avformat/mov: don't use sizeof(AVMasteringDisplayMetadata)

It's not part of the libavutil ABI.

Signed-off-by: James Almer <jamrial@gmail.com>

libavformat/isom.h

@@ -250,6 +250,7 @@ typedef struct MOVStreamContext {
     AVSphericalMapping *spherical;
     size_t spherical_size;
     AVMasteringDisplayMetadata *mastering;
+    size_t mastering_size;
     AVContentLightMetadata *coll;
     size_t coll_size;
     AVAmbientViewingEnvironment *ambient;

libavformat/mov.c

@@ -6138,7 +6138,7 @@ static int mov_read_smdm(MOVContext *c, AVIOContext *pb, MOVAtom atom)
 
     avio_skip(pb, 3); /* flags */
 
-    sc->mastering = av_mastering_display_metadata_alloc();
+    sc->mastering = av_mastering_display_metadata_alloc_size(&sc->mastering_size);
     if (!sc->mastering)
         return AVERROR(ENOMEM);
 
@@ -6181,7 +6181,7 @@ static int mov_read_mdcv(MOVContext *c, AVIOContext *pb, MOVAtom atom)
         return 0;
     }
 
-    sc->mastering = av_mastering_display_metadata_alloc();
+    sc->mastering = av_mastering_display_metadata_alloc_size(&sc->mastering_size);
     if (!sc->mastering)
         return AVERROR(ENOMEM);
 
@@ -10043,7 +10043,7 @@ static int mov_read_header(AVFormatContext *s)
             if (sc->mastering) {
                 if (!av_packet_side_data_add(&st->codecpar->coded_side_data, &st->codecpar->nb_coded_side_data,
                                              AV_PKT_DATA_MASTERING_DISPLAY_METADATA,
-                                             (uint8_t *)sc->mastering, sizeof(*sc->mastering), 0))
+                                             (uint8_t *)sc->mastering, sc->mastering_size, 0))
                     return AVERROR(ENOMEM);
 
                 sc->mastering = NULL;