Takashi Iwai wrote: > 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? >> >>> 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.) >> >>> 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? > > Actually, which value does this affected device in ep->maxpacksize? > In the commit mentioned above, we changed the logic to take +25% > frequency as the basis, and it my *reduce* if ep->maxpacksize is lower > than that. > > OTOH, if ep->maxpacksize is sane, we can rely on it rather than the > implicit +25% frequency. That said, maybe we can check > ep->maxpacksize whether it fits within the expected range, then adapt > it, or take +25% freq as fallback? You are describing how the current code behaves. The +25% limit _is_ what the code takes as the expected range. I'm wondering if that unknown device just declares a wrong interval value. Regards, Clemens _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
