LinearFadeStrategy fails to detect fade completion for sub-second durations

[R0ll1ngSt0ne]

Depending on sample frequency and specified fade duration (usually, < 500ms), fade volume increment step can become too large and _currentVolument will overshoot the _targetVolume. Fade completion never gets detected and volume keeps increasing infinitely. Here is the fix:

File: LinearFadeStrategy.cs

Original:

private bool IsFadingFinished()
{
   return Math.Abs(_currentVolume - _targetVolume) < 0.00001f;
}

Fixed:

private bool IsFadingFinished()
{
   return Math.Abs(_currentVolume - _targetVolume) < Math.Abs(_step) ||
      _step > 0.0f && _currentVolume > _targetVolume ||
      _step < 0.0f && _currentVolume < _targetVolume;
}

[filoe]

Thanks for reporting and providing a propper solution! 👍

[R0ll1ngSt0ne]

Sorry, I forgot to cover the case when _step is 0) - fade should finish immediately (probably a check should be added to StartFading so that no cycle is wasted to detect completion:

if (Math.Abs(_step) <= 0.00001f)
... complete fade right away

[filoe]

You mean after this line:

cscore/CSCore/Streams/LinearFadeStrategy.cs

Line 104 in 75242c9

_step = delta / durationInBlocks;

we should add the check and eventually call StopFadingInternal()?

I would suggest adding the following:

if(IsFadingFinished())
    StopFadingInternal();

[R0ll1ngSt0ne]

I rewrote StartFading like this to cover these edge cases:

    public void StartFading(float? from, float to, double duration)
    {
        if (SampleRate <= 0)
            throw new InvalidOperationException("SampleRate property is not set to a valid value.");
        if (Channels <= 0)
            throw new InvalidOperationException("Channels property it not set to a valid value.");
        if (to < 0 || to > 1)
            throw new ArgumentOutOfRangeException("to");

        if (IsFading)
            StopFadingInternal();

        if (!from.HasValue)
            _startVolume = CurrentVolume;
        else
        {
            if (from.Value < 0 || from.Value > 1)
                throw new ArgumentOutOfRangeException("from");
            _startVolume = from.Value;
        }

        _targetVolume = to;
        _currentVolume = _startVolume;

        float delta = _targetVolume - _startVolume;

        // Done immediately if duration is 0 or start end end volumes are the same
        if (Math.Abs(duration) < 1.0 || Math.Abs(delta) < 0.00001f)
        {
            FinalizeFading();
        }
        else
        {
            //calculate the step
            var durationInBlocks = (int)(duration / 1000 * SampleRate);
            _step = delta / durationInBlocks;

            IsFading = true;
        }
    }