[FFmpeg-devel] [PATCH v2] avformat/mpegtsenc: support DVB 6A descriptor for AC-3

lance.lmwang at gmail.com lance.lmwang at gmail.com
Sun Aug 16 03:07:50 EEST 2020


On Sat, Aug 15, 2020 at 11:38:29PM +0800, Guangxin Xu wrote:
> On Sat, Aug 15, 2020 at 10:28 PM <lance.lmwang at gmail.com> wrote:
> 
> > From: Limin Wang <lance.lmwang at gmail.com>
> >
> > Signed-off-by: Limin Wang <lance.lmwang at gmail.com>
> > ---
> >  configure               |  2 +-
> >  libavformat/mpegts.h    | 16 ++++++++++
> >  libavformat/mpegtsenc.c | 84
> > +++++++++++++++++++++++++++++++++++++++++++++++--
> >  3 files changed, 99 insertions(+), 3 deletions(-)
> >
> > diff --git a/configure b/configure
> > index d4a1fea..a9d87b2 100755
> > --- a/configure
> > +++ b/configure
> > @@ -3324,7 +3324,7 @@ mp3_demuxer_select="mpegaudio_parser"
> >  mp3_muxer_select="mpegaudioheader"
> >  mp4_muxer_select="mov_muxer"
> >  mpegts_demuxer_select="iso_media"
> > -mpegts_muxer_select="adts_muxer latm_muxer h264_mp4toannexb_bsf
> > hevc_mp4toannexb_bsf"
> > +mpegts_muxer_select="ac3_parser adts_muxer latm_muxer
> > h264_mp4toannexb_bsf hevc_mp4toannexb_bsf"
> >  mpegtsraw_demuxer_select="mpegts_demuxer"
> >  mxf_muxer_select="golomb pcm_rechunk_bsf"
> >  mxf_d10_muxer_select="mxf_muxer"
> > diff --git a/libavformat/mpegts.h b/libavformat/mpegts.h
> > index fe10b38..d70b25d 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 DVBAC3Descriptor {
> > +    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;
> > +} DVBAC3Descriptor;
> > +
> >  /**
> >   * 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..876ba99 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;
> > +
> > +    DVBAC3Descriptor *dvb_ac3_desc;
> >  } 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) {
> > +                    DVBAC3Descriptor *dvb_ac3_desc = ts_st->dvb_ac3_desc;
> >
> need check   ts_st->dvb_ac3_desc?

Yes, the folloing code will check dvb_ac3_desc, if it's NULL, use the old default.

> 
> 
> +
> >                      *q++=0x6a; // AC3 descriptor see A038 DVB SI
> > -                    *q++=1; // 1 byte, all flags sets to 0
> > -                    *q++=0; // omit all fields...
> > +                    if (dvb_ac3_desc) {
> > +                        int len = 1 +
> > +                                  !!(dvb_ac3_desc->component_type_flag) +
> > +                                  !!(dvb_ac3_desc->bsid_flag) +
> > +                                  !!(dvb_ac3_desc->mainid_flag) +
> > +                                  !!(dvb_ac3_desc->asvc_flag);
> > +
> > +                        *q++ = len;
> > +                        *q++ = dvb_ac3_desc->component_type_flag << 7 |
> > dvb_ac3_desc->bsid_flag << 6 |
> > +                               dvb_ac3_desc->mainid_flag         << 5 |
> > dvb_ac3_desc->asvc_flag << 4;
> > +
> > +                        if (dvb_ac3_desc->component_type_flag) *q++ =
> > dvb_ac3_desc->component_type;
> > +                        if (dvb_ac3_desc->bsid_flag)           *q++ =
> > dvb_ac3_desc->bsid;
> > +                        if (dvb_ac3_desc->mainid_flag)         *q++ =
> > dvb_ac3_desc->mainid;
> > +                        if (dvb_ac3_desc->asvc_flag)           *q++ =
> > dvb_ac3_desc->asvc;
> > +                    } else {
> > +                        *q++=1; // 1 byte, all flags sets to 0
> > +                        *q++=0; // omit all fields...
> > +                    }
> >                  } 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 +1865,63 @@ 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->dvb_ac3_desc) {
> > +         AC3HeaderInfo *hdr = NULL;
> > +
> > +        if (avpriv_ac3_parse_header(&hdr, pkt->data, pkt->size) >= 0) {
> > +            uint8_t number_of_channels_flag;
> > +            uint8_t service_type_flag;
> > +            uint8_t full_service_flag = 1;
> > +            DVBAC3Descriptor *dvb_ac3_desc;
> > +
> > +            dvb_ac3_desc = av_mallocz(sizeof(*dvb_ac3_desc));
> > +            if (!dvb_ac3_desc) {
> > +                av_free(hdr);
> > +                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;
> > +
> > +            dvb_ac3_desc->component_type_flag = 1;
> > +            dvb_ac3_desc->component_type = (full_service_flag << 6)
> >   |
> > +                                     ((service_type_flag      & 0x7) <<
> > 3) |
> > +                                     (number_of_channels_flag & 0x7);
> > +            dvb_ac3_desc->bsid_flag   = 1;
> > +            dvb_ac3_desc->bsid        = hdr->bitstream_id;
> > +            dvb_ac3_desc->mainid_flag = 0;
> > +            dvb_ac3_desc->asvc_flag   = 0;
> > +
> > +            ts_st->dvb_ac3_desc = dvb_ac3_desc;
> > +        }
> > +        av_free(hdr);
> >      }
> >
> >      if (ts_st->payload_size && (ts_st->payload_size + size >
> > ts->pes_payload_size ||
> > @@ -1934,6 +2013,7 @@ static void mpegts_deinit(AVFormatContext *s)
> >          AVStream *st = s->streams[i];
> >          MpegTSWriteStream *ts_st = st->priv_data;
> >          if (ts_st) {
> > +            av_freep(&ts_st->dvb_ac3_desc);
> >              av_freep(&ts_st->payload);
> >              if (ts_st->amux) {
> >                  avformat_free_context(ts_st->amux);
> > --
> > 1.8.3.1
> >
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> >
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-- 
Thanks,
Limin Wang


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