Test 3: copy WakewordModel + models from Test 2, add Reset()

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using Microsoft.ML.OnnxRuntime;
using Microsoft.ML.OnnxRuntime.Tensors;
namespace FullCycleProbe;
// Streaming wakeword inference port of openwakeword 0.6.0's predict pipeline.
// References (read alongside this file):
// openwakeword/utils.py:AudioFeatures._streaming_features (mel + embedding stages)
// openwakeword/utils.py:AudioFeatures._streaming_melspectrogram
// openwakeword/utils.py:AudioFeatures._get_embeddings
// openwakeword/model.py:Model.predict (classifier stage)
internal sealed class WakewordModel : IDisposable
{
// Audio I/O geometry — per-call input contract.
public const int FrameSamples = 1280; // 80 ms @ 16 kHz; each Predict() call.
public const int SampleRate = 16_000;
// Mel model: input is last (FrameSamples + MelContextSamples) raw samples
// -- the +480 is openwakeword's `-n_samples-160*3:` slice (3 hops of context).
public const int MelContextSamples = 480; // 160 * 3
public const int MelInputSamples = FrameSamples + MelContextSamples; // 1760
public const int MelBins = 32; // melspectrogram model output dim
public const int MelBufferMaxFrames = 970; // 10 * 97 (openwakeword `melspectrogram_max_len`)
// Embedding model: 76-mel-frame window in, 96-d embedding out.
public const int EmbeddingWindowMelFrames = 76;
public const int EmbeddingDim = 96;
public const int EmbeddingBufferMax = 120; // openwakeword `feature_buffer_max_len`
public const string EmbeddingInputName = "input_1"; // openwakeword convention; assert at startup
// Classifier: 16 embeddings in, scalar score out.
public const int ClassifierEmbeddings = 16;
// Skip the first N Predict() calls — buffer fill-up window.
public const int WarmupFrames = ClassifierEmbeddings; // 16 frames ≈ 1.28 s
private readonly InferenceSession _mel;
private readonly InferenceSession _emb;
private readonly InferenceSession _cls;
private readonly string _melInputName; // discovered at startup
private readonly string _clsInputName; // discovered at startup
private readonly short[] _rawRing = new short[MelInputSamples];
private int _rawRingFill = 0; // samples buffered (≤ MelInputSamples)
private readonly List<float[]> _melRing = new(MelBufferMaxFrames); // each entry is a length-32 mel frame
private readonly List<float[]> _embRing = new(EmbeddingBufferMax); // each entry is a length-96 embedding
private int _framesSeen = 0;
public WakewordModel(string melPath, string embeddingPath, string classifierPath)
{
var opts = new SessionOptions
{
IntraOpNumThreads = 1,
InterOpNumThreads = 1,
LogSeverityLevel = OrtLoggingLevel.ORT_LOGGING_LEVEL_ERROR,
};
_mel = new InferenceSession(melPath, opts);
PrintShapes(Path.GetFileName(melPath), _mel);
_emb = new InferenceSession(embeddingPath, opts);
PrintShapes(Path.GetFileName(embeddingPath), _emb);
_cls = new InferenceSession(classifierPath, opts);
PrintShapes(Path.GetFileName(classifierPath), _cls);
// Discover input names + assert shape geometry.
_melInputName = _mel.InputMetadata.Keys.Single();
AssertEmbeddingShape(_emb); // input_1: [batch, 76, 32, 1], dtype float
_clsInputName = _cls.InputMetadata.Keys.Single();
AssertClassifierShape(_cls); // [batch, 16, 96], dtype float
}
private static void PrintShapes(string filename, InferenceSession sess)
{
Console.Error.WriteLine($"[wakeword-model] {filename}");
foreach (var kv in sess.InputMetadata)
Console.Error.WriteLine(
$" input '{kv.Key}': shape=[{string.Join(",", kv.Value.Dimensions)}] dtype={kv.Value.ElementType.Name}");
foreach (var kv in sess.OutputMetadata)
Console.Error.WriteLine(
$" output '{kv.Key}': shape=[{string.Join(",", kv.Value.Dimensions)}] dtype={kv.Value.ElementType.Name}");
}
private static void AssertEmbeddingShape(InferenceSession sess)
{
if (!sess.InputMetadata.TryGetValue(EmbeddingInputName, out var meta))
throw new InvalidOperationException(
$"embedding_model.onnx: expected input named '{EmbeddingInputName}', got [{string.Join(",", sess.InputMetadata.Keys)}]");
var d = meta.Dimensions;
// Expected: [batch, 76, 32, 1] — batch may be -1 (dynamic).
if (d.Length != 4 || d[1] != EmbeddingWindowMelFrames || d[2] != MelBins || d[3] != 1)
throw new InvalidOperationException(
$"embedding_model.onnx: expected input shape [batch,{EmbeddingWindowMelFrames},{MelBins},1], got [{string.Join(",", d)}]");
if (meta.ElementType != typeof(float))
throw new InvalidOperationException($"embedding_model.onnx: expected Single input, got {meta.ElementType.Name}");
}
private static void AssertClassifierShape(InferenceSession sess)
{
var inputName = sess.InputMetadata.Keys.Single();
var meta = sess.InputMetadata[inputName];
var d = meta.Dimensions;
// Expected: [batch, 16, 96] — batch may be -1.
