[FFmpeg-devel] [PATCH] libx264: copy A53 closed captions from source

[DeHackEd]

On 09/26/2015 05:26 AM, Anshul wrote:
> 
> 
> On 09/26/2015 05:46 AM, DeHackEd wrote:
>> Assumes 'GA94' format (ATSC standard)
>>
>> Signed-off-by: DHE <git at dehacked.net>
>> ---
>>   doc/encoders.texi    |  5 +++++
>>   libavcodec/libx264.c | 37 +++++++++++++++++++++++++++++++++++++
>>   2 files changed, 42 insertions(+)
>>
>> diff --git a/doc/encoders.texi b/doc/encoders.texi
>> index 3550bcc..bb16dea 100644
>> --- a/doc/encoders.texi
>> +++ b/doc/encoders.texi
>> @@ -2069,6 +2069,11 @@ For example to specify libx264 encoding options with @command{ffmpeg}:
>>   ffmpeg -i foo.mpg -vcodec libx264 -x264opts keyint=123:min-keyint=20 -an out.mkv
>>   @end example
>>
>> + at item a53cc
>> +Import closed captions (which must be ATSC compatible format) into output.
>> +Only the mpeg2 and h264 decoders provide these. Default is 0 (off).
>> +
>> +
>>   @item x264-params (N.A.)
>>   Override the x264 configuration using a :-separated list of key=value
>>   parameters.
>> diff --git a/libavcodec/libx264.c b/libavcodec/libx264.c
>> index 58fcfb0..4227bcc 100644
>> --- a/libavcodec/libx264.c
>> +++ b/libavcodec/libx264.c
>> @@ -83,6 +83,7 @@ typedef struct X264Context {
>>       int avcintra_class;
>>       int motion_est;
>>       int forced_idr;
>> +    int a53_cc;
>>       char *x264_params;
>>   } X264Context;
>>
>> @@ -256,6 +257,7 @@ static int X264_frame(AVCodecContext *ctx, AVPacket *pkt, const AVFrame *frame,
>>       int nnal, i, ret;
>>       x264_picture_t pic_out = {0};
>>       int pict_type;
>> +    AVFrameSideData *side_data;
>>
>>       x264_picture_init( &x4->pic );
>>       x4->pic.img.i_csp   = x4->params.i_csp;
>> @@ -278,6 +280,40 @@ static int X264_frame(AVCodecContext *ctx, AVPacket *pkt, const AVFrame *frame,
>>                                               X264_TYPE_AUTO;
>>
>>           reconfig_encoder(ctx, frame);
>> +
>> +        if (x4->a53_cc) {
>> +            side_data = av_frame_get_side_data(frame, AV_FRAME_DATA_A53_CC);
>> +            if (side_data) {
>> +                x4->pic.extra_sei.num_payloads = 1;
>> +                x4->pic.extra_sei.payloads = av_mallocz(sizeof(x4->pic.extra_sei.payloads[0]));
>> +                x4->pic.extra_sei.sei_free = av_free;
>> +
>> +                x4->pic.extra_sei.payloads[0].payload_size = side_data->size + 11;
>> +                x4->pic.extra_sei.payloads[0].payload = av_mallocz(x4->pic.extra_sei.payloads[0].payload_size);
>> +                x4->pic.extra_sei.payloads[0].payload_type = 4;
>> +                memcpy(x4->pic.extra_sei.payloads[0].payload + 10, side_data->data, side_data->size);
>> +                x4->pic.extra_sei.payloads[0].payload[0] = 181;
>> +                x4->pic.extra_sei.payloads[0].payload[1] = 0;
>> +                x4->pic.extra_sei.payloads[0].payload[2] = 49;
>> +
>> +                /**
>> +                 * 'GA94' is standard in North America for ATSC, but hard coding
>> +                 * this style may not be the right thing to do -- other formats
>> +                 * do exist. This information is not available in the side_data
>> +                 * so we are going with this right now.
>> +                 */
> I think GA94 is correct for this situation, since in our x264 decoder we don't consider any other standard
> for extracting closed caption.
> 
> I don't know if we have any logic which differentiate between ATSC, ISDB or DVB we parse all transport stream
> in same manner. if someone know where we differentiate atsc and dvb in FFmpeg please point me there.
> 
> Note: This logic will also fail when x264 is muxed in formats like gxf where closed caption are kept in vbi instead
> of GA94.
> 
> Overall  LGTM.
> 
> I don't know how to apply encrypted mails using git, and when I save your email in Thunderbird, git am is unable to apply.
> if you can send the same patch as attachment or command to convert encrypted .eml file to normal patch I would test this
> too.

I think the easiest solution is to grab the patch from the github repo I use:
https://github.com/DeHackEd/FFmpeg/commit/16b4c7fc2311d672e99f.patch

I think my mail client wrapped some lines. Sorry, this is my first patch-by-email.

> 
> -Anshul
> 
> 
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