[vdr] FF card A/V sync suggestion

Oliver Endriss o.endriss at gmx.de
Tue Oct 31 05:48:36 CET 2006

Klaus Schmidinger wrote:
> Udo Richter wrote:
> > Klaus Schmidinger wrote:
> >> Morfsta wrote:
> >>> I second that, please don't let it drop again.. Is anyone actually 
> >>> working on this, Klaus, Oliver, ANYONE?
> >>
> >> I'm not working on this, because ATM I wouldn't know what to do.
> > 
> > Any comments on C.Y.M's point that PCR should be recorded/used?
> > -> http://www.linuxtv.org/pipermail/vdr/2006-October/011061.html
> > 
> > As far as I understand this, VDR ignores the TS-layer PCR timing data 
> > (which, as far as I understand this, controls the raw data rate fed to 
> > the decoders) and the syncing is done by DVB driver/firmware based on 
> > the timing information in the underlying PES headers. Since the DVB 
> > playback also works on PES layer and accepts data on all-you-can-eat 
> > base, I'm not sure whether feeding the DVB device on PCR based data 
> > rates would help, or how PCR should be forwarded to the DVB hardware.
> I'm afraid my knowledge here is too limited.
> If somebody can come up with an idea of how additional timing information
> should be inserted in the PES data, let's hear it.

Imho there is no need to add anything to the PES data format.

In live mode PCR is required to synchronize the internal clock of the
decoder to the master clock of the transmitter.

In replay mode the clock of the decoder is running free, i.e. it is the
master clock. No need for a PCR or something like that.

> Generally I don't think that VDR should have to to anything regarding
> A/V sync during replay. It simply feeds the data to the device as fast
> as the device can take it, and syncing audio and video is the device's
> job. Maybe mplayer just generates additional PES headers for this?

Does mplayer really play PES data 'as is'?
Afaik it recodes data to MPEG-1.(?)

Afaics it is a firmware/driver problem. It should be fixed there.
Werner is currently working on a modified A/V sync code.
We will see whether is improves things. Please be patient.


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