[FFmpeg-devel] [PATCH v1] avcodec/h264_parse: retry decoding SPS with complete NAL

[Jun Li]

On Mon, Aug 19, 2019 at 3:45 PM James Almer <jamrial at gmail.com> wrote:

> On 8/18/2019 10:41 PM, Jun Li wrote:
> > Fix #6591
> > The content has no rbsp_stop_one_bit for ending the SPS, that
> > causes the decoding SPS failure, results decoding frame failure as well.
> > The patch is just adding a retry with complete NALU.
> > ---
> >  libavcodec/h264_parse.c | 10 ++++++++--
> >  1 file changed, 8 insertions(+), 2 deletions(-)
> >
> > diff --git a/libavcodec/h264_parse.c b/libavcodec/h264_parse.c
> > index ac31f54e07..a2267a0610 100644
> > --- a/libavcodec/h264_parse.c
> > +++ b/libavcodec/h264_parse.c
> > @@ -376,8 +376,14 @@ static int decode_extradata_ps(const uint8_t *data,
> int size, H264ParamSets *ps,
> >          switch (nal->type) {
> >          case H264_NAL_SPS:
> >              ret = ff_h264_decode_seq_parameter_set(&nal->gb, logctx,
> ps, 0);
> > -            if (ret < 0)
> > -                goto fail;
> > +            if (ret < 0) {
> > +                GetBitContext tmp_gb = nal->gb;
> > +                av_log(logctx, AV_LOG_DEBUG,
> > +                   "SPS decoding failure (maybe missing
> rbsp_stop_one_bit), trying again with the complete NAL\n");
> > +                init_get_bits8(&tmp_gb, nal->raw_data + 1,
> nal->raw_size - 1);
> > +                if ((ret = ff_h264_decode_seq_parameter_set(&tmp_gb,
> logctx, ps, 0)) < 0)
> > +                    goto fail;
> > +            }
> >              break;
> >          case H264_NAL_PPS:
> >              ret = ff_h264_decode_picture_parameter_set(&nal->gb,
> logctx, ps,
>
> Copy instead the code from decode_nal_units() in h264dec.c, which checks
> first with the complete NAL, and then calls
> ff_h264_decode_seq_parameter_set() with the ignore_truncation parameter
> set to 1 as a last resort.
>

Hi James,
My first try was set the ignore_truncation to 1 but then found that
decode_nal_units is already handling this using a different approach.
So I just copied the code here, but without last try ignore_truncation=1.

Are you suggesting modifying the commit message or comment identifying the
code is copied from decide_nal_units, or extract them to one function and
reuse two places ?

-Jun


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