src/cobalt/media/base/fake_audio_render_callback.cc

// Copyright (c) 2012 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.

// MSVC++ requires this to be set before any other includes to get M_PI.
#define _USE_MATH_DEFINES

#include <cmath>

#include "cobalt/media/base/fake_audio_render_callback.h"
#include "starboard/memory.h"

namespace cobalt {
namespace media {

FakeAudioRenderCallback::FakeAudioRenderCallback(double step)
    : half_fill_(false),
      step_(step),
      last_frames_delayed_(-1),
      last_channel_count_(-1),
      volume_(1) {
  reset();
}

FakeAudioRenderCallback::~FakeAudioRenderCallback() {}

int FakeAudioRenderCallback::Render(AudioBus* audio_bus,
                                    uint32_t frames_delayed,
                                    uint32_t frames_skipped) {
  return RenderInternal(audio_bus, frames_delayed, volume_);
}

double FakeAudioRenderCallback::ProvideInput(AudioBus* audio_bus,
                                             uint32_t frames_delayed) {
  // Volume should only be applied by the caller to ProvideInput, so don't bake
  // it into the rendered audio.
  RenderInternal(audio_bus, frames_delayed, 1.0);
  return volume_;
}

int FakeAudioRenderCallback::RenderInternal(AudioBus* audio_bus,
                                            uint32_t frames_delayed,
                                            double volume) {
  DCHECK_LE(frames_delayed, static_cast<uint32_t>(INT_MAX));
  last_frames_delayed_ = static_cast<int>(frames_delayed);
  last_channel_count_ = audio_bus->channels();

  int number_of_frames = audio_bus->frames();
  if (half_fill_) number_of_frames /= 2;

  // Fill first channel with a sine wave.
  for (int i = 0; i < number_of_frames; ++i)
    audio_bus->channel(0)[i] = sin(2 * M_PI * (x_ + step_ * i)) * volume;
  x_ += number_of_frames * step_;

  // Copy first channel into the rest of the channels.
  for (int i = 1; i < audio_bus->channels(); ++i) {
    SbMemoryCopy(audio_bus->channel(i), audio_bus->channel(0),
                 number_of_frames * sizeof(*audio_bus->channel(i)));
  }

  return number_of_frames;
}

}  // namespace media
}  // namespace cobalt