[LAU] Testing sync with 2 sound cards

[Joe Hartley]

On Mon, 3 Mar 2008 19:59:42 +0100
Fons Adriaensen <fons at kokkinizita.net> wrote:
> One way to test for exact sync is to use jdelay, with an analog
> loopback from an output on card A to an input on card B.
> Let it run as long as you can and verify if the delay is stable. 

Thanks for the advice and for jdelay!  

I started jack up:
jackd -R -P70 -dalsa -r44100 -p128 -n2 -D -Cmulti_capture -Pmulti_playback -m -H -M

My first test sent jdelay's output through a port on card 0, which was
patched to an input iput on card 1, which jdelay used to complete the
loop.

I consistently got a delay of 453.485 frames, +/-0.001.

I then patched an output on card 0 to an input on card 0, and got
454.166 or 454.167 frames.

Finally I looped ports on card 1, and got 452.151 frames, +/-0.001.

These seem like perfectly cromulent numbers to me.

Thanks to Fons, Kevin and Mark for the enlightenment.

-- 
======================================================================
       Joe Hartley - UNIX/network Consultant - jh at brainiac.com
Without deviation from the norm, "progress" is not possible. - FZappa