Add video decoding methods in Decryptor and add DecryptingVideoDecoder.

media/filters/decrypting_video_decoder.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_FILTERS_DECRYPTING_VIDEO_DECODER_H_
+#define MEDIA_FILTERS_DECRYPTING_VIDEO_DECODER_H_
+
+#include "base/callback.h"
+#include "base/memory/ref_counted.h"
+#include "media/base/decryptor.h"
+#include "media/base/demuxer_stream.h"
+#include "media/base/video_decoder.h"
+
+namespace base {
+class MessageLoopProxy;
+}
+
+namespace media {
+
+class DecoderBuffer;
+class Decryptor;
+
+// Decryptor-based VideoDecoder implementation that can decrypt and decode
+// encrypted video buffers and return decrypted and decompressed video frames.
+//
+// TODO(xhwang): For now, DecryptingVideoDecoder relies on the decryptor to do
+// both decryption and video decoding. Add the path to use the decryptor for
+// decryption only and use other VideoDecoder implementations within
+// DecryptingVideoDecoder for video decoding.
+class MEDIA_EXPORT DecryptingVideoDecoder : public VideoDecoder {
+ public:
+  typedef base::Callback<
+      scoped_refptr<base::MessageLoopProxy>()> MessageLoopFactoryCB;
+  DecryptingVideoDecoder(const MessageLoopFactoryCB& message_loop_factory_cb,

[ddorwin, 2012/09/28 17:36:40]

// Blah.
// |decryptor| must to outlive this instance.

[xhwang, 2012/09/30 19:58:51]

Done.

+                         Decryptor* decryptor);
+
+  // VideoDecoder implementation.
+  virtual void Initialize(const scoped_refptr<DemuxerStream>& stream,
+                          const PipelineStatusCB& status_cb,
+                          const StatisticsCB& statistics_cb) OVERRIDE;
+  virtual void Read(const ReadCB& read_cb) OVERRIDE;
+  virtual void Reset(const base::Closure& closure) OVERRIDE;
+  virtual void Stop(const base::Closure& closure) OVERRIDE;
+
+ protected:
+  virtual ~DecryptingVideoDecoder();
+
+ private:
+  enum DecoderState {
+    kUninitialized,
+    kNormal,
+    kDecodeFinished
+  };
+
+  // Callback for Decryptor::InitializeVideoDecoder().
+  void OnDecoderInitialized(bool success);
+
+  // Carries out the buffer reading operation scheduled by Read().
+  void DoRead(const ReadCB& read_cb);
+
+  void ReadFromDemuxerStream();
+
+  // Callback for DemuxerStream::Read().
+  void DecryptAndDecodeBuffer(DemuxerStream::Status status,
+                              const scoped_refptr<DecoderBuffer>& buffer);
+
+  // Carries out the buffer decrypting/decoding operation scheduled by
+  // DecryptAndDecodeBuffer().
+  void DoDecryptAndDecodeBuffer(DemuxerStream::Status status,
+                                const scoped_refptr<DecoderBuffer>& buffer);
+
+  // Callback for Decryptor::DecryptAndDecodeVideo().
+  void DeliverFrame(int buffer_size,

[ddorwin, 2012/09/28 17:36:40]

The previous Decryptor callback started with "On".

[xhwang, 2012/09/30 19:58:51]

We use both in media code. I use On* for callbacks that only acknowledge
something has finished (e.g. by calling completion callback). And use imperative
function names for those callbacks that do a lot of real work. But this is just
my opinion and can be persuaded :)

+                    Decryptor::Status status,
+                    const scoped_refptr<VideoFrame>& frame);
+
+  // Carries out the frame delivery operation scheduled by DeliverFrame().
+  void DoDeliverFrame(int buffer_size,
+                      Decryptor::Status status,
+                      const scoped_refptr<VideoFrame>& frame);
+
+  // Reset decoder and call |reset_cb_|.
+  void DoReset();
+
+  // Free decoder resources and call |stop_cb_|.
+  void DoStop();
+
+  // This is !is_null() iff Initialize() hasn't been called.
+  MessageLoopFactoryCB message_loop_factory_cb_;
+
+  scoped_refptr<base::MessageLoopProxy> message_loop_;
+  DecoderState state_;
+  PipelineStatusCB status_cb_;
+  StatisticsCB statistics_cb_;
+  ReadCB read_cb_;
+  base::Closure reset_cb_;
+  base::Closure stop_cb_;
+
+  // Pointer to the demuxer stream that will feed us compressed buffers.
+  scoped_refptr<DemuxerStream> demuxer_stream_;
+
+  // Pointer to a Decryptor that can decrypt and decode encrypted video buffers.

[ddorwin, 2012/09/28 17:36:40]

This comment will need to be updated when you address the main TODO. Does it
need to be this specific? Will you remember to update it? :)

[xhwang, 2012/09/30 19:58:51]

Removed.

+  Decryptor* const decryptor_;
+
+  DISALLOW_COPY_AND_ASSIGN(DecryptingVideoDecoder);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_FILTERS_DECRYPTING_VIDEO_DECODER_H_