Generate and assign media track ids in demuxers.

media/base/demuxer.h

 // Copyright (c) 2012 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_BASE_DEMUXER_H_
 #define MEDIA_BASE_DEMUXER_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 49 matching lines @@
 class MEDIA_EXPORT Demuxer : public DemuxerStreamProvider {
  public:
   // A new potentially encrypted stream has been parsed.
   // First parameter - The type of initialization data.
   // Second parameter - The initialization data associated with the stream.
   using EncryptedMediaInitDataCB =
       base::Callback<void(EmeInitDataType type,
                           const std::vector<uint8_t>& init_data)>;
 
   // Notifies demuxer clients that media track configuration has been updated
-  // (e.g. the inital stream metadata has been parsed successfully, or a new
+  // (e.g. the initial stream metadata has been parsed successfully, or a new
   // init segment has been parsed successfully in MSE case).
   using MediaTracksUpdatedCB =
       base::Callback<void(std::unique_ptr<MediaTracks>)>;
 
   Demuxer();
   ~Demuxer() override;
 
   // Returns the name of the demuxer for logging purpose.
   virtual std::string GetDisplayName() const = 0;
 
@@ skipping 47 matching lines @@
   virtual base::TimeDelta GetStartTime() const = 0;
 
   // Returns Time represented by presentation timestamp 0.
   // If the timstamps are not associated with a Time, then
   // a null Time is returned.
   virtual base::Time GetTimelineOffset() const = 0;
 
   // Returns the memory usage in bytes for the demuxer.
   virtual int64_t GetMemoryUsage() const = 0;
 
+  virtual const DemuxerStream* GetDemuxerStreamByTrackId(

[xhwang, 2016/06/09 06:06:02]

This is actually not used in this CL. Also, in your other CL, it's still TBD
whether we want/need to do this. Shall we drop this change from this CL and then
iterate on this later?

[servolk, 2016/06/09 19:14:46]

At the moment I'm inclined to think it's better to keep this API, since it's
more generic and useful. I'm not sure if I fully understand your suggestions in
https://codereview.chromium.org/1935873002/#msg19. I think this is a useful
generic API that essentially allows translating media track ids (which is what
blink operates with) into demuxer streams, and the functionality might be useful
beyond just enabling/disabling tracks. Let's have some further discussion in
https://codereview.chromium.org/1935873002 before removing this. I'll add my
thoughts in there shortly.

[xhwang, 2016/06/09 21:04:16]

In general we don't add an API because it's generic and could be useful. We add
an API because we use it.

I think it'd be great if we can hide the track ID as an implementation detail of
the demuxer stack and the rest of the media pipeline don't need to know about
it. This API definitely opens a door for that.

+      std::string track_id) const = 0;

[xhwang, 2016/06/09 06:06:02]

const ref

[servolk, 2016/06/09 19:14:46]

Done.

+
  private:
   DISALLOW_COPY_AND_ASSIGN(Demuxer);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_DEMUXER_H_