Mauro Carvalho Chehab wrote: > Let's see the au0828 case: > 48 kHz, 2 bytes/sample, 2 channels, 256 maxpacksize, 1 ms URB > interval (bInterval = 1). > > In this case, there is 192 bytes per 1ms period.
The device's clock and the bus clock are not synchronized, so there will be _approximately_ 192 bytes per USB frame. > Let's assume that the period was set to 3456, with corresponds to > a latency of 18 ms. > > In this case, as NUM_URBS = 12, There is no symbol named NUM_URBS. > it means that the transfer buffer will be set to its maximum value of > 3072 bytes per URB pack (12 * 256) The number of URBs is not the same as the number of packets per URB. > and the URB transfer_callback will be called on every 16 ms. It will be called once per millisecond. > So, what ... definitely not ... > happens is: > > - after 16 ms, the first 3072 bytes arrive. The next > packet will take another 16ms to arrive; > - after 2 ms, underrun, as the period_size was not > filled yet. Regards, Clemens -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
