa-onnx-paraformer-zh-2023-03-28](https://k2-fsa.github.io/sherpa/onnx/pretrained_models/offline-paraformer/paraformer-models.html#csukuangfj-sherpa-onnx-paraformer-zh-2023-03-28-chinese).

-You can use the following command run it:
+You can use the following command to run it:

 ```bash
 wget -q https://github.com/k2-fsa/sherpa-onnx/releases/download/asr-models/sherpa-onnx-paraformer-zh-2023-03-28.tar.bz2
@ -113,7 +113,7 @@ node ./test-offline-paraformer.js
 how to decode a file with a non-streaming transducer model. In the code we use
 [sherpa-onnx-zipformer-en-2023-06-26](https://k2-fsa.github.io/sherpa/onnx/pretrained_models/offline-transducer/zipformer-transducer-models.html#csukuangfj-sherpa-onnx-zipformer-en-2023-06-26-english).

-You can use the following command run it:
+You can use the following command to run it:

 ```bash
 wget -q https://github.com/k2-fsa/sherpa-onnx/releases/download/asr-models/sherpa-onnx-zipformer-en-2023-06-26.tar.bz2
@ -126,7 +126,7 @@ node ./test-offline-transducer.js
 how to decode a file with a Whisper model. In the code we use
 [sherpa-onnx-whisper-tiny.en](https://k2-fsa.github.io/sherpa/onnx/pretrained_models/whisper/tiny.en.html).

-You can use the following command run it:
+You can use the following command to run it:

 ```bash
 wget -q https://github.com/k2-fsa/sherpa-onnx/releases/download/asr-models/sherpa-onnx-whisper-tiny.en.tar.bz2
@ -140,7 +140,7 @@ demonstrates how to do real-time speech recognition from microphone
 with a streaming Paraformer model. In the code we use
 [sherpa-onnx-streaming-paraformer-bilingual-zh-en](https://k2-fsa.github.io/sherpa/onnx/pretrained_models/online-paraformer/paraformer-models.html#csukuangfj-sherpa-onnx-streaming-paraformer-bilingual-zh-en-chinese-english).

-You can use the following command run it:
+You can use the following command to run it:

 ```bash
 wget -q https://github.com/k2-fsa/sherpa-onnx/releases/download/asr-models/sherpa-onnx-streaming-paraformer-bilingual-zh-en.tar.bz2
@ -153,7 +153,7 @@ node ./test-online-paraformer-microphone.js
 how to decode a file using a streaming Paraformer model. In the code we use
 [sherpa-onnx-streaming-paraformer-bilingual-zh-en](https://k2-fsa.github.io/sherpa/onnx/pretrained_models/online-paraformer/paraformer-models.html#csukuangfj-sherpa-onnx-streaming-paraformer-bilingual-zh-en-chinese-english).

-You can use the following command run it:
+You can use the following command to run it:

 ```bash
 wget -q https://github.com/k2-fsa/sherpa-onnx/releases/download/asr-models/sherpa-onnx-streaming-paraformer-bilingual-zh-en.tar.bz2
@ -167,7 +167,7 @@ demonstrates how to do real-time speech recognition with microphone using a stre
 we use [sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20](https://k2-fsa.github.io/sherpa/onnx/pretrained_models/online-transducer/zipformer-transducer-models.html#csukuangfj-sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20-bilingual-chinese-english).


-You can use the following command run it:
+You can use the following command to run it:

 ```bash
 wget -q https://github.com/k2-fsa/sherpa-onnx/releases/download/asr-models/sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20.tar.bz2
@ -180,7 +180,7 @@ node ./test-online-transducer-microphone.js
 how to decode a file using a streaming transducer model. In the code
 we use [sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20](https://k2-fsa.github.io/sherpa/onnx/pretrained_models/online-transducer/zipformer-transducer-models.html#csukuangfj-sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20-bilingual-chinese-english).

-You can use the following command run it:
+You can use the following command to run it:

 ```bash
 wget -q https://github.com/k2-fsa/sherpa-onnx/releases/download/asr-models/sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20.tar.bz2
@ -188,13 +188,26 @@ tar xvf sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20.tar.bz2
 node ./test-online-transducer.js
 ```

+## ./test-online-zipformer2-ctc.js
+[./test-online-zipformer2-ctc.js](./test-online-zipformer2-ctc.js) demonstrates
+how to decode a file using a streaming zipformer2 CTC model. In the code
+we use [sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13](https://k2-fsa.github.io/sherpa/onnx/pretrained_models/online-ctc/zipformer-ctc-models.html#sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13-chinese).
+
+You can use the following command to run it:
+
+```bash
+wget -q https://github.com/k2-fsa/sherpa-onnx/releases/download/asr-models/sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13.tar.bz2
+tar xvf sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13.tar.bz2
+node ./test-online-zipformer2-ctc.js
+```
+
 ## ./test-vad-microphone-offline-paraformer.js

 [./test-vad-microphone-offline-paraformer.js](./test-vad-microphone-offline-paraformer.js)
 demonstrates how to use [silero-vad](https://github.com/snakers4/silero-vad)
 with non-streaming Paraformer for speech recognition from microphone.

-You can use the following command run it:
+You can use the following command to run it:

 ```bash
 wget -q https://github.com/k2-fsa/sherpa-onnx/releases/download/asr-models/silero_vad.onnx
@ -209,7 +222,7 @@ node ./test-vad-microphone-offline-paraformer.js
 demonstrates how to use [silero-vad](https://github.com/snakers4/silero-vad)
 with a non-streaming transducer model for speech recognition from microphone.

-You can use the following command run it:
+You can use the following command to run it:

 ```bash
 wget -q https://github.com/k2-fsa/sherpa-onnx/releases/download/asr-models/silero_vad.onnx
@ -224,7 +237,7 @@ node ./test-vad-microphone-offline-transducer.js
 demonstrates how to use [silero-vad](https://github.com/snakers4/silero-vad)
 with whisper for speech recognition from microphone.

-You can use the following command run it:
+You can use the following command to run it:

 ```bash
 wget -q https://github.com/k2-fsa/sherpa-onnx/releases/download/asr-models/silero_vad.onnx
@ -238,7 +251,7 @@ node ./test-vad-microphone-offline-whisper.js
 [./test-vad-microphone.js](./test-vad-microphone.js)
 demonstrates how to use [silero-vad](https://github.com/snakers4/silero-vad).

-You can use the following command run it:
+You can use the following command to run it:

 ```bash
 wget -q https://github.com/k2-fsa/sherpa-onnx/releases/download/asr-models/silero_vad.onnx
--- a/nodejs-examples/test-online-zipformer2-ctc.js
+++ b/nodejs-examples/test-online-zipformer2-ctc.js
@ -0,0 +1,97 @@
+// Copyright (c)  2023  Xiaomi Corporation (authors: Fangjun Kuang)
+//
+const fs = require('fs');
+const {Readable} = require('stream');
+const wav = require('wav');
+
+const sherpa_onnx = require('sherpa-onnx');
+
+function createRecognizer() {
+  const featConfig = new sherpa_onnx.FeatureConfig();
+  featConfig.sampleRate = 16000;
+  featConfig.featureDim = 80;
+
+  // test online recognizer
+  const zipformer2Ctc = new sherpa_onnx.OnlineZipformer2CtcModelConfig();
+  zipformer2Ctc.model =
+      './sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13/ctc-epoch-20-avg-1-chunk-16-left-128.onnx';
+  const tokens =
+      './sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13/tokens.txt';
+
+  const modelConfig = new sherpa_onnx.OnlineModelConfig();
+  modelConfig.zipformer2Ctc = zipformer2Ctc;
+  modelConfig.tokens = tokens;
+
+  const recognizerConfig = new sherpa_onnx.OnlineRecognizerConfig();
+  recognizerConfig.featConfig = featConfig;
+  recognizerConfig.modelConfig = modelConfig;
+  recognizerConfig.decodingMethod = 'greedy_search';
+
+  recognizer = new sherpa_onnx.OnlineRecognizer(recognizerConfig);
+  return recognizer;
+}
+recognizer = createRecognizer();
+stream = recognizer.createStream();
+
+const waveFilename =
+    './sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13/test_wavs/DEV_T0000000000.wav';
+
+const reader = new wav.Reader();
+const readable = new Readable().wrap(reader);
+
+function decode(samples) {
+  stream.acceptWaveform(recognizer.config.featConfig.sampleRate, samples);
+
+  while (recognizer.isReady(stream)) {
+    recognizer.decode(stream);
+  }
+  const r = recognizer.getResult(stream);
+  console.log(r.text);
+}
+
+reader.on('format', ({audioFormat, bitDepth, channels, sampleRate}) => {
+  if (sampleRate != recognizer.config.featConfig.sampleRate) {
+    throw new Error(`Only support sampleRate ${
+        recognizer.config.featConfig.sampleRate}. Given ${sampleRate}`);
+  }
+
+  if (audioFormat != 1) {
+    throw new Error(`Only support PCM format. Given ${audioFormat}`);
+  }
+
+  if (channels != 1) {
+    throw new Error(`Only a single channel. Given ${channel}`);
+  }
+
+  if (bitDepth != 16) {
+    throw new Error(`Only support 16-bit samples. Given ${bitDepth}`);
+  }
+});
+
+fs.createReadStream(waveFilename, {'highWaterMark': 4096})
+    .pipe(reader)
+    .on('finish', function(err) {
+      // tail padding
+      const floatSamples =
+          new Float32Array(recognizer.config.featConfig.sampleRate * 0.5);
+      decode(floatSamples);
+      stream.free();
+      recognizer.free();
+    });
+
+readable.on('readable', function() {
+  let chunk;
+  while ((chunk = readable.read()) != null) {
+    const int16Samples = new Int16Array(
+        chunk.buffer, chunk.byteOffset,
+        chunk.length / Int16Array.BYTES_PER_ELEMENT);
+
+    const floatSamples = new Float32Array(int16Samples.length);
+
+    for (let i = 0; i < floatSamples.length; i++) {
+      floatSamples[i] = int16Samples[i] / 32768.0;
+    }
+
+    decode(floatSamples);
+  }
+});
--- a/python-api-examples/online-decode-files.py
+++ b/python-api-examples/online-decode-files.py
@ -37,7 +37,20 @@ git lfs pull --include "*.onnx"
  ./sherpa-onnx-streaming-paraformer-bilingual-zh-en/test_wavs/3.wav \
  ./sherpa-onnx-streaming-paraformer-bilingual-zh-en/test_wavs/8k.wav

-(3) Streaming Conformer CTC from WeNet
+(3) Streaming Zipformer2 CTC
+
+wget https://github.com/k2-fsa/sherpa-onnx/releases/download/asr-models/sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13.tar.bz2
+tar xvf sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13.tar.bz2
+rm sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13.tar.bz2
+ls -lh sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13
+
+./python-api-examples/online-decode-files.py \
+  --zipformer2-ctc=./sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13/ctc-epoch-20-avg-1-chunk-16-left-128.onnx \
+  --tokens=./sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13/tokens.txt \
+  ./sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13/test_wavs/DEV_T0000000000.wav \
+  ./sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13/test_wavs/DEV_T0000000001.wav
+
+(4) Streaming Conformer CTC from WeNet

