Add C# API for Kokoro TTS models (#1720)

.github/scripts/test-dot-net.sh

@@ -2,7 +2,11 @@
 
 cd dotnet-examples/
 
-cd ./offline-tts
+cd ./kokoro-tts
+./run-kokoro-en.sh
+ls -lh
+
+cd ../offline-tts
 ./run-matcha-zh.sh
 ls -lh *.wav
 ./run-matcha-en.sh
@@ -19,7 +23,8 @@ pushd ../..
 
 mkdir tts
 
-cp dotnet-examples/offline-tts/*.wav ./tts
+cp -v dotnet-examples/kokoro-tts/*.wav ./tts
+cp -v dotnet-examples/offline-tts/*.wav ./tts
 popd
 
 cd ../offline-speaker-diarization

dotnet-examples/kokoro-tts-play/Program.cs

@@ -0,0 +1,189 @@
+// Copyright (c)  2025  Xiaomi Corporation
+//
+// This file shows how to use a non-streaming Kokoro TTS model
+// for text-to-speech
+// Please refer to
+// https://k2-fsa.github.io/sherpa/onnx/pretrained_models/index.html
+// and
+// https://github.com/k2-fsa/sherpa-onnx/releases/tag/tts-models
+// to download pre-trained models
+using PortAudioSharp;
+using SherpaOnnx;
+using System.Collections.Concurrent;
+using System.Runtime.InteropServices;
+
+class OfflineTtsDemo
+{
+  static void Main(string[] args)
+  {
+    var config = new OfflineTtsConfig();
+    config.Model.Kokoro.Model = "./kokoro-en-v0_19/model.onnx";
+    config.Model.Kokoro.Voices = "./kokoro-en-v0_19/voices.bin";
+    config.Model.Kokoro.Tokens = "./kokoro-en-v0_19/tokens.txt";
+    config.Model.Kokoro.DataDir = "./kokoro-en-v0_19/espeak-ng-data";
+
+    config.Model.NumThreads = 2;
+    config.Model.Debug = 1;
+    config.Model.Provider = "cpu";
+
+    var tts = new OfflineTts(config);
+    var speed = 1.0f;
+    var text = "Today as always, men fall into two groups: slaves and free men. Whoever " +
+      "does not have two-thirds of his day for himself, is a slave, whatever " +
+      "he may be: a statesman, a businessman, an official, or a scholar. " +
+      "Friends fell out often because life was changing so fast. The easiest " +
+      "thing in the world was to lose touch with someone.";
+
+    // mapping of sid to voice name
+    // 0->af, 1->af_bella, 2->af_nicole, 3->af_sarah, 4->af_sky, 5->am_adam
+    // 6->am_michael, 7->bf_emma, 8->bf_isabella, 9->bm_george, 10->bm_lewis
+    var sid = 0;
+
+
+    Console.WriteLine(PortAudio.VersionInfo.versionText);
+    PortAudio.Initialize();
+    Console.WriteLine($"Number of devices: {PortAudio.DeviceCount}");
+
+    for (int i = 0; i != PortAudio.DeviceCount; ++i)
+    {
+      Console.WriteLine($" Device {i}");
+      DeviceInfo deviceInfo = PortAudio.GetDeviceInfo(i);
+      Console.WriteLine($"   Name: {deviceInfo.name}");
+      Console.WriteLine($"   Max output channels: {deviceInfo.maxOutputChannels}");
+      Console.WriteLine($"   Default sample rate: {deviceInfo.defaultSampleRate}");
+    }
+    int deviceIndex = PortAudio.DefaultOutputDevice;
+    if (deviceIndex == PortAudio.NoDevice)
+    {
+      Console.WriteLine("No default output device found. Please use ../offline-tts instead");
+      Environment.Exit(1);
+    }
+
+    var info = PortAudio.GetDeviceInfo(deviceIndex);
+    Console.WriteLine();
+    Console.WriteLine($"Use output default device {deviceIndex} ({info.name})");
+
+    var param = new StreamParameters();
+    param.device = deviceIndex;
+    param.channelCount = 1;
+    param.sampleFormat = SampleFormat.Float32;
+    param.suggestedLatency = info.defaultLowOutputLatency;
+    param.hostApiSpecificStreamInfo = IntPtr.Zero;
+
