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

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.

Co-authored-by: James Almer <jamrial@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.
---
 libavcodec/hevcdec.c | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

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@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;
>