if (d.Length != 3 || d[1] != ClassifierEmbeddings || d[2] != EmbeddingDim)
throw new InvalidOperationException(
$"alexa.onnx: expected input shape [batch,{ClassifierEmbeddings},{EmbeddingDim}], got [{string.Join(",", d)}]");
if (meta.ElementType != typeof(float))
throw new InvalidOperationException($"alexa.onnx: expected Single input, got {meta.ElementType.Name}");
}
public float Predict(short[] frame1280)
{
if (frame1280.Length != FrameSamples)
throw new ArgumentException($"Expected {FrameSamples} samples, got {frame1280.Length}");
// 1. Append 1280 new samples to the raw ring (shift older samples down if full).
if (_rawRingFill < MelInputSamples)
{
int copyToFront = Math.Min(MelInputSamples - _rawRingFill, FrameSamples);
Array.Copy(frame1280, 0, _rawRing, _rawRingFill, copyToFront);
_rawRingFill += copyToFront;
if (copyToFront < FrameSamples)
{
// Boundary case: ring was partially full and the new frame overshoots
// remaining capacity. Fires exactly once during warm-up (typically call 2,
// when _rawRingFill = 1280 and the incoming 1280 samples overshoot the
// remaining 480 capacity). Shift the older samples left to make room,
// then write the leftover at the tail.
int leftover = FrameSamples - copyToFront;
Array.Copy(_rawRing, leftover, _rawRing, 0, MelInputSamples - leftover);
Array.Copy(frame1280, copyToFront, _rawRing, MelInputSamples - leftover, leftover);
}
}
else
{
// Shift older samples left by FrameSamples, then append new at the tail.
Array.Copy(_rawRing, FrameSamples, _rawRing, 0, MelInputSamples - FrameSamples);
Array.Copy(frame1280, 0, _rawRing, MelInputSamples - FrameSamples, FrameSamples);
}
// Skip everything until we have the full mel-context window primed.
if (_rawRingFill < MelInputSamples)
{
_framesSeen++;
return 0f;
}
// 2. Mel stage: feed the full _rawRing as float32 (1, MelInputSamples) into mel model.
var melInputData = new float[MelInputSamples];
for (int i = 0; i < MelInputSamples; i++) melInputData[i] = _rawRing[i]; // int16 → float32, NO normalisation
var melInputTensor = new DenseTensor<float>(melInputData, new[] { 1, MelInputSamples });
using var melResults = _mel.Run(new[] {
NamedOnnxValue.CreateFromTensor(_melInputName, melInputTensor)
});
var melOut = melResults.First().AsTensor<float>(); // shape (1, 1, n_frames, 32)
// Apply openwakeword's `x / 10 + 2` transform and append each new frame to _melRing.
// Mel output shape is (1, 1, n_frames, 32). Note n_frames is at Dimensions[2], not [1].
int nFrames = melOut.Dimensions[2];
for (int f = 0; f < nFrames; f++)
{
var bin = new float[MelBins];
for (int b = 0; b < MelBins; b++)
bin[b] = melOut[0, 0, f, b] / 10f + 2f;
_melRing.Add(bin);
}
if (_melRing.Count > MelBufferMaxFrames)
_melRing.RemoveRange(0, _melRing.Count - MelBufferMaxFrames);
// 3. Embedding stage: need ≥ 76 mel frames; slice the last 76 → (1, 76, 32, 1).
if (_melRing.Count < EmbeddingWindowMelFrames)
{
_framesSeen++;
return 0f;
}
var embInputData = new float[EmbeddingWindowMelFrames * MelBins];
int startMel = _melRing.Count - EmbeddingWindowMelFrames;
for (int f = 0; f < EmbeddingWindowMelFrames; f++)
Array.Copy(_melRing[startMel + f], 0, embInputData, f * MelBins, MelBins);
var embInputTensor = new DenseTensor<float>(embInputData, new[] { 1, EmbeddingWindowMelFrames, MelBins, 1 });
using var embResults = _emb.Run(new[] {
NamedOnnxValue.CreateFromTensor(EmbeddingInputName, embInputTensor)
});
var embOut = embResults.First().AsTensor<float>(); // shape (1, 1, 1, 96)
var newEmb = new float[EmbeddingDim];
for (int i = 0; i < EmbeddingDim; i++) newEmb[i] = embOut[0, 0, 0, i];
_embRing.Add(newEmb);
if (_embRing.Count > EmbeddingBufferMax)
_embRing.RemoveRange(0, _embRing.Count - EmbeddingBufferMax);
_framesSeen++;
// 4. Warm-up + classifier stage.
if (_embRing.Count < ClassifierEmbeddings || _framesSeen <= WarmupFrames)
return 0f;
var clsInputData = new float[ClassifierEmbeddings * EmbeddingDim];
int startEmb = _embRing.Count - ClassifierEmbeddings;
for (int i = 0; i < ClassifierEmbeddings; i++)
Array.Copy(_embRing[startEmb + i], 0, clsInputData, i * EmbeddingDim, EmbeddingDim);
var clsInputTensor = new DenseTensor<float>(clsInputData, new[] { 1, ClassifierEmbeddings, EmbeddingDim });
using var clsResults = _cls.Run(new[] {
NamedOnnxValue.CreateFromTensor(_clsInputName, clsInputTensor)
});
var clsOut = clsResults.First().AsTensor<float>(); // shape (1, 1)
return clsOut[0, 0];
}
public void Reset()
{
_rawRingFill = 0;
_melRing.Clear();
_embRing.Clear();
_framesSeen = 0;
}
public void Dispose()
{
_mel.Dispose();
_emb.Dispose();
_cls.Dispose();
}
}