Implement WebRTC in Chrome for TV

content/renderer/media/rtc_video_decoder_bridge_tv.h

+// Copyright (c) 2013 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 CONTENT_RENDERER_MEDIA_RTC_VIDEO_DECODER_BRIDGE_TV_H_
+#define CONTENT_RENDERER_MEDIA_RTC_VIDEO_DECODER_BRIDGE_TV_H_
+
+#include "base/basictypes.h"
+#include "base/message_loop_proxy.h"
+#include "content/common/content_export.h"
+#include "media/base/audio_decoder_config.h"
+#include "media/base/decoder_buffer_queue.h"
+#include "media/base/demuxer.h"
+#include "media/base/demuxer_stream.h"
+#include "media/base/pipeline_status.h"
+#include "media/base/video_decoder_config.h"
+#include "third_party/webrtc/modules/video_coding/codecs/interface/video_codec_interface.h"
+
+namespace content {
+
+// A singleton object shared between WebMediaPlayerAndroid and WebRTC Video
+// Engine. Note that this class provides the first remote stream.
+//
+// Example use case:
+//
+// // Before using the object:
+// if (!RTCVideoDecoderBridgeTv::Get()->AcquireOwnership())
+//   return;
+//
+// media::Demuxer demuxer = RTCVideoDecoderBridgeTv::Get()->CreateDemuxer(
+//     base::MessageLoopProxy::current());
+// if (demuxer) {
+//   // use |demuxer|.
+// }
+//
+// // When done using the object:
+// RTCVideoDecoderBridgeTv::Get()->ReleaseOwnership();
+class CONTENT_EXPORT RTCVideoDecoderBridgeTv
+    : NON_EXPORTED_BASE(public webrtc::VideoDecoder) {
+ public:
+  // Get RTCVideoDecoderBridgeTv singleton object. If it was not set
+  // before, new default instance will be created.
+  static RTCVideoDecoderBridgeTv* Get();
+
+  // Returns a demuxer object if this object is not owned; otherwise, NULL.

[Ami GONE FROM CHROMIUM, 2013/05/01 22:01:37]

Is the "otherwise, NULL" always an indication of programming error?  If yes then
the comment can be rephrased more strictly, and a DCHECK added to the impl.

[Ami GONE FROM CHROMIUM, 2013/05/01 22:01:37]

Also returns NULL the second time it's called when called twice in a row. 
Generally the API here is pretty gnarly, with *Ownership(==being_used_) and
CreateDemuxer (*generation_) being non-orthogonal.

Does it not work to drop the *Ownership methods and replace CreateDemuxer with
CreateAndAcquireDemuxer() which returns NULL iff it has been called previously
without an intervening ReleaseDemuxer() (new call)?

That way you can drop being_used_ and generation_/demuxer_generation_ (and have
ReleaseDemuxer() simply be demuxer_.reset()).

[wonsik, 2013/05/03 18:31:19]

This singleton is mainly used in two different part --- one is peer connection
through VDF and the other is webmediaplayer_android where it accesses
media::Demuxer object. Since this is a singleton, it should make sure only one
peer connection and one webmediaplayer_android accesses the object. In addition,
the two must be the ones working together. I used MediaStreamDependencyFactory
to find out which is working with which. Perhaps I can use RenderThreadImpl.
Please take a look again.

+  virtual media::Demuxer* CreateDemuxer(
+      const scoped_refptr<base::MessageLoopProxy>& message_loop) = 0;
+
+  // Returns true if acquired the ownership of this object successfully. One
+  // should acquire ownership before using the object, and can't use the object
+  // if this method fails.
+  virtual bool AcquireOwnership() = 0;
+
+  // Releases ownership of this object.
+  virtual void ReleaseOwnership() = 0;
+};
+
+}  // namespace content
+
+#endif  // CONTENT_RENDERER_MEDIA_RTC_VIDEO_DECODER_BRIDGE_TV_H_