[vlc-devel] Re: VLC skips on "reduced" MPEG2-TS streams

Marian Durkovic md at bts.sk
Wed Jan 17 18:23:12 CET 2007

> Indeed the delay between PCR and PTS is too low, and there is not enough
> time from the moment when the packet enters the decoder until the moment
> we're supposed to display it. Theoritically the minimum is 120 ms (one I
> + 2 B's), to which we add 300 ms, so even at the minimum we should have
> time to decode the frames. I suppose the PTS's are in the past then.
> AFAIK there is no specification for this value, at least not in MPEG.
> Conventional broadcaster use a value of 500 ms between the PCR and the
> next PTS.

How is this handled in CATV headends and/or consumer-grade DVB-S
receivers? This sattelite transpoder carries also Sat1 and Pro7 and I'd
expect the broadcaster to be getting tons of complaints if those devices
wouldn't be handling the stream correctly.

The lack of specification for time delta between PCR and PTS, significant
differences between broadcasters and the following picture
lead me to another question: shouldn't we use the PCRs only for keeping
the clock frequency but compute the 300 msec shift not against PCRs
but against the first received PTS ?

	With kind regards,


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