[vdr] DVD A/V syncing

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

Hi all,

There has been some dicussions about the new A/V syncing on the list. 
Klaus has used a somewhat simpler version of the A/V syncing that i'm 
using. To my surprise it works for quite some people out there. This 
proves the at least my test DVD ("The Matrix"), is one of the more 
problematic ones. From the mail's i've seen, it would appear as if at 
least "Star Trek: Resurection" has the same problem. I also had the same 
problems with "Tiger and Dragon".

On all those DVD's the video appears to be jumpy every 30sec or so. This 
is because the cards firmware tries to resync the video to the audio. 
This happens because the card 'thinks' the audio is out of sync.
The real reson is that the PTS (presentaion time stamp) on the audio 
packets is somehow wrong.

The jumpy video has nothing to do with the version of libdvdread (as 
someone suspected).

The AC3 problems some people are seeing are due to the buffering 
performed by the variouse AC3 tools. I've seen at least one tool that 
buffered 200kbyte worth of AC3 imput data and due to way it read those 
data, couldn't start play this until the buffer had been filled, 
resulting in a kind of jumpy audio. Another tool assumed to allways read 
comlplete AC3 frames from the input stream and would fail if it got only 
partial frames.

To summerize: make sure your AC3 tool buffers not more that 2048 Byte of 
input data and reassembles partial received AC3 frames.

BTW: I'm currently not subscribed to the maillinglist, please copy me on 
all replies - Thanks

Have fun

   Andreas