On Thu, Sep 19, 2013 at 08:04:04PM +1000, Patrick Shirkey wrote:
> > 1. Measure the round-trip latency of your sound card (with an
You'd measure something different...
But you could use two computers as follows:
A = computer with jack, PA, audacity
B = second computer with sound card, jack and jack_delay.
1. Measure the round-trip latency on B, with an external
2. Connect B -> A, A -> B, run complete chain on A.
3. Measure again on B, subtract the value from (1).
> > jack_delay -> pa_source -> audacity -> pa_sink -> jack_delay.
Don't know - I'm by no means a PA expert... and I don't know
your Jack period size. Given PA's reputation I'd expect more:
1024 samples would mean that PA imposes almost the same RT-
requirements on apps as Jack does, and it was designed *not*
to do that... But maybe the jack <-> PA interface doesn't
use the same amount of buffering that PA normally adds.
Note that the value measured is modulo 2^16 samples, but I
wouldn't expect anything more than a second, so this probably
> > 3. If pa_source and pa_sink are a single Jack client (probably not),
If they are a single Jack client you create a loop in Jack's
processing graph, this adds one period to the measurement.
> > 4. Add the two values.
Don't see how. You need to do two measurements anyway, no matter
how it's done, then add or substract.
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