[LAU] Cracking sound via USB (ALSA urb.c:480: frame 5 active: -18)

Aurélien Leblond blablack at gmail.com
Thu May 26 15:55:32 UTC 2011


> Ken Restivo wrote:
> > On Wed, May 25, 2011 at 08:55:48AM +0200, Jeremy Jongepier wrote:
> > > http://lists.linuxaudio.org/pipermail/linux-audio-user/2010-June/070353.html
>
> That bug in Intel's Rate Matching Hub would corrupt audio data, but
> is unlikely to result in error messages from the driver.  (Iso packets
> have no error correction; corrupted data is just silently ignored.)
>
> > > So not mixing USB1 and USB2 devices but mixing a device performing
> > > Full-Speed isochronous-out transactions with a device performing
> > > asynchronous transactions. I've tested my Edirol UA-25 with this chipset
> > > too and no matter what I tried, full duplex wouldn't work.
>
> The Linux high speed support is somewhat buggy; this affects full
> speed devices connected to high speed hubs.
>
> The Rate Matching Hub is internally organized as a high speed hub.
>
> > Wait, what?
> >
> > I've been doing way too much reading of USB specs (and the hub.c,
> > message.c, and musb driver source code) for work lately, and even though
> > I'm definitely suffering from early onset of Alzheimer's, I distinctly
> > remember reading that Isochronous and Bulk endpoints were only allowed
> > at High Speed (480Mbps).
> >
> > At Full speed (12Mbps), IIRC, you get Interrupt and Control endpoints,
> > and that's pretty much it.
>
> Iso/bulk are forbidden only at Low speed (1.5Mbps).


So in conclusion, would a High Speed audio card plugged onto a EHCI
port be susceptible of facing issues?
Sorry, I'm getting lost in the technical terms!


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