avformat/matroska: use named constants for ITU-T T.35 metadata

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

libavformat/matroskadec.c

@@ -54,6 +54,7 @@
 #include "libavcodec/bytestream.h"
 #include "libavcodec/defs.h"
 #include "libavcodec/flac.h"
+#include "libavcodec/itut35.h"
 #include "libavcodec/mpeg4audio.h"
 #include "libavcodec/packet_internal.h"
 
@@ -3884,7 +3885,8 @@ static int matroska_parse_block_additional(MatroskaDemuxContext *matroska,
         country_code  = bytestream2_get_byteu(&bc);
         provider_code = bytestream2_get_be16u(&bc);
 
-        if (country_code != 0xB5 || provider_code != 0x3C)
+        if (country_code != ITU_T_T35_COUNTRY_CODE_US ||
+            provider_code != ITU_T_T35_PROVIDER_CODE_SMTPE)
             break; // ignore
 
         provider_oriented_code = bytestream2_get_be16u(&bc);

libavformat/matroskaenc.c

@@ -63,6 +63,7 @@
 #include "libavcodec/codec_desc.h"
 #include "libavcodec/codec_par.h"
 #include "libavcodec/defs.h"
+#include "libavcodec/itut35.h"
 #include "libavcodec/xiph.h"
 #include "libavcodec/mpeg4audio.h"
 
@@ -2824,8 +2825,8 @@ static int mkv_write_block(void *logctx, MatroskaMuxContext *mkv,
             uint8_t *payload = t35_buf;
             size_t payload_size = sizeof(t35_buf) - 6;
 
-            bytestream_put_byte(&payload, 0xB5); // country_code
-            bytestream_put_be16(&payload, 0x3C); // provider_code
+            bytestream_put_byte(&payload, ITU_T_T35_COUNTRY_CODE_US);
+            bytestream_put_be16(&payload, ITU_T_T35_PROVIDER_CODE_SMTPE);
             bytestream_put_be16(&payload, 0x01); // provider_oriented_code
             bytestream_put_byte(&payload, 0x04); // application_identifier