 GIT_LFS_SKIP_SMUDGE=1 git clone https://huggingface.co/csukuangfj/sherpa-onnx-zh-wenet-wenetspeech
 cd sherpa-onnx-zh-wenet-wenetspeech
@ -51,12 +64,9 @@ git lfs pull --include "*.onnx"
  ./sherpa-onnx-zh-wenet-wenetspeech/test_wavs/8k.wav


-
 Please refer to
-https://k2-fsa.github.io/sherpa/onnx/index.html
-and
-https://k2-fsa.github.io/sherpa/onnx/pretrained_models/wenet/index.html
-to install sherpa-onnx and to download streaming pre-trained models.
+https://k2-fsa.github.io/sherpa/onnx/pretrained_models/index.html
+to download streaming pre-trained models.
 """
 import argparse
 import time
@ -97,6 +107,12 @@ def get_args():
        help="Path to the transducer joiner model",
    )

+    parser.add_argument(
+        "--zipformer2-ctc",
+        type=str,
+        help="Path to the zipformer2 ctc model",
+    )
+
    parser.add_argument(
        "--paraformer-encoder",
        type=str,
@ -112,7 +128,7 @@ def get_args():
    parser.add_argument(
        "--wenet-ctc",
        type=str,
-        help="Path to the wenet ctc model model",
+        help="Path to the wenet ctc model",
    )

    parser.add_argument(
@ -275,6 +291,16 @@ def main():
            hotwords_file=args.hotwords_file,
            hotwords_score=args.hotwords_score,
        )
+    elif args.zipformer2_ctc:
+        recognizer = sherpa_onnx.OnlineRecognizer.from_zipformer2_ctc(
+            tokens=args.tokens,
+            model=args.zipformer2_ctc,
+            num_threads=args.num_threads,
+            provider=args.provider,
+            sample_rate=16000,
+            feature_dim=80,
+            decoding_method="greedy_search",
+        )
    elif args.paraformer_encoder:
        recognizer = sherpa_onnx.OnlineRecognizer.from_paraformer(
            tokens=args.tokens,
--- a/python-api-examples/online-websocket-client-decode-file.py
+++ b/python-api-examples/online-websocket-client-decode-file.py
@ -25,6 +25,7 @@ https://github.com/k2-fsa/sherpa-onnx/blob/master/sherpa-onnx/csrc/online-websoc

 import argparse
 import asyncio
+import json
 import logging
 import wave

@ -112,7 +113,7 @@ async def receive_results(socket: websockets.WebSocketServerProtocol):
    async for message in socket:
        if message != "Done!":
            last_message = message
-            logging.info(message)
+            logging.info(json.loads(message))
        else:
            break
    return last_message
@ -151,7 +152,7 @@ async def run(
        await websocket.send("Done")

        decoding_results = await receive_task
-        logging.info(f"\nFinal result is:\n{decoding_results}")
+        logging.info(f"\nFinal result is:\n{json.loads(decoding_results)}")


 async def main():
--- a/python-api-examples/streaming_server.py
+++ b/python-api-examples/streaming_server.py
@ -137,6 +137,12 @@ def add_model_args(parser: argparse.ArgumentParser):
        help="Path to the transducer joiner model.",
    )

+    parser.add_argument(
+        "--zipformer2-ctc",
+        type=str,
+        help="Path to the model file from zipformer2 ctc",
+    )
+
    parser.add_argument(
        "--wenet-ctc",
        type=str,
@ -405,6 +411,20 @@ def create_recognizer(args) -> sherpa_onnx.OnlineRecognizer:
            rule3_min_utterance_length=args.rule3_min_utterance_length,
            provider=args.provider,
        )
+    elif args.zipformer2_ctc:
+        recognizer = sherpa_onnx.OnlineRecognizer.from_zipformer2_ctc(
+            tokens=args.tokens,
+            model=args.zipformer2_ctc,
+            num_threads=args.num_threads,
+            sample_rate=args.sample_rate,
+            feature_dim=args.feat_dim,
+            decoding_method=args.decoding_method,
+            enable_endpoint_detection=args.use_endpoint != 0,
+            rule1_min_trailing_silence=args.rule1_min_trailing_silence,
+            rule2_min_trailing_silence=args.rule2_min_trailing_silence,
+            rule3_min_utterance_length=args.rule3_min_utterance_length,
+            provider=args.provider,
+        )
    elif args.wenet_ctc:
        recognizer = sherpa_onnx.OnlineRecognizer.from_wenet_ctc(
            tokens=args.tokens,
@ -748,6 +768,8 @@ def check_args(args):

        assert args.paraformer_encoder is None, args.paraformer_encoder
        assert args.paraformer_decoder is None, args.paraformer_decoder
+        assert args.zipformer2_ctc is None, args.zipformer2_ctc
+        assert args.wenet_ctc is None, args.wenet_ctc
    elif args.paraformer_encoder:
        assert Path(
            args.paraformer_encoder
@ -756,6 +778,10 @@ def check_args(args):
        assert Path(
            args.paraformer_decoder
        ).is_file(), f"{args.paraformer_decoder} does not exist"
+    elif args.zipformer2_ctc:
+        assert Path(
+            args.zipformer2_ctc
+        ).is_file(), f"{args.zipformer2_ctc} does not exist"
    elif args.wenet_ctc:
        assert Path(args.wenet_ctc).is_file(), f"{args.wenet_ctc} does not exist"
    else:
--- a/scripts/dotnet/online.cs
+++ b/scripts/dotnet/online.cs
@ -50,6 +50,18 @@ namespace SherpaOnnx
    public string Decoder;
  }

+  [StructLayout(LayoutKind.Sequential)]
+  public struct OnlineZipformer2CtcModelConfig
+  {
+    public OnlineZipformer2CtcModelConfig()
+    {
+      Model = "";
+    }
+
+    [MarshalAs(UnmanagedType.LPStr)]
+    public string Model;
+  }
+
  [StructLayout(LayoutKind.Sequential)]
  public struct OnlineModelConfig
  {
@ -57,6 +69,7 @@ namespace SherpaOnnx
    {
      Transducer = new OnlineTransducerModelConfig();
      Paraformer = new OnlineParaformerModelConfig();
+      Zipformer2Ctc = new OnlineZipformer2CtcModelConfig();
      Tokens = "";
      NumThreads = 1;
      Provider = "cpu";
@ -66,6 +79,7 @@ namespace SherpaOnnx

    public OnlineTransducerModelConfig Transducer;
    public OnlineParaformerModelConfig Paraformer;
+    public OnlineZipformer2CtcModelConfig Zipformer2Ctc;

    [MarshalAs(UnmanagedType.LPStr)]
    public string Tokens;
--- a/scripts/go/_internal/streaming-decode-files/run-zipformer2-ctc.sh
+++ b/scripts/go/_internal/streaming-decode-files/run-zipformer2-ctc.sh
@ -0,0 +1 @@
+../../../../go-api-examples/streaming-decode-files/run-zipformer2-ctc.sh
--- a/scripts/go/sherpa_onnx.go
+++ b/scripts/go/sherpa_onnx.go
@ -65,6 +65,13 @@ type OnlineParaformerModelConfig struct {
 	Decoder string // Path to the decoder model.
 }

+// Please refer to
+// https://k2-fsa.github.io/sherpa/onnx/pretrained_models/online-ctc/index.html
+// to download pre-trained models
+type OnlineZipformer2CtcModelConfig struct {
+	Model string // Path to the onnx model
+}
+
 // Configuration for online/streaming models
 //
 // Please refer to
@ -72,13 +79,14 @@ type OnlineParaformerModelConfig struct {
 // https://k2-fsa.github.io/sherpa/onnx/pretrained_models/online-paraformer/index.html
 // to download pre-trained models
 type OnlineModelConfig struct {
-	Transducer OnlineTransducerModelConfig
-	Paraformer OnlineParaformerModelConfig
-	Tokens     string // Path to tokens.txt
-	NumThreads int    // Number of threads to use for neural network computation
-	Provider   string // Optional. Valid values are: cpu, cuda, coreml
-	Debug      int    // 1 to show model meta information while loading it.
-	ModelType  string // Optional. You can specify it for faster model initialization
+	Transducer    OnlineTransducerModelConfig
+	Paraformer    OnlineParaformerModelConfig
+	Zipformer2Ctc OnlineZipformer2CtcModelConfig
+	Tokens        string // Path to tokens.txt
+	NumThreads    int    // Number of threads to use for neural network computation
+	Provider      string // Optional. Valid values are: cpu, cuda, coreml
+	Debug         int    // 1 to show model meta information while loading it.
+	ModelType     string // Optional. You can specify it for faster model initialization
 }

 // Configuration for the feature extractor
@ -157,6 +165,9 @@ func NewOnlineRecognizer(config *OnlineRecognizerConfig) *OnlineRecognizer {
 	c.model_config.paraformer.decoder = C.CString(config.ModelConfig.Paraformer.Decoder)
 	defer C.free(unsafe.Pointer(c.model_config.paraformer.decoder))

+	c.model_config.zipformer2_ctc.model = C.CString(config.ModelConfig.Zipformer2Ctc.Model)
+	defer C.free(unsafe.Pointer(c.model_config.zipformer2_ctc.model))
+
 	c.model_config.tokens = C.CString(config.ModelConfig.Tokens)
 	defer C.free(unsafe.Pointer(c.model_config.tokens))

--- a/scripts/nodejs/index.js
+++ b/scripts/nodejs/index.js
@ -41,9 +41,14 @@ const SherpaOnnxOnlineParaformerModelConfig = StructType({
  "decoder" : cstring,
 });

+const SherpaOnnxOnlineZipformer2CtcModelConfig = StructType({
+  "model" : cstring,
+});
+
 const SherpaOnnxOnlineModelConfig = StructType({
  "transducer" : SherpaOnnxOnlineTransducerModelConfig,
  "paraformer" : SherpaOnnxOnlineParaformerModelConfig,
+  "zipformer2Ctc" : SherpaOnnxOnlineZipformer2CtcModelConfig,
  "tokens" : cstring,
  "numThreads" : int32_t,
  "provider" : cstring,
@ -663,6 +668,7 @@ const OnlineModelConfig = SherpaOnnxOnlineModelConfig;
 const FeatureConfig = SherpaOnnxFeatureConfig;
 const OnlineRecognizerConfig = SherpaOnnxOnlineRecognizerConfig;
 const OnlineParaformerModelConfig = SherpaOnnxOnlineParaformerModelConfig;
+const OnlineZipformer2CtcModelConfig = SherpaOnnxOnlineZipformer2CtcModelConfig;

 // offline asr
 const OfflineTransducerModelConfig = SherpaOnnxOfflineTransducerModelConfig;
@ -692,6 +698,7 @@ module.exports = {
  OnlineRecognizer,
  OnlineStream,
  OnlineParaformerModelConfig,
+  OnlineZipformer2CtcModelConfig,

  // offline asr
  OfflineRecognizer,
--- a/sherpa-onnx/c-api/c-api.cc
+++ b/sherpa-onnx/c-api/c-api.cc
@ -54,6 +54,9 @@ SherpaOnnxOnlineRecognizer *CreateOnlineRecognizer(
  recognizer_config.model_config.paraformer.decoder =
      SHERPA_ONNX_OR(config->model_config.paraformer.decoder, "");

