[FFmpeg-devel] [PATCH 2/2] avformat/mpegts: parse for AC-3 descriptor 6A

[Marton Balint]

On Fri, 14 Aug 2020, lance.lmwang at gmail.com wrote:

> From: Limin Wang <lance.lmwang at gmail.com>

I don't think this patch fits into libavformat. I am not a fan of dumping 
the descriptor data with AV_LOG_DEBUG, because libavformat is not a 
stream analyzer. Also I don't see much benefit of parsing the whole 
descriptor, when you are not doing anything with the parsed value.

Sorry, but I think we are better off if we not apply this.

Regards,
Marton


>
> Signed-off-by: Limin Wang <lance.lmwang at gmail.com>
> ---
> libavformat/mpegts.c | 53 ++++++++++++++++++++++++++++++++++++++++++++++------
> 1 file changed, 47 insertions(+), 6 deletions(-)
>
> diff --git a/libavformat/mpegts.c b/libavformat/mpegts.c
> index f71f18a5..72cc72a 100644
> --- a/libavformat/mpegts.c
> +++ b/libavformat/mpegts.c
> @@ -2075,16 +2075,57 @@ 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);
> -            if (component_type_flag) {
> -                int component_type = get8(pp, desc_end);
> -                int service_type_mask = 0x38;  // 0b00111000
> -                int service_type = ((component_type & service_type_mask) >> 3);
> +            AVDVBAC3Descriptor desc6a;
> +            uint8_t buf;
> +
> +            if (desc_end - *pp < 1)
> +                return AVERROR_INVALIDDATA;
> +
> +            buf = get8(pp, desc_end);
> +            desc6a.component_type_flag = (buf >> 7) & 0x1;
> +            desc6a.bsid_flag           = (buf >> 6) & 0x1;
> +            desc6a.mainid_flag         = (buf >> 5) & 0x1;
> +            desc6a.asvc_flag           = (buf >> 4) & 0x1;
> +
> +            av_log(ts ? ts->stream : fc, AV_LOG_DEBUG, "Stream[0x%x] AC-3(6a):", st->id);
> +            if (desc6a.component_type_flag) {
> +                int service_type;
> +                int number_of_channels;
> +                desc6a.component_type = get8(pp, desc_end);
> +                service_type = ((desc6a.component_type >> 3) & 0x7);
>                 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_log(ts ? ts->stream : fc, AV_LOG_DEBUG,
> +                           " disposition: 0x%x", st->disposition);
> +                }
> +                number_of_channels = desc6a.component_type & 0x7;
> +                av_log(ts ? ts->stream : fc, AV_LOG_DEBUG, " component_type: 0x%x number_of_channels: %u",
> +                        desc6a.component_type, number_of_channels);
> +            }
> +            if (desc6a.bsid_flag) {
> +                if (desc_end - *pp < 1) {
> +                    return AVERROR_INVALIDDATA;
> +                }
> +                desc6a.bsid = get8(pp, desc_end);
> +                av_log(ts ? ts->stream : fc, AV_LOG_DEBUG, " bsid: %u", desc6a.bsid);
> +            }
> +            if (desc6a.mainid_flag) {
> +                if (desc_end - *pp < 1) {
> +                    return AVERROR_INVALIDDATA;
> +                }
> +                desc6a.mainid = get8(pp, desc_end);
> +                av_log(ts ? ts->stream : fc, AV_LOG_DEBUG, " mainid: %u", desc6a.mainid);
> +            }
> +            if (desc6a.asvc_flag) {
> +                if (desc_end - *pp < 1) {
> +                    return AVERROR_INVALIDDATA;
>                 }
> +                desc6a.asvc = get8(pp, desc_end);
> +                av_log(ts ? ts->stream : fc, AV_LOG_DEBUG, " asvc: %u", desc6a.asvc);
>             }
> +            if (desc6a.component_type_flag || desc6a.bsid_flag ||
> +                desc6a.mainid_flag         || desc6a.asvc_flag)
> +                av_log(ts ? ts->stream : fc, AV_LOG_DEBUG, "\n");
>         }
>         break;
>     case 0x7a: /* enhanced_ac-3_descriptor */
> -- 
> 1.8.3.1
>
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