[alsa-devel] Missing exactly 3 of 8 audio packets?

Daniel Griscom griscom at suitable.com
Thu Nov 29 21:35:54 CET 2012

Dear Daniel (M) and Clemens,

I'd like to conclude this thread if I could. It seems clear that 
configuring our USB audio card's descriptor with a bInterval value of 
1 (a packet every microframe) was too aggressive, and was part of 
what caused the packet stuttering issue. (Right?)

We almost certainly should increase bInterval; I'll try 2, and if 
that seems stable will probably go to 3 (4 microframes) for some 
margin. However, I'm still concerned that the symptoms don't sound 
like a simple starvation issue, where I'd expect to have a missing 
frame every once in a while. Instead, we were seeing reliable 
operation interspersed with periods where lots of packets were being 
consistently omitted. To me, this suggests that there's some other 
issue going on, either in the USB stack or in the USB hardware itself.

Given that, I'm worried that increasing bInterval will just move the 
symptoms around, making it harder to duplicate but not truly becoming 

Any thoughts on this? Should I try chasing the issue into the Linux 
USB development mailing list, or will they just say "set bInterval to 
a larger value!"?


Daniel T. Griscom             griscom at suitable.com
Suitable Systems              http://www.suitable.com/
1 Centre Street, Suite 204    (781) 665-0053
Wakefield, MA  01880-2400

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