+  recognizer_config.model_config.zipformer2_ctc.model =
+      SHERPA_ONNX_OR(config->model_config.zipformer2_ctc.model, "");
+
  recognizer_config.model_config.tokens =
      SHERPA_ONNX_OR(config->model_config.tokens, "");
  recognizer_config.model_config.num_threads =
--- a/sherpa-onnx/c-api/c-api.h
+++ b/sherpa-onnx/c-api/c-api.h
@ -66,9 +66,17 @@ SHERPA_ONNX_API typedef struct SherpaOnnxOnlineParaformerModelConfig {
  const char *decoder;
 } SherpaOnnxOnlineParaformerModelConfig;

-SHERPA_ONNX_API typedef struct SherpaOnnxModelConfig {
+// Please visit
+// https://k2-fsa.github.io/sherpa/onnx/pretrained_models/online-ctc/zipformer-ctc-models.html#
+// to download pre-trained streaming zipformer2 ctc models
+SHERPA_ONNX_API typedef struct SherpaOnnxOnlineZipformer2CtcModelConfig {
+  const char *model;
+} SherpaOnnxOnlineZipformer2CtcModelConfig;
+
+SHERPA_ONNX_API typedef struct SherpaOnnxOnlineModelConfig {
  SherpaOnnxOnlineTransducerModelConfig transducer;
  SherpaOnnxOnlineParaformerModelConfig paraformer;
+  SherpaOnnxOnlineZipformer2CtcModelConfig zipformer2_ctc;
  const char *tokens;
  int32_t num_threads;
  const char *provider;
--- a/sherpa-onnx/csrc/CMakeLists.txt
+++ b/sherpa-onnx/csrc/CMakeLists.txt
@ -70,6 +70,8 @@ set(sources
  online-wenet-ctc-model-config.cc
  online-wenet-ctc-model.cc
  online-zipformer-transducer-model.cc
+  online-zipformer2-ctc-model-config.cc
+  online-zipformer2-ctc-model.cc
  online-zipformer2-transducer-model.cc
  onnx-utils.cc
  packed-sequence.cc
--- a/sherpa-onnx/csrc/online-ctc-decoder.h
+++ b/sherpa-onnx/csrc/online-ctc-decoder.h
@ -12,6 +12,9 @@
 namespace sherpa_onnx {

 struct OnlineCtcDecoderResult {
+  /// Number of frames after subsampling we have decoded so far
+  int32_t frame_offset = 0;
+
  /// The decoded token IDs
  std::vector<int64_t> tokens;

--- a/sherpa-onnx/csrc/online-ctc-greedy-search-decoder.cc
+++ b/sherpa-onnx/csrc/online-ctc-greedy-search-decoder.cc
@ -49,12 +49,17 @@ void OnlineCtcGreedySearchDecoder::Decode(

      if (y != blank_id_ && y != prev_id) {
        r.tokens.push_back(y);
-        r.timestamps.push_back(t);
+        r.timestamps.push_back(t + r.frame_offset);
      }

      prev_id = y;
    }  // for (int32_t t = 0; t != num_frames; ++t) {
  }    // for (int32_t b = 0; b != batch_size; ++b)
+
+  // Update frame_offset
+  for (auto &r : *results) {
+    r.frame_offset += num_frames;
+  }
 }

 }  // namespace sherpa_onnx
--- a/sherpa-onnx/csrc/online-ctc-model.cc
+++ b/sherpa-onnx/csrc/online-ctc-model.cc
@ -11,127 +11,35 @@

 #include "sherpa-onnx/csrc/macros.h"
 #include "sherpa-onnx/csrc/online-wenet-ctc-model.h"
+#include "sherpa-onnx/csrc/online-zipformer2-ctc-model.h"
 #include "sherpa-onnx/csrc/onnx-utils.h"

-namespace {
-
-enum class ModelType {
-  kZipformerCtc,
-  kWenetCtc,
-  kUnkown,
-};
-
-}  // namespace
-
 namespace sherpa_onnx {

-static ModelType GetModelType(char *model_data, size_t model_data_length,
-                              bool debug) {
-  Ort::Env env(ORT_LOGGING_LEVEL_WARNING);
-  Ort::SessionOptions sess_opts;
-
-  auto sess = std::make_unique<Ort::Session>(env, model_data, model_data_length,
-                                             sess_opts);
-
-  Ort::ModelMetadata meta_data = sess->GetModelMetadata();
-  if (debug) {
-    std::ostringstream os;
-    PrintModelMetadata(os, meta_data);
-    SHERPA_ONNX_LOGE("%s", os.str().c_str());
-  }
-
-  Ort::AllocatorWithDefaultOptions allocator;
-  auto model_type =
-      meta_data.LookupCustomMetadataMapAllocated("model_type", allocator);
-  if (!model_type) {
-    SHERPA_ONNX_LOGE(
-        "No model_type in the metadata!\n"
-        "If you are using models from WeNet, please refer to\n"
-        "https://github.com/k2-fsa/sherpa-onnx/blob/master/scripts/wenet/"
-        "run.sh\n"
-        "\n"
-        "for how to add metadta to model.onnx\n");
-    return ModelType::kUnkown;
-  }
-
-  if (model_type.get() == std::string("zipformer2")) {
-    return ModelType::kZipformerCtc;
-  } else if (model_type.get() == std::string("wenet_ctc")) {
-    return ModelType::kWenetCtc;
-  } else {
-    SHERPA_ONNX_LOGE("Unsupported model_type: %s", model_type.get());
-    return ModelType::kUnkown;
-  }
-}
-
 std::unique_ptr<OnlineCtcModel> OnlineCtcModel::Create(
    const OnlineModelConfig &config) {
-  ModelType model_type = ModelType::kUnkown;
-
-  std::string filename;
  if (!config.wenet_ctc.model.empty()) {
-    filename = config.wenet_ctc.model;
+    return std::make_unique<OnlineWenetCtcModel>(config);
+  } else if (!config.zipformer2_ctc.model.empty()) {
+    return std::make_unique<OnlineZipformer2CtcModel>(config);
  } else {
    SHERPA_ONNX_LOGE("Please specify a CTC model");
    exit(-1);
  }
-
-  {
-    auto buffer = ReadFile(filename);
-
-    model_type = GetModelType(buffer.data(), buffer.size(), config.debug);
-  }
-
-  switch (model_type) {
-    case ModelType::kZipformerCtc:
-      return nullptr;
-      // return std::make_unique<OnlineZipformerCtcModel>(config);
-      break;
-    case ModelType::kWenetCtc:
-      return std::make_unique<OnlineWenetCtcModel>(config);
-      break;
-    case ModelType::kUnkown:
-      SHERPA_ONNX_LOGE("Unknown model type in online CTC!");
-      return nullptr;
-  }
-
-  return nullptr;
 }

 #if __ANDROID_API__ >= 9

 std::unique_ptr<OnlineCtcModel> OnlineCtcModel::Create(
    AAssetManager *mgr, const OnlineModelConfig &config) {
-  ModelType model_type = ModelType::kUnkown;
-
-  std::string filename;
  if (!config.wenet_ctc.model.empty()) {
-    filename = config.wenet_ctc.model;
+    return std::make_unique<OnlineWenetCtcModel>(mgr, config);
+  } else if (!config.zipformer2_ctc.model.empty()) {
+    return std::make_unique<OnlineZipformer2CtcModel>(mgr, config);
  } else {
    SHERPA_ONNX_LOGE("Please specify a CTC model");
    exit(-1);
  }
-
-  {
-    auto buffer = ReadFile(mgr, filename);
-
-    model_type = GetModelType(buffer.data(), buffer.size(), config.debug);
-  }
-
-  switch (model_type) {
-    case ModelType::kZipformerCtc:
-      return nullptr;
-      // return std::make_unique<OnlineZipformerCtcModel>(mgr, config);
-      break;
-    case ModelType::kWenetCtc:
-      return std::make_unique<OnlineWenetCtcModel>(mgr, config);
-      break;
-    case ModelType::kUnkown:
-      SHERPA_ONNX_LOGE("Unknown model type in online CTC!");
-      return nullptr;
-  }
-
-  return nullptr;
 }
 #endif

--- a/sherpa-onnx/csrc/online-ctc-model.h
+++ b/sherpa-onnx/csrc/online-ctc-model.h
@ -33,6 +33,26 @@ class OnlineCtcModel {
  // Return a list of tensors containing the initial states
  virtual std::vector<Ort::Value> GetInitStates() const = 0;

+  /** Stack a list of individual states into a batch.
+   *
+   * It is the inverse operation of `UnStackStates`.
+   *
+   * @param states states[i] contains the state for the i-th utterance.
+   * @return Return a single value representing the batched state.
+   */
+  virtual std::vector<Ort::Value> StackStates(
+      std::vector<std::vector<Ort::Value>> states) const = 0;
+
+  /** Unstack a batch state into a list of individual states.
+   *
+   * It is the inverse operation of `StackStates`.
+   *
+   * @param states A batched state.
+   * @return ans[i] contains the state for the i-th utterance.
+   */
+  virtual std::vector<std::vector<Ort::Value>> UnStackStates(
+      std::vector<Ort::Value> states) const = 0;
+
  /**
   *
   * @param x A 3-D tensor of shape (N, T, C). N has to be 1.
@ -60,6 +80,9 @@ class OnlineCtcModel {
  // ChunkLength() frames, we advance by ChunkShift() frames
  // before we process the next chunk.
  virtual int32_t ChunkShift() const = 0;
+
+  // Return true if the model supports batch size > 1
+  virtual bool SupportBatchProcessing() const { return true; }
 };

 }  // namespace sherpa_onnx
--- a/sherpa-onnx/csrc/online-model-config.cc
+++ b/sherpa-onnx/csrc/online-model-config.cc
@ -14,6 +14,7 @@ void OnlineModelConfig::Register(ParseOptions *po) {
  transducer.Register(po);
  paraformer.Register(po);
  wenet_ctc.Register(po);
+  zipformer2_ctc.Register(po);

  po->Register("tokens", &tokens, "Path to tokens.txt");

@ -26,10 +27,11 @@ void OnlineModelConfig::Register(ParseOptions *po) {
  po->Register("provider", &provider,
               "Specify a provider to use: cpu, cuda, coreml");

-  po->Register("model-type", &model_type,
-               "Specify it to reduce model initialization time. "
-               "Valid values are: conformer, lstm, zipformer, zipformer2."
-               "All other values lead to loading the model twice.");
+  po->Register(
+      "model-type", &model_type,
+      "Specify it to reduce model initialization time. "
+      "Valid values are: conformer, lstm, zipformer, zipformer2, wenet_ctc"
+      "All other values lead to loading the model twice.");
 }

 bool OnlineModelConfig::Validate() const {
@ -51,6 +53,10 @@ bool OnlineModelConfig::Validate() const {
    return wenet_ctc.Validate();
  }

+  if (!zipformer2_ctc.model.empty()) {
+    return zipformer2_ctc.Validate();
+  }
+
  return transducer.Validate();
 }

