diff --git a/libavformat/matroskadec.c b/libavformat/matroskadec.c
index 98efc7c034..301304b5d9 100644
--- a/libavformat/matroskadec.c
+++ b/libavformat/matroskadec.c
@@ -324,7 +324,7 @@ typedef struct MatroskaBlock {
     int64_t discard_padding;
 } MatroskaBlock;
 
-static EbmlSyntax ebml_header[] = {
+static const EbmlSyntax ebml_header[] = {
     { EBML_ID_EBMLREADVERSION,    EBML_UINT, 0, offsetof(Ebml, version),         { .u = EBML_VERSION } },
     { EBML_ID_EBMLMAXSIZELENGTH,  EBML_UINT, 0, offsetof(Ebml, max_size),        { .u = 8 } },
     { EBML_ID_EBMLMAXIDLENGTH,    EBML_UINT, 0, offsetof(Ebml, id_length),       { .u = 4 } },
@@ -335,12 +335,12 @@ static EbmlSyntax ebml_header[] = {
     { 0 }
 };
 
-static EbmlSyntax ebml_syntax[] = {
+static const EbmlSyntax ebml_syntax[] = {
     { EBML_ID_HEADER, EBML_NEST, 0, 0, { .n = ebml_header } },
     { 0 }
 };
 
-static EbmlSyntax matroska_info[] = {
+static const EbmlSyntax matroska_info[] = {
     { MATROSKA_ID_TIMECODESCALE, EBML_UINT,  0, offsetof(MatroskaDemuxContext, time_scale), { .u = 1000000 } },
     { MATROSKA_ID_DURATION,      EBML_FLOAT, 0, offsetof(MatroskaDemuxContext, duration) },
     { MATROSKA_ID_TITLE,         EBML_UTF8,  0, offsetof(MatroskaDemuxContext, title) },
@@ -351,7 +351,7 @@ static EbmlSyntax matroska_info[] = {
     { 0 }
 };
 
-static EbmlSyntax matroska_track_video[] = {
+static const EbmlSyntax matroska_track_video[] = {
     { MATROSKA_ID_VIDEOFRAMERATE,      EBML_FLOAT, 0, offsetof(MatroskaTrackVideo, frame_rate) },
     { MATROSKA_ID_VIDEODISPLAYWIDTH,   EBML_UINT,  0, offsetof(MatroskaTrackVideo, display_width), { .u=-1 } },
     { MATROSKA_ID_VIDEODISPLAYHEIGHT,  EBML_UINT,  0, offsetof(MatroskaTrackVideo, display_height), { .u=-1 } },
@@ -370,7 +370,7 @@ static EbmlSyntax matroska_track_video[] = {
     { 0 }
 };
 
-static EbmlSyntax matroska_track_audio[] = {
+static const EbmlSyntax matroska_track_audio[] = {
     { MATROSKA_ID_AUDIOSAMPLINGFREQ,    EBML_FLOAT, 0, offsetof(MatroskaTrackAudio, samplerate), { .f = 8000.0 } },
     { MATROSKA_ID_AUDIOOUTSAMPLINGFREQ, EBML_FLOAT, 0, offsetof(MatroskaTrackAudio, out_samplerate) },
     { MATROSKA_ID_AUDIOBITDEPTH,        EBML_UINT,  0, offsetof(MatroskaTrackAudio, bitdepth) },
@@ -378,13 +378,13 @@ static EbmlSyntax matroska_track_audio[] = {
     { 0 }
 };
 
-static EbmlSyntax matroska_track_encoding_compression[] = {
+static const EbmlSyntax matroska_track_encoding_compression[] = {
     { MATROSKA_ID_ENCODINGCOMPALGO,     EBML_UINT, 0, offsetof(MatroskaTrackCompression, algo), { .u = 0 } },
     { MATROSKA_ID_ENCODINGCOMPSETTINGS, EBML_BIN,  0, offsetof(MatroskaTrackCompression, settings) },
     { 0 }
 };
 
