meeting-assistant/MeetingAssistant/Speakers/SpeakerCompositeWav.cs

using MeetingAssistant.Transcription;
using NAudio.Wave;

namespace MeetingAssistant.Speakers;

internal static class SpeakerCompositeWav
{
    public static WaveFileReader? OpenFirstReadableWave(IEnumerable<byte[]> snippets)
    {
        foreach (var bytes in snippets)
        {
            if (bytes.Length == 0)
            {
                continue;
            }

            try
            {
                return new WaveFileReader(new MemoryStream(bytes));
            }
            catch (FormatException)
            {
            }
        }

        return null;
    }

    public static TimeSegment? AppendSnippet(
        WaveFileWriter writer,
        WaveFormat targetFormat,
        byte[] snippet,
        TimeSpan start)
    {
        if (snippet.Length == 0)
        {
            return null;
        }

        using var reader = new WaveFileReader(new MemoryStream(snippet));
        if (!WaveFormatsMatch(reader.WaveFormat, targetFormat))
        {
            throw new InvalidDataException("Speaker identity snippets must use the same WAV format.");
        }

        reader.CopyTo(writer);
        return new TimeSegment(start, start + reader.TotalTime);
    }

    public static void WriteSilence(
        WaveFileWriter writer,
        WaveFormat format,
        TimeSpan duration)
    {
        if (duration <= TimeSpan.Zero)
        {
            return;
        }

        var bytes = new byte[(int)(format.AverageBytesPerSecond * duration.TotalSeconds)];
        writer.Write(bytes, 0, bytes.Length);
    }

    public static string? FindBestSpeaker(
        TimeSegment segment,
        IReadOnlyList<TranscriptionSegment> segments)
    {
        var bestOverlap = 0d;
        string? bestSpeaker = null;
        foreach (var transcriptSegment in segments)
        {
            var overlap = Math.Min(segment.End.TotalSeconds, transcriptSegment.End.TotalSeconds)
                - Math.Max(segment.Start.TotalSeconds, transcriptSegment.Start.TotalSeconds);
            if (overlap > bestOverlap)
            {
                bestOverlap = overlap;
                bestSpeaker = transcriptSegment.Speaker;
            }
        }

        return bestSpeaker;
    }

    public static void TryDelete(string path)
    {
        try
        {
            if (File.Exists(path))
            {
                File.Delete(path);
            }
        }
        catch (IOException)
        {
        }
    }

    private static bool WaveFormatsMatch(WaveFormat left, WaveFormat right)
    {
        return left.Encoding == right.Encoding
            && left.SampleRate == right.SampleRate
            && left.Channels == right.Channels
            && left.BitsPerSample == right.BitsPerSample;
    }
}

internal readonly record struct TimeSegment(TimeSpan Start, TimeSpan End);