[pulseaudio-discuss] [PATCH v4] Make module loopback honor requested latency

Alexander E. Patrakov patrakov at gmail.com
Sun Feb 8 05:03:38 PST 2015

08.02.2015 17:35, Georg Chini wrote:
>>> I think there is some misunderstanding. Let me repeat in a different
>>> way.
>>> The smoother works perfectly (both for timer-based scheduling and for
>>> the needs of your module) on non-batch cards.
>>> But, even for batch cards, where timer-based scheduling is disabled,
>>> the smoother is active and is actually used for reporting the latency
>>> to your module. An attempt to use the smoother for timer-based
>>> scheduling on batch cards has failed. That's why I suspect that it,
>>> on batch cards, also tells lies to your module.
>> OK, understood. I don't have anything to test it though
> Mh, are my USB devices batch cards? I just noticed it says "Disabling
> timer scheduling
> because BATCH flag is set" in the log and I am not sure, what a batch
> card is.

Yes, your USB devices are batch cards. This means that they don't report 
their playback position accurately enough. For USB devices, the 
granularity of position reports is 6 ms (for large period sizes), but 
for others, it may be up to one period size.

Alexander E. Patrakov

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