avformat/matroskaenc: Automatically use right TrackNumber in Cues

mkv_cuepoint (the structure used to store the index entries in the
Matroska muxer) currently contains fields for both the index of the
packet's stream in the AVFormatContext.streams array and for the
Matroska TrackNumber; correspondingly, mkv_add_cuepoint() has parameters
for both. But these two numbers can't be chosen independently, so get
rid of the TrackNumber.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>

libavformat/matroskaenc.c

@@ -78,7 +78,6 @@ typedef struct mkv_seekhead {
 typedef struct mkv_cuepoint {
     uint64_t        pts;
     int             stream_idx;
-    int             tracknum;
     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
@@ -477,7 +476,7 @@ static int mkv_write_seekhead(AVIOContext *pb, MatroskaMuxContext *mkv,
     return 0;
 }
 
-static int mkv_add_cuepoint(MatroskaMuxContext *mkv, int stream, int tracknum, int64_t ts,
+static int mkv_add_cuepoint(MatroskaMuxContext *mkv, int stream, int64_t ts,
                             int64_t cluster_pos, int64_t relative_pos, int64_t duration)
 {
     mkv_cues *cues = &mkv->cues;
@@ -493,7 +492,6 @@ static int mkv_add_cuepoint(MatroskaMuxContext *mkv, int stream, int tracknum, i
 
     cues->entries[cues->num_entries].pts           = ts;
     cues->entries[cues->num_entries].stream_idx    = stream;
-    cues->entries[cues->num_entries].tracknum      = tracknum;
     cues->entries[cues->num_entries].cluster_pos   = cluster_pos - mkv->segment_offset;
     cues->entries[cues->num_entries].relative_pos  = relative_pos;
     cues->entries[cues->num_entries++].duration    = duration;
@@ -532,7 +530,7 @@ static int mkv_assemble_cues(AVStream **streams, AVIOContext *dyn_cp,
                 continue;
             tracks[idx].has_cue = 1;
             track_positions = start_ebml_master(cuepoint, MATROSKA_ID_CUETRACKPOSITION, MAX_CUETRACKPOS_SIZE);
-            put_ebml_uint(cuepoint, MATROSKA_ID_CUETRACK           , entry->tracknum   );
+            put_ebml_uint(cuepoint, MATROSKA_ID_CUETRACK           , tracks[idx].track_num);
             put_ebml_uint(cuepoint, MATROSKA_ID_CUECLUSTERPOSITION , entry->cluster_pos);
             put_ebml_uint(cuepoint, MATROSKA_ID_CUERELATIVEPOSITION, entry->relative_pos);
             if (entry->duration != -1)
@@ -2231,7 +2229,6 @@ static int mkv_write_packet_internal(AVFormatContext *s, AVPacket *pkt, int add_
     int ret;
     int64_t ts = track->write_dts ? pkt->dts : pkt->pts;
     int64_t relative_packet_pos;
-    unsigned tracknum = track->track_num;
 
     if (ts == AV_NOPTS_VALUE) {
         av_log(s, AV_LOG_ERROR, "Can't write packet with unknown timestamp\n");
@@ -2268,7 +2265,7 @@ static int mkv_write_packet_internal(AVFormatContext *s, AVPacket *pkt, int add_
         if (ret < 0)
             return ret;
         if ((s->pb->seekable & AVIO_SEEKABLE_NORMAL) && (par->codec_type == AVMEDIA_TYPE_VIDEO && keyframe || add_cue)) {
-            ret = mkv_add_cuepoint(mkv, pkt->stream_index, tracknum, ts,
+            ret = mkv_add_cuepoint(mkv, pkt->stream_index, ts,
                                    mkv->cluster_pos, relative_packet_pos, -1);
             if (ret < 0) return ret;
         }
@@ -2294,7 +2291,7 @@ FF_ENABLE_DEPRECATION_WARNINGS
         }
 
         if (s->pb->seekable & AVIO_SEEKABLE_NORMAL) {
-            ret = mkv_add_cuepoint(mkv, pkt->stream_index, tracknum, ts,
+            ret = mkv_add_cuepoint(mkv, pkt->stream_index, ts,
                                    mkv->cluster_pos, relative_packet_pos, duration);
             if (ret < 0)
                 return ret;