Re: [alsa-devel] Fw: BUG: Kernel panic when disconnecting Edirol USB2 audio interface

[Lee Revell <rlrevell@joe-job.com>]

On Mon, 2005-06-27 at 19:03 -0700, david-b@pacbell.net wrote:
> > With kernel 2.6.12 + "[PATCH] ehci-hcd - fix page pointer allocation in 
> > itd_patch()"), using jackd in realtime mode at 44.1kHz with 64 
> > frames/period and 4 periods/buffer, I get a stream of xruns of about 
> > 0.020 ms, several per second.
> 
> In USB, one frame == 1 msec.  Most EHCI silicon using the 2.6.12 code
> will get unhappy with 256 msec per ISO URB, so I hope you're using
> "frame" without a necessary adjective ... ;)
> 

"frame" = audio frame (4 bytes with S16LE).

"USB frame" = 1 msec

> 
> > Using the same kernel and jackd settings, but with the sound/ and 
> > include/sound directories from ALSA CVS of about 7:30 this evening, it 
> > seems to work fine, at least for a couple of minutes of stereo playback.
> >
> > At 128 frames/period, both kernels have a crackling background noise: I 
> > haven't experimented with any other settings yet.
> 
> I discourage drivers from using more than 64 msec per ISO URB.
> 

Please clarify.  64msec of what?

Lee



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