Add FFmpeg audio decoder for the clear key CDM.

webkit/media/crypto/ppapi/ffmpeg_cdm_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 WEBKIT_MEDIA_CRYPTO_PPAPI_FFMPEG_CDM_AUDIO_DECODER_H_
+#define WEBKIT_MEDIA_CRYPTO_PPAPI_FFMPEG_CDM_AUDIO_DECODER_H_
+
+#include <vector>
+
+#include "base/basictypes.h"
+#include "base/time.h"
+#include "base/compiler_specific.h"
+#include "webkit/media/crypto/ppapi/content_decryption_module.h"
+
+struct AVCodecContext;
+struct AVFrame;
+
+namespace webkit_media {
+
+class FFmpegCdmAudioDecoder {
+ public:
+  explicit FFmpegCdmAudioDecoder(cdm::Allocator* allocator);
+  ~FFmpegCdmAudioDecoder();
+  bool Initialize(const cdm::AudioDecoderConfig& config);
+  void Deinitialize();
+  void Reset();
+
+  // Returns true when |config| is a valid audio decoder configuration.
+  static bool IsValidConfig(const cdm::AudioDecoderConfig& config);
+
+  // Decodes |compressed_buffer|. Returns |cdm::kSuccess| after storing
+  // output in |decoded_frames| when output is available. Returns
+  // |cdm::kNeedMoreData| when |compressed_frame| does not produce output.
+  // Returns |cdm::kDecodeError| when decoding fails.
+  cdm::Status DecodeBuffer(const uint8_t* compressed_buffer,
+                           int32_t compressed_buffer_size,
+                           int64_t timestamp,
+                           cdm::AudioFrames* decoded_frames);
+
+ private:
+  void ResetAudioTimingData();
+  void ReleaseFFmpegResources();
+
+  base::TimeDelta GetNextOutputTimestamp() const;
+
+  void SerializeInt64(int64_t value);
+
+  bool is_initialized_;
+
+  cdm::Allocator* const allocator_;
+
+  // FFmpeg structures owned by this object.
+  AVCodecContext* codec_context_;
+  AVFrame* av_frame_;
+
+  // Decoded audio format.

[ddorwin, 2012/10/25 01:27:18]

Just "Audio format"?
Decoded makes it sound like a per call thing.

[Tom Finegan, 2012/10/25 01:42:19]

Done.

+  int bits_per_channel_;
+  int samples_per_second_;
+
+  // Used for computing output timestamps.
+  int bytes_per_frame_;
+  base::TimeDelta output_timestamp_base_;
+  int64_t total_frames_decoded_;
+  base::TimeDelta last_input_timestamp_;
+
+  // Number of output sample bytes to drop before generating

[ddorwin, 2012/10/25 01:27:18]

Why would one want to do that?

[Tom Finegan, 2012/10/25 01:42:19]

Because Vorbis and negative timestamps. Comment in .cc files explains a bit
more, and includes a link to the spec. Added some more text to the comment.

Note: from media.

+  // output buffers.
+  int output_bytes_to_drop_;
+
+  typedef std::vector<uint8_t> SerializedAudioFrames;
+  SerializedAudioFrames serialized_audio_frames_;
+
+  DISALLOW_COPY_AND_ASSIGN(FFmpegCdmAudioDecoder);
+};
+
+}  // namespace webkit_media
+
+#endif  // WEBKIT_MEDIA_CRYPTO_PPAPI_FFMPEG_CDM_AUDIO_DECODER_H_