Add support for midstream audio configuration changes.

media/base/audio_buffer_converter.h

+// Copyright 2014 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_BASE_AUDIO_BUFFER_CONVERTER
+#define MEDIA_BASE_AUDIO_BUFFER_CONVERTER
+
+#include <deque>
+
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/time/time.h"
+#include "media/audio/audio_parameters.h"
+#include "media/base/audio_converter.h"
+#include "media/base/audio_timestamp_helper.h"
+#include "media/base/media_export.h"
+
+namespace media {
+
+class AudioBuffer;
+class AudioBus;
+
+// Takes AudioBuffers in any format and uses an AudioConverter to convert them
+// to a common format (usually the hardware output format).
+class AudioBufferConverter : public AudioConverter::InputCallback {

[DaleCurtis, 2014/03/27 20:35:07]

need MEDIA_EXPORT here.

+ public:
+  explicit AudioBufferConverter(const AudioParameters& output_params);
+  virtual ~AudioBufferConverter();
+
+  void AddInput(const scoped_refptr<AudioBuffer>& buffer);
+
+  // Is an output buffer available via GetNextBuffer()?
+  bool HasNextBuffer();
+
+  // This should only be called this is HasNextBuffer() returns true.
+  scoped_refptr<AudioBuffer> GetNextBuffer();
+
+  // Reset internal state.
+  void Reset();
+
+  // Reset internal timestamp state. Upon the next AddInput() call, our base
+  // timestamp will be set to match the input buffer.
+  void ResetTimestampState();
+
+ private:
+  // Callback to provide data to the AudioConverter
+  virtual double ProvideInput(AudioBus* audio_bus,
+                              base::TimeDelta buffer_delay) OVERRIDE;
+
+  // Reset the converter in response to a configuration change.
+  void ResetConverter(const scoped_refptr<AudioBuffer>& input_buffer);
+
+  // Perform conversion if we have enough data.
+  void ConvertIfPossible();
+
+  // Flush remaining output
+  void Flush();
+
+  // The output parameters.
+  AudioParameters output_params_;
+
+  // The current input parameters (we cache these to detect configuration
+  // changes, so we know when to reset the AudioConverter).
+  AudioParameters input_params_;
+
+  typedef std::deque<scoped_refptr<AudioBuffer> > BufferQueue;
+
+  // Queued up inputs (there will never be all that much data stored here, as
+  // soon as there's enough here to produce an output buffer we will do so).
+  BufferQueue queued_inputs_;
+
+  // Offset into the front element of |queued_inputs_|. A ProvideInput() call
+  // doesn't necessarily always consume an entire buffer.
+  int last_input_buffer_offset_;
+
+  // Buffer of output frames, to be returned by GetNextBuffer().
+  BufferQueue queued_outputs_;
+
+  // How many frames of input we have in |queued_inputs_|.
+  int input_frames_;
+
+  // Input frames in the AudioConverter's internal buffers.
+  double buffered_input_frames_;
+
+  // Ratio of sample rates, in/out.
+  double io_sample_rate_ratio_;
+
+  // Computes timestamps in terms of the output sample rate.
+  AudioTimestampHelper timestamp_helper_;
+
+  // Are we flushing everything, without regard for providing AudioConverter
+  // full AudioBuses in ProvideInput()?
+  bool is_flushing_;
+
+  // The AudioConverter which does the real work here.
+  scoped_ptr<AudioConverter> audio_converter_;
+};
+
+}  // namespace media
+
+#endif  // MEDIA_BASE_AUDIO_BUFFER_CONVERTER