Re: [linux-audio-user] latency compensation

From: Sampo Savolainen <v2@email-addr-hidden>
Date: Fri Jul 22 2005 - 18:16:44 EEST

On Fri, 2005-07-22 at 10:31 -0400, Brett McCoy wrote:
> I am going to be setting up a second machine (probably Windows) to use
> as a dedicated machine for VST plugins and instruments, and I plan to
> use SP/DIF between my Linux DAW and the Windows box for the send/return
> (getting a Delta1010 for Linux and moving my M-Audio 2496 to the Windows
> boix). Is latency going to be an issue with this kind of setup and if
> so, how would I compensate in Ardour or other applications?

Quite simple, actually. This example is for Ardour, but it should work
in all Linux software which respect and use the latency values reported
by some LADSPA plugins.

Say you have a Bus:
inputs -> LADSPA 1 -> LADSPA 2 -> INSERT (sp/dif out & in) -> outputs

Newer versions of Ardour (currenty only in CVS) & Jack (the to be
released 0.100.0) will automatically compensate for the latency caused
by jack wiring.

The next step is to use the ingenious plugin by Steve Harris: Artificial
Latency. This plugin does nothing, except return a specified amount of
latency. The amount of latency it reports is controlled like any plugin
is controlled.

Add the plugin somewhere in the bus's chain (doesn't matter where). Now
either measure or calculate (or throw something off the top of your
head) the amount of latency of the "sp/dif -> windows -> vst host ->
vst(s) -> etc. -> sp/dif out" chain and use that value for the
artificial latency plugin.

Make sure the plugin is activated, and ardour will compensate for the

Not all LADSPA plugins report their latency, sometimes this can be
bothersome, but these issues can also be resolved with the artificial
latency plugin.

It's worth mentioning that even though latency compensation works a bit
better in newer versions of Ardour and Jack, this same principle can
also be used in earlier versions (like beta29). There are some problems
with aligning recorded material which were recorded on tracks with
latency compensation. These problems are currently being ironed out.

Sampo Savolainen <v2@email-addr-hidden>
Received on Fri Jul 22 20:15:09 2005

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