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IDCategoryLast Update
0008432bugs2020-09-30 23:09
ReporterahellquistAssigned To 
Reproducibilityalways 
Status newResolutionopen 
PlatformUbuntuOSLinuxOS Version(any)
Product Version 
Fixed in Version 
Summary0008432: Metronome not in sync if jack buffer size is changed.
Descriptioni have a session with 8 software synths and one audio track.

Everything was recorded using a buffer of 256 for low latency and all tracks as well as the built in metronome is in perfect sync.
However, If i change buffer size to a larger size, the metronome will be offset to the tracks and if i change to 4096 it will be way off.
Even changing to 512 is too much to be usable and the click needs to be muted.

Nothing fancy regarding routing or hardware monitoring going on, Every track is routed to master and there are sends to a reverb bus. Pretty standard
.
Laptop with ubuntu+kxstudio repos and a Motu Ultralite AVB connected via USB and headphones from the Motu interface.

See additional information for update on this:
Additional InformationI have always had my click output routed to the audio interface playback channels 1+2 for monitors and 3+4 for my headphones and that is apparently why it only works if I stay at one buffer size. Changed to output my click to Aurdour master bus and then the click will be in sync as expected.

Question. Is that by design and the correct behavior or should Ardour compensate the timing of the click to follow the total latency of the other signals from track to master out even if a user route the click to hardware ? I think it should work the same but maybe it is not possible ?

A side note, when using buffers 4096, the meters in Ardour is not at all in sync but displays audio ahead of the actual output. Is that something that is known or being addressed ? I am running 6.2 so maybe am an "barking up the wrong tree..." ;-)
Tags6.2, compensation, jack, lag, latency

Activities

ahellquist

2020-09-30 22:41

reporter   ~0025090

To make it clear, After rerouting click to Master. Everything is in perfect sync except the metering which is early. Only visual stuff.
My questions still are important I think since there might be things overlooked regarding latency compensation.

x42

2020-09-30 23:09

administrator   ~0025092

Are you using jack2? That is notorious for having issues with sending latency-callbacks. Ardour 6.3 includes a workaround, but I do not know if this specific issue is addressed.
And yes, forcing a connection change is another work-around.

Ardour does not interpolate meters, so at 4k buffers, the meter only update every 80-95ms (depending on sample-rate).

Issue History

Date Modified Username Field Change
2020-09-30 22:37 ahellquist New Issue
2020-09-30 22:37 ahellquist Tag Attached: 6.2
2020-09-30 22:37 ahellquist Tag Attached: compensation
2020-09-30 22:37 ahellquist Tag Attached: jack
2020-09-30 22:37 ahellquist Tag Attached: lag
2020-09-30 22:37 ahellquist Tag Attached: latency
2020-09-30 22:41 ahellquist Note Added: 0025090
2020-09-30 23:09 x42 Note Added: 0025092