feat: add local Resemblyzer speaker recognition

MeetingAssistant/Speakers/SpeakerVoiceVectors.cs

@@ -0,0 +1,191 @@
+using System.Buffers.Binary;
+using System.Security.Cryptography;
+using System.Text;
+
+namespace MeetingAssistant.Speakers;
+
+internal sealed record DecodedSpeakerVoiceVector(
+    SpeakerVoiceVector Stored,
+    float[] Vector);
+
+internal static class ResemblyzerVectorContract
+{
+    public const int Dimensions = 256;
+}
+
+internal static class SpeakerVoiceVectors
+{
+    public static float[] Decode(SpeakerVoiceVector stored)
+    {
+        if (stored.Dimensions != ResemblyzerVectorContract.Dimensions ||
+            stored.VectorBytes.Length != stored.Dimensions * sizeof(float))
+        {
+            throw new InvalidDataException(
+                $"Stored voice vector {stored.Id} has invalid dimension or byte length metadata.");
+        }
+
+        var vector = new float[stored.Dimensions];
+        for (var index = 0; index < vector.Length; index++)
+        {
+            vector[index] = BinaryPrimitives.ReadSingleLittleEndian(
+                stored.VectorBytes.AsSpan(index * sizeof(float), sizeof(float)));
+            if (!float.IsFinite(vector[index]))
+            {
+                throw new InvalidDataException($"Stored voice vector {stored.Id} contains a non-finite value.");
+            }
+        }
+
+        return vector;
+    }
+
+    public static int AddDistinct(
+        SpeakerIdentity identity,
+        IEnumerable<float[]> vectors,
+        string modelId,
+        int maximumCount,
+        DateTimeOffset createdAt)
+    {
+        var limit = Math.Max(1, maximumCount);
+        var fingerprints = identity.VoiceVectors
+            .Select(vector => vector.Fingerprint)
+            .ToHashSet(StringComparer.Ordinal);
+        var added = 0;
+        foreach (var vector in vectors)
+        {
+            if (identity.VoiceVectors.Count >= limit)
+            {
+                break;
+            }
+
+            var bytes = Encode(vector);
+            var fingerprint = Fingerprint(modelId, bytes);
+            if (!fingerprints.Add(fingerprint))
+            {
+                continue;
+            }
+
+            identity.VoiceVectors.Add(new SpeakerVoiceVector
+            {
+                ModelId = modelId,
+                Dimensions = vector.Length,
+                VectorBytes = bytes,
+                Fingerprint = fingerprint,
+                CreatedAt = createdAt
+            });
+            added++;
+        }
+
+        return added;
+    }
+
+    public static IReadOnlyList<float[]> DecodeCompatible(
+        SpeakerIdentity identity,
+        string modelId,
+        ILogger logger)
+    {
+        return DecodeCompatibleEntries(identity, modelId, logger)
+            .Select(entry => entry.Vector)
+            .ToList();
+    }
+
+    public static IReadOnlyList<DecodedSpeakerVoiceVector> DecodeCompatibleEntries(
+        SpeakerIdentity identity,
+        string modelId,
+        ILogger logger)
+    {
+        var vectors = new List<DecodedSpeakerVoiceVector>();
+        foreach (var stored in identity.VoiceVectors
+            .Where(vector => string.Equals(vector.ModelId, modelId, StringComparison.Ordinal))
+            .OrderBy(vector => vector.CreatedAt)
+            .ThenBy(vector => vector.Id))
+        {
+            try
+            {
+                vectors.Add(new DecodedSpeakerVoiceVector(stored, Decode(stored)));
+            }
+            catch (InvalidDataException exception)
+            {
+                logger.LogWarning(
+                    exception,
+                    "Ignoring invalid stored voice vector {VectorId} for identity {IdentityId}",
+                    stored.Id,
+                    identity.Id);
+            }
+        }
+
+        return vectors;
+    }
+
+    public static double Cosine(float[] first, float[] second)
+    {
+        double dot = 0;
+        for (var index = 0; index < first.Length; index++)
+        {
+            dot += first[index] * second[index];
+        }
+
+        return dot;
+    }
+
+    public static float[] Normalize(float[]? vector, string description)
+    {
+        if (vector is null || vector.Length != ResemblyzerVectorContract.Dimensions)
+        {
+            throw new InvalidDataException(
+                $"{description} has {vector?.Length ?? 0} dimensions; expected {ResemblyzerVectorContract.Dimensions}.");
+        }
+
+        double magnitudeSquared = 0;
+        foreach (var value in vector)
+        {
+            if (!float.IsFinite(value))
+            {
+                throw new InvalidDataException($"{description} contains a non-finite value.");
+            }
+
+            magnitudeSquared += value * value;
+        }
+
+        var magnitude = Math.Sqrt(magnitudeSquared);
+        if (magnitude <= double.Epsilon)
+        {
+            throw new InvalidDataException($"{description} has zero magnitude.");
+        }
+
+        return vector.Select(value => (float)(value / magnitude)).ToArray();
+    }
+
+    private static byte[] Encode(float[] vector)
+    {
+        if (vector.Length != ResemblyzerVectorContract.Dimensions)
+        {
+            throw new InvalidDataException(
+                $"Voice vector has {vector.Length} dimensions; expected {ResemblyzerVectorContract.Dimensions}.");
+        }
+
+        var bytes = new byte[vector.Length * sizeof(float)];
+        for (var index = 0; index < vector.Length; index++)
+        {
+            if (!float.IsFinite(vector[index]))
+            {
+                throw new InvalidDataException("Voice vector contains a non-finite value.");
+            }
+
+            BinaryPrimitives.WriteSingleLittleEndian(
+                bytes.AsSpan(index * sizeof(float), sizeof(float)),
+                vector[index]);
+        }
+
+        return bytes;
+    }
+
+    private static string Fingerprint(string modelId, byte[] vectorBytes)
+    {
+        var modelBytes = Encoding.UTF8.GetBytes(modelId);
+        var input = new byte[modelBytes.Length + 1 + vectorBytes.Length];
+        modelBytes.CopyTo(input, 0);
+        input[modelBytes.Length] = 0;
+        vectorBytes.CopyTo(input, modelBytes.Length + 1);
+        return Convert.ToHexString(SHA256.HashData(input));
+    }
+}