-static EbmlSyntax matroska_track_encoding_encryption[] = {
+static const EbmlSyntax matroska_track_encoding_encryption[] = {
     { MATROSKA_ID_ENCODINGENCALGO,        EBML_UINT, 0, offsetof(MatroskaTrackEncryption,algo), {.u = 0} },
     { MATROSKA_ID_ENCODINGENCKEYID,       EBML_BIN, 0, offsetof(MatroskaTrackEncryption,key_id) },
     { MATROSKA_ID_ENCODINGENCAESSETTINGS, EBML_NONE },
@@ -394,7 +394,7 @@ static EbmlSyntax matroska_track_encoding_encryption[] = {
     { MATROSKA_ID_ENCODINGSIGNATURE,      EBML_NONE },
     { 0 }
 };
-static EbmlSyntax matroska_track_encoding[] = {
+static const EbmlSyntax matroska_track_encoding[] = {
     { MATROSKA_ID_ENCODINGSCOPE,       EBML_UINT, 0, offsetof(MatroskaTrackEncoding, scope),       { .u = 1 } },
     { MATROSKA_ID_ENCODINGTYPE,        EBML_UINT, 0, offsetof(MatroskaTrackEncoding, type),        { .u = 0 } },
     { MATROSKA_ID_ENCODINGCOMPRESSION, EBML_NEST, 0, offsetof(MatroskaTrackEncoding, compression), { .n = matroska_track_encoding_compression } },
@@ -403,28 +403,28 @@ static EbmlSyntax matroska_track_encoding[] = {
     { 0 }
 };
 
-static EbmlSyntax matroska_track_encodings[] = {
+static const EbmlSyntax matroska_track_encodings[] = {
     { MATROSKA_ID_TRACKCONTENTENCODING, EBML_NEST, sizeof(MatroskaTrackEncoding), offsetof(MatroskaTrack, encodings), { .n = matroska_track_encoding } },
     { 0 }
 };
 
-static EbmlSyntax matroska_track_plane[] = {
+static const EbmlSyntax matroska_track_plane[] = {
     { MATROSKA_ID_TRACKPLANEUID,  EBML_UINT, 0, offsetof(MatroskaTrackPlane,uid) },
     { MATROSKA_ID_TRACKPLANETYPE, EBML_UINT, 0, offsetof(MatroskaTrackPlane,type) },
     { 0 }
 };
 
-static EbmlSyntax matroska_track_combine_planes[] = {
+static const EbmlSyntax matroska_track_combine_planes[] = {
     { MATROSKA_ID_TRACKPLANE, EBML_NEST, sizeof(MatroskaTrackPlane), offsetof(MatroskaTrackOperation,combine_planes), {.n = matroska_track_plane} },
     { 0 }
 };
 
-static EbmlSyntax matroska_track_operation[] = {
+static const EbmlSyntax matroska_track_operation[] = {
     { MATROSKA_ID_TRACKCOMBINEPLANES, EBML_NEST, 0, 0, {.n = matroska_track_combine_planes} },
     { 0 }
 };
 
-static EbmlSyntax matroska_track[] = {
+static const EbmlSyntax matroska_track[] = {
     { MATROSKA_ID_TRACKNUMBER,           EBML_UINT,  0, offsetof(MatroskaTrack, num) },
     { MATROSKA_ID_TRACKNAME,             EBML_UTF8,  0, offsetof(MatroskaTrack, name) },
     { MATROSKA_ID_TRACKUID,              EBML_UINT,  0, offsetof(MatroskaTrack, uid) },
@@ -454,12 +454,12 @@ static EbmlSyntax matroska_track[] = {
     { 0 }
 };
 
-static EbmlSyntax matroska_tracks[] = {
+static const EbmlSyntax matroska_tracks[] = {
     { MATROSKA_ID_TRACKENTRY, EBML_NEST, sizeof(MatroskaTrack), offsetof(MatroskaDemuxContext, tracks), { .n = matroska_track } },
     { 0 }
 };
 
