[Ardour-Users] time shift when recording from one midi track to another

Victor victor at svictor.net
Thu Jan 25 14:24:48 PST 2018


I’m trying to understand the following behavior in Ardour 5.12.0

1. Create 2 midi tracks, A and B
2. On track A, create a midi region and put 1 note every two beats 
in it
(notes aligned to the grid).
3. On track B record the midi output of track A. 

I would have expected the resulting region on B to be an exact 
copy of
the region on A. Instead, all notes on B are shifted
slightly before the notes on A. The very first note of A is 
actually not
rendered at all on B (maybe because it’d start too early before 
the B region).
I attach a screenshot.

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Is this a side-effect of read-ahead latency compensation[1]?
If so, can I set/disable the read-ahead time somewhere in Ardour?

Looking at latency, I also wonder how to interpret the information 
Window --> Audio/Midi Setup. It says that my buffer size is 128 
and there is an additional 2.7ms between brackets after that. Is 
a latency estimate? 
Qjackctl says that my latency is 8ms.

I start jack from qjacktl with the following settings:
Samplerate: 48000
Frames/Period: 128
Periods/Buffer: 3



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