[linux-dvb] Re: Mplex doesn't work

[Henning Holtschneider <hh@holtschneider.com>]

On Sat, 2 Jun 2001, Klaus Schmidinger wrote:

> > I've been thinking about changing the behaviour of mplex so that it will
> > constantly monitor the a/v delay and insert silence or drop frames (like
> > PVAstrumento does under Windows) but my knowledge about MPEG streams is
> > very limited. If anyone already has a solution for this problem, I would
> > be glad to learn more about it ;-)
>
> So would I, because I really would like to make VDR create 100% correct
> recordings, without the need to remux them afterwards...

Just to avoid misunderstandings here: I'm remultiplexing VDR recordings to
archive them on VCD so that I can replay them on my standalone DVD player.
If I replay a VDR recording with VDR, everything is fine.

> I wonder how it can be that the a/v offset "drifts" throughout a recording.
> The original data that has been broadcast _must_ have been ok, because
> otherwise the live signal would have to show these drifts, too, wouldn't it?

What happens if there are reception errors in the broadcast? From my
understanding so far, the data is broadcasted like this:

V V V V A V V V V A V V V V ...

So, if there is any perturbance, the MPEG decoder will drop frames and
continue to play the audio packet until it gets enough data for the full
video+audio stream again. Is this correct?


> Is the increase of delay you are observing always in the same direction, or is
> it random?

I haven't tried to remux many recordings yet, but so far the delay has
always increased in the same direction (video getting later throughout the
recording). BTW, I'm having the same kind of problem when recording with
Streamreader from my D-Box, so it seems to be normal that the MPEG stream
does not (always?) contain equal length audio and video data.

Regards,
hh



-- 
Info:
To unsubscribe send a mail to listar@linuxtv.org with "unsubscribe linux-dvb" as subject.