[FFmpeg-devel] [PATCH 3/4] avformat/mov: add support for reading Mastering Display Metadata Box

[James Almer]

On 5/26/2017 8:05 PM, Michael Niedermayer wrote:
> On Wed, May 17, 2017 at 09:49:40PM -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
>>
>> Partially based on Matroska decoder code.
>>
>> Signed-off-by: James Almer <jamrial at gmail.com>
>> ---
>>  libavformat/isom.h |  2 ++
>>  libavformat/mov.c  | 65 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
>>  2 files changed, 67 insertions(+)
>>
>> diff --git a/libavformat/isom.h b/libavformat/isom.h
>> index d9956cf63a..426f732247 100644
>> --- a/libavformat/isom.h
>> +++ b/libavformat/isom.h
>> @@ -27,6 +27,7 @@
>>  #include <stddef.h>
>>  #include <stdint.h>
>>  
>> +#include "libavutil/mastering_display_metadata.h"
>>  #include "libavutil/spherical.h"
>>  #include "libavutil/stereo3d.h"
>>  
>> @@ -194,6 +195,7 @@ typedef struct MOVStreamContext {
>>      AVStereo3D *stereo3d;
>>      AVSphericalMapping *spherical;
>>      size_t spherical_size;
>> +    AVMasteringDisplayMetadata *mastering;
>>  
>>      uint32_t format;
>>  
>> diff --git a/libavformat/mov.c b/libavformat/mov.c
>> index afef53b79a..0b5fd849f3 100644
>> --- a/libavformat/mov.c
>> +++ b/libavformat/mov.c
>> @@ -4612,6 +4612,60 @@ static int mov_read_tmcd(MOVContext *c, AVIOContext *pb, MOVAtom atom)
>>      return 0;
>>  }
>>  
>> +static int mov_read_smdm(MOVContext *c, AVIOContext *pb, MOVAtom atom)
>> +{
>> +    MOVStreamContext *sc;
>> +    const int chroma_den = 50000;
>> +    const int luma_den = 10000;
>> +    int version;
>> +
>> +    if (c->fc->nb_streams < 1)
>> +        return AVERROR_INVALIDDATA;
>> +
>> +    sc = c->fc->streams[c->fc->nb_streams - 1]->priv_data;
>> +
>> +    if (atom.size < 5) {
>> +        av_log(c->fc, AV_LOG_ERROR, "Empty Mastering Display Metadata box\n");
>> +        return AVERROR_INVALIDDATA;
>> +    }
>> +
>> +    version = avio_r8(pb);
>> +    if (version) {
>> +        av_log(c->fc, AV_LOG_WARNING, "Unsupported Mastering Display Metadata box version %d\n", version);
>> +        return 0;
>> +    }
>> +    avio_skip(pb, 3); /* flags */
>> +
>> +    sc->mastering = av_mastering_display_metadata_alloc();
>> +    if (!sc->mastering)
>> +        return AVERROR(ENOMEM);
>> +
> 
>> +    sc->mastering->display_primaries[0][0] =
>> +        av_make_q(lrint(((double)avio_rb16(pb) / (1 << 16)) * chroma_den), chroma_den);
> 
> this is not optimal, precission wise
> av_d2q() should produce closer rationals
> alternativly av_reduce() can be used directly
> 
> but iam not sure why a fixed chroma_den and luma_den is fixed
> maybe iam missing something

Does

for (i = 0; i < 3; i++)
  for (j = 0; j < 2; j++)
    av_reduce(&sc->mastering->display_primaries[i][j].num,
              &sc->mastering->display_primaries[i][j].den,
              lrint(((double)avio_rb16(pb) / (1 << 16)) * chroma_den),
              chroma_den, chroma_den);
for (i = 0; i < 2; i++)
  av_reduce(&sc->mastering->white_point[i].num,
            &sc->mastering->white_point[i].den,
            lrint(((double)avio_rb16(pb) / (1 << 16)) * chroma_den),
            chroma_den, chroma_den);
av_reduce(&sc->mastering->max_luminance.num,
          &sc->mastering->max_luminance.den,
          lrint(((double)avio_rb32(pb) / (1 << 8)) * luma_den),
          luma_den, INT_MAX);
av_reduce(&sc->mastering->min_luminance.num,
          &sc->mastering->min_luminance.den,
          lrint(((double)avio_rb32(pb) / (1 << 14)) * luma_den),
          luma_den, INT_MAX);

Look better?