Assistant/tests/02-wakeword-cs/Program.cs

using System.Collections.Concurrent;
using System.Diagnostics;
using System.Runtime.InteropServices;
using Microsoft.ML.OnnxRuntime;
using PortAudioSharp;
using WakewordProbe;
using Stream = PortAudioSharp.Stream;

const int SampleRate = WakewordModel.SampleRate;
const int Channels = 1;
const uint BlockFrames = WakewordModel.FrameSamples; // 1280
const float Threshold = 0.5f;
const double CooldownSeconds = 1.0;
const double BeepHz = 880.0;
const double BeepSeconds = 0.2;

// .NET-side mirror for any readers that go through Environment.GetEnvironmentVariable,
// AND libc setenv so PortAudio / onnxruntime (which use getenv()) see the values.
Environment.SetEnvironmentVariable("PA_ALSA_PLUGHW", "1");
Libc.setenv("PA_ALSA_PLUGHW", "1", 1);
Environment.SetEnvironmentVariable("ORT_LOGGING_LEVEL", "3");
Libc.setenv("ORT_LOGGING_LEVEL", "3", 1);
// ORT 1.26.0: the env var does NOT suppress early GPU-discovery warnings from device_discovery.cc.
// CreateInstanceWithOptions sets the log level at OrtEnv creation time, before EP discovery runs.
var ortEnvOpts = new EnvironmentCreationOptions { logId = "WakewordProbe", logLevel = OrtLoggingLevel.ORT_LOGGING_LEVEL_ERROR };
OrtEnv.CreateInstanceWithOptions(ref ortEnvOpts);

PortAudio.Initialize();
WakewordModel? model = null;
try
{
    int device = FindUsbDevice();
    Console.WriteLine($"Using device {device} ('{PortAudio.GetDeviceInfo(device).name}')");

    Console.WriteLine("Loading WakewordModel...");
    var t0 = DateTime.UtcNow;
    string modelsDir = Path.Combine(AppContext.BaseDirectory, "models");
    model = new WakewordModel(
        Path.Combine(modelsDir, "melspectrogram.onnx"),
        Path.Combine(modelsDir, "embedding_model.onnx"),
        Path.Combine(modelsDir, "alexa.onnx"));
    Console.WriteLine($"Loaded in {(DateTime.UtcNow - t0).TotalSeconds:0.00}s.");

    var queue = new BlockingCollection<short[]>(boundedCapacity: 16);
    using var cts = new CancellationTokenSource();
    Console.CancelKeyPress += (_, e) => { e.Cancel = true; cts.Cancel(); };

    var inParams = new StreamParameters
    {
        device = device,
        channelCount = Channels,
        sampleFormat = SampleFormat.Int16,
        suggestedLatency = PortAudio.GetDeviceInfo(device).defaultLowInputLatency,
        hostApiSpecificStreamInfo = IntPtr.Zero,
    };

    Stream.Callback callback = (IntPtr input, IntPtr _, uint frameCount,
        ref StreamCallbackTimeInfo _2, StreamCallbackFlags status, IntPtr _3) =>
    {
        if (status.HasFlag(StreamCallbackFlags.InputOverflow))
            Console.Error.WriteLine("[status] input overflow");

        if (frameCount != BlockFrames)
        {
            Console.Error.WriteLine($"[status] unexpected callback frameCount={frameCount} (want {BlockFrames})");
            return StreamCallbackResult.Continue;
        }

        var frame = new short[BlockFrames];
        unsafe
        {
            short* src = (short*)input.ToPointer();
            fixed (short* dst = &frame[0])
                Buffer.MemoryCopy(src, dst, BlockFrames * sizeof(short), BlockFrames * sizeof(short));
        }
        if (!queue.TryAdd(frame, 0))
            Console.Error.WriteLine("[status] consumer behind, dropping frame");
        return StreamCallbackResult.Continue;
    };

    using var stream = new Stream(
        inParams, null, SampleRate, BlockFrames, StreamFlags.NoFlag, callback, IntPtr.Zero);
    stream.Start();
    short[] beepBuffer = MakeBeep(BeepHz, BeepSeconds, SampleRate);
    Console.WriteLine("Listening. Say 'alexa'. Ctrl-C to exit.");