@ -61,6 +67,7 @@ std::string OnlineModelConfig::ToString() const {
  os << "transducer=" << transducer.ToString() << ", ";
  os << "paraformer=" << paraformer.ToString() << ", ";
  os << "wenet_ctc=" << wenet_ctc.ToString() << ", ";
+  os << "zipformer2_ctc=" << zipformer2_ctc.ToString() << ", ";
  os << "tokens=\"" << tokens << "\", ";
  os << "num_threads=" << num_threads << ", ";
  os << "debug=" << (debug ? "True" : "False") << ", ";
--- a/sherpa-onnx/csrc/online-model-config.h
+++ b/sherpa-onnx/csrc/online-model-config.h
@ -9,6 +9,7 @@
 #include "sherpa-onnx/csrc/online-paraformer-model-config.h"
 #include "sherpa-onnx/csrc/online-transducer-model-config.h"
 #include "sherpa-onnx/csrc/online-wenet-ctc-model-config.h"
+#include "sherpa-onnx/csrc/online-zipformer2-ctc-model-config.h"

 namespace sherpa_onnx {

@ -16,6 +17,7 @@ struct OnlineModelConfig {
  OnlineTransducerModelConfig transducer;
  OnlineParaformerModelConfig paraformer;
  OnlineWenetCtcModelConfig wenet_ctc;
+  OnlineZipformer2CtcModelConfig zipformer2_ctc;
  std::string tokens;
  int32_t num_threads = 1;
  bool debug = false;
@ -25,7 +27,8 @@ struct OnlineModelConfig {
  //  - conformer, conformer transducer from icefall
  //  - lstm, lstm transducer from icefall
  //  - zipformer, zipformer transducer from icefall
-  //  - zipformer2, zipformer2 transducer from icefall
+  //  - zipformer2, zipformer2 transducer or CTC from icefall
+  //  - wenet_ctc, wenet CTC model
  //
  // All other values are invalid and lead to loading the model twice.
  std::string model_type;
@ -34,11 +37,13 @@ struct OnlineModelConfig {
  OnlineModelConfig(const OnlineTransducerModelConfig &transducer,
                    const OnlineParaformerModelConfig &paraformer,
                    const OnlineWenetCtcModelConfig &wenet_ctc,
+                    const OnlineZipformer2CtcModelConfig &zipformer2_ctc,
                    const std::string &tokens, int32_t num_threads, bool debug,
                    const std::string &provider, const std::string &model_type)
      : transducer(transducer),
        paraformer(paraformer),
        wenet_ctc(wenet_ctc),
+        zipformer2_ctc(zipformer2_ctc),
        tokens(tokens),
        num_threads(num_threads),
        debug(debug),
--- a/sherpa-onnx/csrc/online-recognizer-ctc-impl.h
+++ b/sherpa-onnx/csrc/online-recognizer-ctc-impl.h
@ -96,8 +96,67 @@ class OnlineRecognizerCtcImpl : public OnlineRecognizerImpl {
  }

  void DecodeStreams(OnlineStream **ss, int32_t n) const override {
+    if (n == 1 || !model_->SupportBatchProcessing()) {
+      for (int32_t i = 0; i != n; ++i) {
+        DecodeStream(ss[i]);
+      }
+      return;
+    }
+
+    // batch processing
+    int32_t chunk_length = model_->ChunkLength();
+    int32_t chunk_shift = model_->ChunkShift();
+
+    int32_t feat_dim = ss[0]->FeatureDim();
+
+    std::vector<OnlineCtcDecoderResult> results(n);
+    std::vector<float> features_vec(n * chunk_length * feat_dim);
+    std::vector<std::vector<Ort::Value>> states_vec(n);
+    std::vector<int64_t> all_processed_frames(n);
+
    for (int32_t i = 0; i != n; ++i) {
-      DecodeStream(ss[i]);
+      const auto num_processed_frames = ss[i]->GetNumProcessedFrames();
+      std::vector<float> features =
+          ss[i]->GetFrames(num_processed_frames, chunk_length);
+
+      // Question: should num_processed_frames include chunk_shift?
+      ss[i]->GetNumProcessedFrames() += chunk_shift;
+
+      std::copy(features.begin(), features.end(),
+                features_vec.data() + i * chunk_length * feat_dim);
+
+      results[i] = std::move(ss[i]->GetCtcResult());
+      states_vec[i] = std::move(ss[i]->GetStates());
+      all_processed_frames[i] = num_processed_frames;
+    }
+
+    auto memory_info =
+        Ort::MemoryInfo::CreateCpu(OrtDeviceAllocator, OrtMemTypeDefault);
+
+    std::array<int64_t, 3> x_shape{n, chunk_length, feat_dim};
+
+    Ort::Value x = Ort::Value::CreateTensor(memory_info, features_vec.data(),
+                                            features_vec.size(), x_shape.data(),
+                                            x_shape.size());
+
+    auto states = model_->StackStates(std::move(states_vec));
+    int32_t num_states = states.size();
+    auto out = model_->Forward(std::move(x), std::move(states));
+    std::vector<Ort::Value> out_states;
+    out_states.reserve(num_states);
+
+    for (int32_t k = 1; k != num_states + 1; ++k) {
+      out_states.push_back(std::move(out[k]));
+    }
+
+    std::vector<std::vector<Ort::Value>> next_states =
+        model_->UnStackStates(std::move(out_states));
+
+    decoder_->Decode(std::move(out[0]), &results);
+
+    for (int32_t k = 0; k != n; ++k) {
+      ss[k]->SetCtcResult(results[k]);
+      ss[k]->SetStates(std::move(next_states[k]));
    }
  }

--- a/sherpa-onnx/csrc/online-recognizer-impl.cc
+++ b/sherpa-onnx/csrc/online-recognizer-impl.cc
@ -20,7 +20,8 @@ std::unique_ptr<OnlineRecognizerImpl> OnlineRecognizerImpl::Create(
    return std::make_unique<OnlineRecognizerParaformerImpl>(config);
  }

-  if (!config.model_config.wenet_ctc.model.empty()) {
+  if (!config.model_config.wenet_ctc.model.empty() ||
+      !config.model_config.zipformer2_ctc.model.empty()) {
    return std::make_unique<OnlineRecognizerCtcImpl>(config);
  }

@ -39,7 +40,8 @@ std::unique_ptr<OnlineRecognizerImpl> OnlineRecognizerImpl::Create(
    return std::make_unique<OnlineRecognizerParaformerImpl>(mgr, config);
  }

-  if (!config.model_config.wenet_ctc.model.empty()) {
+  if (!config.model_config.wenet_ctc.model.empty() ||
+      !config.model_config.zipformer2_ctc.model.empty()) {
    return std::make_unique<OnlineRecognizerCtcImpl>(mgr, config);
  }

--- a/sherpa-onnx/csrc/online-wenet-ctc-model.cc
+++ b/sherpa-onnx/csrc/online-wenet-ctc-model.cc
@ -1,4 +1,4 @@
-// sherpa-onnx/csrc/online-paraformer-model.cc
+// sherpa-onnx/csrc/online-wenet-ctc-model.cc
 //
 // Copyright (c)  2023  Xiaomi Corporation

@ -239,4 +239,21 @@ std::vector<Ort::Value> OnlineWenetCtcModel::GetInitStates() const {
  return impl_->GetInitStates();
 }

+std::vector<Ort::Value> OnlineWenetCtcModel::StackStates(
+    std::vector<std::vector<Ort::Value>> states) const {
+  if (states.size() != 1) {
+    SHERPA_ONNX_LOGE("wenet CTC model supports only batch_size==1. Given: %d",
+                     static_cast<int32_t>(states.size()));
+  }
+
+  return std::move(states[0]);
+}
+
+std::vector<std::vector<Ort::Value>> OnlineWenetCtcModel::UnStackStates(
+    std::vector<Ort::Value> states) const {
+  std::vector<std::vector<Ort::Value>> ans(1);
+  ans[0] = std::move(states);
+  return ans;
+}
+
 }  // namespace sherpa_onnx
--- a/sherpa-onnx/csrc/online-wenet-ctc-model.h
+++ b/sherpa-onnx/csrc/online-wenet-ctc-model.h
@ -35,6 +35,12 @@ class OnlineWenetCtcModel : public OnlineCtcModel {
  //  - offset
  std::vector<Ort::Value> GetInitStates() const override;

+  std::vector<Ort::Value> StackStates(
+      std::vector<std::vector<Ort::Value>> states) const override;
+
+  std::vector<std::vector<Ort::Value>> UnStackStates(
+      std::vector<Ort::Value> states) const override;
+
  /**
   *
   * @param x A 3-D tensor of shape (N, T, C). N has to be 1.
@ -63,6 +69,8 @@ class OnlineWenetCtcModel : public OnlineCtcModel {
  // before we process the next chunk.
  int32_t ChunkShift() const override;