-static EbmlSyntax matroska_attachment[] = {
+static const EbmlSyntax matroska_attachment[] = {
     { MATROSKA_ID_FILEUID,      EBML_UINT, 0, offsetof(MatroskaAttachment, uid) },
     { MATROSKA_ID_FILENAME,     EBML_UTF8, 0, offsetof(MatroskaAttachment, filename) },
     { MATROSKA_ID_FILEMIMETYPE, EBML_STR,  0, offsetof(MatroskaAttachment, mime) },
@@ -468,18 +468,18 @@ static EbmlSyntax matroska_attachment[] = {
     { 0 }
 };
 
-static EbmlSyntax matroska_attachments[] = {
+static const EbmlSyntax matroska_attachments[] = {
     { MATROSKA_ID_ATTACHEDFILE, EBML_NEST, sizeof(MatroskaAttachment), offsetof(MatroskaDemuxContext, attachments), { .n = matroska_attachment } },
     { 0 }
 };
 
-static EbmlSyntax matroska_chapter_display[] = {
+static const EbmlSyntax matroska_chapter_display[] = {
     { MATROSKA_ID_CHAPSTRING, EBML_UTF8, 0, offsetof(MatroskaChapter, title) },
     { MATROSKA_ID_CHAPLANG,   EBML_NONE },
     { 0 }
 };
 
-static EbmlSyntax matroska_chapter_entry[] = {
+static const EbmlSyntax matroska_chapter_entry[] = {
     { MATROSKA_ID_CHAPTERTIMESTART,   EBML_UINT, 0, offsetof(MatroskaChapter, start), { .u = AV_NOPTS_VALUE } },
     { MATROSKA_ID_CHAPTERTIMEEND,     EBML_UINT, 0, offsetof(MatroskaChapter, end),   { .u = AV_NOPTS_VALUE } },
     { MATROSKA_ID_CHAPTERUID,         EBML_UINT, 0, offsetof(MatroskaChapter, uid) },
@@ -491,7 +491,7 @@ static EbmlSyntax matroska_chapter_entry[] = {
     { 0 }
 };
 
-static EbmlSyntax matroska_chapter[] = {
+static const EbmlSyntax matroska_chapter[] = {
     { MATROSKA_ID_CHAPTERATOM,        EBML_NEST, sizeof(MatroskaChapter), offsetof(MatroskaDemuxContext, chapters), { .n = matroska_chapter_entry } },
     { MATROSKA_ID_EDITIONUID,         EBML_NONE },
     { MATROSKA_ID_EDITIONFLAGHIDDEN,  EBML_NONE },
@@ -500,12 +500,12 @@ static EbmlSyntax matroska_chapter[] = {
     { 0 }
 };
 
-static EbmlSyntax matroska_chapters[] = {
+static const EbmlSyntax matroska_chapters[] = {
     { MATROSKA_ID_EDITIONENTRY, EBML_NEST, 0, 0, { .n = matroska_chapter } },
     { 0 }
 };
 
-static EbmlSyntax matroska_index_pos[] = {
+static const EbmlSyntax matroska_index_pos[] = {
     { MATROSKA_ID_CUETRACK,           EBML_UINT, 0, offsetof(MatroskaIndexPos, track) },
     { MATROSKA_ID_CUECLUSTERPOSITION, EBML_UINT, 0, offsetof(MatroskaIndexPos, pos) },
     { MATROSKA_ID_CUERELATIVEPOSITION,EBML_NONE },
@@ -514,18 +514,18 @@ static EbmlSyntax matroska_index_pos[] = {
     { 0 }
 };
 
-static EbmlSyntax matroska_index_entry[] = {
+static const EbmlSyntax matroska_index_entry[] = {
     { MATROSKA_ID_CUETIME,          EBML_UINT, 0,                        offsetof(MatroskaIndex, time) },
     { MATROSKA_ID_CUETRACKPOSITION, EBML_NEST, sizeof(MatroskaIndexPos), offsetof(MatroskaIndex, pos), { .n = matroska_index_pos } },
     { 0 }
 };
 
-static EbmlSyntax matroska_index[] = {
+static const EbmlSyntax matroska_index[] = {
     { MATROSKA_ID_POINTENTRY, EBML_NEST, sizeof(MatroskaIndex), offsetof(MatroskaDemuxContext, index), { .n = matroska_index_entry } },
     { 0 }
 };
 
