add operation to add generic track

Change-Id: I34e4ab14c0a5b022b77b98d9403125550024e730

mkvmuxer.cpp

@@ -880,13 +880,23 @@ bool Tracks::AddTrack(Track* track, int32 number) {
   if (number < 0)
     return false;
 
+  // This muxer only supports track numbers in the range [1, 126], in
+  // order to be able (to use Matroska integer representation) to
+  // serialize the block header (of which the track number is a part)
+  // for a frame using exactly 4 bytes.
+
+  if (number > 0x7E)
+    return false;
+
   uint32 track_num = number;
 
+  if (track_num > 0) {
     // Check to make sure a track does not already have |track_num|.
     for (uint32 i = 0; i < track_entries_size_; ++i) {
       if (track_entries_[i]->number() == track_num)
         return false;
     }
+  }
 
   const uint32 count = track_entries_size_ + 1;
 
@@ -1584,6 +1594,20 @@ bool Segment::Finalize() {
   return true;
 }
 
+Track* Segment::AddTrack(int32 number) {
+  Track* const track = new (std::nothrow) Track;  // NOLINT
+
+  if (!track)
+    return NULL;
+
+  if (!tracks_.AddTrack(track, number)) {
+    delete track;
+    return NULL;
+  }
+
+  return track;
+}
+
 uint64 Segment::AddVideoTrack(int32 width, int32 height, int32 number) {
   VideoTrack* const vid_track = new (std::nothrow) VideoTrack();  // NOLINT
   if (!vid_track)

mkvmuxer.hpp

@@ -668,6 +668,13 @@ class Segment {
   // |ptr_writer| is NULL.
   bool Init(IMkvWriter* ptr_writer);
 
+  // Adds a generic track to the segment.  Returns the newly-allocated
+  // track object (which is owned by the segment) on success, NULL on
+  // error. |number| is the number to use for the track.  |number|
+  // must be >= 0. If |number| == 0 then the muxer will decide on the
+  // track number.
+  Track* AddTrack(int32 number);
+
   // Adds an audio track to the segment. Returns the number of the track on
   // success, 0 on error. |number| is the number to use for the audio track.
   // |number| must be >= 0. If |number| == 0 then the muxer will decide on