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IDProjectCategoryView StatusLast Update
0007604ardourbugspublic2018-04-17 15:26
ReporterUnderhand Assigned To 
Status newResolutionopen 
PlatformPCOSUbuntu StudioOS Version17.10
Summary0007604: JACK transport master behaves differently during tempo ramp if playhead has been moved after playback has started
DescriptionWhen a track includes a tempo ramp, and Ardour is the JACK transport master, the timing sent to JACK depends on whether the playhead has been moved since playback started.

If the playhead has been moved, JACK arrives at the beats at the same time as Ardour during the ramp.

If the playhead has not been moved, JACK sees the beats at the wrong time. If the tempo is ramping down, the beats during the ramp arrive early.

This behaviour has been observed using Hydrogen, and verified with QjackCtl.

I have only tried tempo ramps that slow down.
Steps To ReproduceCreate a track which has a tempo ramp (getting slower by a significant amount).

Set Ardour as JACK transport master.

Use something such as Hydrogen which can tick along to the beat as seen via JACK and set it to JACK transport slave.

Press Play in Ardour.

Observe that the beats in Ardour and the beats from Hydrogen are not together during the ramp.

Press Stop in Ardour.

Press Play in Ardour.

Move the playhead in Ardour. It doesn't matter how much time there is between where the playhead is, and the tempo ramp.

Observe that the beats in Ardour and the beats from Hydrogen are together this time during the ramp.
Additional InformationSeen in 5.11. I'll update once I get an opportunity to test in 5.12.
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Issue History

Date Modified Username Field Change
2018-04-17 15:26 Underhand New Issue