Messages in this thread |  | | | Date | Wed, 16 Nov 2005 12:07:19 +0100 | | From | Markus Rechberger <> | | Subject | Re: snd_usb_audio |
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On 11/16/05, Clemens Ladisch <clemens@ladisch.de> wrote: > Markus Rechberger wrote: > > finally the em28xx driver made it into the kerneltree, but one > > problem still remains > > the snd_usb_audio driver. > > > > The problem with the snd_usb_audio driver is that it only supports > > up to 10 isochronous packets. > > This is packets per URB; we typically have 8 URBs. > > > If people watch TV using such a framegrabber device and set audio > > to > 8000hz the video isoc transfer will break and the video will > > stop. > > What exactly breaks? Are you using playback or capture? >
the video isoc transfer screws up, finally it even stops. submitting the video isoc urbs starts to fail.
> If there is an underrun when starting a _playback_ stream, then it's a > known bug that has been fixed in 2.6.15-rc1. >
it's playback, I'll test the release canditate tonight hopefully it's solved.
> > regarding usbaudio.c (in 2.6.14): > > #define MAX_PACKS 10 > > #define MAX_PACKS_HS (MAX_PACKS * 8) /* in high speed mode */ > > > > MAX_PACKS is the upper limit that is adjustable, the second one > > isn't used at all > > > > an easy hack would be to allow up to 100 packets but I also have a > > usb 1.1 soundblaster that might have problems with too many packets. > > > > The correct value for em28xx devices is around 80 packets. > > Did you test this? Capturing doesn't use MAX_PACKS. >
yes I tested this regarding the sniffed windows logfile 80 would probably the best value for it, the stream didn't break with that value actually. as I already wrote it's playback.
> > does anyone know more about the packet limitations on USB 1.1 and > > 2.0 devices? > > The only limitation are the host controller drivers. > ok thanks so far!
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