Add microphone example for .Net keyword spotting (#1120)

+// Copyright (c)  2024  Xiaomi Corporation
+//
+// This file shows how to do keyword spotting with sherpa-onnx.
+//
+// 1. Download a model from
+// https://github.com/k2-fsa/sherpa-onnx/releases/tag/kws-models
+//
+// wget https://github.com/k2-fsa/sherpa-onnx/releases/download/kws-models/sherpa-onnx-kws-zipformer-wenetspeech-3.3M-2024-01-01.tar.bz2
+// tar xvf sherpa-onnx-kws-zipformer-wenetspeech-3.3M-2024-01-01.tar.bz2
+//
+// 2. Now run it
+//
+// dotnet run
+
+using SherpaOnnx;
+using System.Collections.Generic;
+using System.Runtime.InteropServices;
+using System;
+
+using PortAudioSharp;
+
+class KeywordSpotterDemo
+{
+  static void Main(string[] args)
+  {
+    var config = new KeywordSpotterConfig();
+    config.FeatConfig.SampleRate = 16000;
+    config.FeatConfig.FeatureDim = 80;
+
+    config.ModelConfig.Transducer.Encoder = "./sherpa-onnx-kws-zipformer-wenetspeech-3.3M-2024-01-01/encoder-epoch-12-avg-2-chunk-16-left-64.onnx";
+    config.ModelConfig.Transducer.Decoder = "./sherpa-onnx-kws-zipformer-wenetspeech-3.3M-2024-01-01/decoder-epoch-12-avg-2-chunk-16-left-64.onnx";
+    config.ModelConfig.Transducer.Joiner = "./sherpa-onnx-kws-zipformer-wenetspeech-3.3M-2024-01-01/joiner-epoch-12-avg-2-chunk-16-left-64.onnx";
+
+    config.ModelConfig.Tokens = "./sherpa-onnx-kws-zipformer-wenetspeech-3.3M-2024-01-01/tokens.txt";
+    config.ModelConfig.Provider = "cpu";
+    config.ModelConfig.NumThreads = 1;
+    config.ModelConfig.Debug = 1;
+    config.KeywordsFile = "./sherpa-onnx-kws-zipformer-wenetspeech-3.3M-2024-01-01/test_wavs/test_keywords.txt";
+
+    var kws = new KeywordSpotter(config);
+
+    var filename = "./sherpa-onnx-kws-zipformer-wenetspeech-3.3M-2024-01-01/test_wavs/3.wav";
+
+    WaveReader waveReader = new WaveReader(filename);
+
+    Console.WriteLine("----------Use pre-defined keywords----------");
+
+    OnlineStream s = kws.CreateStream();
+
+    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 input channels: {deviceInfo.maxInputChannels}");
+      Console.WriteLine($"   Default sample rate: {deviceInfo.defaultSampleRate}");
+    }
+    int deviceIndex = PortAudio.DefaultInputDevice;
+    if (deviceIndex == PortAudio.NoDevice)
+    {
+      Console.WriteLine("No default input device found");
+      Environment.Exit(1);
+    }
+
+    DeviceInfo info = PortAudio.GetDeviceInfo(deviceIndex);
+
+    Console.WriteLine();
+    Console.WriteLine($"Use default device {deviceIndex} ({info.name})");
+
+    StreamParameters param = new StreamParameters();
+    param.device = deviceIndex;
+    param.channelCount = 1;
+    param.sampleFormat = SampleFormat.Float32;
+    param.suggestedLatency = info.defaultLowInputLatency;
+    param.hostApiSpecificStreamInfo = IntPtr.Zero;
+
+    PortAudioSharp.Stream.Callback callback = (IntPtr input, IntPtr output,
+        UInt32 frameCount,
+        ref StreamCallbackTimeInfo timeInfo,
+        StreamCallbackFlags statusFlags,
+        IntPtr userData
+        ) =>
+    {
+      float[] samples = new float[frameCount];
+      Marshal.Copy(input, samples, 0, (Int32)frameCount);
+
+      s.AcceptWaveform(config.FeatConfig.SampleRate, samples);
+
+      return StreamCallbackResult.Continue;
+    };
+
+    PortAudioSharp.Stream stream = new PortAudioSharp.Stream(inParams: param, outParams: null, sampleRate: config.FeatConfig.SampleRate,
+        framesPerBuffer: 0,
+        streamFlags: StreamFlags.ClipOff,
+        callback: callback,
+        userData: IntPtr.Zero
+        );
+
+    Console.WriteLine(param);
+    Console.WriteLine("Started! Please speak");
+
+    stream.Start();
+
+    while (true)
+    {
+      while (kws.IsReady(s))
+      {
+        kws.Decode(s);
+      }
+
+      var result = kws.GetResult(s);
+      if (result.Keyword != "")
+      {
+        Console.WriteLine("Detected: {0}", result.Keyword);
+      }
+
+      Thread.Sleep(200); // ms
+    }
+
+    PortAudio.Terminate();
+  }
+}
+

+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+    <RootNamespace>keyword_spotting_from_microphone</RootNamespace>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="PortAudioSharp2" Version="*" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\Common\Common.csproj" />
+  </ItemGroup>
+
+</Project>

+#!/usr/bin/env bash
+
+set -ex
+
+if [ ! -f ./sherpa-onnx-kws-zipformer-wenetspeech-3.3M-2024-01-01/tokens.txt ]; then
+  curl -SL -O https://github.com/k2-fsa/sherpa-onnx/releases/download/kws-models/sherpa-onnx-kws-zipformer-wenetspeech-3.3M-2024-01-01.tar.bz2
+  tar xvf sherpa-onnx-kws-zipformer-wenetspeech-3.3M-2024-01-01.tar.bz2
+  rm sherpa-onnx-kws-zipformer-wenetspeech-3.3M-2024-01-01.tar.bz2
+fi
+
+dotnet run -c Release

@@ -27,6 +27,8 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Common", "Common\Common.csp
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "keyword-spotting-from-files", "keyword-spotting-from-files\keyword-spotting-from-files.csproj", "{A87EDD31-D654-4C9F-AED7-F6F2825659BD}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "keyword-spotting-from-microphone", "keyword-spotting-from-microphone\keyword-spotting-from-microphone.csproj", "{AEE0ED2B-C86F-4952-863C-EAD3219CB4EC}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -81,6 +83,10 @@ Global
 		{A87EDD31-D654-4C9F-AED7-F6F2825659BD}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{A87EDD31-D654-4C9F-AED7-F6F2825659BD}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{A87EDD31-D654-4C9F-AED7-F6F2825659BD}.Release|Any CPU.Build.0 = Release|Any CPU
+		{AEE0ED2B-C86F-4952-863C-EAD3219CB4EC}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{AEE0ED2B-C86F-4952-863C-EAD3219CB4EC}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{AEE0ED2B-C86F-4952-863C-EAD3219CB4EC}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{AEE0ED2B-C86F-4952-863C-EAD3219CB4EC}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE