All:

I have had problems with compensating with latency before, and have successfully dealt with them.  Please consider the information below as food for thought. 

I noticed I was hitting the polyphony limits of my synthesizer, yet I wanted to add still more parts.  I tried to solve the problem by recording my piano part as an audio track, muting the original MIDI piano track, but leaving the other MIDI tracks. 

This solved the polyphony limit problem, but the audio track was not quite in-sync with the other parts due to latency.  Note that the Jack Audio Connection Kit (used for audio tracks) indicates in its configuration, that it has a latency (on my machines) of 46 milliseconds (0.046 seconds). 

I tried dealing with this by selecting the audio track segment, and doing a "Jog Left" on it, which helped, but it was still not quite right.  Repeating the process made it worse, so I un-did that, being left with it okay, but not quite right. 

Having been burned by this, I approached the latency problem a little differently in later projects.  Note that my approach depends on not using the metronome feature of Rosegarden. 

I would start out, recording tracks, until I approached the polyphony limit of my synthesizer.  At that point, I would record all those tracks to an audio track, and mute all the tracks used to make the audio track. 

All additional tracks would be recorded, improvising against the audio track, rather than against any of the original MIDI tracks used to record the audio track (now muted). 

With this approach, the unavoidable latency was built-in, and since the new tracks were relative to the audio track, there were no latency problems. 

To repeat the process (if you approached the polyphony limits with the new MIDI tracks), you would have to make new audio track from BOTH the audio track, and the new MIDI tracks, because the latency of recording an additional audio track from the new MIDI tracks would make it no longer be in-sync with the first audio track. 

If you're adding instrumental parts to an original guitar/vocal audio track, you improvise your MIDI tracks against the original audio track.  To get your final recording, you must record a single audio track from both the audio track, and your MIDI tracks simultaneously. 

If you record your MIDI tracks to another audio track, that audio track will be out-of-sync with the original audio track. 

This approach has worked for me since then, successfully avoiding the latency problems I encountered before.

Another thing I found that helped, is to record the percussion track(s) early in the process, since a percussion track provides a sort of 'automatic metronome', helping you keep the parts together. 

I hope this information is helpful. 

- Aere

On Thu, 2012-09-27 at 13:55 +0200, Holger Marzen wrote:
On Thu, 27 Sep 2012, D. Michael McIntyre wrote:

> On 09/27/2012 06:07 AM, Holger Marzen wrote:
> 
> > Any facts or ideas? Maybe 1000 times discussed already?
> 
> I seem to remember some controversy over latency compensation involving 
> Chris Cannam and/or Richard Bown, but that was all so very long ago.
> 
> I have to leave any meaningful discussion of this problem up to people 
> with bigger brains than mine.

This is a really serious issue. Obviously latency compensation is
already in Rosegarden - but with errors. Now I begin to understand why I
had to shift audio segments to get them in sync again after adding oder
removing LADSPA-plugins to or from *other* tracks.

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-- 

Sincerely,
Aere