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

[Petter Ericson]

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.

/P

-- 
Petter Ericson
Systems developer, Codemill AB
petter.ericson at codemill.se

-------------- next part --------------
A non-text attachment was scrubbed...
Name: 0001-mov.c.patch
Type: text/x-diff
Size: 3952 bytes
Desc: not available
URL: <http://ffmpeg.org/pipermail/ffmpeg-devel/attachments/20121019/db2ea7c3/attachment.bin>