[linux-dvb] Re: Trying to get a ``polished'' MPEG stream from DVB

[Marcus Metzler <mocm@mocm.de>]

>>>>> "Måns" == Måns Rullgård <mru@pronto.tv> writes:

    Måns> Chris Chatfield <C.Chatfield@Teamphone.com> writes:
    >>> > I can't be the only one trying to transcode DVB output. What
    >>> does > everyone else do?
    >>> 
    >>> I've been playing around with DVB a bit, never had any
    >>> problems like that.
    >> I can't offer a solution to the original problem, but at least
    >> I can explain briefly what's going on - DVB is transmitting
    >> over the air, and you'd be doing very well to get 100% of the
    >> TS packets. I suspect the OP had a moment of less than perfect
    >> reception at that point - hence a missing packet.

    Måns> This is the reason TS uses fixed-size packets and other
    Måns> things that make recovery easy.

    >> Transcode and other mpeg utilities generally expect a perfect
    >> mpeg stream.  We're not able to supply one unless you convert
    >> the TS to mpeg with a utility that can cater for unreliable
    >> input.
    >> 
    >> It's worse if you demultiplex the stream into separate audio
    >> and video streams before transcoding - a loss of a single audio
    >> frame can play havoc with a/v synchronisation.

    Måns> Isn't that what PTS is for?

The problem is that DVD players expect an unbroken stream since a DVD
is supposed to be mastered from a reliable source. In contrast, DVB
decoders expect errors and are prepared to correct them.

Would it be a good idea to insert of drop audio frames in replex to
avoid PTS inconsitencies? I am not sure how I should fix video frames.
Any ideas for a consistent strategy?

Marcus

-- 
/--------------------------------------------------------------------\
| Dr. Marcus O.C. Metzler        |                                   |
| mocm@metzlerbros.de            | http://www.metzlerbros.de/        |
\--------------------------------------------------------------------/
 |>>>             Quis custodiet ipsos custodies                 <<<|


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