+    // https://learn.microsoft.com/en-us/dotnet/standard/collections/thread-safe/blockingcollection-overview
+    var dataItems = new BlockingCollection<float[]>();
+
+    var MyCallback = (IntPtr samples, int n, float progress) =>
+    {
+      Console.WriteLine($"Progress {progress*100}%");
+
+      float[] data = new float[n];
+
+      Marshal.Copy(samples, data, 0, n);
+
+      dataItems.Add(data);
+
+      // 1 means to keep generating
+      // 0 means to stop generating
+      return 1;
+    };
+
+    var playFinished = false;
+
+    float[]? lastSampleArray = null;
+    int lastIndex = 0; // not played
+
+    PortAudioSharp.Stream.Callback playCallback = (IntPtr input, IntPtr output,
+        UInt32 frameCount,
+        ref StreamCallbackTimeInfo timeInfo,
+        StreamCallbackFlags statusFlags,
+        IntPtr userData
+        ) =>
+    {
+      if (dataItems.IsCompleted && lastSampleArray == null && lastIndex == 0)
+      {
+        Console.WriteLine($"Finished playing");
+        playFinished = true;
+        return StreamCallbackResult.Complete;
+      }
+
+      int expected = Convert.ToInt32(frameCount);
+      int i = 0;
+
+      while ((lastSampleArray != null || dataItems.Count != 0) && (i < expected))
+      {
+        int needed = expected - i;
+
+        if (lastSampleArray != null)
+        {
+          int remaining = lastSampleArray.Length - lastIndex;
+          if (remaining >= needed)
+          {
+            float[] this_block = lastSampleArray.Skip(lastIndex).Take(needed).ToArray();
+            lastIndex += needed;
+            if (lastIndex == lastSampleArray.Length)
+            {
+              lastSampleArray = null;
+              lastIndex = 0;
+            }
+
+            Marshal.Copy(this_block, 0, IntPtr.Add(output, i * sizeof(float)), needed);
+            return StreamCallbackResult.Continue;
+          }
+
+          float[] this_block2 = lastSampleArray.Skip(lastIndex).Take(remaining).ToArray();
+          lastIndex = 0;
+          lastSampleArray = null;
+
+          Marshal.Copy(this_block2, 0, IntPtr.Add(output, i * sizeof(float)), remaining);
+          i += remaining;
+          continue;
+        }
+
+        if (dataItems.Count != 0)
+        {
+          lastSampleArray = dataItems.Take();
+          lastIndex = 0;
+        }
+      }
+
+      if (i < expected)
+      {
+        int sizeInBytes = (expected - i) * 4;
+        Marshal.Copy(new byte[sizeInBytes], 0, IntPtr.Add(output, i * sizeof(float)), sizeInBytes);
+      }
+
+      return StreamCallbackResult.Continue;
+    };
+
+    PortAudioSharp.Stream stream = new PortAudioSharp.Stream(inParams: null, outParams: param, sampleRate: tts.SampleRate,
+        framesPerBuffer: 0,
+        streamFlags: StreamFlags.ClipOff,
+        callback: playCallback,
+        userData: IntPtr.Zero
+        );
+
+    stream.Start();
+
+    var callback = new OfflineTtsCallbackProgress(MyCallback);
+
+    var audio = tts.GenerateWithCallbackProgress(text, speed, sid, callback);
+    var outputFilename = "./generated-kokoro-0.wav";
+    var ok = audio.SaveToWaveFile(outputFilename);
+
+    if (ok)
+    {
+      Console.WriteLine($"Wrote to {outputFilename} succeeded!");
+    }
+    else
+    {
+      Console.WriteLine($"Failed to write {outputFilename}");
+    }
+    dataItems.CompleteAdding();
+
+    while (!playFinished)
+    {
+      Thread.Sleep(100); // 100ms
+    }
+  }
+}

