[FFmpeg-devel] [PATCH 1/2] avformat/mpegtsenc: support DVB 6A descriptor for AC-3

[Marton Balint]

On Fri, 14 Aug 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>
> ---
> Sorry, fix for the patch order for fate test
>
> libavformat/mpegts.h    | 16 +++++++++++
> libavformat/mpegtsenc.c | 76 +++++++++++++++++++++++++++++++++++++++++++++++++

I think the ac3_parser dependency of the mpegts muxer should be added to 
configure.

> 2 files changed, 92 insertions(+)
>
> diff --git a/libavformat/mpegts.h b/libavformat/mpegts.h
> index fe10b38..951aa61 100644
> --- a/libavformat/mpegts.h
> +++ b/libavformat/mpegts.h
> @@ -175,6 +175,22 @@ typedef struct Mp4Descr {
>     SLConfigDescr sl;
> } Mp4Descr;
> 
> +/*
> + * ETSI 300 468 descriptor 0x6A(AC-3)
> + * Refer to: ETSI EN 300 468 V1.11.1 (2010-04) (SI in DVB systems)
> + */
> +typedef struct AVDVBAC3Descriptor {
> +    uint8_t  component_type_flag;
> +    uint8_t  bsid_flag;
> +    uint8_t  mainid_flag;
> +    uint8_t  asvc_flag;
> +    uint8_t  reserved_flags;
> +    uint8_t  component_type;
> +    uint8_t  bsid;
> +    uint8_t  mainid;
> +    uint8_t  asvc;
> +} AVDVBAC3Descriptor;

As others suggested, remove AV prefix.

> +
> /**
>  * Parse an MPEG-2 descriptor
>  * @param[in] fc                    Format context (used for logging only)
> diff --git a/libavformat/mpegtsenc.c b/libavformat/mpegtsenc.c
> index 718ddab..e9ac08d 100644
> --- a/libavformat/mpegtsenc.c
> +++ b/libavformat/mpegtsenc.c
> @@ -27,6 +27,7 @@
> #include "libavutil/mathematics.h"
> #include "libavutil/opt.h"
> 
> +#include "libavcodec/ac3_parser_internal.h"
> #include "libavcodec/internal.h"
> 
> #include "avformat.h"
> @@ -244,6 +245,8 @@ typedef struct MpegTSWriteStream {
>     /* For Opus */
>     int opus_queued_samples;
>     int opus_pending_trim_start;
> +
> +    AVDVBAC3Descriptor *desc6a;

Sorry, can you name the variable dvb_ac3_desc or something? This 6a still 
does not speak for itself...

> } MpegTSWriteStream;
> 
> static void mpegts_write_pat(AVFormatContext *s)
> @@ -486,9 +489,28 @@ static int mpegts_write_pmt(AVFormatContext *s, MpegTSService *service)
>         case AVMEDIA_TYPE_AUDIO:
>             if (ts->flags & MPEGTS_FLAG_SYSTEM_B) {
>                 if (codec_id == AV_CODEC_ID_AC3) {
> +                    AVDVBAC3Descriptor *desc6a = ts_st->desc6a;
> +
>                      *q++=0x6a; // AC3 descriptor see A038 DVB SI
> +                    if (desc6a) {
> +                        int len = 1 +
> +                                  !!(desc6a->component_type_flag) +
> +                                  !!(desc6a->bsid_flag) +
> +                                  !!(desc6a->mainid_flag) +
> +                                  !!(desc6a->asvc_flag);
> +
> +                        *q++ = len;
> +                        *q++ = desc6a->component_type_flag << 7 | desc6a->bsid_flag << 6 |
> +                               desc6a->mainid_flag         << 5 | desc6a->asvc_flag << 4;
> +
> +                        if (desc6a->component_type_flag) *q++ = desc6a->component_type;
> +                        if (desc6a->bsid_flag)           *q++ = desc6a->bsid;
> +                        if (desc6a->mainid_flag)         *q++ = desc6a->mainid;
> +                        if (desc6a->asvc_flag)           *q++ = desc6a->asvc;
> +                    } else {
>                     *q++=1; // 1 byte, all flags sets to 0
>                     *q++=0; // omit all fields...

