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      1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #ifndef MEDIA_FILTERS_DECRYPTING_AUDIO_DECODER_H_
      6 #define MEDIA_FILTERS_DECRYPTING_AUDIO_DECODER_H_
      7 
      8 #include "base/callback.h"
      9 #include "base/memory/ref_counted.h"
     10 #include "base/memory/scoped_ptr.h"
     11 #include "base/memory/weak_ptr.h"
     12 #include "base/time/time.h"
     13 #include "media/base/audio_decoder.h"
     14 #include "media/base/decryptor.h"
     15 #include "media/base/demuxer_stream.h"
     16 
     17 namespace base {
     18 class SingleThreadTaskRunner;
     19 }
     20 
     21 namespace media {
     22 
     23 class AudioTimestampHelper;
     24 class DecoderBuffer;
     25 class Decryptor;
     26 
     27 // Decryptor-based AudioDecoder implementation that can decrypt and decode
     28 // encrypted audio buffers and return decrypted and decompressed audio frames.
     29 // All public APIs and callbacks are trampolined to the |task_runner_| so
     30 // that no locks are required for thread safety.
     31 class MEDIA_EXPORT DecryptingAudioDecoder : public AudioDecoder {
     32  public:
     33   // We do not currently have a way to let the Decryptor choose the output
     34   // audio sample format and notify us of its choice. Therefore, we require all
     35   // Decryptor implementations to decode audio into a fixed integer sample
     36   // format designated by kSupportedBitsPerChannel.
     37   // TODO(xhwang): Remove this restriction after http://crbug.com/169105 fixed.
     38   static const int kSupportedBitsPerChannel;
     39 
     40   DecryptingAudioDecoder(
     41       const scoped_refptr<base::SingleThreadTaskRunner>& task_runner,
     42       const SetDecryptorReadyCB& set_decryptor_ready_cb);
     43   virtual ~DecryptingAudioDecoder();
     44 
     45   // AudioDecoder implementation.
     46   virtual std::string GetDisplayName() const OVERRIDE;
     47   virtual void Initialize(const AudioDecoderConfig& config,
     48                           const PipelineStatusCB& status_cb,
     49                           const OutputCB& output_cb) OVERRIDE;
     50   virtual void Decode(const scoped_refptr<DecoderBuffer>& buffer,
     51                       const DecodeCB& decode_cb) OVERRIDE;
     52   virtual void Reset(const base::Closure& closure) OVERRIDE;
     53 
     54  private:
     55   // For a detailed state diagram please see this link: http://goo.gl/8jAok
     56   // TODO(xhwang): Add a ASCII state diagram in this file after this class
     57   // stabilizes.
     58   // TODO(xhwang): Update this diagram for DecryptingAudioDecoder.
     59   enum State {
     60     kUninitialized = 0,
     61     kDecryptorRequested,
     62     kPendingDecoderInit,
     63     kIdle,
     64     kPendingDecode,
     65     kWaitingForKey,
     66     kDecodeFinished,
     67     kError
     68   };
     69 
     70   // Callback for DecryptorHost::RequestDecryptor(). |decryptor_attached_cb| is
     71   // called when the decryptor has been completely attached to the pipeline.
     72   void SetDecryptor(Decryptor* decryptor,
     73                     const DecryptorAttachedCB& decryptor_attached_cb);
     74 
     75   // Initializes the audio decoder on the |decryptor_| with |config_|.
     76   void InitializeDecoder();
     77 
     78   // Callback for Decryptor::InitializeAudioDecoder() during initialization.
     79   void FinishInitialization(bool success);
     80 
     81   void DecodePendingBuffer();
     82 
     83   // Callback for Decryptor::DecryptAndDecodeAudio().
     84   void DeliverFrame(int buffer_size,
     85                     Decryptor::Status status,
     86                     const Decryptor::AudioBuffers& frames);
     87 
     88   // Callback for the |decryptor_| to notify this object that a new key has been
     89   // added.
     90   void OnKeyAdded();
     91 
     92   // Resets decoder and calls |reset_cb_|.
     93   void DoReset();
     94 
     95   // Sets timestamps for |frames| and then passes them to |output_cb_|.
     96   void ProcessDecodedFrames(const Decryptor::AudioBuffers& frames);
     97 
     98   scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
     99 
    100   State state_;
    101 
    102   PipelineStatusCB init_cb_;
    103   OutputCB output_cb_;
    104   DecodeCB decode_cb_;
    105   base::Closure reset_cb_;
    106 
    107   // The current decoder configuration.
    108   AudioDecoderConfig config_;
    109 
    110   // Callback to request/cancel decryptor creation notification.
    111   SetDecryptorReadyCB set_decryptor_ready_cb_;
    112 
    113   Decryptor* decryptor_;
    114 
    115   // The buffer that needs decrypting/decoding.
    116   scoped_refptr<media::DecoderBuffer> pending_buffer_to_decode_;
    117 
    118   // Indicates the situation where new key is added during pending decode
    119   // (in other words, this variable can only be set in state kPendingDecode).
    120   // If this variable is true and kNoKey is returned then we need to try
    121   // decrypting/decoding again in case the newly added key is the correct
    122   // decryption key.
    123   bool key_added_while_decode_pending_;
    124 
    125   scoped_ptr<AudioTimestampHelper> timestamp_helper_;
    126 
    127   // NOTE: Weak pointers must be invalidated before all other member variables.
    128   base::WeakPtrFactory<DecryptingAudioDecoder> weak_factory_;
    129   base::WeakPtr<DecryptingAudioDecoder> weak_this_;
    130 
    131   DISALLOW_COPY_AND_ASSIGN(DecryptingAudioDecoder);
    132 };
    133 
    134 }  // namespace media
    135 
    136 #endif  // MEDIA_FILTERS_DECRYPTING_AUDIO_DECODER_H_
    137