12 Apr
2016
12 Apr
'16
7:15 a.m.
On 04/12/2016 10:42 AM, mdrslmr wrote:
Hi,
we are running a system with two sound cards. The second sound card is
attached to the jackd2 daemon using jack_load audioadapter.
Just for the record, I'm not familiar with audioadapter. I'm using
zita-ajbridge, and it works very well.
We use a script starting:
aplay -q -D $channel Test-Ton.wav &
arecord -q -D $channel -f S16_LE -r 48000 -c 1 -d 8 $result/recorded.wav
Why are you using alsa tools when you are otherwise working with JACK?
This will make the problem analysis more complicated...
The resulting wav file shows that the time between the
start of the
recording
and the start of the actual sound continuously increases.
In the beginning (after starting the system up) the time difference is
just about 3ms. It increases
constantly to almost one second now
after 8 weeks of uptime.
If audioadapter works by just providing a big buffer (without any
resampling), the reason would be clock drift. Such a minuscule clock
drift between two consumer cards however would be sensationally good.
This happens most significantly on the channels of the
second sound card
included by jack_load audioadapter and not noticeable on the first sound
card.
To be expected.
The invocation of jackd and jack_load is shown below:
jackd -R -P59 -p 256 -d alsa --device hw:${CARDNUM_0},0 -p 512 --nperiods 3
jack_load -i "-i4 -o4 -q1 -C5 -p512 -n3 -r48000 -d hw:${CARDNUM_1},0"\
jackadapter audioadapter
jackd2 version is: 1.9.8~dfsg.4+20120529git007cdc37-5
I'm, not sure if we a consistent set of options for jackd and
audioadapter.
Do you have a suggestion how we can set things up to prevent the
increase in time difference between recording and playback?
First of all, consider if you can actually sync the cards. If both have
an SPDIF i/o, you can use that. Just connect the secondary card's SPDIF
in to the master's SPDIF out (no matter whether you use toslink or RCA),
and you can be sure your cards will be locked.
Secondly, try zita-ajbridge. If you can sync the cards in hardware,
there is an option for zita-ajbridge to skip the resampling, which will
conserve cpu power.
All best,
Jörn
--
Jörn Nettingsmeier
Lortzingstr. 11, 45128 Essen, Tel. +49 177 7937487
Meister für Veranstaltungstechnik (Bühne/Studio)
Tonmeister VDT
http://stackingdwarves.net