[BUG] PlaybackSpeed leads to bad audio quality

[BlyZeDev]

Requirements

• I have searched the existing issues to ensure this bug has not already been reported.
• I have provided a clear and concise description of the bug.
• I have provided detailed steps to reproduce the bug.
• I have included a minimal reproducible example (MRE) if applicable.
• I have provided error messages and stack traces if applicable.
• I have completed the environment information.

1. Describe the Bug

If the playback speed is changed to a value other than 1.0f the quality gets really bad.

2. Steps to Reproduce

Call PlaybackSpeed with any value other than 1.0f

3. Expected Behavior

The sound to play faster and not lose quality

4. Current Behavior

The sound plays inconsistently faster and the quality gets very bad

5. Minimal Reproducible Example (MRE)

private static readonly MiniAudioDeviceConfig _deviceConfig = new MiniAudioDeviceConfig
{
    NoFixedSizedCallback = true,
    Wasapi = new WasapiSettings
    {
        Usage = WasapiUsage.ProAudio
    }
};
private static readonly AudioFormat _audioFormat = new AudioFormat
{
    Channels = 2,
    Format = SampleFormat.F32,
    SampleRate = 48000
};

private readonly MiniAudioEngine _audioEngine;

public void Play(string filepath)
{
      if (!File.Exists(filepath)) return;

      playbackDevice = _audioEngine.InitializePlaybackDevice(device._deviceInfo, _audioFormat, _deviceConfig);
      
      if (!playbackDevice.Capability.HasFlag(Capability.Playback))
      {
          playbackDevice.Dispose();
          return;
      }
      
      var player = new SurroundPlayer(_audioEngine, _audioFormat, new ChunkedDataProvider(_audioEngine, _audioFormat, filepath));
      player.SetSpeakerConfiguration(SurroundPlayer.SpeakerConfiguration.Stereo);
      
      playbackDevice.MasterMixer.AddComponent(player);
      playbackDevice.Start();

      player.Play();
      
      mySound.PlaybackSpeed = Random.Shared.NextSingle() * 2f;
}

6. Error Messages and Stack Trace (if applicable)

No error just bad audio quality

SoundFlow Version

1.2.1

.NET Version

.NET 9.0

Operating System

Windows 11

Architecture

x64

Audio Backend Used (if known)

WASAPI

Specific Audio Hardware (if relevant)

Logitech G733 Headset

8. Affected Components/Modules (if known)

SoundPlayer and SurroundPlayer

9. Impact

Incorrect audio output

10. Possible Workaround (if known)

11. Additional Context

[LSXPrime]

Thanks for reporting this, and sorry for delayed response, I have been so busy lately.

Yes, I'm aware of this issue. It originates directly from the WsolaTimeStretcher. The problem is that it’s doing a ton of allocations, and the Waveform Similarity Overlap-Add (WSOLA) time stretching algorithm isn't well optimized. This combination produces high latency, which is what causes the breakages in audio

The quick and performant solution we used previously was just altering the pitch alongside the playback speed. When I originally implemented WSOLA, I did it purely as an experiment—no one had requested it, and no one seemed interested. Well, you are the first person to actually use it or report it so far!

The logic for time stretching is quite complicated (mainly because of my poor design decision to create it as a self-contained component), and fixing it properly will need dedicated time.

Unfortunately, it won't be in the upcoming update. My remaining time is completely focused on implementing proper MIDI support and a better surround playback system. Well, honestly, with 40+ changed files and 120+ new files, I almost forget what this entire update was supposed to be about! However, my remaining time will be focused on those core features and fixes. If I still have any time left before my mandatory military deployment, I will absolutely work on making the time stretching much more stable.

[BlyZeDev]

@LSXPrime Thank you very much for the response :)
Take your time I appreciate the effort you put in this library.