Takashi Iwai wrote:
Clemens Ladisch wrote:
Takashi Iwai wrote:
Raymond Yau wrote:
usb-audio seem update when each URB send/receive (in 1ms intervals)
The default is to use larger intervals.
The usb-audio driver behaved in a BATCH way in the very early version, but it was improved.
The delay reporting is more precise, but the DMA position still jumps for each URB.
So we can get rid of the flag from this driver now.
How well does timer-scheduling work with large URBs?
I thought PCM runtime delay should give the accurate sample position, irrespective to URB size?
The position of the sample that is currently being played is accurate (rounded to a USB frame). The DMA position, however, changes only in URB-sized increments. (And that is accurate too, because it describes exactly how the data is copied out of the buffer.)
It should suffice for PA to control via timer scheduling.
Large jumps in the DMA position mean that there is a large part of the buffer which cannot be safely changed by PA. If this is why PA wants to disable tsched, then the BATCH flag should stay.
Regards, Clemens