[vdr] FF card A/V sync suggestion

C.Y.M syphir at syphir.sytes.net
Sat Oct 21 02:14:33 CEST 2006


Juri Haberland wrote:
> Klaus Schmidinger <Klaus.Schmidinger at cadsoft.de> wrote:
>> C.Y.M wrote:
>>> Since it has been several years now and I have never been able to solve the a/v
>>> desync issues with my Nexus-S FF card when playing back recordings...
>> I'm replaying many recordings (actually most of what I watch
>> are recordings ;-) and don't even remember when was the last
>> time I had an A/V desync.
> 
> I also have A/V desyncs. This is with one TT-DVB-T (and a
> TT-DVB-C, most of the time we record and watch via the DVB-T card).
> 
> In most cases it is bad reception.
> Pausing and restarting the video fixes it - most of the time - but
> sometimes I have to switch back to live TV and restart the video.
> 
>> Are you getting this with recordings from particular channels,
>> or does it happen all the time?
>> Also, is this with MPEG audio or AC3?
> 
> There is no AC3 involved - just plain replay via FBAS and audio out
> of the TT card.
> 

The A/V desync problem would not be so critical if it corrected itself with some
type of time code.  In fact, even playing bad recordings back with some kind of
software decoder can give you a desync once in a while, but the difference is
that the software method fixes the desync automatically (without having to fast
forward or rewind to the next GOP).  Utilizing mpegpes is really the best of
both worlds.  We would still be using the video output on the FF card but having
software to process the actual mpeg decoding.  There would be no transcoding
involved because obviously the recording would already be in a DVB resolution
format.  The CPU usage would be very minimal and I would not need to install
X-windows or some type of framebuffer. I am just talking about regular MPEG
audio/video.  It doesn't seem like it would "that" hard to modify the mplayer
plugin for just this purpose.  In fact, it already works.  But there are a few
minor issues with it.

1) Mplayer can not get the correct seek time when playing back VDR recordings
for some reason (causing the time bar to show incorrect values).
2) Mplayer can not handle playing back split files (ie; 001.vdr, 002.vdr). As of
now each one must be selected individually.
3) Sometimes when playing back a video with mplayer (using only a single FF card
in the machine), something puts a lock on something in /dev/dvb/adapter0/*. So,
if a timer should happen to go off in VDR while you are playing back a video
with mplayer, VDR will crash when attempting to start recording with the timer.

Best Regards.





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