[ardour-dev] exact sample sync

[Jesse Chappell]

On 6/16/06, Robin Gareus <robin at gareus.org> wrote:
> I recently played with the jack transport API, trying several
> applications to play back the same audio file with inverted polarity.
>
> As I did get flange effects instead of the expected silence (using
> ardour and ecasound), I started investigation and in need for a third
> opinion made a small player that does the trick. (source attached if you
> want to reproduce this.)
>
> empiric results:
>
> ecasound v2.4.4: plays audio-frame starting @ jack-transport frame.
>
> ardour 0.99.2 (libardour 0.906.1): the output is exactly one
> jack-buffer-size ahead in time!

I assume there are no plugins.  Check the setting for latency
compensation on the track, in one of the context menus of the track
header area.

> ardour2 svn-604: channel 1 (left) behaves like ardour 0.99.2
> channel 2 (right) does not. (different volume, phase shift or panning? -
> I couldn't get this one to superimpose to zero. )

That sounds bad.

> That sounds like a bug in ardour (read-ahead feature ?!?) to me.
>
> If I drop the file at the left-most position in the timeline: the
> playback is always a jack-buffersize frames early!

Did you do any of these tests by starting transport playback from a
location other than zero?  Also, what happens when you don't put the
region at ardour's 0?

jlc