-static EbmlSyntax matroska_simpletag[] = {
+static const EbmlSyntax matroska_simpletag[] = {
     { MATROSKA_ID_TAGNAME,        EBML_UTF8, 0,                   offsetof(MatroskaTag, name) },
     { MATROSKA_ID_TAGSTRING,      EBML_UTF8, 0,                   offsetof(MatroskaTag, string) },
     { MATROSKA_ID_TAGLANG,        EBML_STR,  0,                   offsetof(MatroskaTag, lang), { .s = "und" } },
@@ -535,7 +535,7 @@ static EbmlSyntax matroska_simpletag[] = {
     { 0 }
 };
 
-static EbmlSyntax matroska_tagtargets[] = {
+static const EbmlSyntax matroska_tagtargets[] = {
     { MATROSKA_ID_TAGTARGETS_TYPE,       EBML_STR,  0, offsetof(MatroskaTagTarget, type) },
     { MATROSKA_ID_TAGTARGETS_TYPEVALUE,  EBML_UINT, 0, offsetof(MatroskaTagTarget, typevalue), { .u = 50 } },
     { MATROSKA_ID_TAGTARGETS_TRACKUID,   EBML_UINT, 0, offsetof(MatroskaTagTarget, trackuid) },
@@ -544,29 +544,29 @@ static EbmlSyntax matroska_tagtargets[] = {
     { 0 }
 };
 
-static EbmlSyntax matroska_tag[] = {
+static const EbmlSyntax matroska_tag[] = {
     { MATROSKA_ID_SIMPLETAG,  EBML_NEST, sizeof(MatroskaTag), offsetof(MatroskaTags, tag),    { .n = matroska_simpletag } },
     { MATROSKA_ID_TAGTARGETS, EBML_NEST, 0,                   offsetof(MatroskaTags, target), { .n = matroska_tagtargets } },
     { 0 }
 };
 
-static EbmlSyntax matroska_tags[] = {
+static const EbmlSyntax matroska_tags[] = {
     { MATROSKA_ID_TAG, EBML_NEST, sizeof(MatroskaTags), offsetof(MatroskaDemuxContext, tags), { .n = matroska_tag } },
     { 0 }
 };
 
-static EbmlSyntax matroska_seekhead_entry[] = {
+static const EbmlSyntax matroska_seekhead_entry[] = {
     { MATROSKA_ID_SEEKID,       EBML_UINT, 0, offsetof(MatroskaSeekhead, id) },
     { MATROSKA_ID_SEEKPOSITION, EBML_UINT, 0, offsetof(MatroskaSeekhead, pos), { .u = -1 } },
     { 0 }
 };
 
-static EbmlSyntax matroska_seekhead[] = {
+static const EbmlSyntax matroska_seekhead[] = {
     { MATROSKA_ID_SEEKENTRY, EBML_NEST, sizeof(MatroskaSeekhead), offsetof(MatroskaDemuxContext, seekhead), { .n = matroska_seekhead_entry } },
     { 0 }
 };
 
-static EbmlSyntax matroska_segment[] = {
+static const EbmlSyntax matroska_segment[] = {
     { MATROSKA_ID_INFO,        EBML_LEVEL1, 0, 0, { .n = matroska_info } },
     { MATROSKA_ID_TRACKS,      EBML_LEVEL1, 0, 0, { .n = matroska_tracks } },
     { MATROSKA_ID_ATTACHMENTS, EBML_LEVEL1, 0, 0, { .n = matroska_attachments } },
@@ -578,23 +578,23 @@ static EbmlSyntax matroska_segment[] = {
     { 0 }
 };
 
-static EbmlSyntax matroska_segments[] = {
+static const EbmlSyntax matroska_segments[] = {
     { MATROSKA_ID_SEGMENT, EBML_NEST, 0, 0, { .n = matroska_segment } },
     { 0 }
 };
 
-static EbmlSyntax matroska_blockmore[] = {
+static const EbmlSyntax matroska_blockmore[] = {
     { MATROSKA_ID_BLOCKADDID,      EBML_UINT, 0, offsetof(MatroskaBlock,additional_id) },
     { MATROSKA_ID_BLOCKADDITIONAL, EBML_BIN,  0, offsetof(MatroskaBlock,additional) },
     { 0 }
 };
 
