Add DecryptingDemuxerStream.

media/filters/decrypting_demuxer_stream.h

Index: media/filters/decrypting_demuxer_stream.h
diff --git a/media/filters/decrypting_demuxer_stream.h b/media/filters/decrypting_demuxer_stream.h
new file mode 100644
index 0000000000000000000000000000000000000000..a2546bdbaa9fc4b07e8e42a6e482b6d573d01a48
--- /dev/null
+++ b/media/filters/decrypting_demuxer_stream.h
@@ -0,0 +1,147 @@
+// 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_DEMUXER_STREAM_H_
+#define MEDIA_FILTERS_DECRYPTING_DEMUXER_STREAM_H_
+
+#include "base/callback.h"
+#include "base/memory/ref_counted.h"
+#include "media/base/decryptor.h"
+#include "media/base/demuxer_stream.h"
+
+namespace base {
+class MessageLoopProxy;
+}
+
+namespace media {
+
+class DecoderBuffer;
+
+// Decryptor-based DemuxerStream implementation that converts an encrypted
+// demuxer stream to a clear demuxer stream.

[ddorwin, 2012/11/13 01:08:49]

Does it really convert the stream? Is the stream encrypted or the blocks within
it?

[xhwang, 2012/11/13 21:10:21]

Hmm, let's say the video elementary stream is compressed, it actually mean all
frames(buffers/blocks) are compressed. Similarly, an encrypted stream means that
all blocks within it are encrypted. WDYT?

[ddorwin, 2012/11/13 22:52:33]

Not _all_ blocks within the encrypted stream (at least the stream this demuxer
receives/produces) are encrypted. This class is created for the entire life of
the stream. Some blocks may be unencrypted.

The comment is fine and gets the point across.

[xhwang, 2012/11/14 18:01:52]

Right. Added "potentially" to be accurate.

+// All public APIs and callbacks are trampolined to the |message_loop_| so
+// that no locks are required for thread safety.
+class MEDIA_EXPORT DecryptingDemuxerStream : public DemuxerStream {
+ public:
+  // Callback to get a message loop.
+  typedef base::Callback<
+      scoped_refptr<base::MessageLoopProxy>()> MessageLoopFactoryCB;
+  // Callback to notify decryptor creation.
+  typedef base::Callback<void(Decryptor*)> DecryptorNotificationCB;
+  // Callback to request/cancel decryptor creation notification.
+  // Calling this callback with a non-null callback registers decryptor creation
+  // notification. When the decryptor is created, notification will be sent
+  // through the provided callback.
+  // Calling this callback with a null callback cancels previously registered
+  // decryptor creation notification. Any previously provided callback will be
+  // fired immediately with NULL.
+  typedef base::Callback<void(const DecryptorNotificationCB&)>
+      RequestDecryptorNotificationCB;
+
+  DecryptingDemuxerStream(
+      const MessageLoopFactoryCB& message_loop_factory_cb,
+      const RequestDecryptorNotificationCB& request_decryptor_notification_cb);
+
+  void Initialize(const scoped_refptr<DemuxerStream>& stream,
+                  const PipelineStatusCB& status_cb);
+  void Reset(const base::Closure& closure);
+
+  // DemuxerStream implementation.
+  virtual void Read(const ReadCB& read_cb) OVERRIDE;
+  virtual const AudioDecoderConfig& audio_decoder_config() OVERRIDE;
+  virtual const VideoDecoderConfig& video_decoder_config() OVERRIDE;
+  virtual Type type() OVERRIDE;
+  virtual void EnableBitstreamConverter() OVERRIDE;
+
+ protected:
+  virtual ~DecryptingDemuxerStream();
+
+ private:
+  // For a detailed state diagram please see this link: http://goo.gl/8jAok
+  // TODO(xhwang): Add a ASCII state diagram in this file after this class
+  // stabilizes.
+  // TODO(xhwang): Update this diagram for DecryptingDemuxerStream.
+  enum State {
+    kUninitialized = 0,
+    kDecryptorRequested,
+    kIdle,
+    kPendingDemuxerRead,
+    kPendingDecrypt,
+    kWaitingForKey,
+  };
+
+  // Carries out the initialization operation scheduled by Initialize().
+  void DoInitialize(const scoped_refptr<DemuxerStream>& stream,
+                    const PipelineStatusCB& status_cb);
+
+  // Callback for DecryptorHost::RequestDecryptor().
+  void SetDecryptor(Decryptor* decryptor);
+
+  // Callback for DemuxerStream::Read().
+  void DecryptBuffer(DemuxerStream::Status status,
+                     const scoped_refptr<DecoderBuffer>& buffer);
+
+  // Carries out the buffer decryption operation scheduled by DecryptBuffer().
+  void DoDecryptBuffer(DemuxerStream::Status status,
+                       const scoped_refptr<DecoderBuffer>& buffer);
+
+  void DecryptPendingBuffer();
+
+  // Callback for Decryptor::Decrypt().
+  void DeliverBuffer(Decryptor::Status status,
+                     const scoped_refptr<DecoderBuffer>& decrypted_buffer);
+
+  // Carries out the frame delivery operation scheduled by DeliverBuffer().
+  void DoDeliverBuffer(Decryptor::Status status,
+                       const scoped_refptr<DecoderBuffer>& decrypted_buffer);
+
+  // Callback for the |decryptor_| to notify the DecryptingDemuxerStream that

