Implement WebKitClientImpl::loadAudioResource() to decode in-memory audio fil...

media/filters/audio_file_reader.h

+// Copyright (c) 2010 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_AUDIO_FILE_READER_H_
+#define MEDIA_FILTERS_AUDIO_FILE_READER_H_
+
+#include <vector>
+#include "media/filters/ffmpeg_glue.h"
+
+struct AVCodec;
+struct AVCodecContext;
+struct AVFormatContext;
+
+namespace media {
+
+class FFmpegURLProtocol;
+
+class AudioFileReader {
+ public:
+  // Audio file data will be read using the given protocol.
+  // Optionally, NULL may be passed in and SetProtocal() can be called
+  // later on before Open() is called.
+  explicit AudioFileReader(FFmpegURLProtocol* protocol);
+  virtual ~AudioFileReader();
+
+  // SetProtocol() may be set before a call to Open().
+  void SetProtocol(FFmpegURLProtocol* protocol) { protocol_ = protocol; }
+
+  int Open();

[scherkus (not reviewing), 2010/12/09 17:35:40]

what's the result of this operation?

it looks like the callee simply treats it as a bool -- perhaps we're better off
returning true/false since we don't want to leak FFmpeg error codes to the
callee

[Chris Rogers, 2010/12/10 23:34:00]

You're right, returning bool is better - switched to that.

On 2010/12/09 17:35:40, scherkus wrote:

+  void Close();
+
+  // After a call to Open(), reads |number_of_frames| into |audio_data|.
+  // |audio_data| must be of the same size as NumberOfChannels().
+  // The audio data will be decoded as floating-point linear PCM with
+  // a nominal range of -1.0 -> +1.0.
+  // Returns 0 on success.
+  int Read(const std::vector<float*>& audio_data, size_t number_of_frames);
+
+  size_t NumberOfChannels() const;

[scherkus (not reviewing), 2010/12/09 17:35:40]

these look like simple accessors and should be named:
channels()
sample_rate()
duration()
length()

[Chris Rogers, 2010/12/10 23:34:00]

Done.

+  double GetSampleRate() const;
+  double GetDuration() const;
+  size_t Length() const;

[scherkus (not reviewing), 2010/12/09 17:35:40]

what is length computing?

judging by the call perhaps this should be renamed frames or number_of_frames

[Chris Rogers, 2010/12/10 23:34:00]

changed method name to number_of_frames()

On 2010/12/09 17:35:40, scherkus wrote:

+
+ private:
+  FFmpegURLProtocol* protocol_;
+  AVFormatContext* format_context_;
+  AVCodecContext* codec_context_;
+  AVCodec* codec_;
+
+  DISALLOW_COPY_AND_ASSIGN(AudioFileReader);
+};
+
+class InMemoryDataReader : public FFmpegURLProtocol {
+ public:
+  explicit InMemoryDataReader(const char* data, int64 size);

[scherkus (not reviewing), 2010/12/09 17:35:40]

no need for explicit

[Chris Rogers, 2010/12/10 23:34:00]

Done.

+
+  virtual int Read(int size, uint8* data);
+  virtual bool GetPosition(int64* position_out);
+  virtual bool SetPosition(int64 position);
+  virtual bool GetSize(int64* size_out);
+  virtual bool IsStreaming();
+
+ private:
+  const char* data_;
+  int64 size_;
+  int64 position_;
+
+  DISALLOW_COPY_AND_ASSIGN(InMemoryDataReader);
+};
+
+class InMemoryAudioFileReader : public AudioFileReader {

[scherkus (not reviewing), 2010/12/09 17:35:40]

will we ever have different AudioFileReaders?

I'm thinking we can either:
 1) Merge this class back into AudioFileReader (and get rid of the
constructor/SetProtocol)
 2) Remove this class, leave AudioFileReader as is and change
DecodeAudioFileData to instantiate the InMemoryDataReader + pass it into
AudioFileReader

[Chris Rogers, 2010/12/10 23:34:00]

I've switched the code to use option (2).  Strangely enough, I used to have the
code using this approach...

On 2010/12/09 17:35:40, scherkus wrote:

+ public:
+  InMemoryAudioFileReader(const char* data, size_t data_size)
+    : AudioFileReader(NULL),
+      data_reader_(data, data_size) {
+    SetProtocol(&data_reader_);
+  }
+
+ private:
+  InMemoryDataReader data_reader_;
+
+  DISALLOW_COPY_AND_ASSIGN(InMemoryAudioFileReader);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_FILTERS_AUDIO_FILE_READER_H_