+  bool SupportBatchProcessing() const override { return false; }
+
 private:
  class Impl;
  std::unique_ptr<Impl> impl_;
--- a/sherpa-onnx/csrc/online-zipformer2-ctc-model-config.cc
+++ b/sherpa-onnx/csrc/online-zipformer2-ctc-model-config.cc
@ -0,0 +1,41 @@
+// sherpa-onnx/csrc/online-zipformer2-ctc-model-config.cc
+//
+// Copyright (c)  2023  Xiaomi Corporation
+
+#include "sherpa-onnx/csrc/online-zipformer2-ctc-model-config.h"
+
+#include "sherpa-onnx/csrc/file-utils.h"
+#include "sherpa-onnx/csrc/macros.h"
+
+namespace sherpa_onnx {
+
+void OnlineZipformer2CtcModelConfig::Register(ParseOptions *po) {
+  po->Register("zipformer2-ctc-model", &model,
+               "Path to CTC model.onnx. See also "
+               "https://github.com/k2-fsa/icefall/pull/1413");
+}
+
+bool OnlineZipformer2CtcModelConfig::Validate() const {
+  if (model.empty()) {
+    SHERPA_ONNX_LOGE("--zipformer2-ctc-model is empty!");
+    return false;
+  }
+
+  if (!FileExists(model)) {
+    SHERPA_ONNX_LOGE("--zipformer2-ctc-model %s does not exist", model.c_str());
+    return false;
+  }
+
+  return true;
+}
+
+std::string OnlineZipformer2CtcModelConfig::ToString() const {
+  std::ostringstream os;
+
+  os << "OnlineZipformer2CtcModelConfig(";
+  os << "model=\"" << model << "\")";
+
+  return os.str();
+}
+
+}  // namespace sherpa_onnx
--- a/sherpa-onnx/csrc/online-zipformer2-ctc-model-config.h
+++ b/sherpa-onnx/csrc/online-zipformer2-ctc-model-config.h
@ -0,0 +1,29 @@
+// sherpa-onnx/csrc/online-zipformer2-ctc-model-config.h
+//
+// Copyright (c)  2023  Xiaomi Corporation
+#ifndef SHERPA_ONNX_CSRC_ONLINE_ZIPFORMER2_CTC_MODEL_CONFIG_H_
+#define SHERPA_ONNX_CSRC_ONLINE_ZIPFORMER2_CTC_MODEL_CONFIG_H_
+
+#include <string>
+
+#include "sherpa-onnx/csrc/parse-options.h"
+
+namespace sherpa_onnx {
+
+struct OnlineZipformer2CtcModelConfig {
+  std::string model;
+
+  OnlineZipformer2CtcModelConfig() = default;
+
+  explicit OnlineZipformer2CtcModelConfig(const std::string &model)
+      : model(model) {}
+
+  void Register(ParseOptions *po);
+  bool Validate() const;
+
+  std::string ToString() const;
+};
+
+}  // namespace sherpa_onnx
+
+#endif  // SHERPA_ONNX_CSRC_ONLINE_ZIPFORMER2_CTC_MODEL_CONFIG_H_
--- a/sherpa-onnx/csrc/online-zipformer2-ctc-model.cc
+++ b/sherpa-onnx/csrc/online-zipformer2-ctc-model.cc
@ -0,0 +1,464 @@
+// sherpa-onnx/csrc/online-zipformer2-ctc-model.cc
+//
+// Copyright (c)  2023  Xiaomi Corporation
+
+#include "sherpa-onnx/csrc/online-zipformer2-ctc-model.h"
+
+#include <assert.h>
+#include <math.h>
+
+#include <algorithm>
+#include <cmath>
+#include <numeric>
+#include <string>
+
+#if __ANDROID_API__ >= 9
+#include "android/asset_manager.h"
+#include "android/asset_manager_jni.h"
+#endif
+
+#include "sherpa-onnx/csrc/cat.h"
+#include "sherpa-onnx/csrc/macros.h"
+#include "sherpa-onnx/csrc/onnx-utils.h"
+#include "sherpa-onnx/csrc/session.h"
+#include "sherpa-onnx/csrc/text-utils.h"
+#include "sherpa-onnx/csrc/unbind.h"
+
+namespace sherpa_onnx {
+
+class OnlineZipformer2CtcModel::Impl {
+ public:
+  explicit Impl(const OnlineModelConfig &config)
+      : config_(config),
+        env_(ORT_LOGGING_LEVEL_ERROR),
+        sess_opts_(GetSessionOptions(config)),
+        allocator_{} {
+    {
+      auto buf = ReadFile(config.zipformer2_ctc.model);
+      Init(buf.data(), buf.size());
+    }
+  }
+
+#if __ANDROID_API__ >= 9
+  Impl(AAssetManager *mgr, const OnlineModelConfig &config)
+      : config_(config),
+        env_(ORT_LOGGING_LEVEL_WARNING),
+        sess_opts_(GetSessionOptions(config)),
+        allocator_{} {
+    {
+      auto buf = ReadFile(mgr, config.zipformer2_ctc.model);
+      Init(buf.data(), buf.size());
+    }
+  }
+#endif
+
+  std::vector<Ort::Value> Forward(Ort::Value features,
+                                  std::vector<Ort::Value> states) {
+    std::vector<Ort::Value> inputs;
+    inputs.reserve(1 + states.size());
+
+    inputs.push_back(std::move(features));
+    for (auto &v : states) {
+      inputs.push_back(std::move(v));
+    }
+
+    return sess_->Run({}, input_names_ptr_.data(), inputs.data(), inputs.size(),
+                      output_names_ptr_.data(), output_names_ptr_.size());
+  }
+
+  int32_t VocabSize() const { return vocab_size_; }
+
+  int32_t ChunkLength() const { return T_; }
+
+  int32_t ChunkShift() const { return decode_chunk_len_; }
+
+  OrtAllocator *Allocator() const { return allocator_; }
+
+  // Return a vector containing 3 tensors
+  // - attn_cache
+  // - conv_cache
+  // - offset
+  std::vector<Ort::Value> GetInitStates() {
+    std::vector<Ort::Value> ans;
+    ans.reserve(initial_states_.size());
+    for (auto &s : initial_states_) {
+      ans.push_back(View(&s));
+    }
+    return ans;
+  }
+
+  std::vector<Ort::Value> StackStates(
+      std::vector<std::vector<Ort::Value>> states) const {
+    int32_t batch_size = static_cast<int32_t>(states.size());
+    int32_t num_encoders = static_cast<int32_t>(num_encoder_layers_.size());
+
+    std::vector<const Ort::Value *> buf(batch_size);
+
+    std::vector<Ort::Value> ans;
+    int32_t num_states = static_cast<int32_t>(states[0].size());
+    ans.reserve(num_states);
+
+    for (int32_t i = 0; i != (num_states - 2) / 6; ++i) {
+      {
+        for (int32_t n = 0; n != batch_size; ++n) {
+          buf[n] = &states[n][6 * i];
+        }
+        auto v = Cat(allocator_, buf, 1);
+        ans.push_back(std::move(v));
+      }
+      {
+        for (int32_t n = 0; n != batch_size; ++n) {
+          buf[n] = &states[n][6 * i + 1];
+        }
+        auto v = Cat(allocator_, buf, 1);
+        ans.push_back(std::move(v));
+      }
+      {
+        for (int32_t n = 0; n != batch_size; ++n) {
+          buf[n] = &states[n][6 * i + 2];
+        }
+        auto v = Cat(allocator_, buf, 1);
+        ans.push_back(std::move(v));
+      }
+      {
+        for (int32_t n = 0; n != batch_size; ++n) {
+          buf[n] = &states[n][6 * i + 3];
+        }
+        auto v = Cat(allocator_, buf, 1);
+        ans.push_back(std::move(v));
+      }
+      {
+        for (int32_t n = 0; n != batch_size; ++n) {
+          buf[n] = &states[n][6 * i + 4];
+        }
+        auto v = Cat(allocator_, buf, 0);
+        ans.push_back(std::move(v));
+      }
+      {
+        for (int32_t n = 0; n != batch_size; ++n) {
+          buf[n] = &states[n][6 * i + 5];
+        }
+        auto v = Cat(allocator_, buf, 0);
+        ans.push_back(std::move(v));
+      }
+    }
+
+    {
+      for (int32_t n = 0; n != batch_size; ++n) {
+        buf[n] = &states[n][num_states - 2];
+      }
+      auto v = Cat(allocator_, buf, 0);
+      ans.push_back(std::move(v));
+    }
+
+    {
+      for (int32_t n = 0; n != batch_size; ++n) {
+        buf[n] = &states[n][num_states - 1];
+      }
+      auto v = Cat<int64_t>(allocator_, buf, 0);
+      ans.push_back(std::move(v));
+    }
+    return ans;
+  }
+
+  std::vector<std::vector<Ort::Value>> UnStackStates(
+      std::vector<Ort::Value> states) const {
+    int32_t m = std::accumulate(num_encoder_layers_.begin(),
+                                num_encoder_layers_.end(), 0);
+    assert(states.size() == m * 6 + 2);
+
+    int32_t batch_size = states[0].GetTensorTypeAndShapeInfo().GetShape()[1];
+    int32_t num_encoders = num_encoder_layers_.size();
+
+    std::vector<std::vector<Ort::Value>> ans;
+    ans.resize(batch_size);
+
+    for (int32_t i = 0; i != m; ++i) {
+      {
+        auto v = Unbind(allocator_, &states[i * 6], 1);
+        assert(v.size() == batch_size);
+
+        for (int32_t n = 0; n != batch_size; ++n) {
+          ans[n].push_back(std::move(v[n]));
+        }
+      }
+      {
+        auto v = Unbind(allocator_, &states[i * 6 + 1], 1);
+        assert(v.size() == batch_size);
+
+        for (int32_t n = 0; n != batch_size; ++n) {
+          ans[n].push_back(std::move(v[n]));
+        }
+      }
+      {
+        auto v = Unbind(allocator_, &states[i * 6 + 2], 1);
+        assert(v.size() == batch_size);
+
+        for (int32_t n = 0; n != batch_size; ++n) {
+          ans[n].push_back(std::move(v[n]));
+        }
+      }
+      {
+        auto v = Unbind(allocator_, &states[i * 6 + 3], 1);
+        assert(v.size() == batch_size);
+
+        for (int32_t n = 0; n != batch_size; ++n) {
+          ans[n].push_back(std::move(v[n]));
+        }
+      }
+      {
+        auto v = Unbind(allocator_, &states[i * 6 + 4], 0);
+        assert(v.size() == batch_size);
+
+        for (int32_t n = 0; n != batch_size; ++n) {
+          ans[n].push_back(std::move(v[n]));
+        }
+      }
+      {
+        auto v = Unbind(allocator_, &states[i * 6 + 5], 0);
+        assert(v.size() == batch_size);
+
+        for (int32_t n = 0; n != batch_size; ++n) {
+          ans[n].push_back(std::move(v[n]));
+        }
+      }
+    }
+
+    {
+      auto v = Unbind(allocator_, &states[m * 6], 0);
+      assert(v.size() == batch_size);
+
+      for (int32_t n = 0; n != batch_size; ++n) {
+        ans[n].push_back(std::move(v[n]));
+      }
+    }
+    {
+      auto v = Unbind<int64_t>(allocator_, &states[m * 6 + 1], 0);
+      assert(v.size() == batch_size);
+
+      for (int32_t n = 0; n != batch_size; ++n) {
+        ans[n].push_back(std::move(v[n]));
+      }
+    }
+
+    return ans;
+  }
+
+ private:
+  void Init(void *model_data, size_t model_data_length) {
+    sess_ = std::make_unique<Ort::Session>(env_, model_data, model_data_length,
+                                           sess_opts_);
+
+    GetInputNames(sess_.get(), &input_names_, &input_names_ptr_);
+
+    GetOutputNames(sess_.get(), &output_names_, &output_names_ptr_);
+
+    // get meta data
