[alsa-devel] [PATCH 1/3 v1] ALSA: usb-audio: more tolerant packetsize

[Jiada Wang]

Hello Clemens

On 11/30/2016 11:41 PM, Clemens Ladisch wrote:
> Jiada Wang wrote:
>> since commit 57e6dae1087bbaa6b33d3dd8a8e90b63888939a3 the expected packetsize is always limited to
>> nominal + 25%. It was discovered, that some devices
> Which devices?
It was a LG nexus
>
>> have a much higher jitter in used packetsizes than 25%
> How high?  (Please note that the USB specification restricts the jitter
> to at most one frame in consecutive packets.)
the nominal packet size was somewhere around 176bytes
+25% would result in max expected packets to be ~220bytes
We observed some packets exceeding this size (256byte)
which caused the babble and dropping of that packets.

Thanks,
Jiada

>> which would result in BABBLE condition and dropping of packets.
>> A better solution is so assume the jitter to be the nominal packetsize
> This solution is better for this one particular device, but how does it
> affect normal devices, or the Scarlett 2i4 on EHCI affected?
>
>
> Regards,
> Clemens