[FFmpeg-devel] [PATCHv3] avcodec: Add support for Closed Caption export in h264

[Pavel Koshevoy]

On Thu, Jul 2, 2015 at 12:18 PM, Kieran Kunhya <kierank at ob-encoder.com>
wrote:

> ---
>  libavcodec/h264.c     | 11 +++++++++++
>  libavcodec/h264.h     |  2 ++
>  libavcodec/h264_sei.c | 35 ++++++++++++++++++++++++++++++++++-
>  3 files changed, 47 insertions(+), 1 deletion(-)
>
> diff --git a/libavcodec/h264.c b/libavcodec/h264.c
> index 1cbd4cb..1569ec8 100644
> --- a/libavcodec/h264.c
> +++ b/libavcodec/h264.c
> @@ -609,6 +609,8 @@ static int h264_init_context(AVCodecContext *avctx,
> H264Context *h)
>      h->prev_frame_num        = -1;
>      h->sei_fpa.frame_packing_arrangement_cancel_flag = -1;
>      h->has_afd               = 0;
> +    h->a53_caption_size      = 0;
> +    h->a53_caption           = NULL;
>
>      h->next_outputed_poc = INT_MIN;
>      for (i = 0; i < MAX_DELAYED_PIC_COUNT; i++)
> @@ -879,6 +881,15 @@ static void decode_postinit(H264Context *h, int
> setup_finished)
>          }
>      }
>
> +    if (h->a53_caption) {
> +        AVFrameSideData *sd =
> +            av_frame_new_side_data(cur->f, AV_FRAME_DATA_A53_CC,
> h->a53_caption_size);
> +        if (sd)
> +            memcpy(sd->data, h->a53_caption, h->a53_caption_size);
> +        av_freep(&h->a53_caption);
> +        h->a53_caption_size = 0;
> +    }
> +
>      cur->mmco_reset = h->mmco_reset;
>      h->mmco_reset = 0;
>
> diff --git a/libavcodec/h264.h b/libavcodec/h264.h
> index 7565e03..3aef49f 100644
> --- a/libavcodec/h264.h
> +++ b/libavcodec/h264.h
> @@ -784,6 +784,8 @@ typedef struct H264Context {
>      uint8_t afd;
>      int has_afd;
>
> +    int a53_caption_size;
> +    uint8_t *a53_caption;
>
>      // Timestamp stuff
>      int sei_buffering_period_present;   ///< Buffering period SEI flag
> diff --git a/libavcodec/h264_sei.c b/libavcodec/h264_sei.c
> index b6ec5c7..5c6fcc0 100644
> --- a/libavcodec/h264_sei.c
> +++ b/libavcodec/h264_sei.c
> @@ -111,7 +111,7 @@ static int decode_picture_timing(H264Context *h)
>  static int decode_user_data_itu_t_t35(H264Context *h, int size)
>  {
>      uint32_t user_identifier;
> -    int dtg_active_format;
> +    int dtg_active_format, cc_count, user_data_type_code;
>
>      if (size < 7)
>          return -1;
> @@ -143,6 +143,39 @@ FF_ENABLE_DEPRECATION_WARNINGS
>                  skip_bits(&h->gb, 6);
>              }
>              break;
> +        case 0x47413934: // "GA94" closed captions
>


Pardon my ignorance, but is this endian safe?  0x47413934 is "GA94" on
big-endian architectures, won't it be 0x34394147 on little-endian?




> +            if (size < 3)
> +                return AVERROR(EINVAL);
> +            user_data_type_code = get_bits(&h->gb, 8);
> +            if (user_data_type_code == 0x3) {
> +                skip_bits(&h->gb, 1);
> +                if (get_bits(&h->gb, 1)) {
> +                    skip_bits(&h->gb, 1);
> +                    cc_count = get_bits(&h->gb, 5);
> +                    skip_bits(&h->gb, 8);
> +                    size -= 2;
> +                    if (cc_count && size >= cc_count*3) {
> +                        int i;
> +                        uint8_t *tmp;
> +                        if ((int64_t)h->a53_caption_size +
> (int64_t)cc_count*3 > INT_MAX)
> +                            return AVERROR(EINVAL);
> +
> +                        // Allow merging of the cc data from two fields
> +                        tmp = av_realloc(h->a53_caption,
> h->a53_caption_size + cc_count*3);
> +                        if (!tmp)
> +                            return AVERROR(ENOMEM);
> +                        h->a53_caption = tmp;
> +                        for (i = 0; i < cc_count; i++) {
> +                            h->a53_caption[h->a53_caption_size++] =
> get_bits(&h->gb, 8);
> +                            h->a53_caption[h->a53_caption_size++] =
> get_bits(&h->gb, 8);
> +                            h->a53_caption[h->a53_caption_size++] =
> get_bits(&h->gb, 8);
> +                        }
> +
> +                        skip_bits(&h->gb, 8);
> +                    }
> +                }
> +            }
> +            break;
>          default:
>              skip_bits(&h->gb, size * 8);
>              break;
> --
> 1.9.1
>
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