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

[Hendrik Leppkes]

On Thu, Jul 2, 2015 at 11:17 PM, Pavel Koshevoy <pkoshevoy at gmail.com> wrote:
> 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?
>

The way the value is read will always fill the variable with this
exact value, no matter what the endianness of the underlying memory
actually is.

- Hendrik