-static EbmlSyntax matroska_blockadditions[] = {
+static const EbmlSyntax matroska_blockadditions[] = {
     { MATROSKA_ID_BLOCKMORE, EBML_NEST, 0, 0, {.n = matroska_blockmore} },
     { 0 }
 };
 
-static EbmlSyntax matroska_blockgroup[] = {
+static const EbmlSyntax matroska_blockgroup[] = {
     { MATROSKA_ID_BLOCK,          EBML_BIN,  0, offsetof(MatroskaBlock, bin) },
     { MATROSKA_ID_BLOCKADDITIONS, EBML_NEST, 0, 0, { .n = matroska_blockadditions} },
     { MATROSKA_ID_SIMPLEBLOCK,    EBML_BIN,  0, offsetof(MatroskaBlock, bin) },
@@ -606,7 +606,7 @@ static EbmlSyntax matroska_blockgroup[] = {
     { 0 }
 };
 
-static EbmlSyntax matroska_cluster[] = {
+static const EbmlSyntax matroska_cluster[] = {
     { MATROSKA_ID_CLUSTERTIMECODE, EBML_UINT, 0,                     offsetof(MatroskaCluster, timecode) },
     { MATROSKA_ID_BLOCKGROUP,      EBML_NEST, sizeof(MatroskaBlock), offsetof(MatroskaCluster, blocks), { .n = matroska_blockgroup } },
     { MATROSKA_ID_SIMPLEBLOCK,     EBML_PASS, sizeof(MatroskaBlock), offsetof(MatroskaCluster, blocks), { .n = matroska_blockgroup } },
@@ -615,7 +615,7 @@ static EbmlSyntax matroska_cluster[] = {
     { 0 }
 };
 
-static EbmlSyntax matroska_clusters[] = {
+static const EbmlSyntax matroska_clusters[] = {
     { MATROSKA_ID_CLUSTER,  EBML_NEST, 0, 0, { .n = matroska_cluster } },
     { MATROSKA_ID_INFO,     EBML_NONE },
     { MATROSKA_ID_CUES,     EBML_NONE },
@@ -624,7 +624,7 @@ static EbmlSyntax matroska_clusters[] = {
     { 0 }
 };
 
-static EbmlSyntax matroska_cluster_incremental_parsing[] = {
+static const EbmlSyntax matroska_cluster_incremental_parsing[] = {
     { MATROSKA_ID_CLUSTERTIMECODE, EBML_UINT, 0,                     offsetof(MatroskaCluster, timecode) },
     { MATROSKA_ID_BLOCKGROUP,      EBML_NEST, sizeof(MatroskaBlock), offsetof(MatroskaCluster, blocks), { .n = matroska_blockgroup } },
     { MATROSKA_ID_SIMPLEBLOCK,     EBML_PASS, sizeof(MatroskaBlock), offsetof(MatroskaCluster, blocks), { .n = matroska_blockgroup } },
@@ -638,7 +638,7 @@ static EbmlSyntax matroska_cluster_incremental_parsing[] = {
     { 0 }
 };
 
-static EbmlSyntax matroska_cluster_incremental[] = {
+static const EbmlSyntax matroska_cluster_incremental[] = {
     { MATROSKA_ID_CLUSTERTIMECODE, EBML_UINT, 0, offsetof(MatroskaCluster, timecode) },
     { MATROSKA_ID_BLOCKGROUP,      EBML_STOP },
     { MATROSKA_ID_SIMPLEBLOCK,     EBML_STOP },
@@ -647,7 +647,7 @@ static EbmlSyntax matroska_cluster_incremental[] = {
     { 0 }
 };
 
-static EbmlSyntax matroska_clusters_incremental[] = {
+static const EbmlSyntax matroska_clusters_incremental[] = {
     { MATROSKA_ID_CLUSTER,  EBML_NEST, 0, 0, { .n = matroska_cluster_incremental } },
     { MATROSKA_ID_INFO,     EBML_NONE },
     { MATROSKA_ID_CUES,     EBML_NONE },