Re: Re: [Fwd: Re: [MPlayer-dev-eng] AV out of sync with "-ao alsa" in gmplayer, mplayer works ok]

[Takashi Iwai <tiwai@suse.de>]

At Tue, 18 Jan 2005 21:23:09 +0100,
Reimar Döffinger wrote:
> 
> Hi,
> On Thu, Jan 13, 2005 at 03:11:15PM -0500, Lee Revell wrote:
> > Are there any plans to fix the ALSA output so that it doesn't reset the
> > stream with every xrun?  Since you don't use a realtime thread to handle
> > the audio there are certain to be some xruns, for example whenever using
> > the GUI controls in any way or moving the mouse.
> 
> xruns just should not happen. Ignoring them seems to be the very wrong
> way. Also a real-time thread should not be necessary just to avoid xruns
> when only moving the mouse IMHO.

No, it's not guaranteed at all.

> Maybe you can just increase the buffer size somehow? At least for
> MPlayer a big buffer should cause no problems.

The hardware buffer size is limited.  Suppose the hardware which
can have the max buffer size 64kB.  When you play a DVD with 5.1
output, it corresponds to 0.11 second.

The dedicated audio thread works better than the single thread model
because of the following reasons (maybe more):

- It has a large intermediate buffer.  The buffer size can be as large
  as you like.
- It runs only in short time and sleeps.
  This is the preferred behavior for the kernel scheduler.  So, this
  thread may receive higher priority bonus.
- You can change the priority of only audio thread but keep others.


Takashi


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