avformat/matroskaenc: support writing Chroma Location elements

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

libavformat/matroskaenc.c

@@ -832,6 +832,14 @@ static int mkv_write_video_color(AVIOContext *pb, AVCodecParameters *par, AVStre
         par->color_range < AVCOL_RANGE_NB) {
         put_ebml_uint(dyn_cp, MATROSKA_ID_VIDEOCOLORRANGE, par->color_range);
     }
+    if (par->chroma_location != AVCHROMA_LOC_UNSPECIFIED &&
+        par->chroma_location <= AVCHROMA_LOC_TOP) {
+        int xpos, ypos;
+
+        avcodec_enum_to_chroma_pos(&xpos, &ypos, par->chroma_location);
+        put_ebml_uint(dyn_cp, MATROSKA_ID_VIDEOCOLORCHROMASITINGHORZ, (xpos >> 7) + 1);
+        put_ebml_uint(dyn_cp, MATROSKA_ID_VIDEOCOLORCHROMASITINGVERT, (ypos >> 7) + 1);
+    }
     if (side_data_size == sizeof(AVMasteringDisplayMetadata)) {
         ebml_master meta_element = start_ebml_master(
             dyn_cp, MATROSKA_ID_VIDEOCOLORMASTERINGMETA, 0);