demux: mp4: change reserved to known value

modules/demux/mp4/libmp4.c

@@ -887,7 +887,7 @@ static int MP4_ReadBox_mdhd( stream_t *p_stream, MP4_Box_t *p_box )
     decodeQtLanguageCode( i_language, p_box->data.p_mdhd->rgs_language,
                           &p_box->data.p_mdhd->b_mac_encoding );
 
-    MP4_GET2BYTES( p_box->data.p_mdhd->i_predefined );
+    MP4_GET2BYTES( p_box->data.p_mdhd->i_quality );
 
 #ifdef MP4_VERBOSE
     MP4_ConvertDate2Str( s_creation_time, p_box->data.p_mdhd->i_creation_time, false );

modules/demux/mp4/libmp4.h

@@ -390,7 +390,7 @@ typedef struct MP4_Box_data_mdhd_s
     char     rgs_language[3]; /* ISO-639-2/T or Mac lang table */
     bool     b_mac_encoding;  /* media using mac encoding */
 
-    uint16_t i_predefined;
+    uint16_t i_quality;
 
 } MP4_Box_data_mdhd_t;