track slows down in case of buffer underflows

[mixxxbot]

Reported by: daschuer
Date: 2013-07-05T19:05:52Z
Status: Triaged
Importance: High
Launchpad Issue: lp1198306

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On aggressife latency settings, underflows may happen in unexpected bussy situations.
Wgile this is already a bad situation things are getting worth due to the fact that Mixxx tryes to repeat the missed frames.
Effectifely the track slows down what effect a dancing crowed more than a dropout of a few miliseconds.

Is a fix to this bug possible included in our master sync aproach?

[mixxxbot]

Commented by: ywwg
Date: 2013-07-05T21:54:59Z

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I wouldn't count on master sync to fix this issue. If the master were set to internal it might be possible that the other tracks would catch up, but in general master sync is about setting relative rates, not enforcing an atomic clock.

[mixxxbot]

Commented by: rryan
Date: 2014-03-13T13:54:24Z

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I don't believe we try to repeat missed frames. We respond to each callback with no regard to how long it took us so there is no repetition... just late delivery.

[mixxxbot]

Commented by: daschuer
Date: 2014-03-13T16:07:15Z

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Yes, exactly this is the issue. Maybe repeat it the wrong word here. When an underflow happens I think the sound card plays the samples that are in the its ring buffer from the last call. The intended samples are just shifted to the next round.
This late delivery leads to a notable speed change of the track.

A solution for this bug will drop the samples outdated samples and continues with the right samples as if there was not underflow.
We need a micro seek for all decks or something.

[mixxxbot]

Commented by: daschuer
Date: 2014-04-03T13:47:59Z

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http://www.mixxx.org/forums/viewtopic.php?f=3&t=4839