[FFmpeg-devel] [PATCH 1/4] avformat/movenc: add support for writing Mastering Display Metadata Box

[James Almer]

On 5/26/2017 7:48 PM, Michael Niedermayer wrote:
> On Wed, May 17, 2017 at 09:49:38PM -0300, James Almer wrote:
>> As defined in "VP Codec ISO Media File Format Binding v1.0"
>> https://github.com/webmproject/vp9-dash/blob/master/VPCodecISOMediaFileFormatBinding.md
>>
>> Signed-off-by: James Almer <jamrial at gmail.com>
>> ---
>>  libavformat/movenc.c | 37 +++++++++++++++++++++++++++++++++++++
>>  1 file changed, 37 insertions(+)
>>
>> diff --git a/libavformat/movenc.c b/libavformat/movenc.c
>> index a6c0662cd0..cd436df7a4 100644
>> --- a/libavformat/movenc.c
>> +++ b/libavformat/movenc.c
>> @@ -42,6 +42,7 @@
>>  #include "libavutil/avstring.h"
>>  #include "libavutil/intfloat.h"
>>  #include "libavutil/mathematics.h"
>> +#include "libavutil/mastering_display_metadata.h"
>>  #include "libavutil/libm.h"
>>  #include "libavutil/opt.h"
>>  #include "libavutil/dict.h"
>> @@ -1118,6 +1119,41 @@ static int mov_write_vpcc_tag(AVFormatContext *s, AVIOContext *pb, MOVTrack *tra
>>      return update_size(pb, pos);
>>  }
>>  
>> +static int mov_write_smdm_tag(AVFormatContext *s, AVIOContext *pb, MOVTrack *track)
>> +{
>> +    int size = 0;
>> +    int64_t pos;
>> +    const AVMasteringDisplayMetadata *mastering =
>> +        (const AVMasteringDisplayMetadata *) av_stream_get_side_data(track->st,
>> +                                                 AV_PKT_DATA_MASTERING_DISPLAY_METADATA,
>> +                                                 &size);
>> +    if (!size)
>> +        return 0;
>> +
>> +    if (!mastering->has_primaries || !mastering->has_luminance) {
>> +        av_log(s, AV_LOG_WARNING, "Incomplete Mastering Display metadata. Both luminance "
>> +                                  "and display primaries are needed\n");
>> +        return 0;
>> +    }
>> +
>> +    pos = avio_tell(pb);
>> +
>> +    avio_wb32(pb, 0);
>> +    ffio_wfourcc(pb, "SmDm");
>> +    avio_wb32(pb, 0); /* version & flags */
> 
>> +    avio_wb16(pb, lrint(av_q2d(mastering->display_primaries[0][0]) * (1 << 16)));
>> +    avio_wb16(pb, lrint(av_q2d(mastering->display_primaries[0][1]) * (1 << 16)));
>> +    avio_wb16(pb, lrint(av_q2d(mastering->display_primaries[1][0]) * (1 << 16)));
>> +    avio_wb16(pb, lrint(av_q2d(mastering->display_primaries[1][1]) * (1 << 16)));
>> +    avio_wb16(pb, lrint(av_q2d(mastering->display_primaries[2][0]) * (1 << 16)));
>> +    avio_wb16(pb, lrint(av_q2d(mastering->display_primaries[2][1]) * (1 << 16)));
>> +    avio_wb16(pb, lrint(av_q2d(mastering->white_point[0])          * (1 << 16)));
>> +    avio_wb16(pb, lrint(av_q2d(mastering->white_point[1])          * (1 << 16)));
>> +    avio_wb32(pb, lrint(av_q2d(mastering->max_luminance)           * (1 <<  8)));
>> +    avio_wb32(pb, lrint(av_q2d(mastering->min_luminance)           * (1 << 14)));
> 
> These may need range checks.
> Our API doesnt seem to define limits, so they might fall outside the
> 16/32 bit range used to store them, unless i miss something

I guess. How do you suggest to check this? Range checking the
AVRationals with av_cmp_q()?

This could have been avoided if mastering metadata fields were
implemented as integer values, like content light does.