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

xing wang wangxingchao2011 at gmail.com
Sun Jul 24 18:27:12 PDT 2011

Hi Pierre, Colin,

Any comments?


2011/7/22 xing wang <wangxingchao2011 at gmail.com>
> 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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