diff --git a/libavformat/matroskaenc.c b/libavformat/matroskaenc.c
index 0d21ab055a..9df3f929d7 100644
--- a/libavformat/matroskaenc.c
+++ b/libavformat/matroskaenc.c
@@ -80,7 +80,7 @@ typedef struct mkv_cuepoint {
     uint64_t        pts;
     int             stream_idx;
     int             tracknum;
-    int64_t         cluster_pos;        ///< file offset of the cluster containing the block
+    int64_t         cluster_pos;        ///< offset of the cluster containing the block relative to the segment
     int64_t         relative_pos;       ///< relative offset from the position of the cluster containing the block
     int64_t         duration;           ///< duration of the block according to time base
 } mkv_cuepoint;
@@ -584,11 +584,12 @@ static int64_t mkv_write_cues(AVFormatContext *s, mkv_cues *cues, mkv_track *tra
         for (j = 0; j < num_tracks; j++)
             tracks[j].has_cue = 0;
         for (j = 0; j < cues->num_entries - i && entry[j].pts == pts; j++) {
-            int tracknum = entry[j].stream_idx;
-            av_assert0(tracknum>=0 && tracknum<num_tracks);
-            if (tracks[tracknum].has_cue && s->streams[tracknum]->codecpar->codec_type != AVMEDIA_TYPE_SUBTITLE)
+            int idx = entry[j].stream_idx;
+
+            av_assert0(idx >= 0 && idx < num_tracks);
+            if (tracks[idx].has_cue && s->streams[idx]->codecpar->codec_type != AVMEDIA_TYPE_SUBTITLE)
                 continue;
-            tracks[tracknum].has_cue = 1;
+            tracks[idx].has_cue = 1;
             ctp_nb ++;
         }
 
@@ -600,11 +601,11 @@ static int64_t mkv_write_cues(AVFormatContext *s, mkv_cues *cues, mkv_track *tra
         for (j = 0; j < num_tracks; j++)
             tracks[j].has_cue = 0;
         for (j = 0; j < cues->num_entries - i && entry[j].pts == pts; j++) {
-            int tracknum = entry[j].stream_idx;
+            int idx = entry[j].stream_idx;
 
-            if (tracks[tracknum].has_cue && s->streams[tracknum]->codecpar->codec_type != AVMEDIA_TYPE_SUBTITLE)
+            if (tracks[idx].has_cue && s->streams[idx]->codecpar->codec_type != AVMEDIA_TYPE_SUBTITLE)
                 continue;
-            tracks[tracknum].has_cue = 1;
+            tracks[idx].has_cue = 1;
             track_positions = start_ebml_master(dyn_cp, MATROSKA_ID_CUETRACKPOSITION, MAX_CUETRACKPOS_SIZE);
             put_ebml_uint(dyn_cp, MATROSKA_ID_CUETRACK           , entry[j].tracknum   );
             put_ebml_uint(dyn_cp, MATROSKA_ID_CUECLUSTERPOSITION , entry[j].cluster_pos);
@@ -2102,13 +2103,13 @@ static void mkv_write_block(AVFormatContext *s, AVIOContext *pb,
     mkv_track *track = &mkv->tracks[pkt->stream_index];
     uint8_t *data = NULL, *side_data = NULL;
     int offset = 0, size = pkt->size, side_data_size = 0;
-    int64_t ts = mkv->tracks[pkt->stream_index].write_dts ? pkt->dts : pkt->pts;
+    int64_t ts = track->write_dts ? pkt->dts : pkt->pts;
     uint64_t additional_id = 0;
     int64_t discard_padding = 0;
     uint8_t track_number = (mkv->is_dash ? mkv->dash_track_number : (pkt->stream_index + 1));
     ebml_master block_group, block_additions, block_more;
 
-    ts += mkv->tracks[pkt->stream_index].ts_offset;
+    ts += track->ts_offset;
 
     /* The following string is identical to the one in mkv_write_vtt_blocks
      * so that only one copy needs to exist in binaries. */
@@ -2364,21 +2365,21 @@ static int mkv_check_new_extra_data(AVFormatContext *s, AVPacket *pkt)
 static int mkv_write_packet_internal(AVFormatContext *s, AVPacket *pkt, int add_cue)
 {
     MatroskaMuxContext *mkv = s->priv_data;
-    AVIOContext *pb         = s->pb;
+    AVIOContext *pb;
     AVCodecParameters *par  = s->streams[pkt->stream_index]->codecpar;
     mkv_track *track        = &mkv->tracks[pkt->stream_index];
     int keyframe            = !!(pkt->flags & AV_PKT_FLAG_KEY);
     int duration            = pkt->duration;
     int ret;
-    int64_t ts = mkv->tracks[pkt->stream_index].write_dts ? pkt->dts : pkt->pts;
+    int64_t ts = track->write_dts ? pkt->dts : pkt->pts;
     int64_t relative_packet_pos;
-    int dash_tracknum = mkv->is_dash ? mkv->dash_track_number : pkt->stream_index + 1;
+    int tracknum = mkv->is_dash ? mkv->dash_track_number : pkt->stream_index + 1;
 
     if (ts == AV_NOPTS_VALUE) {
         av_log(s, AV_LOG_ERROR, "Can't write packet with unknown timestamp\n");
         return AVERROR(EINVAL);
     }
-    ts += mkv->tracks[pkt->stream_index].ts_offset;
+    ts += track->ts_offset;
 
     if (mkv->cluster_pos != -1) {
         int64_t cluster_time = ts - mkv->cluster_pts;
@@ -2407,7 +2408,7 @@ static int mkv_write_packet_internal(AVFormatContext *s, AVPacket *pkt, int add_
     if (par->codec_type != AVMEDIA_TYPE_SUBTITLE) {
         mkv_write_block(s, pb, MATROSKA_ID_SIMPLEBLOCK, pkt, keyframe);
         if ((s->pb->seekable & AVIO_SEEKABLE_NORMAL) && (par->codec_type == AVMEDIA_TYPE_VIDEO && keyframe || add_cue)) {
-            ret = mkv_add_cuepoint(mkv->cues, pkt->stream_index, dash_tracknum, ts, mkv->cluster_pos, relative_packet_pos, -1);
+            ret = mkv_add_cuepoint(mkv->cues, pkt->stream_index, tracknum, ts, mkv->cluster_pos, relative_packet_pos, -1);
             if (ret < 0) return ret;
         }
     } else {
@@ -2432,15 +2433,14 @@ FF_ENABLE_DEPRECATION_WARNINGS
         }
 
         if (s->pb->seekable & AVIO_SEEKABLE_NORMAL) {
-            ret = mkv_add_cuepoint(mkv->cues, pkt->stream_index, dash_tracknum, ts,
+            ret = mkv_add_cuepoint(mkv->cues, pkt->stream_index, tracknum, ts,
                                    mkv->cluster_pos, relative_packet_pos, duration);
             if (ret < 0)
                 return ret;
         }
     }
 
-    mkv->duration = FFMAX(mkv->duration, ts + duration);
-
+    mkv->duration   = FFMAX(mkv->duration,   ts + duration);
     track->duration = FFMAX(track->duration, ts + duration);
 
     return 0;
