[vdr] Re: LiveAC3 and PW

["Dr. Werner Fink" <werner@suse.de>]

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).

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).


        Werner


> >===== dvbapi.h 1.6 vs edited =====
> >--- 1.6/dvbapi.h        Mon Apr 22 12:34:02 2002
> >+++ edited/dvbapi.h     Sun Apr 28 15:28:52 2002
> >@@ -461,7 +461,7 @@
> >    sigset_t oldset;
> >    bool active;
> >    bool busy;
> >-  uint8_t buffer[6144];
> >+  uint8_t buffer[12*1024];
> >    int fd_dolby;
> >    virtual void StripAudioPackets(unsigned char *b, int Length, unsigned 
> > char
> >Except = 0x00);
> >    virtual bool SetDpid1(int Dpid, dmxOutput_t Output);