Alan Stern wrote: > 256 samples/period / (44100 samples/second) * 8000 microframes/second > = 46.44 microframes/period. > > Therefore I would expect to see snd-usb-audio submitting isochronous > URBs with 46 or 47 packets, with a pipeline depth of 2 URBs. > > However, that's not what actually happens. The audio-out stream uses 8 > URBs each containing about 7 packets on average, for a latency of 7 ms. > The audio-in stream uses 8 URBs each containing 1 packet, for a latency > of 0.125 ms and a pipeline duration of 1 ms -- which is too small for > the current version of ehci-hcd to accept. IIRC 8 x 1 frames worked once upon a time. Anyway, the driver attempts to keep a minimum size of 1 ms for each URB, but also uses wMaxPacketSize to compute this and assumes that this is not too far off from the actual packet size. This appears to be the first device to use a ridiculously large value of 1024 bytes. I'll fix this in the driver. Regards, Clemens -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
