[pulseaudio-discuss] avoid increase watermark for low latency capture

[xing wang]

2011/7/23 pl bossart <bossart.nospam at gmail.com>

> > When meet Overrun or Underrun, PA will increase watermark. Due to some
> > hardware limitation, the hw_ptr will not be updated in PA's request
> latency.
> > So there maybe some cases "faked overrun/underrun". Take capture for
> > example, when Pulseaudio was waken up to read new capture data from
> driver,
> > and find the "available" area is much more than the record space.
> Although
> > it's fast enough to read out all data in short time, PA regard that as
> > "overrun" and increase watermark/latency step by step, that's really
> > useless.
> > So attached patch used to avoid such case and only increase
> > watermark/latency in real "overrun" case.
>
> Humm, it's not clear what problem you are trying to solve and on what
> platform. Looks like a very old MRST firmware/driver?
> If your driver doesn't update the hw_ptr, then how can you know if
> this is a real or a fake overrun?
>

In fact it's a solution for such firmware hasing  low hw_ptr updating rate.
Pulseaudio use hw_unused field to track the unused buffer, the real overrun
means the "avail" space is geting close to hwbuf_size.

--xingchao

> -Pierre
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