0007604: JACK transport master behaves differently during tempo ramp if playhead has been moved after playback has started - MantisBT

ID	Project	Category	View Status	Date Submitted	Last Update

0007604	ardour	bugs	public	2018-04-17 15:26	2018-04-17 15:26

Reporter	Underhand	Assigned To
Priority	normal	Severity	minor	Reproducibility	always
Status	new	Resolution	open
Platform	PC	OS	Ubuntu Studio	OS Version	17.10

Summary	0007604: JACK transport master behaves differently during tempo ramp if playhead has been moved after playback has started
Description	When 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 Reproduce	Create 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 Information	Seen in 5.11. I'll update once I get an opportunity to test in 5.12.
Tags	No tags attached.

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