    var sw = Stopwatch.StartNew();
    TimeSpan lastTrigger = TimeSpan.FromSeconds(-CooldownSeconds);

    try
    {
        while (!cts.IsCancellationRequested)
        {
            short[] frame = queue.Take(cts.Token);
            float score = model.Predict(frame);
            var now = sw.Elapsed;
            if (score >= Threshold && (now - lastTrigger).TotalSeconds >= CooldownSeconds)
            {
                Console.WriteLine($"DETECTED alexa score={score:0.000} t={now.TotalSeconds:0.0}s");
                lastTrigger = now;
                FireAndForgetBeep(device, beepBuffer);
            }
        }
    }
    catch (OperationCanceledException) { /* Ctrl-C path */ }

    stream.Stop();
    Console.WriteLine("\nbye");
}
finally
{
    model?.Dispose();
    PortAudio.Terminate();
}

static int FindUsbDevice()
{
    int count = PortAudio.DeviceCount;
    for (int i = 0; i < count; i++)
    {
        var info = PortAudio.GetDeviceInfo(i);
        if (info.name.ToLowerInvariant().Contains("usb") && info.maxInputChannels >= 1)
            return i;
    }
    Console.Error.WriteLine("USB audio device not found. Devices:");
    for (int i = 0; i < count; i++)
    {
        var info = PortAudio.GetDeviceInfo(i);
        Console.Error.WriteLine(
            $"  [{i}] {info.name} in={info.maxInputChannels} out={info.maxOutputChannels}");
    }
    Environment.Exit(1);
    return -1; // unreachable
}

static short[] MakeBeep(double freqHz, double durationS, int sampleRate)
{
    int n = (int)(sampleRate * durationS);
    var buf = new short[n];
    for (int i = 0; i < n; i++)
    {
        double t = i / (double)sampleRate;
        double v = 0.3 * Math.Sin(2.0 * Math.PI * freqHz * t);
        buf[i] = (short)(v * short.MaxValue);
    }
    return buf;
}

static void FireAndForgetBeep(int device, short[] beepBuffer)
{
    int offset = 0;
    var done = new ManualResetEventSlim(false);

    var outParams = new StreamParameters
    {
        device = device,
        channelCount = 1,
        sampleFormat = SampleFormat.Int16,
        suggestedLatency = PortAudio.GetDeviceInfo(device).defaultLowOutputLatency,
        hostApiSpecificStreamInfo = IntPtr.Zero,
    };

    Stream.Callback playCb = (IntPtr _, IntPtr output, uint frameCount,
        ref StreamCallbackTimeInfo _2, StreamCallbackFlags _3, IntPtr _4) =>
    {
        int remaining = beepBuffer.Length - offset;
        int take = (int)Math.Min(frameCount, (uint)remaining);
        unsafe
        {
            short* dst = (short*)output.ToPointer();
            if (take > 0)
            {
                fixed (short* src = &beepBuffer[offset])
                    Buffer.MemoryCopy(src, dst, take * sizeof(short), take * sizeof(short));
                offset += take;
            }
            for (int i = take; i < frameCount; i++) dst[i] = 0;
        }
        if (offset >= beepBuffer.Length)
        {
            done.Set();
            return StreamCallbackResult.Complete;
        }
        return StreamCallbackResult.Continue;
    };

    var stream = new Stream(
        null, outParams, WakewordModel.SampleRate, 1024, StreamFlags.NoFlag, playCb, IntPtr.Zero);
    try
    {
        stream.Start();
    }
    catch
    {
        stream.Dispose();
        done.Dispose();
        throw;
    }
    Task.Run(() =>
    {
        // 2 s timeout so a failed callback (which PortAudio silently swallows
        // and would leave 'done' unset) eventually releases the stream + handle
        // instead of leaking them for the process lifetime.
        done.Wait(TimeSpan.FromSeconds(2));
        Thread.Sleep(200);
        stream.Stop();
        stream.Dispose();
        done.Dispose();
    });
}

static class Libc
{
    [DllImport("libc", EntryPoint = "setenv")]
    public static extern int setenv(string name, string value, int overwrite);
}