[FFmpeg-devel] [PATCH V1] lavf/oggparsevorbis: Fix change the case of metadata keys issue

[Michael Niedermayer]

On Tue, Apr 16, 2019 at 09:33:08AM +0800, mypopy at gmail.com wrote:
> On Tue, Apr 16, 2019 at 5:51 AM Michael Niedermayer
> <michael at niedermayer.cc> wrote:
> >
> > On Mon, Apr 15, 2019 at 09:58:30AM +0800, Jun Zhao wrote:
> > > From: Jun Zhao <barryjzhao at tencent.com>
> > >
> > > The spec in https://xiph.org/vorbis/doc/v-comment.html states that
> > > the metadata keys are case-insensitive, so don't change the case
> > > and update the fate test case.
> > >
> > > Fix #7784
> > >
> > > Signed-off-by: Jun Zhao <barryjzhao at tencent.com>
> > > ---
> > >  libavformat/oggparsevorbis.c             |    9 ++++-----
> > >  tests/ref/fate/limited_input_seek        |    2 +-
> > >  tests/ref/fate/limited_input_seek-copyts |    2 +-
> > >  3 files changed, 6 insertions(+), 7 deletions(-)
> > >
> > > diff --git a/libavformat/oggparsevorbis.c b/libavformat/oggparsevorbis.c
> > > index bcfd246..c3c8d38 100644
> > > --- a/libavformat/oggparsevorbis.c
> > > +++ b/libavformat/oggparsevorbis.c
> > > @@ -44,7 +44,7 @@ static int ogm_chapter(AVFormatContext *as, uint8_t *key, uint8_t *val)
> > >      int i, cnum, h, m, s, ms, keylen = strlen(key);
> > >      AVChapter *chapter = NULL;
> > >
> > > -    if (keylen < 9 || sscanf(key, "CHAPTER%03d", &cnum) != 1)
> > > +    if (keylen < 9 || (av_strcasecmp(key, "CHAPTER")!=0 && sscanf(key+7, "%03d", &cnum) != 1))
> >
> > this looks a bit odd, shouldnt this use av_strncasecmp() ?
> >
> It's  in order to be compatible with the fate test case
> vorbis-1833-chapthers, in this test,
> we use lower case in test clip but check upper case in the code.

av_strcasecmp() will only succeed if the string ends after "CHAPTER" and
contains no number which is why av_strncasecmp() feels like more effective.
The problem is ultimatle that keylen is at this point >= 9 while
the only case where av_strcasecmp with "CHAPTER" == 0 is with a
keylen of 7. Thats tricky to achieve ;)

Or said differently this code is not a case insensitive version of the
previous 


[...]
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Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Why not whip the teacher when the pupil misbehaves? -- Diogenes of Sinope
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