[vdr] Re: LiveAC3 and PW

[Andreas Schultz <aschultz@cs.uni-magdeburg.de>]

On Thursday 02 May 2002 18:06, Dr. Werner Fink wrote:
> On Thu, May 02, 2002 at 05:29:14PM +0200, Stephan Schreiber wrote:
> > Hi,
> >
> > I had to even increase the size to 16k to make it work.
> > Strange: where does that different bahaviour of my machine come from?
> > For the first time, LiveAC3 works for me now! :-)))))
> >
> > Thanks,
> > Stephan
>
> Strange ... on Pro7 the frames read from are less or equal than 2048
> bytes (the real payload its self is about 1728 bytes). Sometimes it
> happens that the LiveAC3 thread will started reading the end of
> such a frame and therefore the thrad should have buffer for 2*2048 bytes
> ... and now it may happen that the LiveAC3 thread `sees' the beginning of
> the next frame at the end of the current frame ... therefore 3*2048 should
> be enough.  Maybe PW provides AC3 in groups of 2048
> bytes frames and not reading them may cause an buffer overflow in
> the DVB driver which leads to an reset of this buffer (and at least
> to drop outs).

PW sends PES frames that are much larger (about 7k or so), the included AC3 
frames are normal 1536bytes per frame.

> You may test the ac3play 0.5.2f which I've developed for LiveAC3
> as a replacment for the original ac3play 0.5.0, my former ac3play 0.5.1f
> and ac3dec.  You found this at
>
>      http://www.alsa-project.org/~iwai/ac3play-0.5.2f.tar.bz2
>      http://www.alsa-project.org/~iwai/ac3play-0.5.2f-0.i686.rpm
>
> this ac3play should be lip synchrony.  This ac3play version has a
> special LOW sound chip buffer state handling for reading from
> pipes (as VDR provides): Read as fast as possible, scan and put the fetched
> AC3 into the sound chip buffer and then wait for next input (instead of
> waiting of getting more input to fully refill the input buffer).

strange, when i use LiveAC3 with a52dec to output through a SBLive on Pro7, 
audio is a bit to early compared to the DVB output. I already thought about 
introducing a small delay in LiveAC3 to get it syncronized.

Andreas

-- 
Andreas Schultz <aschultz@cs.uni-magdeburg.de>
Student of computer science

"In accordance with plans for Linux OS world domination
      infiltration of governments is vital (:-))."