[mpeg2] Re: question about the mpex and vbv buffer and vbv delay

[Andrew de Quincey <adq_dvb@lidskialf.net>]

On Monday 07 Jun 2004 11:35, Luca Abeni wrote:
> Hi Samuel,
>
> [...]
>
> >   Well, finally I've written that code. Using the decoding time to
> > calculate the bitrate of the PES stream, the audio bitrate is perfectly
> > constant, but the video's does not look constant at all. Plotting the
> > result with xgraph you can see a saw with sharp teeth.
>
> I did some other similar measurements, and my results are similar to
> yours...
>
> I was encoding CBR video at 4000kbps, MPEG1 layer 2 audio at 256kbps,
> and I set the TS bitrate at 6000kbps.
>
> After a lot of experiments, I tried to encode CBR video at 4000kbps,
> audio at 256kbps, and to set the TS bitrate at 4500, and... It did the
> trick! Now, the video bitrate is almost constant - but the ts analyzer
> is complaining about buffer overruns and underruns... :(

I found the card was very sensitive to the bitrate parameters used.. if I 
chose the wrong ones it would start to lock up after a few minutes, and/or 
have data loss.

I spoke to a guy in Philips at one point - he said that there is actually an 
SDK available that gives sample code etc, and probably explains the 
contraints on the bitrate settings.

I never got round to investigating this further however.. knowing Philips, 
you'd probably have to pay quite a lot for it.