On Sat, Jul 6, 2013 at 9:36 PM, James Stone <jamesmstone@xxxxxxxxx> wrote: > On Sat, Jul 6, 2013 at 3:41 PM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: >> On Sat, 6 Jul 2013, James Stone wrote: >> >>> The output when I try to start jack with 128 frames/period is: >>> >>> /usr/bin/jackd -dalsa -r44100 -p128 -n2 -D -Chw:USB,0 -Phw:USB,0 -I512 -O512 -S >>> jackdmp 1.9.9.5 >>> Copyright 2001-2005 Paul Davis and others. >>> Copyright 2004-2012 Grame. >>> jackdmp comes with ABSOLUTELY NO WARRANTY >>> This is free software, and you are welcome to redistribute it >>> under certain conditions; see the file COPYING for details >>> no message buffer overruns >>> no message buffer overruns >>> no message buffer overruns >>> JACK server starting in realtime mode with priority 10 >>> audio_reservation_init >>> Acquire audio card Audio0 >>> creating alsa driver ... hw:USB,0|hw:USB,0|128|2|44100|0|0|nomon|swmeter|-|16bit >>> Using ALSA driver USB-Audio running on card 0 - Focusrite Scarlett 2i4 >>> USB at usb-0000:00:12.2-3, high speed >>> configuring for 44100Hz, period = 128 frames (2.9 ms), buffer = 2 periods >>> ALSA: final selected sample format for capture: 32bit integer little-endian >>> ALSA: use 2 periods for capture >>> ALSA: final selected sample format for playback: 32bit integer little-endian >>> ALSA: use 2 periods for playback >>> ^CJack main caught signal 2 >>> >>> ..the device is unusable with the lights flashing on and off. Jack >>> then shuts down as seen above. >>> >>> At 256 frames/period it starts OK. >> >> What happens if you run JACK with input only, no audio out? >> >> Alan Stern >> > > It works fine with both input only or output only - down to 16 > frames/period. At 8 frames/period it shows the same behaviour as at > 256 frames/period in duplex - but that is a ridiculously low latency > of 0.2ms, so hardly surprising it won't work. > > I have now got an error message when jack fails to start in duplex mode: > > ALSA: prepare error for playback on "hw:USB,0" (Protocol error) > JackAudioDriver::ProcessAsync: read error, stopping... > > James Sorry - slight misinformation there. I can go down to 16 frames/period for capture only, but for playback only, it will only go down to 128 frames/period. Anything lower: /usr/bin/jackd -dalsa -r44100 -p64 -n2 -Phw:USB,0 -I512 -O512 -S jackdmp 1.9.9.5 Copyright 2001-2005 Paul Davis and others. Copyright 2004-2012 Grame. jackdmp comes with ABSOLUTELY NO WARRANTY This is free software, and you are welcome to redistribute it under certain conditions; see the file COPYING for details no message buffer overruns no message buffer overruns no message buffer overruns JACK server starting in realtime mode with priority 10 audio_reservation_init Acquire audio card Audio0 creating alsa driver ... hw:USB,0|-|64|2|44100|0|0|nomon|swmeter|-|16bit Using ALSA driver USB-Audio running on card 0 - Focusrite Scarlett 2i4 USB at usb-0000:00:12.2-3, high speed configuring for 44100Hz, period = 64 frames (1.5 ms), buffer = 2 periods ALSA: final selected sample format for playback: 32bit integer little-endian ALSA: use 2 periods for playback ALSA: poll time out, polled for 2176094 usecs JackAudioDriver::ProcessAsync: read error, stopping... This is a definite reduction in performance compared to earlier kernels. James -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
