[linux-audio-user] Latency

[David Baron]

There are several latency problems, especially on older hardware but still 
around on that 64-bit dual core screamer:

1. Sync of MIDI (~0 latency) and audio (> 0 latency). On Windows, N-track 
could not do it, Jazz did not work. Only Cakewalk--I mean, solid. I can 
record vocals over MIDI, digitize the MIDI, record more vocals, etc., without 
any ado. The clips start precisely where needed. Nothing else worked.

I have not gotten to trying this on Rosegarden yet (because my better sound 
card has no alsa driver) and the MIDIs are produced on Windows programs so I 
just work with Cakewalk going to audio. I could load the MIDI into Rosegarden 
or Muse and try recording with what I have, I suppose. Have any list members 
been successful with this?

2. Sync of VST or DX plugins with their input audio data. This is handled in 
correctly programmed plugins by look-ahead. Sometimes, on must set up the 
host for enough latency to "cover" the plugin's internal latency. Most of 
this stuff simply plays without intervention but I have had plugins with the 
wet result delayed if the host latency is set too low. In one case, the other 
track needed to be delayed appropriately to use the pluging (very rare).

3. Sync of direct playing of a file and live play and synthesis. Try this one: 
Fire up "horgand", a cute little software organ with accompaniment. Turn on 
the accompaniment and try to play along. On older hardware, this is 
impossible, on newer stuff, near-impossible. Key-press to sound is delayed 
while the accompaniment plays on.

Even if I had a tap-tempo thingie (as proposed here), this timing problem 
would remain.

So some kind of triggering is needed. After all, in live performance, the 
accompaniment follows the lead, not visa-versa :-)