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

[Michael Niedermayer]

On Fri, May 26, 2017 at 09:14:19PM -0300, James Almer wrote:
> 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()?

If i would write the code, i probably would use a temporare variable
and check that before storing with avio_wbXY()
strictly one needs long long for that probably and iam not sure the
denominator needs to be checked for 0
maybe theres some simpler way though, i dont know


> 
> This could have been avoided if mastering metadata fields were
> implemented as integer values, like content light does.
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-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

The misfortune of the wise is better than the prosperity of the fool.
-- Epicurus
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