[Ardour-Users] Sync between internal and external sources

[Noel Darlow]

On Wed, 21 Jan 2009 14:50:02 +0000
Mark Greenwood <fatgerman at ntlworld.com> wrote:

> I'm using Jack. I have Ardour set to JACK Time Master. I have Hydrogen
> set up to sync to Jack and play a beat. I have Ardour set up to record
> me playing the bass through my soundcard. I press the Play button -
> Hydrogen starts playing, I start playing, Ardour starts recording me. 
> 
> Question 1 : When I play back my recording of me playing bass, and
> have Hydrogen playing along - are they in sync? Or is my bass part now
> delayed relative to Hydrogen by a value equal to the latency of my
> sound card?
Try recording hydrogen into ardour and then playing the same track back
along with hydrogen: that'll let you hear your latency. It will be
noticable although not necessarily musically relevant. A reverb-like
effect with the live/recorded signals is fine but if you can hear a
distinct delay you probably want to get the latency down some. I can
easily get 5.33ms on an m-audio 2496 (RT kernel, naturally). That's
small enough to ignore. 

When recording, be careful to monitor only the ardour (or hydrogen &
other software) outputs but not the input signals which you are
recording. With both in the mix, you'll hear a slight reverb effect
(the raw input signal and the same after passing through ardour & FX).
That gives a misleading impression of the sound if you're trying to
tweak EQ or set levels (it'll be slightly louder). Check Jack
connections carefully.

Or you could monitor only the input sound and no software outs - but of
course that would only work for a solo instrument piece.

That's about all I know, There may be ways to dial in latency
compensation?

> Question 2 : When, at a later date, I mix down by recording the output
> from Hydrogen into tracks in Ardour, does the sync change?
The new hydrogen track will have the same latency as the other tracks
so this will actually correct a latency gap between recorded audio
and live hydrogen. However, in a good setup with just a few ms
latency, that's a purely theoretical issue. Not enough to be musically
relevant.


Noel