[FFmpeg-devel] [PATCH] mpeg12enc: Use Closed Captions if available

[Carl Eugen Hoyos]

2019-02-07 20:16 GMT+01:00, Mathieu Duponchelle <mathieu at centricular.com>:
> ---
>  doc/encoders.texi      |  3 +++
>  libavcodec/mpeg12enc.c | 31 +++++++++++++++++++++++++++++++
>  libavcodec/mpegvideo.h |  2 ++
>  3 files changed, 36 insertions(+)
>
> diff --git a/doc/encoders.texi b/doc/encoders.texi
> index e86ae69cc5..378a2ca8eb 100644
> --- a/doc/encoders.texi
> +++ b/doc/encoders.texi
> @@ -2574,6 +2574,9 @@ Specifies the video_format written into the sequence
> display extension
>  indicating the source of the video pictures. The default is
> @samp{unspecified},
>  can be @samp{component}, @samp{pal}, @samp{ntsc}, @samp{secam} or
> @samp{mac}.
>  For maximum compatibility, use @samp{component}.
> + at item a53cc @var{boolean}
> +Import closed captions (which must be ATSC compatible format) into output.

> +Only the mpeg2 and h264 decoders provide these.

Sorry for the late comment:
This is not a helpful sentence imo, many features are not provided
by all parts of FFmpeg and it is (too) difficult to keep such lists up-to-date.
Which other decoder are you thinking about?

>  Default is 1 (on).

>  @end table
>
>  @section png
> diff --git a/libavcodec/mpeg12enc.c b/libavcodec/mpeg12enc.c
> index d0b458e34b..0e2ab6da47 100644
> --- a/libavcodec/mpeg12enc.c
> +++ b/libavcodec/mpeg12enc.c
> @@ -61,6 +61,8 @@ static uint32_t mpeg1_chr_dc_uni[512];
>  static uint8_t mpeg1_index_run[2][64];
>  static int8_t  mpeg1_max_level[2][64];
>
> +#define A53_MAX_CC_COUNT 0x1f
> +
>  static av_cold void init_uni_ac_vlc(RLTable *rl, uint8_t *uni_ac_vlc_len)
>  {
>      int i;
> @@ -544,6 +546,35 @@ void ff_mpeg1_encode_picture_header(MpegEncContext *s,
> int picture_number)
>          }
>      }
>
> +    if (s->codec_id == AV_CODEC_ID_MPEG2VIDEO && s->a53_cc) {
> +        side_data = av_frame_get_side_data(s->current_picture_ptr->f,
> +            AV_FRAME_DATA_A53_CC);
> +        if (side_data) {
> +            if (side_data->size <= A53_MAX_CC_COUNT) {
> +                int i = 0;
> +
> +                put_header (s, USER_START_CODE);
> +
> +                put_bits(&s->pb, 8, 'G');                   //
> user_identifier
> +                put_bits(&s->pb, 8, 'A');
> +                put_bits(&s->pb, 8, '9');
> +                put_bits(&s->pb, 8, '4');
> +                put_bits(&s->pb, 8, 3);                     //
> user_data_type_code
> +                put_bits(&s->pb, 8,

> +                    ((side_data->size / 3) & A53_MAX_CC_COUNT) | 0x40); //
> flags, cc_count

If you decide to send another version, please remove the
superfluous brackets.

Carl Eugen