+    Ort::ModelMetadata meta_data = sess_->GetModelMetadata();
+    if (config_.debug) {
+      std::ostringstream os;
+      os << "---zipformer2_ctc---\n";
+      PrintModelMetadata(os, meta_data);
+      SHERPA_ONNX_LOGE("%s", os.str().c_str());
+    }
+
+    Ort::AllocatorWithDefaultOptions allocator;  // used in the macro below
+    SHERPA_ONNX_READ_META_DATA_VEC(encoder_dims_, "encoder_dims");
+    SHERPA_ONNX_READ_META_DATA_VEC(query_head_dims_, "query_head_dims");
+    SHERPA_ONNX_READ_META_DATA_VEC(value_head_dims_, "value_head_dims");
+    SHERPA_ONNX_READ_META_DATA_VEC(num_heads_, "num_heads");
+    SHERPA_ONNX_READ_META_DATA_VEC(num_encoder_layers_, "num_encoder_layers");
+    SHERPA_ONNX_READ_META_DATA_VEC(cnn_module_kernels_, "cnn_module_kernels");
+    SHERPA_ONNX_READ_META_DATA_VEC(left_context_len_, "left_context_len");
+
+    SHERPA_ONNX_READ_META_DATA(T_, "T");
+    SHERPA_ONNX_READ_META_DATA(decode_chunk_len_, "decode_chunk_len");
+
+    {
+      auto shape =
+          sess_->GetOutputTypeInfo(0).GetTensorTypeAndShapeInfo().GetShape();
+      vocab_size_ = shape[2];
+    }
+
+    if (config_.debug) {
+      auto print = [](const std::vector<int32_t> &v, const char *name) {
+        fprintf(stderr, "%s: ", name);
+        for (auto i : v) {
+          fprintf(stderr, "%d ", i);
+        }
+        fprintf(stderr, "\n");
+      };
+      print(encoder_dims_, "encoder_dims");
+      print(query_head_dims_, "query_head_dims");
+      print(value_head_dims_, "value_head_dims");
+      print(num_heads_, "num_heads");
+      print(num_encoder_layers_, "num_encoder_layers");
+      print(cnn_module_kernels_, "cnn_module_kernels");
+      print(left_context_len_, "left_context_len");
+      SHERPA_ONNX_LOGE("T: %d", T_);
+      SHERPA_ONNX_LOGE("decode_chunk_len_: %d", decode_chunk_len_);
+      SHERPA_ONNX_LOGE("vocab_size_: %d", vocab_size_);
+    }
+
+    InitStates();
+  }
+
+  void InitStates() {
+    int32_t n = static_cast<int32_t>(encoder_dims_.size());
+    int32_t m = std::accumulate(num_encoder_layers_.begin(),
+                                num_encoder_layers_.end(), 0);
+    initial_states_.reserve(m * 6 + 2);
+
+    for (int32_t i = 0; i != n; ++i) {
+      int32_t num_layers = num_encoder_layers_[i];
+      int32_t key_dim = query_head_dims_[i] * num_heads_[i];
+      int32_t value_dim = value_head_dims_[i] * num_heads_[i];
+      int32_t nonlin_attn_head_dim = 3 * encoder_dims_[i] / 4;
+
+      for (int32_t j = 0; j != num_layers; ++j) {
+        {
+          std::array<int64_t, 3> s{left_context_len_[i], 1, key_dim};
+          auto v =
+              Ort::Value::CreateTensor<float>(allocator_, s.data(), s.size());
+          Fill(&v, 0);
+          initial_states_.push_back(std::move(v));
+        }
+
+        {
+          std::array<int64_t, 4> s{1, 1, left_context_len_[i],
+                                   nonlin_attn_head_dim};
+          auto v =
+              Ort::Value::CreateTensor<float>(allocator_, s.data(), s.size());
+          Fill(&v, 0);
+          initial_states_.push_back(std::move(v));
+        }
+
+        {
+          std::array<int64_t, 3> s{left_context_len_[i], 1, value_dim};
+          auto v =
+              Ort::Value::CreateTensor<float>(allocator_, s.data(), s.size());
+          Fill(&v, 0);
+          initial_states_.push_back(std::move(v));
+        }
+
+        {
+          std::array<int64_t, 3> s{left_context_len_[i], 1, value_dim};
+          auto v =
+              Ort::Value::CreateTensor<float>(allocator_, s.data(), s.size());
+          Fill(&v, 0);
+          initial_states_.push_back(std::move(v));
+        }
+
+        {
+          std::array<int64_t, 3> s{1, encoder_dims_[i],
+                                   cnn_module_kernels_[i] / 2};
+          auto v =
+              Ort::Value::CreateTensor<float>(allocator_, s.data(), s.size());
+          Fill(&v, 0);
+          initial_states_.push_back(std::move(v));
+        }
+
+        {
+          std::array<int64_t, 3> s{1, encoder_dims_[i],
+                                   cnn_module_kernels_[i] / 2};
+          auto v =
+              Ort::Value::CreateTensor<float>(allocator_, s.data(), s.size());
+          Fill(&v, 0);
+          initial_states_.push_back(std::move(v));
+        }
+      }
+    }
+
+    {
+      std::array<int64_t, 4> s{1, 128, 3, 19};
+      auto v = Ort::Value::CreateTensor<float>(allocator_, s.data(), s.size());
+      Fill(&v, 0);
+      initial_states_.push_back(std::move(v));
+    }
+
+    {
+      std::array<int64_t, 1> s{1};
+      auto v =
+          Ort::Value::CreateTensor<int64_t>(allocator_, s.data(), s.size());
+      Fill<int64_t>(&v, 0);
+      initial_states_.push_back(std::move(v));
+    }
+  }
+
+ private:
+  OnlineModelConfig config_;
+  Ort::Env env_;
+  Ort::SessionOptions sess_opts_;
+  Ort::AllocatorWithDefaultOptions allocator_;
+
+  std::unique_ptr<Ort::Session> sess_;
+
+  std::vector<std::string> input_names_;
+  std::vector<const char *> input_names_ptr_;
+
+  std::vector<std::string> output_names_;
+  std::vector<const char *> output_names_ptr_;
+
+  std::vector<Ort::Value> initial_states_;
+
+  std::vector<int32_t> encoder_dims_;
+  std::vector<int32_t> query_head_dims_;
+  std::vector<int32_t> value_head_dims_;
+  std::vector<int32_t> num_heads_;
+  std::vector<int32_t> num_encoder_layers_;
+  std::vector<int32_t> cnn_module_kernels_;
+  std::vector<int32_t> left_context_len_;
+
+  int32_t T_ = 0;
+  int32_t decode_chunk_len_ = 0;
+  int32_t vocab_size_ = 0;
+};
+
+OnlineZipformer2CtcModel::OnlineZipformer2CtcModel(
+    const OnlineModelConfig &config)
+    : impl_(std::make_unique<Impl>(config)) {}
+
+#if __ANDROID_API__ >= 9
+OnlineZipformer2CtcModel::OnlineZipformer2CtcModel(
+    AAssetManager *mgr, const OnlineModelConfig &config)
+    : impl_(std::make_unique<Impl>(mgr, config)) {}
+#endif
+
+OnlineZipformer2CtcModel::~OnlineZipformer2CtcModel() = default;
+
+std::vector<Ort::Value> OnlineZipformer2CtcModel::Forward(
+    Ort::Value x, std::vector<Ort::Value> states) const {
+  return impl_->Forward(std::move(x), std::move(states));
+}
+
+int32_t OnlineZipformer2CtcModel::VocabSize() const {
+  return impl_->VocabSize();
+}
+
+int32_t OnlineZipformer2CtcModel::ChunkLength() const {
+  return impl_->ChunkLength();
+}
+
+int32_t OnlineZipformer2CtcModel::ChunkShift() const {
+  return impl_->ChunkShift();
+}
+
+OrtAllocator *OnlineZipformer2CtcModel::Allocator() const {
+  return impl_->Allocator();
+}
+
+std::vector<Ort::Value> OnlineZipformer2CtcModel::GetInitStates() const {
+  return impl_->GetInitStates();
+}
+
+std::vector<Ort::Value> OnlineZipformer2CtcModel::StackStates(
+    std::vector<std::vector<Ort::Value>> states) const {
+  return impl_->StackStates(std::move(states));
+}
+
+std::vector<std::vector<Ort::Value>> OnlineZipformer2CtcModel::UnStackStates(
+    std::vector<Ort::Value> states) const {
+  return impl_->UnStackStates(std::move(states));
+}
+
+}  // namespace sherpa_onnx
--- a/sherpa-onnx/csrc/online-zipformer2-ctc-model.h
+++ b/sherpa-onnx/csrc/online-zipformer2-ctc-model.h
@ -0,0 +1,80 @@
+// sherpa-onnx/csrc/online-zipformer2-ctc-model.h
+//
+// Copyright (c)  2023  Xiaomi Corporation
+#ifndef SHERPA_ONNX_CSRC_ONLINE_ZIPFORMER2_CTC_MODEL_H_
+#define SHERPA_ONNX_CSRC_ONLINE_ZIPFORMER2_CTC_MODEL_H_
+
+#include <memory>
+#include <utility>
+#include <vector>
+
+#if __ANDROID_API__ >= 9
+#include "android/asset_manager.h"
+#include "android/asset_manager_jni.h"
+#endif
+
+#include "onnxruntime_cxx_api.h"  // NOLINT
+#include "sherpa-onnx/csrc/online-ctc-model.h"
+#include "sherpa-onnx/csrc/online-model-config.h"
+
+namespace sherpa_onnx {
+
+class OnlineZipformer2CtcModel : public OnlineCtcModel {
+ public:
+  explicit OnlineZipformer2CtcModel(const OnlineModelConfig &config);
+
+#if __ANDROID_API__ >= 9
+  OnlineZipformer2CtcModel(AAssetManager *mgr, const OnlineModelConfig &config);
+#endif
+
+  ~OnlineZipformer2CtcModel() override;
+
+  // A list of tensors.
+  // See also
+  // https://github.com/k2-fsa/icefall/pull/1413
+  // and
+  // https://github.com/k2-fsa/icefall/pull/1415
+  std::vector<Ort::Value> GetInitStates() const override;
+
+  std::vector<Ort::Value> StackStates(
+      std::vector<std::vector<Ort::Value>> states) const override;
+
+  std::vector<std::vector<Ort::Value>> UnStackStates(
+      std::vector<Ort::Value> states) const override;
+
+  /**
+   *
+   * @param x A 3-D tensor of shape (N, T, C). N has to be 1.
+   * @param states  It is from GetInitStates() or returned from this method.
+   *
+   * @return Return a list of tensors
+   *    - ans[0] contains log_probs, of shape (N, T, C)
+   *    - ans[1:] contains next_states
+   */
+  std::vector<Ort::Value> Forward(
+      Ort::Value x, std::vector<Ort::Value> states) const override;
+
+  /** Return the vocabulary size of the model
+   */
+  int32_t VocabSize() const override;
+
+  /** Return an allocator for allocating memory
+   */
+  OrtAllocator *Allocator() const override;
+
+  // The model accepts this number of frames before subsampling as input
+  int32_t ChunkLength() const override;
+
+  // Similar to frame_shift in feature extractor, after processing
+  // ChunkLength() frames, we advance by ChunkShift() frames
+  // before we process the next chunk.
+  int32_t ChunkShift() const override;
+
+ private:
+  class Impl;
+  std::unique_ptr<Impl> impl_;
+};
+
+}  // namespace sherpa_onnx
+
+#endif  // SHERPA_ONNX_CSRC_ONLINE_ZIPFORMER2_CTC_MODEL_H_
--- a/sherpa-onnx/csrc/sherpa-onnx.cc
+++ b/sherpa-onnx/csrc/sherpa-onnx.cc
@ -26,6 +26,8 @@ int main(int32_t argc, char *argv[]) {
  const char *kUsageMessage = R"usage(
 Usage:

