[FFmpeg-devel] [PATCH] avcodec/hevcdec: set the SEI parameters early on the AVCodecContext

[James Almer]

On 5/24/2019 4:11 AM, Steve Lhomme wrote:
> It's better to do it before the buffers are actually created. At least in VLC
> we currently don't support changing some parameters dynamically easily so we
> don't use the information if it comes after the buffer are created.

Glad to know my solution worked :D

> 
> Co-authored-by: James Almer <jamrial at gmail.com>
> ---
> The same problem may exist with H264 alternative_transfer but I don't have a
> sample to test with and the code seems a bit different.

Should be a matter of moving the relevant chunk to h264_init_ps(), i think.

> ---
>  libavcodec/hevcdec.c | 18 +++++++++++-------
>  1 file changed, 11 insertions(+), 7 deletions(-)
> 
> diff --git a/libavcodec/hevcdec.c b/libavcodec/hevcdec.c
> index 515b346535..f54f46aa5d 100644
> --- a/libavcodec/hevcdec.c
> +++ b/libavcodec/hevcdec.c
> @@ -313,6 +313,7 @@ static int decode_lt_rps(HEVCContext *s, LongTermRPS *rps, GetBitContext *gb)
>  static void export_stream_params(AVCodecContext *avctx, const HEVCParamSets *ps,
>                                   const HEVCSPS *sps)
>  {
> +    const HEVCContext *s = avctx->priv_data;

Maybe instead change the export_stream_params() prototype to have the
callers directly pass HEVCContext *s and HEVSPS *sps, then declare
HEVCParamSets *ps = &s->ps here. Could also do HEVCSEI *sei = &s->sei,
so it's consistent.

>      const HEVCVPS *vps = (const HEVCVPS*)ps->vps_list[sps->vps_id]->data;
>      const HEVCWindow *ow = &sps->output_window;
>      unsigned int num = 0, den = 0;
> @@ -355,6 +356,16 @@ static void export_stream_params(AVCodecContext *avctx, const HEVCParamSets *ps,
>      if (num != 0 && den != 0)
>          av_reduce(&avctx->framerate.den, &avctx->framerate.num,
>                    num, den, 1 << 30);
> +
> +    if (s->sei.a53_caption.a53_caption) {

I don't think these are available at this point. It's a per frame SEI,
and this function is called before slice data is parsed.

Notice how a53_caption is freed as soon as it's exported as frame side
data in set_side_data().

> +        avctx->properties |= FF_CODEC_PROPERTY_CLOSED_CAPTIONS;
> +    }
> +
> +    if (s->sei.alternative_transfer.present &&
> +        av_color_transfer_name(s->sei.alternative_transfer.preferred_transfer_characteristics) &&
> +        s->sei.alternative_transfer.preferred_transfer_characteristics != AVCOL_TRC_UNSPECIFIED) {
> +        avctx->color_trc = s->sei.alternative_transfer.preferred_transfer_characteristics;
> +    }
>  }
>  
>  static enum AVPixelFormat get_format(HEVCContext *s, const HEVCSPS *sps)
> @@ -2775,13 +2786,6 @@ static int set_side_data(HEVCContext *s)
>              memcpy(sd->data, s->sei.a53_caption.a53_caption, s->sei.a53_caption.a53_caption_size);
>          av_freep(&s->sei.a53_caption.a53_caption);
>          s->sei.a53_caption.a53_caption_size = 0;
> -        s->avctx->properties |= FF_CODEC_PROPERTY_CLOSED_CAPTIONS;
> -    }
> -
> -    if (s->sei.alternative_transfer.present &&
> -        av_color_transfer_name(s->sei.alternative_transfer.preferred_transfer_characteristics) &&
> -        s->sei.alternative_transfer.preferred_transfer_characteristics != AVCOL_TRC_UNSPECIFIED) {
> -        s->avctx->color_trc = out->color_trc = s->sei.alternative_transfer.preferred_transfer_characteristics;
>      }
>  
>      return 0;
>