[linux-dvb] Re: AW: VDR 0.80pre8, current CVS OSD problems

[Ralph Metzler <rjkm@convergence.de>]

Klaus Schmidinger writes:
 > I'm currently thinking: would it be possible to rearrange the audio/video
 > packets in VDR when recording, so that these audio underruns would no longer
 > occur? That way we might be able to get back the OSD memory.
 > 
 > The idea is that the overall timing of the a/v packets must be ok, since
 > it works when viewing the live broadcast. During the several conversions
 > on the way to the recording file the packaging apparently gets changed in a way
 > that there are too many video packets in a row and the next audio packet comes
 > too late (please correct me if I'm wrong here). So the whole problem would


Viewing the live broadcast works because the firmware(ROM)/RTSL 
offers a mechanism which uses an overflow buffer in DRAM (as opposed 
to the SDRAM where the normal buffers, OSD, etc. have to be).
This overflow buffer (if configured) is automatically used when the 
video buffer is full. Data is DMAed to/from the buffer as needed.
Without this normal TV watching also does not work correctly with the
increased OSD memory. 
This mechanism is only implemented for the "watching mode" and
hidden somewhere inside the black box made up of firmware ROM and
binary only TI libraries.


 > appear to be solvable if VDR would hold back the video packets just long enough
 > until the next audio packet arrives, and then deliver several of the video packets,
 > then the audio packet, and then more video packets - and then start all over again.
 > The overall error can't accumulate, since in long term viewing the a/v timing
 > must be ok.
 > 
 > I hope I'm making some sense here and would appreciate any comments on this idea.
 > 
 > What I would need to learn about is, if I have a sequence of a/v packets, like
 > 
 >   V V V V V V V A V V V V V
 > 
 > which should actually be stored as 
 > 
 >   V V V V V A V V V V V V V
 > 
 > (note that the A packet moved a little to the front): how can I tell where to
 > insert the audio packet? Any ideas?


By looking at the PTS.
But exactly those channels which make problems also are the ones with
very long times between video PTS.


Ralph


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