[Ardour-Dev] zita-a2j and capture alignment

Paul Davis paul at linuxaudiosystems.com
Tue Sep 10 05:32:51 PDT 2013

On Tue, Sep 10, 2013 at 8:03 AM, Ben Bell <bjb-ardour-dev at deus.net> wrote:

> On Sat, Sep 07, 2013 at 03:27:21PM +0100, Ben Bell wrote:
> > 2) When I capture a mix of jack driven and zita-a2j driven inputs, the
> >    alighment is out. I don't just mean audio latency, I mean that the
> >    captured regions have different start times. I'm guessing something is
> >    trying to be smart about re-aligning the two sources but it's not
> >    getting it right. In addition, by moving the region starts it seems
> >    to break the edit-group synching of region edits.
> Having been through this in more detail with Fons's help and a new version
> of zita-a2j, it looks like there is definitely something going in on Ardour
> itself here.
> The regions being captured from the Zita and Jack driver cards are of
> slightly (e.g. 12 samples) different lengths, and this seems to mean that
> the code in ardour which handles ganging of edits for regions in an edit
> group is being fooled. Assuming that the different length regions are a
> valid response to what's happening, does Ardour need to use a different
> method of deciding whether a pair of regions are part of the same take and
> hence should be edited together -- maybe just start time? Or should the
> regions be artificially made the same length if they are recorded together
> in an edit group?

Ardour cannot correct the case where the source (the JACK backend or zita)
are not in agreement. Sorry, this is asking for the absurd. The regions are
not a different length - they contain different data. Pop up the region
properties editor (right click on a region > properties) to establish this.
Their data is different because there is a skew between the two sources.
Nothing ardour can do (or know) will improve this.
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