Encrypted Media: Enforcing the CDM to decode audio into S16 integers.

media/filters/decrypting_audio_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_AUDIO_DECODER_H_
 #define MEDIA_FILTERS_DECRYPTING_AUDIO_DECODER_H_
 
 #include "base/callback.h"
 #include "base/memory/ref_counted.h"
 #include "media/base/audio_decoder.h"
 #include "media/base/decryptor.h"
 #include "media/base/demuxer_stream.h"
 
 namespace base {
 class MessageLoopProxy;
 }
 
 namespace media {
 
 class DecoderBuffer;
 class Decryptor;
 
 // Decryptor-based AudioDecoder implementation that can decrypt and decode
 // encrypted audio buffers and return decrypted and decompressed audio frames.
 // All public APIs and callbacks are trampolined to the |message_loop_| so
 // that no locks are required for thread safety.
 class MEDIA_EXPORT DecryptingAudioDecoder : public AudioDecoder {
  public:
+  // We do not currently have a way to let the Decryptor choose the output
+  // audio sample format and notify us of its choice. Therefore, we require all
+  // Decryptor implementations to decode audio into a fixed integer sample
+  // format designated by kSupportedBitsPerChannel.
+  // TODO(xhwang): Remove this restriction after http://crbug.com/169105 fixed.
+  static const int kSupportedBitsPerChannel;
+
   DecryptingAudioDecoder(
       const scoped_refptr<base::MessageLoopProxy>& message_loop,
       const SetDecryptorReadyCB& set_decryptor_ready_cb);
 
   // AudioDecoder 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;
@@ skipping 112 matching lines @@
 
   base::TimeDelta output_timestamp_base_;
   int total_samples_decoded_;
 
   DISALLOW_COPY_AND_ASSIGN(DecryptingAudioDecoder);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_FILTERS_DECRYPTING_AUDIO_DECODER_H_