chromium/media/base/audio_converter.h

// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
//
// AudioConverter is a complete mixing, resampling, buffering, and channel
// mixing solution for converting data from one set of AudioParameters to
// another.
//
// For efficiency, pieces are only invoked when necessary; i.e.,
//    - The resampler is only used if sample rates differ.
//    - The FIFO is only used if buffer sizes differ.
//    - The channel mixer is only used if channel layouts differ.
//
// Additionally, since resampling is the most expensive operation, input mixing
// and channel down mixing are done prior to resampling.  Likewise, channel up
// mixing is performed after resampling.

#ifndef MEDIA_BASE_AUDIO_CONVERTER_H_
#define MEDIA_BASE_AUDIO_CONVERTER_H_

#include <list>
#include <memory>

#include "base/functional/callback.h"
#include "base/memory/raw_ptr.h"
#include "media/base/audio_glitch_info.h"
#include "media/base/audio_parameters.h"
#include "media/base/media_export.h"

namespace media {

class AudioBus;
class AudioPullFifo;
class ChannelMixer;
class MultiChannelResampler;

// Converts audio data between two AudioParameters formats.  Sample usage:
//   AudioParameters input(...), output(...);
//   AudioConverter ac(input, output);
//   std::unique_ptr<AudioBus> output_audio_bus = AudioBus::Create(output);
//   ac.AddInput(<AudioConverter::InputCallback* 1>);
//   ac.AddInput(<AudioConverter::InputCallback* 2>);
//   ac.Convert(output_audio_bus.get());
//
// Convert() will ask for input audio data from each InputCallback and convert
// the data into the provided AudioBus.
class MEDIA_EXPORT AudioConverter { … };

}  // namespace media

#endif  // MEDIA_BASE_AUDIO_CONVERTER_H_