[FFmpeg-devel] [HACK] mov.c: Handle MPEG-in-MOV (#241 and friends)

[Michael Niedermayer]

On Fri, Oct 19, 2012 at 11:23:53AM +0200, Petter Ericson wrote:
> On Fri, Oct 19, 2012 at 10:32:26AM +0200, Tomas Härdin wrote:
> > > From d5c1223d03dd8147d04b53a59ef655e9d87af129 Mon Sep 17 00:00:00 2001
> > > From: Petter Ericson <petter.ericson at codemill.se>
> > > Date: Wed, 17 Oct 2012 16:53:19 +0200
> > > Subject: [PATCH] mov.c:     Check for stsd + m1s tag indicating MOV-wrapped
> > >  MPEG-PS, and force     continued probing if found.
> > > 
> > > ---
> > >  libavformat/mov.c |   45 +++++++++++++++++++++++++++++++++++++--------
> > >  1 file changed, 37 insertions(+), 8 deletions(-)
> > > 
> > > diff --git a/libavformat/mov.c b/libavformat/mov.c
> > > index b817bc9..8899227 100644
> > > --- a/libavformat/mov.c
> > > +++ b/libavformat/mov.c
> > > @@ -2861,43 +2861,72 @@ static int mov_probe(AVProbeData *p)
> > >      unsigned int offset;
> > >      uint32_t tag;
> > >      int score = 0;
> > > +    int moov_offset = -1;
> > >  
> > >      /* check file header */
> > >      offset = 0;
> > >      for (;;) {
> > >          /* ignore invalid offset */
> > >          if ((offset + 8) > (unsigned int)p->buf_size)
> > > -            return score;
> > > +            break;
> > >          tag = AV_RL32(p->buf + offset + 4);
> > >          switch(tag) {
> > >          /* check for obvious tags */
> > > -        case MKTAG('j','P',' ',' '): /* jpeg 2000 signature */
> > >          case MKTAG('m','o','o','v'):
> > > +            moov_offset = offset + 4;
> > > +        case MKTAG('j','P',' ',' '): /* jpeg 2000 signature */
> > >          case MKTAG('m','d','a','t'):
> > >          case MKTAG('p','n','o','t'): /* detect movs with preview pics like ew.mov and april.mov */
> > >          case MKTAG('u','d','t','a'): /* Packet Video PVAuthor adds this and a lot of more junk */
> > >          case MKTAG('f','t','y','p'):
> > > -            return AVPROBE_SCORE_MAX;
> > > +            score  = FFMAX(score, AVPROBE_SCORE_MAX);
> > 
> > score = AVPROBE_SCORE_MAX; is enough
> > 
> > > +            offset = FFMAX(1, (unsigned int)AV_RB32(p->buf+offset)) + offset;
> > 
> > You could/should change the 1 to a 4
> > AV_RB32() is unsigned, so the cast is useless.
> > 
> > > +            break;
> > >          /* those are more common words, so rate then a bit less */
> > >          case MKTAG('e','d','i','w'): /* xdcam files have reverted first tags */
> > >          case MKTAG('w','i','d','e'):
> > >          case MKTAG('f','r','e','e'):
> > >          case MKTAG('j','u','n','k'):
> > >          case MKTAG('p','i','c','t'):
> > > -            return AVPROBE_SCORE_MAX - 5;
> > > +            score  = FFMAX(score, AVPROBE_SCORE_MAX - 5);
> > > +            offset = FFMAX(1, AV_RB32(p->buf+offset)) + offset;
> > 
> > 1 -> 4
> > 
> > > +            break;
> > >          case MKTAG(0x82,0x82,0x7f,0x7d):
> > >          case MKTAG('s','k','i','p'):
> > >          case MKTAG('u','u','i','d'):
> > >          case MKTAG('p','r','f','l'):
> > > -            offset = AV_RB32(p->buf+offset) + offset;
> > >              /* if we only find those cause probedata is too small at least rate them */
> > > -            score = AVPROBE_SCORE_MAX - 50;
> > > +            score  = FFMAX(score, AVPROBE_SCORE_MAX - 50);
> > > +            offset = FFMAX(1, AV_RB32(p->buf+offset)) + offset;
> > 
> > 1 -> 4
> > 
> > >              break;
> > >          default:
> > > -            /* unrecognized tag */
> > > -            return score;
> > > +            offset = FFMAX(1, AV_RB32(p->buf+offset)) + offset;
> > 
> > 1 -> 4
> > 
> > > +        }
> > > +    }
> > > +    if(tag > AVPROBE_SCORE_MAX - 50 && moov_offset != -1){
> > 
> > nit: if (...) {
> > 
> > > +        /* moov atom in the header - we should make sure that this is not a
> > > +         * MOV-packed MPEG-PS */
> > > +        offset = moov_offset;
> > > +        
> > > +        while(offset < (p->buf_size - 20)){ /* Sufficient space */
> > > +               /* We found an actual stsd atom */
> > > +            if(AV_RL32(p->buf+offset)       == MKTAG('s','t','s','d') &&
> > > +               /* Make sure there's only one stream */
> > > +               AV_RB32(p->buf + offset + 8)  == 1 &&
> > > +               AV_RL32(p->buf + offset + 16) == MKTAG('m','1','s',' ')
> > > +               ){
> > > +                av_log(NULL, AV_LOG_WARNING, "Found m1s tag indicating this is a MOV-packed MPEG-PS.\n");
> > > +                /* We found an stsd atom describing an MPEG-PS-in-MOV, return a
> > > +                 * low score to force expanding the probe window until
> > > +                 * mpegps_probe finds what it needs */
> > > +                return 5;
> > > +            }else
> > > +                /* Keep looking */
> > > +                offset++;
> > 
> > IIRC MOV mandates two-byte alignment. offset += 2; would speed this up.
> > 
> > Looks reasonable, apart from formatting nitpickery.
> > 
> 
> Fixed formatting issues as indicated.

applied

thanks

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Breaking DRM is a little like attempting to break through a door even
though the window is wide open and the only thing in the house is a bunch
of things you dont want and which you would get tomorrow for free anyway
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