Re: [alsa-devel] USB Audio questions

On 08/15/2011 10:31 PM, Pierre-Louis Bossart wrote:

• Increasing the number of packets/urbs solves my power issue but not the

synchronization issue. If I reduce the number of urbs to reduce the interrupt rate, then the accuracy of the hw_pointer is decreased big time and it becomes difficult to synchronize with video.

I think the same thing is a problem for quite a few other devices as well - I wonder if we need some kind of "pointer granularity" variable to be exported through the ALSA API? PulseAudio could use that to determine whether or not to enable timer-based scheduling. And in these cases, maybe a call to hw_pointer could return hw_pointer and time, and then PulseAudio etc could use that for extrapolation (or the extrapolation could be done in alsa-lib).