[FFmpeg-devel] [PATCH v4] mpeg12enc: Use Closed Captions if available

[Michael Niedermayer]

On Thu, Feb 07, 2019 at 09:03:16PM +0100, Mathieu Duponchelle wrote:
> ---
>  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..a283b9fddf 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.
> +Default is 1 (on).
>  @end table
>  
>  @section png
> diff --git a/libavcodec/mpeg12enc.c b/libavcodec/mpeg12enc.c
> index d0b458e34b..15a3db9e6d 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

what if size is not a multiple of 3 ?

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

I am the wisest man alive, for I know one thing, and that is that I know
nothing. -- Socrates
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