[ardour-users] Ardour and Latency Handling

Wolfgang Woehl tito at rumford.de
Sun Apr 30 08:01:36 PDT 2006

Sunday 30 April 2006 06:52, Andrew Johnston:

> on the #ardour irc channel last night, I was informed that for standard
> multitrack recording and overdubbing, latency does not factor into the
> situation if not using softsynths, or live dsp performing as ardour handles
> the latency internally, and syncs all the tracks to line up with each
> other, based on the latencies reported to it by jack and by the ladspa
> plugins.

Couldn't say it better. It works like that. What's your Ardour version, jackd 

> I have an RME HDSP9652 connected via adat to a Behringer DDX3216.  I routed

Have you measured the DDX3216's latency? It'll have some and you can add those 
numbers to your jackd startup options with -I and -O  -- if your external 
routing always includes the DDX.

> the click track out channel one, and on my mixer rerouted channel one input
> back out to channel 2.  I then recorded channel 2 in ardour and therefore
> got the click track recording at the same time as playing.  I then played
> back from the beginning with click track still enabled.  At -p 64 there was

To choose Ardour live click for loopback tests is not the best choice because 
click is special. That is unfortunate but non-trivial to change I think. 
Record the click to a track and start from there.

> no delay between the two.  At -p 1024 there was a noticeable delay.  I went

When testing this stuff I find it really helpful to have some actual numbers 
like audio frames. More telling than "noticeable". Right-click the clocks to 
change their format and write down the delta between edit cursor and playhead 
for example. Looking at the numbers can give you a clue about what's going 
on. Remember to measure the latency of your external gear.

> one step further and switched off the click, and used the exisiting
> recorded material (now it's own click track) and routed it out and back in
> on another track.  I returned the same results, and regardless of the
> toggling the alignment options, there was no difference.  This leads me to
> believe that in fact ardour does not handle latency internally and

Ardour does compensate for latency. With the -I and -O numbers in the picture 
you get sample-perfect alignment.

I wonder what's mixed up in your setup. On connecting tracks to sources Ardour 
asks JACK what kind of source that is: Hardware or software source. And it 
sets up alignment of the track accordingly. This can get messed up when you 
change connections later on. This is still buggy in Ardour.


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