[FFmpeg-devel] [PATCH]Improce auto-detection for cdata files

[Reimar Döffinger]

On Wed, Dec 30, 2009 at 11:29:09PM +0000, M?ns Rullg?rd wrote:
> Reimar D?ffinger <Reimar.Doeffinger at gmx.de> writes:
> 
> > On Wed, Dec 30, 2009 at 08:54:15PM +0100, Carl Eugen Hoyos wrote:
> >> Hi!
> >> 
> >> Attached patch improves cdata auto-detection (and "fixes" issue 1634 by 
> >> not trying to decode the sample any more).
> >> Details from 
> >> http://wiki.multimedia.cx/index.php?title=EA_Command_And_Conquer_3_Audio_Codec
> >> 
> >> The new detection passes probetest, and I would like to raise the score to 
> >> 26, is that ok?
> >> 
> >> Please comment, Carl Eugen
> >
> >> Index: libavformat/eacdata.c
> >> ===================================================================
> >> --- libavformat/eacdata.c	(revision 20959)
> >> +++ libavformat/eacdata.c	(working copy)
> >> @@ -39,7 +39,8 @@
> >>  {
> >>      const uint8_t *b = p->buf;
> >>  
> >> -    if (b[0] == 0x04 && (b[1] == 0x00 || b[1] == 0x04 || b[1] == 0x0C))
> >> +    if (b[0] == 0x04 && (b[1] == 0x00 || b[1] == 0x04 || b[1] == 0x0C) &&
> >> +        ((uint32_t *)b)[1] == ((uint32_t *)b)[3] && ((uint32_t *)b)[1])
> >>          return AVPROBE_SCORE_MAX/8;
> >
> > You should check for a valid sample_rate (since that is essential for
> > decoding), and the new checks for "total samples" should only be used to
> > raise the score above AVPROBE_SCORE_MAX/4 (since those are non-essential
> > they should not be "required" by the probe if possible).
> > Also since speed does not matter, I think
> > AV_RB32(b + 4) == AV_RB32(b + 12)
> > etc. is more readable than the casts.
> 
> Those casts WILL CRASH on some hardware if the data is unaligned.  Use
> AV_RN32().

Yes, but I don't think we have to assume that the probe buffer might be
aligned by less that 4 bytes, so that's not a concern here.