[FFmpeg-devel] [PATCH 1/8] avformat/mpegts: add dvb ac3 descriptor metadata

[Marton Balint]

On Wed, 22 Jul 2020, lance.lmwang at gmail.com wrote:

> From: Limin Wang <lance.lmwang at gmail.com>
>
> Below is one metadata information for the ts with dvb ac3 descriptor audio:
> ./ffmpeg -i ac3_desc.ts
>    ...
>    Stream #0:1[0x294]: Audio: ac3 ([6][0][0][0] / 0x0006), 48000 Hz, 5.1(side), fltp, 448 kb/s
>    Metadata:
>      dvb.ac3_desc.component_type: 68
>      dvb.ac3_desc.bsid: 6
>      dvb.ac3_desc.mainid: 0

I don't think it is a good idea to use metadata for this. See how dolby 
vision stores the descripor data, it is using side data and not metadata. 
Also it might make sense to create a generic mpegts descriptor side data 
type?

Regards.
Marton

>
> Signed-off-by: Limin Wang <lance.lmwang at gmail.com>
> ---
> libavformat/mpegts.c | 22 ++++++++++++++++++++--
> 1 file changed, 20 insertions(+), 2 deletions(-)
>
> diff --git a/libavformat/mpegts.c b/libavformat/mpegts.c
> index c6fd3e1..1ed7eaf 100644
> --- a/libavformat/mpegts.c
> +++ b/libavformat/mpegts.c
> @@ -2073,15 +2073,33 @@ int ff_parse_mpeg2_descriptor(AVFormatContext *fc, AVStream *st, int stream_type
>         break;
>     case 0x6a: /* ac-3_descriptor */
>         {
> -            int component_type_flag = get8(pp, desc_end) & (1 << 7);
> +            uint8_t flags = get8(pp, desc_end);
> +            uint8_t component_type_flag = flags & (1 << 7);
> +            uint8_t bsid_flag           = flags & (1 << 6);
> +            uint8_t mainid_flag         = flags & (1 << 5);
> +            uint8_t asvc_flag           = flags & (1 << 4);
> +
>             if (component_type_flag) {
> -                int component_type = get8(pp, desc_end);
> +                uint8_t component_type = get8(pp, desc_end);
>                 int service_type_mask = 0x38;  // 0b00111000
>                 int service_type = ((component_type & service_type_mask) >> 3);
>                 if (service_type == 0x02 /* 0b010 */) {
>                     st->disposition |= AV_DISPOSITION_DESCRIPTIONS;
>                     av_log(ts ? ts->stream : fc, AV_LOG_DEBUG, "New track disposition for id %u: %u\n", st->id, st->disposition);
>                 }
> +                av_dict_set_int(&st->metadata, "dvb.ac3_desc.component_type", component_type, 0);
> +            }
> +            if (bsid_flag) {
> +                uint8_t bsid = get8(pp, desc_end);
> +                av_dict_set_int(&st->metadata, "dvb.ac3_desc.bsid", bsid, 0);
> +            }
> +            if (mainid_flag) {
> +                uint8_t mainid = get8(pp, desc_end);
> +                av_dict_set_int(&st->metadata, "dvb.ac3_desc.mainid", mainid, 0);
> +            }
> +            if (asvc_flag) {
> +                uint8_t asvc = get8(pp, desc_end);
> +                av_dict_set_int(&st->metadata, "dvb.ac3_desc.asvc", asvc, 0);
>             }
>         }
>         break;
> -- 
> 1.8.3.1
>
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