[FFmpeg-devel] [PATCH 2/8] avformat/mpegts: decode and export ATSC AC-3 descriptor

[Marton Balint]

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

> From: Limin Wang <lance.lmwang at gmail.com>
>
> Signed-off-by: Limin Wang <lance.lmwang at gmail.com>
> ---
> libavformat/mpegts.c | 42 ++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 42 insertions(+)
>
> diff --git a/libavformat/mpegts.c b/libavformat/mpegts.c
> index 1ed7eaf..d450507 100644
> --- a/libavformat/mpegts.c
> +++ b/libavformat/mpegts.c
> @@ -1990,6 +1990,48 @@ int ff_parse_mpeg2_descriptor(AVFormatContext *fc, AVStream *st, int stream_type
>                 st->request_probe = 50;
>         }
>         break;
> +    case 0x81: /* ATSC AC-3 descriptor */
> +        {
> +            uint8_t buf;
> +            uint8_t sample_rate_code, bsid,bitrate_code,surround_mode, bsmod;
> +            uint8_t num_channels, full_svc, mainid, priority, asvcflags;
> +
> +            if (desc_len < 4)
> +                return AVERROR_INVALIDDATA;
> +
> +            buf = get8(pp, desc_end);
> +            sample_rate_code = (buf >> 5 ) & 0x07;
> +            bsid             =  buf        & 0x1F;
> +            av_dict_set_int(&st->metadata, "atsc.ac3_desc.sample_rate_code", sample_rate_code, 0);
> +            av_dict_set_int(&st->metadata, "atsc.ac3_desc.bsid", bsid, 0);

Same comments as for patch 1/8, do not use metadata for this, either 
define a new side data type for the descriptor data or a side data type 
for arbitrary descriptors...

Regards,
Marton

> +
> +            buf = get8(pp, desc_end);
> +            bitrate_code = (buf >> 2 ) & 0x1F;
> +            surround_mode = buf        & 0x03;
> +            av_dict_set_int(&st->metadata, "atsc.ac3_desc.bitrate_code", bitrate_code, 0);
> +            av_dict_set_int(&st->metadata, "atsc.ac3_desc.surround_mode", surround_mode, 0);
> +
> +            buf = get8(pp, desc_end);
> +            bsmod        = (buf >> 5) & 0x07;
> +            num_channels = (buf >> 1) & 0x0F;
> +            full_svc     = buf & 0x01;
> +            av_dict_set_int(&st->metadata, "atsc.ac3_desc.bsmod", bsmod, 0);
> +            av_dict_set_int(&st->metadata, "atsc.ac3_desc.num_channels", num_channels, 0);
> +            av_dict_set_int(&st->metadata, "atsc.ac3_desc.full_svc", full_svc, 0);
> +
> +            buf = get8(pp, desc_end);
> +            if (bsmod < 2) {
> +                mainid   = (buf >> 5) & 0x7;
> +                priority = (buf >> 3) & 0x3;
> +                av_dict_set_int(&st->metadata, "atsc.ac3_desc.mainid", mainid, 0);
> +                av_dict_set_int(&st->metadata, "atsc.ac3_desc.priority", priority, 0);
> +            } else {
> +                asvcflags = buf;
> +                av_dict_set_int(&st->metadata, "atsc.ac3_desc.asvc", asvcflags, 0);
> +            }
> +            /* other field in standard will be skipped  */
> +        }
> +        break;
>     case 0x52: /* stream identifier descriptor */
>         st->stream_identifier = 1 + get8(pp, desc_end);
>         break;
> -- 
> 1.8.3.1
>
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