[Jack-Devel] alsa_in/out increasing time between record and play on second card

mdrslmr mdrslmr at online.de
Tue Apr 12 10:42:37 CEST 2016


we are running a system with two sound cards. The second sound card is
attached to the jackd2 daemon using jack_load audioadapter.

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

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.

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.

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

Do you have a suggestion how we can set things up to prevent the
increase in time difference between recording and playback?

The absolute latency is not critical for us as long as it stays within a
limited range.

Best regards

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