media/base/audio_buffer_converter.h

   1 // Copyright 2014 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_BASE_AUDIO_BUFFER_CONVERTER
   6 #define MEDIA_BASE_AUDIO_BUFFER_CONVERTER
   7
   8 #include <deque>
   9
  10 #include "base/memory/ref_counted.h"
  11 #include "base/memory/scoped_ptr.h"
  12 #include "base/time/time.h"
  13 #include "media/audio/audio_parameters.h"
  14 #include "media/base/audio_converter.h"
  15 #include "media/base/audio_timestamp_helper.h"
  16 #include "media/base/media_export.h"
  17
  18 namespace media {
  19
  20 class AudioBuffer;
  21 class AudioBus;
  22
  23 // Takes AudioBuffers in any format and uses an AudioConverter to convert them
  24 // to a common format (usually the hardware output format).
  25 class MEDIA_EXPORT AudioBufferConverter : public AudioConverter::InputCallback {
  26  public:
  27   explicit AudioBufferConverter(const AudioParameters& output_params);
  28   ~AudioBufferConverter() override;
  29
  30   void AddInput(const scoped_refptr<AudioBuffer>& buffer);
  31
  32   // Is an output buffer available via GetNextBuffer()?
  33   bool HasNextBuffer();
  34
  35   // This should only be called this is HasNextBuffer() returns true.
  36   scoped_refptr<AudioBuffer> GetNextBuffer();
  37
  38   // Reset internal state.
  39   void Reset();
  40
  41   // Reset internal timestamp state. Upon the next AddInput() call, our base
  42   // timestamp will be set to match the input buffer.
  43   void ResetTimestampState();
  44
  45   int input_buffer_size_for_testing() const {
  46     return input_params_.frames_per_buffer();
  47   }
  48   int input_frames_left_for_testing() const {
  49     return input_frames_;
  50   }
  51
  52  private:
  53   // Callback to provide data to the AudioConverter
  54   double ProvideInput(AudioBus* audio_bus,
  55                       base::TimeDelta buffer_delay) override;
  56
  57   // Reset the converter in response to a configuration change.
  58   void ResetConverter(const scoped_refptr<AudioBuffer>& input_buffer);
  59
  60   // Perform conversion if we have enough data.
  61   void ConvertIfPossible();
  62
  63   // Flush remaining output
  64   void Flush();
  65
  66   // The output parameters.
  67   AudioParameters output_params_;
  68
  69   // The current input parameters (we cache these to detect configuration
  70   // changes, so we know when to reset the AudioConverter).
  71   AudioParameters input_params_;
  72
  73   typedef std::deque<scoped_refptr<AudioBuffer> > BufferQueue;
  74
  75   // Queued up inputs (there will never be all that much data stored here, as
  76   // soon as there's enough here to produce an output buffer we will do so).
  77   BufferQueue queued_inputs_;
  78
  79   // Offset into the front element of |queued_inputs_|. A ProvideInput() call
  80   // doesn't necessarily always consume an entire buffer.
  81   int last_input_buffer_offset_;
  82
  83   // Buffer of output frames, to be returned by GetNextBuffer().
  84   BufferQueue queued_outputs_;
  85
  86   // How many frames of input we have in |queued_inputs_|.
  87   int input_frames_;
  88
  89   // Input frames in the AudioConverter's internal buffers.
  90   double buffered_input_frames_;
  91
  92   // Ratio of sample rates, in/out.
  93   double io_sample_rate_ratio_;
  94
  95   // Computes timestamps in terms of the output sample rate.
  96   AudioTimestampHelper timestamp_helper_;
  97
  98   // Are we flushing everything, without regard for providing AudioConverter
  99   // full AudioBuses in ProvideInput()?
 100   bool is_flushing_;
 101
 102   // The AudioConverter which does the real work here.
 103   scoped_ptr<AudioConverter> audio_converter_;
 104 };
 105
 106 }  // namespace media
 107
 108 #endif  // MEDIA_BASE_AUDIO_BUFFER_CONVERTER