+(1) Streaming transducer
+
  ./bin/sherpa-onnx \
    --tokens=/path/to/tokens.txt \
    --encoder=/path/to/encoder.onnx \
@ -36,6 +38,30 @@ Usage:
    --decoding-method=greedy_search \
    /path/to/foo.wav [bar.wav foobar.wav ...]

+(2) Streaming zipformer2 CTC
+
+  wget -q https://github.com/k2-fsa/sherpa-onnx/releases/download/asr-models/sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13.tar.bz2
+  tar xvf sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13.tar.bz2
+
+  ./bin/sherpa-onnx \
+    --debug=1 \
+    --zipformer2-ctc-model=./sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13/ctc-epoch-20-avg-1-chunk-16-left-128.int8.onnx \
+    --tokens=./sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13/tokens.txt \
+    ./sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13/test_wavs/DEV_T0000000000.wav \
+    ./sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13/test_wavs/DEV_T0000000001.wav \
+    ./sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13/test_wavs/DEV_T0000000002.wav
+
+(3) Streaming paraformer
+
+  wget https://github.com/k2-fsa/sherpa-onnx/releases/download/asr-models/sherpa-onnx-streaming-paraformer-bilingual-zh-en.tar.bz2
+  tar xvf sherpa-onnx-streaming-paraformer-bilingual-zh-en.tar.bz2
+
+  ./bin/sherpa-onnx \
+    --tokens=./sherpa-onnx-streaming-paraformer-bilingual-zh-en/tokens.txt \
+    --paraformer-encoder=./sherpa-onnx-streaming-paraformer-bilingual-zh-en/encoder.onnx \
+    --paraformer-decoder=./sherpa-onnx-streaming-paraformer-bilingual-zh-en/decoder.onnx \
+    ./sherpa-onnx-streaming-paraformer-bilingual-zh-en/test_wavs/0.wav
+
 Note: It supports decoding multiple files in batches

 Default value for num_threads is 2.
--- a/sherpa-onnx/csrc/symbol-table.cc
+++ b/sherpa-onnx/csrc/symbol-table.cc
@ -8,9 +8,6 @@
 #include <fstream>
 #include <sstream>

-#include "sherpa-onnx/csrc/base64-decode.h"
-#include "sherpa-onnx/csrc/onnx-utils.h"
-
 #if __ANDROID_API__ >= 9
 #include <strstream>

@ -18,6 +15,9 @@
 #include "android/asset_manager_jni.h"
 #endif

+#include "sherpa-onnx/csrc/base64-decode.h"
+#include "sherpa-onnx/csrc/onnx-utils.h"
+
 namespace sherpa_onnx {

 SymbolTable::SymbolTable(const std::string &filename) {
--- a/sherpa-onnx/jni/jni.cc
+++ b/sherpa-onnx/jni/jni.cc
@ -262,22 +262,34 @@ static OnlineRecognizerConfig GetConfig(JNIEnv *env, jobject config) {
  fid = env->GetFieldID(model_config_cls, "paraformer",
                        "Lcom/k2fsa/sherpa/onnx/OnlineParaformerModelConfig;");
  jobject paraformer_config = env->GetObjectField(model_config, fid);
-  jclass paraformer_config_config_cls = env->GetObjectClass(paraformer_config);
+  jclass paraformer_config_cls = env->GetObjectClass(paraformer_config);

-  fid = env->GetFieldID(paraformer_config_config_cls, "encoder",
-                        "Ljava/lang/String;");
+  fid = env->GetFieldID(paraformer_config_cls, "encoder", "Ljava/lang/String;");
  s = (jstring)env->GetObjectField(paraformer_config, fid);
  p = env->GetStringUTFChars(s, nullptr);
  ans.model_config.paraformer.encoder = p;
  env->ReleaseStringUTFChars(s, p);

-  fid = env->GetFieldID(paraformer_config_config_cls, "decoder",
-                        "Ljava/lang/String;");
+  fid = env->GetFieldID(paraformer_config_cls, "decoder", "Ljava/lang/String;");
  s = (jstring)env->GetObjectField(paraformer_config, fid);
  p = env->GetStringUTFChars(s, nullptr);
  ans.model_config.paraformer.decoder = p;
  env->ReleaseStringUTFChars(s, p);

+  // streaming zipformer2 CTC
+  fid =
+      env->GetFieldID(model_config_cls, "zipformer2Ctc",
+                      "Lcom/k2fsa/sherpa/onnx/OnlineZipformer2CtcModelConfig;");
+  jobject zipformer2_ctc_config = env->GetObjectField(model_config, fid);
+  jclass zipformer2_ctc_config_cls = env->GetObjectClass(zipformer2_ctc_config);
+
+  fid =
+      env->GetFieldID(zipformer2_ctc_config_cls, "model", "Ljava/lang/String;");
+  s = (jstring)env->GetObjectField(zipformer2_ctc_config, fid);
+  p = env->GetStringUTFChars(s, nullptr);
+  ans.model_config.zipformer2_ctc.model = p;
+  env->ReleaseStringUTFChars(s, p);
+
  fid = env->GetFieldID(model_config_cls, "tokens", "Ljava/lang/String;");
  s = (jstring)env->GetObjectField(model_config, fid);
  p = env->GetStringUTFChars(s, nullptr);
--- a/sherpa-onnx/python/csrc/CMakeLists.txt
+++ b/sherpa-onnx/python/csrc/CMakeLists.txt
@ -27,6 +27,7 @@ pybind11_add_module(_sherpa_onnx
  online-stream.cc
  online-transducer-model-config.cc
  online-wenet-ctc-model-config.cc
+  online-zipformer2-ctc-model-config.cc
  sherpa-onnx.cc
  silero-vad-model-config.cc
  vad-model-config.cc
--- a/sherpa-onnx/python/csrc/offline-model-config.cc
+++ b/sherpa-onnx/python/csrc/offline-model-config.cc
@ -58,6 +58,7 @@ void PybindOfflineModelConfig(py::module *m) {
      .def_readwrite("debug", &PyClass::debug)
      .def_readwrite("provider", &PyClass::provider)
      .def_readwrite("model_type", &PyClass::model_type)
+      .def("validate", &PyClass::Validate)
      .def("__str__", &PyClass::ToString);
 }

--- a/sherpa-onnx/python/csrc/online-model-config.cc
+++ b/sherpa-onnx/python/csrc/online-model-config.cc
@ -12,6 +12,7 @@
 #include "sherpa-onnx/python/csrc/online-paraformer-model-config.h"
 #include "sherpa-onnx/python/csrc/online-transducer-model-config.h"
 #include "sherpa-onnx/python/csrc/online-wenet-ctc-model-config.h"
+#include "sherpa-onnx/python/csrc/online-zipformer2-ctc-model-config.h"

 namespace sherpa_onnx {

@ -19,26 +20,31 @@ void PybindOnlineModelConfig(py::module *m) {
  PybindOnlineTransducerModelConfig(m);
  PybindOnlineParaformerModelConfig(m);
  PybindOnlineWenetCtcModelConfig(m);
+  PybindOnlineZipformer2CtcModelConfig(m);

  using PyClass = OnlineModelConfig;
  py::class_<PyClass>(*m, "OnlineModelConfig")
      .def(py::init<const OnlineTransducerModelConfig &,
                    const OnlineParaformerModelConfig &,
-                    const OnlineWenetCtcModelConfig &, const std::string &,
+                    const OnlineWenetCtcModelConfig &,
+                    const OnlineZipformer2CtcModelConfig &, const std::string &,
                    int32_t, bool, const std::string &, const std::string &>(),
           py::arg("transducer") = OnlineTransducerModelConfig(),
           py::arg("paraformer") = OnlineParaformerModelConfig(),
           py::arg("wenet_ctc") = OnlineWenetCtcModelConfig(),
+           py::arg("zipformer2_ctc") = OnlineZipformer2CtcModelConfig(),
           py::arg("tokens"), py::arg("num_threads"), py::arg("debug") = false,
           py::arg("provider") = "cpu", py::arg("model_type") = "")
      .def_readwrite("transducer", &PyClass::transducer)
      .def_readwrite("paraformer", &PyClass::paraformer)
      .def_readwrite("wenet_ctc", &PyClass::wenet_ctc)
+      .def_readwrite("zipformer2_ctc", &PyClass::zipformer2_ctc)
      .def_readwrite("tokens", &PyClass::tokens)
      .def_readwrite("num_threads", &PyClass::num_threads)
      .def_readwrite("debug", &PyClass::debug)
      .def_readwrite("provider", &PyClass::provider)
      .def_readwrite("model_type", &PyClass::model_type)
+      .def("validate", &PyClass::Validate)
      .def("__str__", &PyClass::ToString);
 }

--- a/sherpa-onnx/python/csrc/online-zipformer2-ctc-model-config.cc
+++ b/sherpa-onnx/python/csrc/online-zipformer2-ctc-model-config.cc
@ -0,0 +1,22 @@
+// sherpa-onnx/python/csrc/online-zipformer2-ctc-model-config.cc
+//
+// Copyright (c)  2023  Xiaomi Corporation
+
+#include "sherpa-onnx/python/csrc/online-zipformer2-ctc-model-config.h"
+
+#include <string>
+#include <vector>
+
+#include "sherpa-onnx/csrc/online-zipformer2-ctc-model-config.h"
+
+namespace sherpa_onnx {
+
+void PybindOnlineZipformer2CtcModelConfig(py::module *m) {
+  using PyClass = OnlineZipformer2CtcModelConfig;
+  py::class_<PyClass>(*m, "OnlineZipformer2CtcModelConfig")
+      .def(py::init<const std::string &>(), py::arg("model"))
+      .def_readwrite("model", &PyClass::model)
+      .def("__str__", &PyClass::ToString);
+}
+
+}  // namespace sherpa_onnx
--- a/sherpa-onnx/python/csrc/online-zipformer2-ctc-model-config.h
+++ b/sherpa-onnx/python/csrc/online-zipformer2-ctc-model-config.h
@ -0,0 +1,16 @@
+// sherpa-onnx/python/csrc/online-zipformer2-ctc-model-config.h
+//
+// Copyright (c)  2023  Xiaomi Corporation
+
+#ifndef SHERPA_ONNX_PYTHON_CSRC_ONLINE_ZIPFORMER2_CTC_MODEL_CONFIG_H_
+#define SHERPA_ONNX_PYTHON_CSRC_ONLINE_ZIPFORMER2_CTC_MODEL_CONFIG_H_
+
+#include "sherpa-onnx/python/csrc/sherpa-onnx.h"
+
+namespace sherpa_onnx {
+
+void PybindOnlineZipformer2CtcModelConfig(py::module *m);
+
+}
+
+#endif  // SHERPA_ONNX_PYTHON_CSRC_ONLINE_ZIPFORMER2_CTC_MODEL_CONFIG_H_
--- a/sherpa-onnx/python/sherpa_onnx/online_recognizer.py
+++ b/sherpa-onnx/python/sherpa_onnx/online_recognizer.py
@ -8,11 +8,14 @@ from _sherpa_onnx import (
    OnlineLMConfig,
    OnlineModelConfig,
    OnlineParaformerModelConfig,
-    OnlineRecognizer as _Recognizer,
+)
+from _sherpa_onnx import OnlineRecognizer as _Recognizer
+from _sherpa_onnx import (
    OnlineRecognizerConfig,
    OnlineStream,
    OnlineTransducerModelConfig,
    OnlineWenetCtcModelConfig,
+    OnlineZipformer2CtcModelConfig,
 )


@ -272,6 +275,101 @@ class OnlineRecognizer(object):
        self.config = recognizer_config
        return self

