Bug 1726 – Linux: MIDI playback timing / synchronisation problems

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Audacity 3.0.3 development began 19th April 2021

Audacity Bugzilla

Bug 1726 - Linux: MIDI playback timing / synchronisation problems


Summary:	Linux: MIDI playback timing / synchronisation problems

Status:	RESOLVED FIXED

Product:	Audacity
Classification:	Unclassified
Component:	MIDI
Version:	2.2.0
Hardware:	Per OS Linux

Importance:	P2 Repeatable
Assigned To:	Default Assignee for New Bugs

URL:
Keywords:

Depends on:
Blocks:
	Show dependency tree / graph

Reported:	2017-08-20 16:54 UTC by Steve Daulton
Modified:	2018-08-20 11:45 UTC (History)
CC List:	7 users (show)

See Also:
Steps To Reproduce:	Import and play a MIDI track that has quick tempo regular beats. Notice that on playback the rhythm sounds irregular.
Release Note:	GROUP: MIDI *(Linux) The timing of notes during MIDI playback may sound erratic on some machines. Optimizing the system for low latency MIDI playback can help to reduce the inaccuracies.
First Git SHA:
Group:	---
Workaround:
Closed:	2018-08-20 00:00:00

Flags:	petersampsonaudacity: Test‑OK‑Win+ petersampsonaudacity: Test‑OK‑Mac+ stevethefiddle: Test‑OK‑Lin+

Attachments
120 bpm Middle C (1.82 KB, audio/midi) 2017-11-21 21:07 UTC, Steve Daulton	Details
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Description Steve Daulton 2017-08-20 16:54:17 UTC

Tested on Linux, but could affect other platforms to a lesser extent (not yet tested).

When playing note tracks, the time at which notes play is imprecise, causing the rhythm to be erratic.

Comment 1 Peter Sampson 2017-11-21 07:36:44 UTC

(In reply to Steve Daulton from comment #0)
@Steve:  do you have a suitable (quick tempo regular beats) MIDI file that you can attach here that I (and others) could test on Windows and Mac?

Comment 2 Steve Daulton 2017-11-21 21:07:56 UTC

Created attachment 741 [details]
120 bpm Middle C

MIDI file with repeated single note at 120 bpm quaver rhythm.

Comment 3 Peter Sampson 2017-11-22 05:52:48 UTC

(In reply to Steve Daulton from comment #2)
Testing that 120 bpm Middle C MIDI file on W10 with 2.2.0 and the latest 2.2.1 alpha build that I got from James produces a very regular metronomic outpout.

Similar testing on macOS 10.13.1 High Sierra with 2.2.0 and 2.2.1 alpha of 21Nov17 also produces a very regular metronomic outpout.

Comment 4 Steve Daulton 2017-11-22 07:09:08 UTC

I'm seeing "jitter" (timing errors) of around 10 ms. While this still leaves room for improvement, it is low enough to be unnoticeable in most situations, so I'm marking this as fixed. Further improvement would be an enhancement, and not the original code bug.