[FFmpeg-devel] [PATCH] lavf/aiffdec: handle files with ID3 data larger than ID3 chunk size

Matthieu Bouron matthieu.bouron at gmail.com
Wed Jan 16 12:01:38 CET 2013


On Wed, Jan 16, 2013 at 10:37:03AM +0000, Paul B Mahol wrote:
> On 1/16/13, Matthieu Bouron <matthieu.bouron at gmail.com> wrote:
> > On Wed, Jan 16, 2013 at 02:37:19AM +0100, Michael Niedermayer wrote:
> >> On Wed, Jan 16, 2013 at 01:18:09AM +0100, Matthieu Bouron wrote:
> >> > On Wed, Jan 16, 2013 at 12:34:31AM +0100, Michael Niedermayer wrote:
> >> > > On Tue, Jan 15, 2013 at 10:49:01PM +0100, Matthieu Bouron wrote:
> >> > > > ---
> >> > > >  libavformat/aiffdec.c | 7 +++++++
> >> > > >  1 file changed, 7 insertions(+)
> >> > > >
> >> > > > diff --git a/libavformat/aiffdec.c b/libavformat/aiffdec.c
> >> > > > index 8d466fa..b6a7946 100644
> >> > > > --- a/libavformat/aiffdec.c
> >> > > > +++ b/libavformat/aiffdec.c
> >> > > > @@ -193,6 +193,7 @@ static int aiff_read_header(AVFormatContext *s)
> >> > > >  {
> >> > > >      int ret, size, filesize;
> >> > > >      int64_t offset = 0;
> >> > > > +    int64_t tag_size, tag_offset;
> >> > > >      uint32_t tag;
> >> > > >      unsigned version = AIFF_C_VERSION1;
> >> > > >      AVIOContext *pb = s->pb;
> >> > > > @@ -236,6 +237,7 @@ static int aiff_read_header(AVFormatContext *s)
> >> > > >                  goto got_sound;
> >> > > >              break;
> >> > > >          case MKTAG('I', 'D', '3', ' '):
> >> > > > +            tag_offset = avio_tell(pb);
> >> > > >              ff_id3v2_read(s, ID3v2_DEFAULT_MAGIC,
> >> > > > &id3v2_extra_meta);
> >> > > >              if (id3v2_extra_meta)
> >> > > >                  if ((ret = ff_id3v2_parse_apic(s,
> >> > > > &id3v2_extra_meta)) < 0) {
> >> > > > @@ -243,6 +245,11 @@ static int aiff_read_header(AVFormatContext
> >> > > > *s)
> >> > > >                      return ret;
> >> > > >                  }
> >> > > >              ff_id3v2_free_extra_meta(&id3v2_extra_meta);
> >> > > > +            tag_size = avio_tell(pb) - tag_offset;
> >> > > > +            if (tag_size > size) {
> >> > > > +                av_log(s, AV_LOG_WARNING, "ID3 data is larger than
> >> > > > ID3 chunk size\n");
> >> > > > +                avio_seek(pb, tag_size - size, SEEK_SET);
> >> > > > +            }
> >> > >
> >> > > to which point do you try to seek here ?
> >> > > this looks like you try to do a absolute seek with a relative value
> >> > >
> >> >
> >> > Sorry for the messy patch :(, I didn't intend to seek anywhere but
> >> > just to decrease the filesize variable according to the difference
> >> > between tag_size and size.
> >> > New patch attached.
> >>
> >> so when the sizes mismatch a correct tag is at position after the
> >> larger size ?
> >
> > No, the samples i have have the ID3 chunk at the end of the file and the
> > ID3
> > data is larger than the declared ID3 chunk size by one byte.
> 
> aligned to 2 byte boundary?

It seems to be. For example:
ID3 data offset = 80988992
ID3 data size = 151960
Declared ID3 chunk size = 151959
File offset after reading the ID3 data: 81140952 (which corresponds to the
filesize)


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