I think these two lines are small enough to reindent in the same patch.

> +                    }
>                 } else if (codec_id == AV_CODEC_ID_EAC3) {
>                     *q++=0x7a; // EAC3 descriptor see A038 DVB SI
>                     *q++=1; // 1 byte, all flags sets to 0
> @@ -1843,6 +1865,59 @@ static int mpegts_write_packet_internal(AVFormatContext *s, AVPacket *pkt)
>              * need to count the samples of that too! */
>             av_log(s, AV_LOG_WARNING, "Got MPEG-TS formatted Opus data, unhandled");
>         }
> +    } else if (st->codecpar->codec_id == AV_CODEC_ID_AC3 && !ts_st->desc6a) {
> +        uint8_t number_of_channels_flag;
> +        uint8_t service_type_flag;
> +        uint8_t full_service_flag = 1;
> +        AC3HeaderInfo *hdr = NULL;
> +        AVDVBAC3Descriptor *desc6a;

push most of these initializers one level down

> +
> +        if (avpriv_ac3_parse_header(&hdr, pkt->data, pkt->size) >= 0) {

Aren't you leaking hdr in the return path and at the end of this block?

> +            desc6a = av_mallocz(sizeof(*desc6a));
> +            if (!desc6a)
> +                return AVERROR(ENOMEM);
> +
> +            service_type_flag = hdr->bitstream_mode;
> +            switch (hdr->channel_mode) {
> +                case AC3_CHMODE_DUALMONO:
> +                    number_of_channels_flag = 1;
> +                    break;
> +                case AC3_CHMODE_MONO:
> +                    number_of_channels_flag = 0;
> +                    break;
> +                case AC3_CHMODE_STEREO:
> +                    if (hdr->dolby_surround_mode == AC3_DSURMOD_ON)
> +                        number_of_channels_flag = 3;
> +                    else
> +                        number_of_channels_flag = 2;
> +                    break;
> +                case AC3_CHMODE_3F:
> +                case AC3_CHMODE_2F1R:
> +                case AC3_CHMODE_3F1R:
> +                case AC3_CHMODE_2F2R:
> +                case AC3_CHMODE_3F2R:
> +                    number_of_channels_flag = 4;
> +                    break;
> +                default: /* reserved */
> +                    number_of_channels_flag = 7;
> +                    break;
> +            }
> +
> +            if (service_type_flag  == 1 || service_type_flag == 4 ||
> +                (service_type_flag == 7 && !number_of_channels_flag))
> +                full_service_flag = 0;
> +
> +            desc6a->component_type_flag = 1;
> +            desc6a->component_type = (full_service_flag << 6)              |
> +                                     ((service_type_flag      & 0x7) << 3) |
> +                                     (number_of_channels_flag & 0x7);
> +            desc6a->bsid_flag   = 1;
> +            desc6a->bsid        = hdr->bitstream_id;
> +            desc6a->mainid_flag = 0;
> +            desc6a->asvc_flag   = 0;
> +
> +            ts_st->desc6a = desc6a;
> +        }
>     }
>
>     if (ts_st->payload_size && (ts_st->payload_size + size > ts->pes_payload_size ||
> @@ -1934,6 +2009,7 @@ static void mpegts_deinit(AVFormatContext *s)
>         AVStream *st = s->streams[i];
>         MpegTSWriteStream *ts_st = st->priv_data;
>         if (ts_st) {
> +            av_freep(&ts_st->desc6a);
>             av_freep(&ts_st->payload);
>             if (ts_st->amux) {
>                 avformat_free_context(ts_st->amux);
> --

Regards,
Marton