[FFmpeg-devel] [RFC] special "broken DV" demuxer

[Roman V Shaposhnik]

On Tue, 2009-03-10 at 20:04 +0100, Reimar D?ffinger wrote:
> On Tue, Mar 10, 2009 at 11:58:57AM -0700, Roman V Shaposhnik wrote:
> > > > > Since it seems all DV decoders and demuxers including ours have no
> > > > > error checking whatsoever it still plays "fine".
> > > > > Unfortunately, the recently added autodetection, that also allows to
> > > > > play badly cut DV files, can not handle it.
> > > > 
> > > > Right. So the problem would be a regression, as far as I can tell.
> > > > Thus the question: can the autodetection code be fixed?
> > > 
> > > What do you mean?
> > 
> > I meant, that the file was playable before the change to the 
> > autodetection.
> 
> My suggestion with the separate demuxer will restore exactly the same
> behaviour, except that it will also play badly cut files if the have a
> header section and in addition will never require seeking.

So the only issue at hand is how to support autodetection, right? 
Would it be possible to read a 1st frame and feed it to the decoder?

> > I have to know more details on what exactly seems to be broken
> > in that stream to make a call. Its ok for reserved things to be
> > whatever they are. 
> 
> Then someone should simplify our DV encoder because it is full of stuff
> like
>                    0xc;       /* reserved -- always b1100 */
> If that is not necessary that is an extreme amount of bloat.

Well, sticking to the spec does add complexity. Which is, I suspect,
the reason quite a few hardware DV encoders don't give a rip about
some of these. Michael had a good summary of how the specs in general
are supposed to be implemented.

Thanks,
Roman.