[alsa-devel] USB Data Dropping

Charles Eidsness charles.eidsness at ieee.org
Mon May 26 20:45:36 CEST 2008

Charles Eidsness wrote:
> Hi All,
> I'm developing a USB DAC and I've ran into an issue that has me scratching my 
> head. Every once in a while (30 seconds or so) my USB DAC gets sent a USB frame 
> that's missing a few samples, unless I'm also streaming audio through my 
> laptop's built-in audio interface, i.e. playing audio through my USB DAC alone 
> and I get dropped data, playing audio through my USB DAC and the built-in audio 
> device at the same time (unique streams to each device) and I get no dropped 
> data to my USB DAC. Once I stop playing audio on the built-in device I start 
> getting dropped data to my USB DAC again.

I'm still not completely sure what's going on but if I turn off acpi support in 
the kernel I no longer have this issue. I guess there's some sort of unexpected 
IRQ interaction. Strangely setting acpi=noirq doesn't solve the problem so maybe 
it's related to interrupts that ACPI is throwing up. It may just be related to 
the configuration of my laptop (Acer 8104).


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