tooll3--t3/Core/Audio/AudioAnalysis.cs

using System;
using ManagedBass;
using T3.Core.Logging;

namespace T3.Core.Audio;

/// <summary>
/// Analyze audio input from internal soundtrack or from selected Wasapi device.
/// Transforms the FFT buffer generated by BASS and generates frequency bands and peaks.
/// 
/// <para><b>Note:</b> This static class delegates to <see cref="AudioAnalysisContext.Default"/>.
/// For multithreaded analysis, create separate <see cref="AudioAnalysisContext"/> instances.</para>
/// </summary>
public static class AudioAnalysis
{
    private static AudioAnalysisContext Context => AudioAnalysisContext.Default;

    /// <summary>
    /// Processes FFT data to compute frequency bands, peaks, and attacks.
    /// Delegates to <see cref="AudioAnalysisContext.Default"/>.
    /// </summary>
    internal static void ProcessUpdate(float gainFactor = 1f, float decayFactor = 0.9f)
    {
        Context.ProcessFftUpdate(gainFactor, decayFactor);
    }

    #region Buffer Accessors (delegate to default context)

    /// <summary>
    /// Result of the FFT analysis in gain. Delegates to <see cref="AudioAnalysisContext.Default"/>.
    /// </summary>
    public static float[] FftGainBuffer => Context.FftGainBuffer;

    /// <summary>
    /// Result of the FFT analysis converted to dB and mapped to normalized range.
    /// Delegates to <see cref="AudioAnalysisContext.Default"/>.
    /// </summary>
    public static float[] FftNormalizedBuffer => Context.FftNormalizedBuffer;

    /// <summary>
    /// Current frequency band levels (0-1 normalized).
    /// Delegates to <see cref="AudioAnalysisContext.Default"/>.
    /// </summary>
    public static float[] FrequencyBands => Context.FrequencyBands;

    /// <summary>
    /// Peak-hold values for frequency bands with decay.
    /// Delegates to <see cref="AudioAnalysisContext.Default"/>.
    /// </summary>
    public static float[] FrequencyBandPeaks => Context.FrequencyBandPeaks;

    /// <summary>
    /// Attack values for frequency bands (rate of increase).
    /// Delegates to <see cref="AudioAnalysisContext.Default"/>.
    /// </summary>
    public static float[] FrequencyBandAttacks => Context.FrequencyBandAttacks;

    /// <summary>
    /// Peak attack values with slower decay.
    /// Delegates to <see cref="AudioAnalysisContext.Default"/>.
    /// </summary>
    public static float[] FrequencyBandAttackPeaks => Context.FrequencyBandAttackPeaks;

    /// <summary>
    /// Onset detection values for beat synchronization.
    /// Delegates to <see cref="AudioAnalysisContext.Default"/>.
    /// </summary>
    internal static float[] FrequencyBandOnSets => Context.FrequencyBandOnSets;

    #endregion

    internal const DataFlags BassFlagForFftBufferSize = DataFlags.FFT2048;
    internal const int FftBufferSize = 1024; // For Bass DataFlags.FFT2048

    /// <summary>
    /// Computes FFT from a PCM buffer during export.
    /// Creates a temporary stream, populates it with the buffer data, and extracts FFT.
    /// Uses the default context's FftGainBuffer.
    /// </summary>
    /// <param name="pcmBuffer">Interleaved stereo float buffer</param>
    public static void ComputeFftFromBuffer(float[] pcmBuffer)
    {
        ComputeFftFromBuffer(pcmBuffer, Context);
    }

    /// <summary>
    /// Computes FFT from a PCM buffer during export into a specific context.
    /// Creates a temporary stream, populates it with the buffer data, and extracts FFT.
    /// </summary>
    /// <param name="pcmBuffer">Interleaved stereo float buffer</param>
    /// <param name="context">The analysis context to store results in</param>
    internal static void ComputeFftFromBuffer(float[] pcmBuffer, AudioAnalysisContext context)
    {
        if (pcmBuffer == null || pcmBuffer.Length < 4)
        {
            Array.Clear(context.FftGainBuffer, 0, context.FftGainBuffer.Length);
            return;
        }

        // Create a temporary push stream
        int tempStream = Bass.CreateStream(
            AudioConfig.MixerFrequency,
            2, // stereo
            BassFlags.Float | BassFlags.Decode,
            StreamProcedureType.Push);

        if (tempStream == 0)
        {
            Log.Warning($"[AudioAnalysis] Failed to create temp stream for FFT: {Bass.LastError}");
            return;
        }

        try
        {
            // Push the PCM data into the stream
            int bytesToPush = pcmBuffer.Length * sizeof(float);
            Bass.StreamPutData(tempStream, pcmBuffer, bytesToPush);

            // Get FFT data from the stream
            Bass.ChannelGetData(tempStream, context.FftGainBuffer, (int)DataFlags.FFT2048);
        }
        finally
        {
            // Clean up the temporary stream
            Bass.StreamFree(tempStream);
        }
    }
}