hollunder@xxxxxx schrieb: > On Sun, 25 Oct 2009 18:03:09 +0800 > Ray Rashif <schivmeister@xxxxxxxxx> wrote: > > >> 2009/10/25 <hollunder@xxxxxx> >> >> >>> On Sun, 25 Oct 2009 11:40:16 +0100 >>> rosea grammostola <rosea.grammostola@xxxxxxxxx> wrote: >>> >>> >>>> Hi, >>>> >>>> I found this info: >>>> >>>> >>>> "USB and jack >>>> >>>> The USB interrupt period is 1 msec. To be able to get lower >>>> latency with jack when using it with an USB device, you have to >>>> use a setting as 48kHz and 3 period. It will makes the buffer >>>> time a multiple of 1 msec and you will get a much lower latency >>>> as with the default 2 period. Additionaly, loading the >>>> snd-usb-audio with the parameter "nrpacks=1" will give you a much >>>> lower latency (for this to work take care that >>>> CONFIG_USB_BANDWIDTH is not set and CONFIG_USB_DYNAMIC_MINORS is >>>> not set in your running kernel)." >>>> >>>> >>>> >>>> >>> http://proaudio.tuxfamily.org/wiki/index.php?title=Howto_RT_Kernel#USB_and_jack >>> >>>> 1) is this info still up-to-date? >>>> 2) how do I exactly take care of this: >>>> "Additionaly, loading the snd-usb-audio with the parameter >>>> "nrpacks=1" will give you a much lower latency (for this to work >>>> take care that CONFIG_USB_BANDWIDTH is not set and >>>> CONFIG_USB_DYNAMIC_MINORS is not set in your running kernel)" >>>> >>>> (Debian (based) systems) >>>> >>>> \r >>>> >>> In my experience 48kHz/3 periods works a bit more stable, the >>> possible latency settings in jack don't really change, 64 frames is >>> still the lower boundary and unstable. >>> >>> But I haven't heard about 2) and am very curious about this >>> myself. >>> >>> Philipp >>> >> 2) Edit /etc/modprobe.conf or /etc/modprobe.d/modprobe.conf with: >> >> options snd-usb-audio nrpacks=1 >> >> And to "make sure". you have to have the kernel options changed. make >> menuconfig, and press "/" to search for the two options. >> >> Philipp: we already dealt with that one but _without_ substantial >> cause-and-effect http://bugs.archaudio.org/task/5 >> > > Thanks, you're right, CONFIG_USB_DYNAMIC_MINORS is not set and CONFIG_USB_BANDWIDTH doesn't > even show up. > > I'll try to load with that option tomorrow and see how it goes. > > Philipp > _______________________________________________ > Linux-audio-user mailing list > Linux-audio-user@xxxxxxxxxxxxxxxxxxxx > http://lists.linuxaudio.org/mailman/listinfo/linux-audio-user > Hi, don't know where I found this on the net that setting the buffer size for usb audio a multiple of 1 ms duration, e.g. for 48000 kHz p=48 will allow very low latencies. I tried this today with the latest rt kernel and the cheap burr brown usb codec pcm2902 used in my behringer uca202: options snd_usb_audio nrpacks=1 /usr/bin/jackd -R -P79 -dalsa -dhw:1,0 -r48000 -p48 -n2 -Xseq It runs smoothly on a centrino laptop (pentium M, cpu freq stepping between 0.6 and 1.6 GHz). I built a plain vanilla 2.6.31.12 with the latest rt20 patch applied, debs available my repo - read more: http://www.sidux.com/index.php?name=PNphpBB2&file=viewtopic&t=9396&start=87 Imho the latest rt20 is much more robust than rt19 - I like it! Maybe some of the jack and usb gurus (Paul?, Clemens?) can confirm the -p48 -n2 setting. Ciao Martin _______________________________________________ Linux-audio-user mailing list Linux-audio-user@xxxxxxxxxxxxxxxxxxxx http://lists.linuxaudio.org/listinfo/linux-audio-user
