Implemented Multiple video track recoding.

media/capture/webm_muxer.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MEDIA_FILTERS_LIBWEBM_MUXER_H_
 #define MEDIA_FILTERS_LIBWEBM_MUXER_H_
 
 #include <set>
 
 #include "base/callback.h"
@@ skipping 18 matching lines @@
 // containing a single encoded video frame. WebM container has no Trailer.
 // Clients will push encoded VPx video frames one by one via OnEncodedVideo().
 // libwebm will eventually ping the WriteDataCB passed on contructor with the
 // wrapped encoded data.
 // WebmMuxer is designed for single thread use throughout.
 // [1] http://www.webmproject.org/docs/container/
 // [2] http://www.matroska.org/technical/specs/index.html
 // TODO(mcasas): Add support for Audio muxing.
 class MEDIA_EXPORT WebmMuxer : public NON_EXPORTED_BASE(mkvmuxer::IMkvWriter) {
  public:
+  using EncodedVideoCB =
+      base::Callback<void(const scoped_refptr<VideoFrame>& video_frame,
+                          scoped_ptr<std::string> encoded_data,
+                          base::TimeTicks timestamp,
+                          bool is_key_frame)>;
+
   // Callback to be called when WebmMuxer is ready to write a chunk of data,
   // either any file header or a SingleBlock.
   using WriteDataCB = base::Callback<void(base::StringPiece)>;
 
   explicit WebmMuxer(const WriteDataCB& write_data_callback);
   ~WebmMuxer() override;
 
+  EncodedVideoCB GenerateOnEncodedVideoCallback();
+
+ private:
+  friend class WebmMuxerTest;
+  struct VideoMuxerArg {
+    VideoMuxerArg(
+        const base::TimeTicks& first_frame_timestamp, uint64 track_number)
+        : first_frame_timestamp(first_frame_timestamp),
+          track_number(track_number) {}
+
+    base::TimeTicks first_frame_timestamp;
+    uint64 track_number;
+  };
+
   // Adds a |video_frame| with |encoded_data.data()| to WebM Segment.
-  void OnEncodedVideo(const scoped_refptr<VideoFrame>& video_frame,
+  void OnEncodedVideo(int track_index,
+                      const scoped_refptr<VideoFrame>& video_frame,
                       scoped_ptr<std::string> encoded_data,
                       base::TimeTicks timestamp,
                       bool is_key_frame);
 
- private:
-  friend class WebmMuxerTest;
+  int GetNextVideoTrackIndex() const;
 
   // Creates and adds a new video track. Called upon receiving the first
   // frame of a given Track, adds |frame_size| and |frame_rate| to the Segment
   // info, although individual frames passed to OnEncodedVideo() can have any
   // frame size.
-  void AddVideoTrack(const gfx::Size& frame_size, double frame_rate);
+  uint64 AddVideoTrack(const gfx::Size& frame_size, double frame_rate);
 
   // IMkvWriter interface.
   mkvmuxer::int32 Write(const void* buf, mkvmuxer::uint32 len) override;
   mkvmuxer::int64 Position() const override;
   mkvmuxer::int32 Position(mkvmuxer::int64 position) override;
   bool Seekable() const override;
   void ElementStartNotify(mkvmuxer::uint64 element_id,
                           mkvmuxer::int64 position) override;
 
   // Used to DCHECK that we are called on the correct thread.
   base::ThreadChecker thread_checker_;
 
-  // A caller-side identifier to interact with |segment_|, initialised upon
-  // first frame arrival by AddVideoTrack().
-  uint64_t track_index_;
-
-  // Origin of times for frame timestamps.
-  base::TimeTicks first_frame_timestamp_;
+  // Arguments for each tracks to mkvmuxer.
+  std::vector<VideoMuxerArg> video_muxer_args_;
 
   // Callback to dump written data as being called by libwebm.
   const WriteDataCB write_data_callback_;
 
   // Rolling counter of the position in bytes of the written goo.
   base::CheckedNumeric<mkvmuxer::int64> position_;
 
   // The MkvMuxer active element.
   mkvmuxer::Segment segment_;
 
   DISALLOW_COPY_AND_ASSIGN(WebmMuxer);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_FILTERS_LIBWEBM_MUXER_H_