[FFmpeg-devel] [PATCH v2 1/2] avcodec/mpeg12dec: parse A53 caption data embedded in SCTE-20 user data

[Aman Gupta]

On Wed, Mar 15, 2017 at 2:06 PM, Michael Niedermayer <michael at niedermayer.cc
> wrote:

> On Wed, Mar 15, 2017 at 12:53:03PM -0700, Aman Gupta wrote:
> > From: Aman Gupta <aman at tmm1.net>
> >
> > includes a fate test, which requires
> > https://s3.amazonaws.com/tmm1/ccaptions/scte20.ts
> > to be uploaded as sub/scte20.ts
>
> uploaded
>
>
>
> > ---
> >  libavcodec/mpeg12dec.c       | 39 ++++++++++++++++++++++++++++++
> +++++++++
> >  tests/fate/subtitles.mak     |  3 +++
> >  tests/ref/fate/sub-cc-scte20 | 15 +++++++++++++++
> >  3 files changed, 57 insertions(+)
> >  create mode 100644 tests/ref/fate/sub-cc-scte20
> >
> > diff --git a/libavcodec/mpeg12dec.c b/libavcodec/mpeg12dec.c
> > index e49167f..cea8963 100644
> > --- a/libavcodec/mpeg12dec.c
> > +++ b/libavcodec/mpeg12dec.c
> > @@ -2260,6 +2260,45 @@ static int mpeg_decode_a53_cc(AVCodecContext
> *avctx,
> >              avctx->properties |= FF_CODEC_PROPERTY_CLOSED_CAPTIONS;
> >          }
> >          return 1;
> > +    } else if (buf_size >= 2 &&
> > +               p[0] == 0x03 && (p[1]&0x7f) == 0x01) {
> > +        /* extract SCTE-20 CC data */
> > +        GetBitContext gb;
> > +        int cc_count = 0;
> > +        int i;
> > +
> > +        init_get_bits(&gb, p + 2, buf_size - 2);
> > +        cc_count = get_bits(&gb, 5);
> > +        if (cc_count > 0) {
>
> remainig bits or buf_size should be checked to be large enough for
> cc_count
>

Good catch. Changing to buf_size>=3 in the outer conditional should be
sufficient, right?


>
> [...]
> --
> Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
>
> Complexity theory is the science of finding the exact solution to an
> approximation. Benchmarking OTOH is finding an approximation of the exact
>
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