dotnet-examples/kokoro-tts-play/kokoro-tts-play.csproj

@@ -0,0 +1,19 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net8.0</TargetFramework>
+    <RootNamespace>kokoro_tts_play</RootNamespace>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="PortAudioSharp2" Version="*" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\Common\Common.csproj" />
+  </ItemGroup>
+
+</Project>

dotnet-examples/kokoro-tts-play/run-kokoro-en.sh

@@ -0,0 +1,10 @@
+#!/usr/bin/env bash
+set -ex
+
+if [ ! -f ./kokoro-en-v0_19/model.onnx ]; then
+  curl -SL -O https://github.com/k2-fsa/sherpa-onnx/releases/download/tts-models/kokoro-en-v0_19.tar.bz2
+  tar xf kokoro-en-v0_19.tar.bz2
+  rm kokoro-en-v0_19.tar.bz2
+fi
+
+dotnet run

dotnet-examples/kokoro-tts/Program.cs

@@ -0,0 +1,70 @@
+// Copyright (c)  2025  Xiaomi Corporation
+//
+// This file shows how to use a non-streaming Kokoro TTS model
+// for text-to-speech
+// Please refer to
+// https://k2-fsa.github.io/sherpa/onnx/pretrained_models/index.html
+// and
+// https://github.com/k2-fsa/sherpa-onnx/releases/tag/tts-models
+// to download pre-trained models
+using SherpaOnnx;
+using System.Runtime.InteropServices;
+
+class OfflineTtsDemo
+{
+  static void Main(string[] args)
+  {
+    var config = new OfflineTtsConfig();
+    config.Model.Kokoro.Model = "./kokoro-en-v0_19/model.onnx";
+    config.Model.Kokoro.Voices = "./kokoro-en-v0_19/voices.bin";
+    config.Model.Kokoro.Tokens = "./kokoro-en-v0_19/tokens.txt";
+    config.Model.Kokoro.DataDir = "./kokoro-en-v0_19/espeak-ng-data";
+
+    config.Model.NumThreads = 2;
+    config.Model.Debug = 1;
+    config.Model.Provider = "cpu";
+
+    var tts = new OfflineTts(config);
+    var speed = 1.0f;
+    var text = "Today as always, men fall into two groups: slaves and free men. Whoever " +
+      "does not have two-thirds of his day for himself, is a slave, whatever " +
+      "he may be: a statesman, a businessman, an official, or a scholar. " +
+      "Friends fell out often because life was changing so fast. The easiest " +
+      "thing in the world was to lose touch with someone.";
+
+    // mapping of sid to voice name
+    // 0->af, 1->af_bella, 2->af_nicole, 3->af_sarah, 4->af_sky, 5->am_adam
+    // 6->am_michael, 7->bf_emma, 8->bf_isabella, 9->bm_george, 10->bm_lewis
+    var sid = 0;
+
+    var MyCallback = (IntPtr samples, int n, float progress) =>
+    {
+      float[] data = new float[n];
+      Marshal.Copy(samples, data, 0, n);
+      // You can process samples here, e.g., play them.
+      // See ../kokoro-tts-playback for how to play them
+      Console.WriteLine($"Progress {progress*100}%");
+
+      // 1 means to keep generating
+      // 0 means to stop generating
+      return 1;
+    };
+
+    var callback = new OfflineTtsCallbackProgress(MyCallback);
+
+    var audio = tts.GenerateWithCallbackProgress(text, speed, sid, callback);
+
+    var outputFilename = "./generated-kokoro-0.wav";
+    var ok = audio.SaveToWaveFile(outputFilename);
+
+    if (ok)
+    {
+      Console.WriteLine($"Wrote to {outputFilename} succeeded!");
+    }
+    else
+    {
+      Console.WriteLine($"Failed to write {outputFilename}");
+    }
+  }
+}
+

dotnet-examples/kokoro-tts/kokoro-tts.csproj

@@ -0,0 +1,15 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net8.0</TargetFramework>
+    <RootNamespace>kokoro_tts</RootNamespace>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\Common\Common.csproj" />
+  </ItemGroup>
+
+</Project>

dotnet-examples/kokoro-tts/run-kokoro-en.sh

@@ -0,0 +1,10 @@
+#!/usr/bin/env bash
+set -ex
+
+if [ ! -f ./kokoro-en-v0_19/model.onnx ]; then
+  curl -SL -O https://github.com/k2-fsa/sherpa-onnx/releases/download/tts-models/kokoro-en-v0_19.tar.bz2
+  tar xf kokoro-en-v0_19.tar.bz2
+  rm kokoro-en-v0_19.tar.bz2
+fi
+
+dotnet run

dotnet-examples/sherpa-onnx.sln

@@ -31,6 +31,10 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "keyword-spotting-from-micro
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "offline-speaker-diarization", "offline-speaker-diarization\offline-speaker-diarization.csproj", "{D3A1FF28-A77D-429D-AEAC-2BA77CA682BC}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "kokoro-tts", "kokoro-tts\kokoro-tts.csproj", "{9C0ABE6C-1F54-42B5-804E-C3FED6668F52}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "kokoro-tts-play", "kokoro-tts-play\kokoro-tts-play.csproj", "{EC0BCEAB-1B4E-4129-82CE-9880426AFA0B}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -93,6 +97,14 @@ Global
 		{D3A1FF28-A77D-429D-AEAC-2BA77CA682BC}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{D3A1FF28-A77D-429D-AEAC-2BA77CA682BC}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{D3A1FF28-A77D-429D-AEAC-2BA77CA682BC}.Release|Any CPU.Build.0 = Release|Any CPU
+		{9C0ABE6C-1F54-42B5-804E-C3FED6668F52}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{9C0ABE6C-1F54-42B5-804E-C3FED6668F52}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{9C0ABE6C-1F54-42B5-804E-C3FED6668F52}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{9C0ABE6C-1F54-42B5-804E-C3FED6668F52}.Release|Any CPU.Build.0 = Release|Any CPU
+		{EC0BCEAB-1B4E-4129-82CE-9880426AFA0B}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{EC0BCEAB-1B4E-4129-82CE-9880426AFA0B}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{EC0BCEAB-1B4E-4129-82CE-9880426AFA0B}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{EC0BCEAB-1B4E-4129-82CE-9880426AFA0B}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE

