media/filters/audio_file_reader.h

   1 // Copyright (c) 2011 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_AUDIO_FILE_READER_H_
   6 #define MEDIA_FILTERS_AUDIO_FILE_READER_H_
   7
   8 #include "base/basictypes.h"
   9 #include "base/memory/scoped_ptr.h"
  10 #include "media/base/media_export.h"
  11
  12 struct AVCodecContext;
  13
  14 namespace base { class TimeDelta; }
  15
  16 namespace media {
  17
  18 class AudioBus;
  19 class FFmpegGlue;
  20 class FFmpegURLProtocol;
  21
  22 class MEDIA_EXPORT AudioFileReader {
  23  public:
  24   // Audio file data will be read using the given protocol.
  25   // The AudioFileReader does not take ownership of |protocol| and
  26   // simply maintains a weak reference to it.
  27   explicit AudioFileReader(FFmpegURLProtocol* protocol);
  28   virtual ~AudioFileReader();
  29
  30   // Open() reads the audio data format so that the sample_rate(),
  31   // channels(), duration(), and number_of_frames() methods can be called.
  32   // It returns |true| on success.
  33   bool Open();
  34   void Close();
  35
  36   // After a call to Open(), attempts to fully fill |audio_bus| with decoded
  37   // audio data.  Any unfilled frames will be zeroed out.
  38   // |audio_data| must be of the same size as channels().
  39   // The audio data will be decoded as floating-point linear PCM with
  40   // a nominal range of -1.0 -> +1.0.
  41   // Returns the number of sample-frames actually read which will always be
  42   // <= audio_bus->frames()
  43   int Read(AudioBus* audio_bus);
  44
  45   // These methods can be called once Open() has been called.
  46   int channels() const { return channels_; }
  47   int sample_rate() const { return sample_rate_; }
  48
  49   // Please note that duration() and number_of_frames() attempt to be accurate,
  50   // but are only estimates.  For some encoded formats, the actual duration
  51   // of the file can only be determined once all the file data has been read.
  52   // The Read() method returns the actual number of sample-frames it has read.
  53   base::TimeDelta duration() const;
  54   int64 number_of_frames() const;
  55
  56  private:
  57   scoped_ptr<FFmpegGlue> glue_;
  58   AVCodecContext* codec_context_;
  59   int stream_index_;
  60   FFmpegURLProtocol* protocol_;
  61   int channels_;
  62   int sample_rate_;
  63
  64   // AVSampleFormat initially requested; not Chrome's SampleFormat.
  65   int av_sample_format_;
  66
  67   DISALLOW_COPY_AND_ASSIGN(AudioFileReader);
  68 };
  69
  70 }  // namespace media
  71
  72 #endif  // MEDIA_FILTERS_AUDIO_FILE_READER_H_