115 lines
4.0 KiB
C++
115 lines
4.0 KiB
C++
/*
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* Copyright (c) 2019 The WebRTC project authors. All Rights Reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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#include "modules/audio_coding/acm2/acm_remixing.h"
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#include "rtc_base/checks.h"
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namespace webrtc {
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void DownMixFrame(const AudioFrame& input, rtc::ArrayView<int16_t> output) {
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RTC_DCHECK_EQ(input.num_channels_, 2);
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RTC_DCHECK_EQ(output.size(), input.samples_per_channel_);
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if (input.muted()) {
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std::fill(output.begin(), output.begin() + input.samples_per_channel_, 0);
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} else {
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const int16_t* const input_data = input.data();
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for (size_t n = 0; n < input.samples_per_channel_; ++n) {
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output[n] = rtc::dchecked_cast<int16_t>(
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(int32_t{input_data[2 * n]} + int32_t{input_data[2 * n + 1]}) >> 1);
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}
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}
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}
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void ReMixFrame(const AudioFrame& input,
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size_t num_output_channels,
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std::vector<int16_t>* output) {
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const size_t output_size = num_output_channels * input.samples_per_channel_;
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RTC_DCHECK(!(input.num_channels_ == 0 && num_output_channels > 0 &&
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input.samples_per_channel_ > 0));
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if (output->size() != output_size) {
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output->resize(output_size);
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}
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// For muted frames, fill the frame with zeros.
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if (input.muted()) {
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std::fill(output->begin(), output->end(), 0);
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return;
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}
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// Ensure that the special case of zero input channels is handled correctly
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// (zero samples per channel is already handled correctly in the code below).
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if (input.num_channels_ == 0) {
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return;
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}
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const int16_t* const input_data = input.data();
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size_t out_index = 0;
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// When upmixing is needed and the input is mono copy the left channel
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// into the left and right channels, and set any remaining channels to zero.
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if (input.num_channels_ == 1 && input.num_channels_ < num_output_channels) {
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for (size_t k = 0; k < input.samples_per_channel_; ++k) {
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(*output)[out_index++] = input_data[k];
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(*output)[out_index++] = input_data[k];
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for (size_t j = 2; j < num_output_channels; ++j) {
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(*output)[out_index++] = 0;
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}
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RTC_DCHECK_EQ(out_index, (k + 1) * num_output_channels);
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}
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RTC_DCHECK_EQ(out_index, input.samples_per_channel_ * num_output_channels);
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return;
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}
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size_t in_index = 0;
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// When upmixing is needed and the output is surround, copy the available
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// channels directly, and set the remaining channels to zero.
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if (input.num_channels_ < num_output_channels) {
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for (size_t k = 0; k < input.samples_per_channel_; ++k) {
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for (size_t j = 0; j < input.num_channels_; ++j) {
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(*output)[out_index++] = input_data[in_index++];
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}
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for (size_t j = input.num_channels_; j < num_output_channels; ++j) {
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(*output)[out_index++] = 0;
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}
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RTC_DCHECK_EQ(in_index, (k + 1) * input.num_channels_);
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RTC_DCHECK_EQ(out_index, (k + 1) * num_output_channels);
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}
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RTC_DCHECK_EQ(in_index, input.samples_per_channel_ * input.num_channels_);
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RTC_DCHECK_EQ(out_index, input.samples_per_channel_ * num_output_channels);
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return;
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}
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// When downmixing is needed, and the input is stereo, average the channels.
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if (input.num_channels_ == 2) {
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for (size_t n = 0; n < input.samples_per_channel_; ++n) {
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(*output)[n] = rtc::dchecked_cast<int16_t>(
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(int32_t{input_data[2 * n]} + int32_t{input_data[2 * n + 1]}) >> 1);
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}
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return;
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}
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// When downmixing is needed, and the input is multichannel, drop the surplus
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// channels.
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const size_t num_channels_to_drop = input.num_channels_ - num_output_channels;
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for (size_t k = 0; k < input.samples_per_channel_; ++k) {
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for (size_t j = 0; j < num_output_channels; ++j) {
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(*output)[out_index++] = input_data[in_index++];
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}
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in_index += num_channels_to_drop;
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}
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}
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} // namespace webrtc
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