diff --git a/libavformat/matroska.h b/libavformat/matroska.h
index b39517709c..ead7c085b9 100644
--- a/libavformat/matroska.h
+++ b/libavformat/matroska.h
@@ -360,9 +360,13 @@ typedef enum {
 
 typedef enum {
   MATROSKA_BLOCK_ADD_ID_TYPE_DEFAULT                = 0,
+  MATROSKA_BLOCK_ADD_ID_TYPE_OPAQUE                 = 1,
   MATROSKA_BLOCK_ADD_ID_TYPE_ITU_T_T35              = 4,
+  MATROSKA_BLOCK_ADD_ID_TYPE_DVCC                   = 0x64766343, // MKBETAG('d','v','c','C')
+  MATROSKA_BLOCK_ADD_ID_TYPE_DVVC                   = 0x64767643, // MKBETAG('d','v','v','C')
 } MatroskaBlockAddIDType;
 
+#define MATROSKA_BLOCK_ADD_ID_OPAQUE 1
 #define MATROSKA_BLOCK_ADD_ID_ITU_T_T35 4
 
 /*
diff --git a/libavformat/matroskadec.c b/libavformat/matroskadec.c
index 32907f413a..3c7c2b7c70 100644
--- a/libavformat/matroskadec.c
+++ b/libavformat/matroskadec.c
@@ -767,7 +767,7 @@ static EbmlSyntax matroska_segments[] = {
 };
 
 static EbmlSyntax matroska_blockmore[] = {
-    { MATROSKA_ID_BLOCKADDID,      EBML_UINT, 0, 0, offsetof(MatroskaBlockMore,additional_id), { .u = 1 } },
+    { MATROSKA_ID_BLOCKADDID,      EBML_UINT, 0, 0, offsetof(MatroskaBlockMore,additional_id), { .u = MATROSKA_BLOCK_ADD_ID_OPAQUE } },
     { MATROSKA_ID_BLOCKADDITIONAL, EBML_BIN,  0, 0, offsetof(MatroskaBlockMore,additional) },
     CHILD_OF(matroska_blockadditions)
 };
@@ -2404,8 +2404,8 @@ static int mkv_parse_block_addition_mappings(AVFormatContext *s, AVStream *st, M
             }
             track->blockaddid_itu_t_t35 = 1;
             break;
-        case MKBETAG('d','v','c','C'):
-        case MKBETAG('d','v','v','C'):
+        case MATROSKA_BLOCK_ADD_ID_TYPE_DVCC:
+        case MATROSKA_BLOCK_ADD_ID_TYPE_DVVC:
             if ((ret = mkv_parse_dvcc_dvvc(s, st, track, &mapping->extradata)) < 0)
                 return ret;
 
diff --git a/libavformat/matroskaenc.c b/libavformat/matroskaenc.c
index 954b7d828f..6b24d26d59 100644
--- a/libavformat/matroskaenc.c
+++ b/libavformat/matroskaenc.c
@@ -1612,9 +1612,9 @@ static void mkv_write_dovi(AVFormatContext *s, AVIOContext *pb, AVStream *st)
                                 + (2 + 1 + 4) + (2 + 1 + ISOM_DVCC_DVVC_SIZE);
 
         if (dovi->dv_profile > 7) {
-            type = MKBETAG('d', 'v', 'v', 'C');
+            type = MATROSKA_BLOCK_ADD_ID_TYPE_DVVC;
         } else {
-            type = MKBETAG('d', 'v', 'c', 'C');
+            type = MATROSKA_BLOCK_ADD_ID_TYPE_DVCC;
         }
 
         ff_isom_put_dvcc_dvvc(s, buf, dovi);
@@ -2657,7 +2657,7 @@ static int mkv_write_block(void *logctx, MatroskaMuxContext *mkv,
                                         &side_data_size);
     if (side_data && side_data_size >= 8 &&
         // Only the Codec-specific BlockMore (id == 1) is currently supported.
-        (additional_id = AV_RB64(side_data)) == 1) {
+        (additional_id = AV_RB64(side_data)) == MATROSKA_BLOCK_ADD_ID_TYPE_OPAQUE) {
         ebml_writer_open_master(&writer, MATROSKA_ID_BLOCKADDITIONS);
         ebml_writer_open_master(&writer, MATROSKA_ID_BLOCKMORE);
         /* Until dbc50f8a our demuxer used a wrong default value