[pulseaudio-discuss] alsa sink latency - how to account for startup delay

[Raymond Yau]

>>
>> The USB driver will submit N silence URBs on startup in the prepare and
you will have to wait for those URBs to retire before the samples are
queued. There is very little 'USB processing'. If you want to reduce this
delay you have to use smaller periods, it'll decrease the size of the URBs.
I guess it could be possible to change the URB size after the start but
that's not implemented atm.
>>

For loopback, the source capture the same amount of data while you wait for
the retitement of those urbs

> I don't want to shorten the latency. I only want the latency reported
correctly. To me it still
> looks like the real latency of the driver is not what it reports, because
the time that the
> audio spends in the URB's is not taken into account. What I am seeing is,
that the real
> latency is around 10ms longer than expected.

The total number of URBs for the endpoint is not allowed to exceed MAX_URBS
(which the patch increases from 8 to 12).

Do this match with your measurement
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