[alsa-devel] Improving status timestamp accuracy

[Alan Young]

On 06/06/16 15:53, Pierre-Louis Bossart wrote:
> I probably need more coffee but how is this patch helping track audio 
> v. wallclock drift? The additional precision is based on wallclock 
> deltas... 


Of course, it wouldn't, due to being buggy. I think I needed more coffee 
too.

But the basic point is that if the difference between tstamp and 
(trigger_tstamp + audio_tstamp) varies over time, this will be the drift 
between the audio output and wallclock time.

Depending upon the specific goal, a calculation based on tstamp + delay 
may be appropriate.

This is true today with a granularity of about period time. The idea 
behind my change is to make the granularity much smaller, preferably < ~1ms.

I'll work on developing and testing a patch for consideration before 
coming back to the last. It will be easier to discuss the merits or 
otherwise of my proposal with a concrete, working patch to consider.

Alan.