Re: [FFmpeg-devel] [PATCH 2/4] avcodec/hevc_parse: check the size of hvcC is at least 23

["Zhao Zhili" <quinkblack@foxmail.com>]

> -----Original Message-----
> From: ffmpeg-devel <ffmpeg-devel-bounces@ffmpeg.org> On Behalf Of Lance Wang
> Sent: 2023年6月13日 22:10
> To: FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org>
> Subject: Re: [FFmpeg-devel] [PATCH 2/4] avcodec/hevc_parse: check the size of hvcC is at least 23
> 
> On Tue, Jun 13, 2023 at 3:37 PM Zhao Zhili <quinkblack@foxmail.com> wrote:
> 
> > From: Zhao Zhili <zhilizhao@tencent.com>
> >
> > The code after the check skip 21 bytes and then read two bytes.
> >
> > Signed-off-by: Zhao Zhili <zhilizhao@tencent.com>
> > ---
> >  libavcodec/hevc_parse.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/libavcodec/hevc_parse.c b/libavcodec/hevc_parse.c
> > index 1f3beed183..7bc28fd081 100644
> > --- a/libavcodec/hevc_parse.c
> > +++ b/libavcodec/hevc_parse.c
> > @@ -88,8 +88,10 @@ int ff_hevc_decode_extradata(const uint8_t *data, int
> > size, HEVCParamSets *ps,
> >
> >      /* data[0] == 1 is configurationVersion from 14496-15.
> >       * data[0] == 0 is for backward compatibility predates the standard.
> > +     *
> > +     * Minimum number of bytes of hvcC with 0 numOfArrays is 23.
> >       */
> > -    if (size > 3 && ((data[0] == 1) || (data[0] == 0 && (data[1] ||
> > data[2] > 1)))) {
> > +    if (size >= 23 && ((data[0] == 1) || (data[0] == 0 && (data[1] ||
> > data[2] > 1)))) {
> >
> 
> I think it's better to move the size checking before 21 byte are skipped,
> or it'll go to the else logic which
> is different.

It's not avcC if size is less than 23, go to the else branch is the intended behavior.

> 
>          /* It seems the extradata is encoded as hvcC format. */
> >          int i, j, num_arrays, nal_len_size;
> >
> > --
> > 2.25.1
> >
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