buffer_crossfader.cc

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/*

Copyright 2018 Google Inc. All Rights Reserved.

Licensed under the Apache License, Version 2.0 (the "License");

you may not use this file except in compliance with the License.

You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software

distributed under the License is distributed on an "AS-IS" BASIS,

WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

See the License for the specific language governing permissions and

limitations under the License.

*/

#include "utils/buffer_crossfader.h"

#include "base/constants_and_types.h"

#include "base/simd_utils.h"

namespace vraudio {

BufferCrossfader::BufferCrossfader(size_t num_frames)

    : crossfade_buffer_(kNumStereoChannels, num_frames) {

  DCHECK_NE(num_frames, 0);

  // Initialize the |crossfade_buffer_|.

  auto* fade_in_channel = &crossfade_buffer_[0];

  auto* fade_out_channel = &crossfade_buffer_[1];

  for (size_t frame = 0; frame < num_frames; ++frame) {

    const float crossfade_factor =

        static_cast<float>(frame) / static_cast<float>(num_frames);

    (*fade_in_channel)[frame] = crossfade_factor;

    (*fade_out_channel)[frame] = 1.0f - crossfade_factor;

void BufferCrossfader::ApplyLinearCrossfade(const AudioBuffer& input_fade_in,

                                            const AudioBuffer& input_fade_out,

                                            AudioBuffer* output) const {

  DCHECK(output);

  DCHECK_NE(output, &input_fade_in);

  DCHECK_NE(output, &input_fade_out);

  const size_t num_channels = input_fade_in.num_channels();

  const size_t num_frames = input_fade_in.num_frames();

  DCHECK_EQ(num_channels, input_fade_out.num_channels());

  DCHECK_EQ(num_channels, output->num_channels());

  DCHECK_EQ(num_frames, input_fade_out.num_frames());

  DCHECK_EQ(num_frames, output->num_frames());

  DCHECK_EQ(num_frames, crossfade_buffer_.num_frames());

  const auto* gain_fade_in_channel = crossfade_buffer_[0].begin();

  const auto* gain_fade_out_channel = crossfade_buffer_[1].begin();

  for (size_t channel = 0; channel < num_channels; ++channel) {

    const auto* input_fade_in_channel = input_fade_in[channel].begin();

    const auto* input_fade_out_channel = input_fade_out[channel].begin();

    auto* output_channel = ((*output)[channel]).begin();

    MultiplyPointwise(num_frames, gain_fade_in_channel, input_fade_in_channel,

                      output_channel);

    MultiplyAndAccumulatePointwise(num_frames, gain_fade_out_channel,

                                   input_fade_out_channel, output_channel);

}  // namespace vraudio