+    @classmethod
+    def from_zipformer2_ctc(
+        cls,
+        tokens: str,
+        model: str,
+        num_threads: int = 2,
+        sample_rate: float = 16000,
+        feature_dim: int = 80,
+        enable_endpoint_detection: bool = False,
+        rule1_min_trailing_silence: float = 2.4,
+        rule2_min_trailing_silence: float = 1.2,
+        rule3_min_utterance_length: float = 20.0,
+        decoding_method: str = "greedy_search",
+        provider: str = "cpu",
+    ):
+        """
+        Please refer to
+        `<https://k2-fsa.github.io/sherpa/onnx/pretrained_models/online-ctc/index.html>`_
+        to download pre-trained models for different languages, e.g., Chinese,
+        English, etc.
+
+        Args:
+          tokens:
+            Path to ``tokens.txt``. Each line in ``tokens.txt`` contains two
+            columns::
+
+                symbol integer_id
+
+          model:
+            Path to ``model.onnx``.
+          num_threads:
+            Number of threads for neural network computation.
+          sample_rate:
+            Sample rate of the training data used to train the model.
+          feature_dim:
+            Dimension of the feature used to train the model.
+          enable_endpoint_detection:
+            True to enable endpoint detection. False to disable endpoint
+            detection.
+          rule1_min_trailing_silence:
+            Used only when enable_endpoint_detection is True. If the duration
+            of trailing silence in seconds is larger than this value, we assume
+            an endpoint is detected.
+          rule2_min_trailing_silence:
+            Used only when enable_endpoint_detection is True. If we have decoded
+            something that is nonsilence and if the duration of trailing silence
+            in seconds is larger than this value, we assume an endpoint is
+            detected.
+          rule3_min_utterance_length:
+            Used only when enable_endpoint_detection is True. If the utterance
+            length in seconds is larger than this value, we assume an endpoint
+            is detected.
+          decoding_method:
+            The only valid value is greedy_search.
+          provider:
+            onnxruntime execution providers. Valid values are: cpu, cuda, coreml.
+        """
+        self = cls.__new__(cls)
+        _assert_file_exists(tokens)
+        _assert_file_exists(model)
+
+        assert num_threads > 0, num_threads
+
+        zipformer2_ctc_config = OnlineZipformer2CtcModelConfig(model=model)
+
+        model_config = OnlineModelConfig(
+            zipformer2_ctc=zipformer2_ctc_config,
+            tokens=tokens,
+            num_threads=num_threads,
+            provider=provider,
+        )
+
+        feat_config = FeatureExtractorConfig(
+            sampling_rate=sample_rate,
+            feature_dim=feature_dim,
+        )
+
+        endpoint_config = EndpointConfig(
+            rule1_min_trailing_silence=rule1_min_trailing_silence,
+            rule2_min_trailing_silence=rule2_min_trailing_silence,
+            rule3_min_utterance_length=rule3_min_utterance_length,
+        )
+
+        recognizer_config = OnlineRecognizerConfig(
+            feat_config=feat_config,
+            model_config=model_config,
+            endpoint_config=endpoint_config,
+            enable_endpoint=enable_endpoint_detection,
+            decoding_method=decoding_method,
+        )
+
+        self.recognizer = _Recognizer(recognizer_config)
+        self.config = recognizer_config
+        return self
+
    @classmethod
    def from_wenet_ctc(
        cls,
@ -352,7 +450,6 @@ class OnlineRecognizer(object):
            tokens=tokens,
            num_threads=num_threads,
            provider=provider,
-            model_type="wenet_ctc",
        )

        feat_config = FeatureExtractorConfig(
--- a/sherpa-onnx/python/tests/test_online_recognizer.py
+++ b/sherpa-onnx/python/tests/test_online_recognizer.py
@ -143,6 +143,57 @@ class TestOnlineRecognizer(unittest.TestCase):
                    print(f"{wave_filename}\n{result}")
                    print("-" * 10)

+    def test_zipformer2_ctc(self):
+        m = "sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13"
+        for use_int8 in [True, False]:
+            name = (
+                "ctc-epoch-20-avg-1-chunk-16-left-128.int8.onnx"
+                if use_int8
+                else "ctc-epoch-20-avg-1-chunk-16-left-128.onnx"
+            )
+            model = f"{d}/{m}/{name}"
+            tokens = f"{d}/{m}/tokens.txt"
+            wave0 = f"{d}/{m}/test_wavs/DEV_T0000000000.wav"
+            wave1 = f"{d}/{m}/test_wavs/DEV_T0000000001.wav"
+            wave2 = f"{d}/{m}/test_wavs/DEV_T0000000002.wav"
+            if not Path(model).is_file():
+                print("skipping test_zipformer2_ctc()")
+                return
+            print(f"testing {model}")
+
+            recognizer = sherpa_onnx.OnlineRecognizer.from_zipformer2_ctc(
+                model=model,
+                tokens=tokens,
+                num_threads=1,
+                provider="cpu",
+            )
+
+            streams = []
+            waves = [wave0, wave1, wave2]
+            for wave in waves:
+                s = recognizer.create_stream()
+                samples, sample_rate = read_wave(wave)
+                s.accept_waveform(sample_rate, samples)
+
+                tail_paddings = np.zeros(int(0.2 * sample_rate), dtype=np.float32)
+                s.accept_waveform(sample_rate, tail_paddings)
+                s.input_finished()
+                streams.append(s)
+
+            while True:
+                ready_list = []
+                for s in streams:
+                    if recognizer.is_ready(s):
+                        ready_list.append(s)
+                if len(ready_list) == 0:
+                    break
+                recognizer.decode_streams(ready_list)
+
+            results = [recognizer.get_result(s) for s in streams]
+            for wave_filename, result in zip(waves, results):
+                print(f"{wave_filename}\n{result}")
+                print("-" * 10)
+
    def test_wenet_ctc(self):
        models = [
            "sherpa-onnx-zh-wenet-aishell",
--- a/swift-api-examples/.gitignore
+++ b/swift-api-examples/.gitignore
@ -5,3 +5,4 @@ tts
 vits-vctk
 sherpa-onnx-paraformer-zh-2023-09-14
 !*.sh
+*.bak
--- a/swift-api-examples/SherpaOnnx.swift
+++ b/swift-api-examples/SherpaOnnx.swift
@ -60,6 +60,14 @@ func sherpaOnnxOnlineParaformerModelConfig(
  )
 }

+func sherpaOnnxOnlineZipformer2CtcModelConfig(
+  model: String = ""
+) -> SherpaOnnxOnlineZipformer2CtcModelConfig {
+  return SherpaOnnxOnlineZipformer2CtcModelConfig(
+    model: toCPointer(model)
+  )
+}
+
 /// Return an instance of SherpaOnnxOnlineModelConfig.
 ///
 /// Please refer to
@ -75,6 +83,8 @@ func sherpaOnnxOnlineModelConfig(
  tokens: String,
  transducer: SherpaOnnxOnlineTransducerModelConfig = sherpaOnnxOnlineTransducerModelConfig(),
  paraformer: SherpaOnnxOnlineParaformerModelConfig = sherpaOnnxOnlineParaformerModelConfig(),
+  zipformer2Ctc: SherpaOnnxOnlineZipformer2CtcModelConfig =
+    sherpaOnnxOnlineZipformer2CtcModelConfig(),
  numThreads: Int = 1,
  provider: String = "cpu",
  debug: Int = 0,
@ -83,6 +93,7 @@ func sherpaOnnxOnlineModelConfig(
  return SherpaOnnxOnlineModelConfig(
    transducer: transducer,
    paraformer: paraformer,
+    zipformer2_ctc: zipformer2Ctc,
    tokens: toCPointer(tokens),
    num_threads: Int32(numThreads),
    provider: toCPointer(provider),
--- a/swift-api-examples/decode-file.swift
+++ b/swift-api-examples/decode-file.swift
@ -13,24 +13,47 @@ extension AVAudioPCMBuffer {
 }

 func run() {
-  let encoder =
-    "./sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20/encoder-epoch-99-avg-1.onnx"
-  let decoder =
-    "./sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20/decoder-epoch-99-avg-1.onnx"
-  let joiner =
-    "./sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20/joiner-epoch-99-avg-1.onnx"
-  let tokens = "./sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20/tokens.txt"
+  var modelConfig: SherpaOnnxOnlineModelConfig
+  var modelType = "zipformer2-ctc"
+  var filePath: String

-  let transducerConfig = sherpaOnnxOnlineTransducerModelConfig(
-    encoder: encoder,
-    decoder: decoder,
-    joiner: joiner
-  )
+  modelType = "transducer"

-  let modelConfig = sherpaOnnxOnlineModelConfig(
-    tokens: tokens,
-    transducer: transducerConfig
-  )
+  if modelType == "transducer" {
+    filePath = "./sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20/test_wavs/1.wav"
+    let encoder =
+      "./sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20/encoder-epoch-99-avg-1.onnx"
+    let decoder =
+      "./sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20/decoder-epoch-99-avg-1.onnx"
+    let joiner =
+      "./sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20/joiner-epoch-99-avg-1.onnx"
+    let tokens = "./sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20/tokens.txt"
+
+    let transducerConfig = sherpaOnnxOnlineTransducerModelConfig(
+      encoder: encoder,
+      decoder: decoder,
+      joiner: joiner
+    )
+
+    modelConfig = sherpaOnnxOnlineModelConfig(
+      tokens: tokens,
+      transducer: transducerConfig
+    )
+  } else {
+    filePath =
+      "./sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13/test_wavs/DEV_T0000000000.wav"
+    let model =
+      "./sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13/ctc-epoch-20-avg-1-chunk-16-left-128.onnx"
+    let tokens = "./sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13/tokens.txt"
+    let zipfomer2CtcModelConfig = sherpaOnnxOnlineZipformer2CtcModelConfig(
+      model: model
+    )
+
+    modelConfig = sherpaOnnxOnlineModelConfig(
+      tokens: tokens,
+      zipformer2Ctc: zipfomer2CtcModelConfig
+    )
+  }

  let featConfig = sherpaOnnxFeatureConfig(
    sampleRate: 16000,
@ -43,7 +66,6 @@ func run() {

  let recognizer = SherpaOnnxRecognizer(config: &config)

-  let filePath = "./sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20/test_wavs/1.wav"
  let fileURL: NSURL = NSURL(fileURLWithPath: filePath)
  let audioFile = try! AVAudioFile(forReading: fileURL as URL)

--- a/swift-api-examples/run-decode-file.sh
+++ b/swift-api-examples/run-decode-file.sh
@ -20,6 +20,12 @@ if [ ! -d ./sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20 ]; then
  rm sherpa-onnx-streaming-zipformer-bilingual-zh-en-2023-02-20.tar.bz2
 fi

+if [ ! -d ./sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13 ]; then
+  wget -q https://github.com/k2-fsa/sherpa-onnx/releases/download/asr-models/sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13.tar.bz2
+  tar xvf sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13.tar.bz2
+  rm sherpa-onnx-streaming-zipformer-ctc-multi-zh-hans-2023-12-13.tar.bz2
+fi
+
 if [ ! -e ./decode-file ]; then
  # Note: We use -lc++ to link against libc++ instead of libstdc++
  swiftc \
--- a/swift-api-examples/run-generate-subtitles.sh
+++ b/swift-api-examples/run-generate-subtitles.sh
@ -22,7 +22,7 @@ if [ ! -d ./sherpa-onnx-whisper-tiny.en ]; then
 fi
 if [ ! -f ./silero_vad.onnx ]; then
  echo "downloading silero_vad"
-  wget https://github.com/k2-fsa/sherpa-onnx/releases/download/asr-models/silero_vad.onnx
+  wget -q https://github.com/k2-fsa/sherpa-onnx/releases/download/asr-models/silero_vad.onnx
 fi

 if [ ! -e ./generate-subtitles ]; then
				`@ -0,0 +1 @@`
				`../../../../go-api-examples/streaming-decode-files/run-zipformer2-ctc.sh`