[vdr] Re: Nasty bug in StillPicture()

[Klaus Schmidinger <Klaus.Schmidinger@cadsoft.de>]

Oliver Endriss wrote:
> 
> On Saturday 18 October 2003 17:48, Thomas Heiligenmann wrote:
> > Oliver Endriss schrieb:
> > > On Saturday 18 October 2003 14:57, Thomas Heiligenmann wrote:
> > >
> > >>Oops - just seen it. Here comes the updated patch :-)
> > >
> > >
> > > I suggest to stop scanning immediately if we encounter an error.
> > > For example (MPEG-2 case):
> > >
> > >               if ((Data[i + 6] & 0xC0) == 0x80) {
> > >                  // MPEG-2 PES header
> > >                  if (i + 8 >= Length)
> > >                     break;
> > >                  offs += 3;
> > >                  offs += Data[i + 8];
> > >                  len -= 3;
> > >                  len -= Data[i + 8];
> > >                  if (len < 0 || offs + len >= Length)
> > >                     break;
> > >                  }
> > >               else {
> > >                  // MPEG-1 PES header
> > >                  ...
> >
> > Wouldn't it be better then to "return" immediately? After "break"-ing
> > the "while" loop a part of the (erratic) stream would be sent to the
> > driver anyway.
> >
> > if (len < 0 || offs + len >= Length) {
> >    free(buf);
> >    return;
> >    }
> > ...
> 
> IIRC, these extensions are only included in the first PES header of a
> picture. If we use 'return' we enforce that data must be passed
> correctly. We don't accept garbled data in the buffer. (If the first
> extension header is garbled there is no difference.)
> 
> If we use 'break' we are a little bit more liberal in what we accept.
> Maybe the decoder can do something useful with the data processed so far.
> IMHO, displaying a partial picture might be better that doing nothing.
> 
> Oliver

Since I don't have too much time to test this stuff today, can you
folks please agree on a patch against VDR 1.2.6pre1 that I can apply
for a 1.2.6pre2 to be uploaded today?

Klaus


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