On 23.11.20 17:17, David Kastrup wrote: > Giso Grimm <gg3137@xxxxxxxxx> writes: > >> Here is data for the Focusrite Scarlett solo for all period sizes P from >> 16 to 240 frames in steps of 16 frames: >> >> P frames ms >> 16 114.847 2.393 >> 32 176.847 3.684 >> 48 232.847 4.851 >> 64 294.847 6.143 >> 80 368.847 7.684 >> 96 424.847 8.851 >> 112 498.847 10.393 >> 128 566.847 11.809 >> 144 616.847 12.851 >> 160 684.847 14.268 >> 176 752.847 15.684 >> 192 802.847 16.726 >> 208 876.847 18.268 >> 240 1000.847 20.851 >> >> This is almost perfectly 4*P+48, for all P. I can also start it with P = >> 37 (an arbitrary prime number), so it looks that there is no limitation >> on the period size. Also for such odd numbers it remains 4*P+48 (the >> exact delay varies a bit between jack starts, which is normal for USB >> devices). >> >> This is jackd2 - I don't know if jackd1 behaves differently (although >> both would use the underlying ALSA layer). >> >> I started jack with >> >> jackd --sync -P 90 -d alsa -d hw:$CARD -r $RATE -p $PERIODSIZE > > --sync is not documented in jackd2's man page. What does it do? > without --sync jackd2 uses multiple cores whenever possible, at the cost of one extra buffer. With --sync jackd2 behaves single-threaded but has one buffer less delay (i.e., two buffers like in jackd1). Using --sync is thus mostly relevant when delay is the primary concern, and not performance. -- Giso _______________________________________________ Linux-audio-user mailing list Linux-audio-user@xxxxxxxxxxxxxxxxxxxx https://lists.linuxaudio.org/listinfo/linux-audio-user
