[FFmpeg-devel] [PATCH] fix issue434

[Michael Niedermayer]

On Mon, Apr 28, 2008 at 11:28:23PM +0100, M?ns Rullg?rd wrote:
> Michael Niedermayer <michaelni at gmx.at> writes:
> 
> > On Mon, Apr 21, 2008 at 02:04:08AM +0200, Michael Niedermayer wrote:
> >> On Mon, Apr 21, 2008 at 12:21:07AM +0100, M?ns Rullg?rd wrote:
> >> > Michael Niedermayer <michaelni at gmx.at> writes:
> >> > 
> >> > > Hi
> >> > >
> >> > > The patch below fixes issue434, i will commit it in 24h unless
> >> > > mans objects
> >> > >
> >> > > Index: libavformat/mpeg.c
> >> > > ===================================================================
> >> > > --- libavformat/mpeg.c	(revision 12867)
> >> > > +++ libavformat/mpeg.c	(working copy)
> >> > > @@ -341,12 +341,13 @@
> >> > >          if (flags & 0x01) { /* PES extension */
> >> > >              pes_ext = get_byte(s->pb);
> >> > >              header_len--;
> >> > > -            if (pes_ext & 0x40) { /* pack header - should be zero in PS */
> >> > > -                goto error_redo;
> >> > > -            }
> >> > >              /* Skip PES private data, program packet sequence counter and P-STD buffer */
> >> > >              skip = (pes_ext >> 4) & 0xb;
> >> > >              skip += skip & 0x9;
> >> > > +            if (pes_ext & 0x40 || skip > header_len){
> >> > > +                av_log(s, AV_LOG_WARNING, "pes_ext %X is invalid\n", pes_ext);
> >> > > +                pes_ext=skip=0;
> >> > > +            }
> >> > >              url_fskip(s->pb, skip);
> >> > >              header_len -= skip;
> >> > 
> >> > Workarounds for out-of-spec streams are only acceptable if explicitly
> >> > requested.  Does lavf have something equivalent to lavc's
> >> > AVCodecContext.strict_std_compliance?
> >> 
> >> No, also strict_std_compliance is a pure encoder side thing. Used for
> >> preventing users to shoot themselfs in their foot (encoding expermental
> >> codecs like snow, storing non jpeg YUV in jpeg, ...).
> >> 
> >> The variable with a matching purpose is error_resilience (bad name, yes ...)
> >> It does select between how much spec non compliance should be ignored and
> >> how much should be considered an error. Thus its a tradeoff between early
> >> detection of errors in damaged streams vs. supporting streams which dont
> >> conform to the specs.
> >> 
> >> We certainly could add such a variable to AVFormatContext as well.
> >
> > ping
> > What shall be done about this issue?
> > * This does not affect valid files
> > * It does print a big and nasty "blah is invalid"
> > * Its ffmpegs "policy" to support broken files by default
> >
> > I can add a error_resilience variable to AVFormatContext if you want, but
> > its default would be what has the highest chance to result in correct
> > playaback.
> 
> You may apply this if you give me the head of a vdr author on a silver
> plate first.  There is no excuse for knowingly creating invalid files.

No problem

             _||||||_
            / VDR DEV\
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          O|    |     |O
           |   /_     |
         ---\ -===-  /----
     ----    |   U  |      ----
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     ----   SILVER PLATE   ----
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[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Those who are too smart to engage in politics are punished by being
governed by those who are dumber. -- Plato 
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