[ddorwin, 2012/11/13 01:08:49]

s/the DecryptingDemuxerStream/this object/
We should make similar changes in DVD and DAD.

[xhwang, 2012/11/13 21:10:21]

Done.

+  // a new key has been added.
+  void OnKeyAdded();
+
+  // Resets decoder and calls |reset_cb_|.
+  void DoReset();
+
+  // Returns Decryptor::StreamType converted from |stream_type_|.

[ddorwin, 2012/11/13 01:08:49]

Should we just move Type to a common location in media/base?

[xhwang, 2012/11/13 21:10:21]

Agreed. In another CL? TOTO added in decryptor.h

+  Decryptor::StreamType GetDecryptorStreamType() const;
+
+  // This is !is_null() iff Initialize() hasn't been called.
+  MessageLoopFactoryCB message_loop_factory_cb_;
+
+  scoped_refptr<base::MessageLoopProxy> message_loop_;
+
+  // Current state of the DecryptingDemuxerStream.

[ddorwin, 2012/11/13 01:08:49]

s/DecryptingDemuxerStream/object/
But you can probably just remove this comment since that's what State/state_
should be.

[xhwang, 2012/11/13 21:10:21]

Done.

+  State state_;
+
+  PipelineStatusCB init_cb_;
+  ReadCB read_cb_;
+  base::Closure reset_cb_;
+
+  // Pointer to the input demuxer stream that will feed us encrypted buffers.
+  scoped_refptr<DemuxerStream> demuxer_stream_;
+
+  Type stream_type_;
+  scoped_ptr<AudioDecoderConfig> audio_config_;
+  scoped_ptr<VideoDecoderConfig> video_config_;
+
+  // Callback to request/cancel decryptor creation notification.
+  RequestDecryptorNotificationCB request_decryptor_notification_cb_;
+
+  Decryptor* decryptor_;
+
+  // The buffer returned by the demuxer that needs to be decrypted.
+  scoped_refptr<media::DecoderBuffer> pending_buffer_to_decrypt_;
+
+  // Indicates the situation where new key is added during pending decryption
+  // (in other words, this variable can only be set in state kPendingDecrypt).
+  // If this variable is true and kNoKey is returned then we need to try
+  // decrypting again in case the newly added key is the correct decryption key.
+  bool key_added_while_pending_decrypt_;

[ddorwin, 2012/11/13 01:08:49]

Does "...decrypt_pending_" make more sense? "... while a decrypt is pending".
The way it is sounds like the class is pending (waiting for?) a decrypt.

[xhwang, 2012/11/13 21:10:21]

Done.

+
+  DISALLOW_COPY_AND_ASSIGN(DecryptingDemuxerStream);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_FILTERS_DECRYPTING_DEMUXER_STREAM_H_