On Mon, Jul 1, 2013 at 9:27 PM, Clemens Ladisch <clemens@xxxxxxxxxx> wrote: > Ming Lei wrote: >> On Mon, Jul 1, 2013 at 9:06 PM, Clemens Ladisch <clemens@xxxxxxxxxx> wrote: >>> Ming Lei wrote: >>>> I understand the latency is effected by packet count in one URB, >>>> and it shouldn't be related with URB count, >>> >>> This is true only when capturing. For playback, the latency is the >>> length of the entire pipeline. >> >> For playback, every URB submitted is added into hw table >> immediately, then the data will be played to speaker. I don't >> understand why the latency is the entire pipeline. > > A submitted packet will be transmitted only after all the other packets > in the pipeline have been transmitted. Yes, that is always true since EHCI HW will send out data(packet) to device one by one at the scheduled frame/uframe according to the order of URB submitting , so the USB audio driver can submit URBs in advance, can't it? Also could you provide the typical time one URB in audio driver may span? Thanks, -- Ming Lei -- 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
