Playback of short length loops is off-tune

[merumerutho]

Instruments based on looping of samples of short length (less than 100 samples more or less) are a common practice in chiptune.

However, when played back by libxm7 they result in off-tune sounds. The bug can probably be traced back to the inaccuracies related to short waveforms being imprecise in relation to something like timer callbacks or similar.

[merumerutho]

Update: problem seems to be restricted to cases where len(sample) is around 50 or less