scripts/dotnet/OfflineTts.cs

@@ -7,6 +7,7 @@ namespace SherpaOnnx
 {
     // IntPtr is actually a `const float*` from C++
     public delegate int OfflineTtsCallback(IntPtr samples, int n);
+    public delegate int OfflineTtsCallbackProgress(IntPtr samples, int n, float progress);
 
     public class OfflineTts : IDisposable
     {
@@ -36,6 +37,16 @@ namespace SherpaOnnx
             return new OfflineTtsGeneratedAudio(p);
         }
 
+        public OfflineTtsGeneratedAudio GenerateWithCallbackProgress(String text, float speed, int speakerId, OfflineTtsCallbackProgress callback)
+        {
+            byte[] utf8Bytes = Encoding.UTF8.GetBytes(text);
+            byte[] utf8BytesWithNull = new byte[utf8Bytes.Length + 1]; // +1 for null terminator
+            Array.Copy(utf8Bytes, utf8BytesWithNull, utf8Bytes.Length);
+            utf8BytesWithNull[utf8Bytes.Length] = 0; // Null terminator
+            IntPtr p = SherpaOnnxOfflineTtsGenerateWithProgressCallback(_handle.Handle, utf8BytesWithNull, speakerId, speed, callback);
+            return new OfflineTtsGeneratedAudio(p);
+        }
+
         public void Dispose()
         {
             Cleanup();
@@ -92,5 +103,8 @@ namespace SherpaOnnx
 
         [DllImport(Dll.Filename, CallingConvention = CallingConvention.Cdecl)]
         private static extern IntPtr SherpaOnnxOfflineTtsGenerateWithCallback(IntPtr handle, [MarshalAs(UnmanagedType.LPArray, ArraySubType = UnmanagedType.I1)] byte[] utf8Text, int sid, float speed, OfflineTtsCallback callback);
+
+        [DllImport(Dll.Filename, CallingConvention = CallingConvention.Cdecl)]
+        private static extern IntPtr SherpaOnnxOfflineTtsGenerateWithProgressCallback(IntPtr handle, [MarshalAs(UnmanagedType.LPArray, ArraySubType = UnmanagedType.I1)] byte[] utf8Text, int sid, float speed, OfflineTtsCallbackProgress callback);
     }
 }

scripts/dotnet/OfflineTtsKokoroModelConfig.cs

@@ -0,0 +1,33 @@
+/// Copyright (c)  2025  Xiaomi Corporation (authors: Fangjun Kuang)
+
+using System.Runtime.InteropServices;
+
+namespace SherpaOnnx
+{
+    [StructLayout(LayoutKind.Sequential)]
+    public struct OfflineTtsKokoroModelConfig
+    {
+        public OfflineTtsKokoroModelConfig()
+        {
+            Model = "";
+            Voices = "";
+            Tokens = "";
+            DataDir = "";
+
+            LengthScale = 1.0F;
+        }
+        [MarshalAs(UnmanagedType.LPStr)]
+        public string Model;
+
+        [MarshalAs(UnmanagedType.LPStr)]
+        public string Voices;
+
+        [MarshalAs(UnmanagedType.LPStr)]
+        public string Tokens;
+
+        [MarshalAs(UnmanagedType.LPStr)]
+        public string DataDir;
+
+        public float LengthScale;
+    }
+}

scripts/dotnet/OfflineTtsModelConfig.cs

@@ -12,6 +12,7 @@ namespace SherpaOnnx
         {
             Vits = new OfflineTtsVitsModelConfig();
             Matcha = new OfflineTtsMatchaModelConfig();
+            Kokoro = new OfflineTtsKokoroModelConfig();
             NumThreads = 1;
             Debug = 0;
             Provider = "cpu";
@@ -24,5 +25,6 @@ namespace SherpaOnnx
         public string Provider;
 
         public OfflineTtsMatchaModelConfig Matcha;
+        public OfflineTtsKokoroModelConfig Kokoro;
     }
 }