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 "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 {
+public:

[DaleCurtis, 2014/03/20 01:36:26]

1 space indent, no line after.  I'd just run "git cl format" and it should fix
all this...

[rileya (GONE FROM CHROMIUM), 2014/03/21 20:58:49]

Fixed.

+
+  AudioBufferConverter(const AudioParameters& output_params);

[DaleCurtis, 2014/03/20 01:36:26]

explicit

[rileya (GONE FROM CHROMIUM), 2014/03/21 20:58:49]

Done.

+  virtual ~AudioBufferConverter();
+
+  void AddInput(const scoped_refptr<AudioBuffer>& buffer);
+
+  bool HasNextBuffer();
+  scoped_refptr<AudioBuffer> GetNextBuffer();
+
+private:

[DaleCurtis, 2014/03/20 01:36:26]

ditto on style

[rileya (GONE FROM CHROMIUM), 2014/03/21 20:58:49]

Fixed.

+
+  // 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 AudioParameters& input_params);
+
+  // Determine the AudioParameters of an AudioBuffer.
+  AudioParameters AudioBufferToAudioParameters(
+      const scoped_refptr<AudioBuffer>& buffer);
+
+  // Get an AudioBuffer from |audio_converter_|.
+  scoped_refptr<AudioBuffer> Convert();
+
+  // Flush remaining output
+  void Flush();
+
+  // Is |new_params| a config change from |input_params_|?
+  bool IsConfigChange(const AudioParameters& new_params);
+
+  // 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_;
+
+  // Ratio of sample rates between input and output params (we use this to
+  // compute how many frames of output we'll get out of a given number of
+  // input frames).
+  double sample_rate_ratio_;
+
+  // 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.
+  std::list<scoped_refptr<AudioBuffer> > queued_inputs_;
+
+  // Offset into the front element of |queued_inputs_|. A ProvideInput() call
+  // doesn't necessarily always consume an entire buffer.
+  int offset_into_queue_;

[rileya (GONE FROM CHROMIUM), 2014/03/20 00:55:11]

This probably needs a better name.

+
+  // Buffer of output frames, to be returned by GetNextBuffer().
+  std::list<scoped_refptr<AudioBuffer> > queued_outputs_;

[DaleCurtis, 2014/03/20 01:36:26]

deque?

[rileya (GONE FROM CHROMIUM), 2014/03/21 20:58:49]

Sounds good. Done.

+
+  // How many frames of input we have on hand.
+  int input_frames_;
+
+  // Compute 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