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/*
* Copyright (C) 2013 Google Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following disclaimer
* in the documentation and/or other materials provided with the
* distribution.
* * Neither the name of Google Inc. nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#ifdef UNSAFE_BUFFERS_BUILD
// TODO(crbug.com/351564777): Remove this and convert code to safer constructs.
#pragma allow_unsafe_buffers
#endif
#include "third_party/blink/renderer/platform/audio/up_sampler.h"
#include <memory>
#include "third_party/blink/renderer/platform/wtf/math_extras.h"
#include "third_party/fdlibm/ieee754.h"
namespace blink {
namespace {
// Computes ideal band-limited filter coefficients to sample in between each
// source sample-frame. This filter will be used to compute the odd
// sample-frames of the output.
std::unique_ptr<AudioFloatArray> MakeKernel(size_t size) {
std::unique_ptr<AudioFloatArray> kernel =
std::make_unique<AudioFloatArray>(size);
// Blackman window parameters.
double alpha = 0.16;
double a0 = 0.5 * (1.0 - alpha);
double a1 = 0.5;
double a2 = 0.5 * alpha;
int n = kernel->size();
int half_size = n / 2;
double subsample_offset = -0.5;
for (int i = 0; i < n; ++i) {
// Compute the sinc() with offset.
double s = kPiDouble * (i - half_size - subsample_offset);
double sinc = !s ? 1.0 : fdlibm::sin(s) / s;
// Compute Blackman window, matching the offset of the sinc().
double x = (i - subsample_offset) / n;
double window = a0 - a1 * fdlibm::cos(kTwoPiDouble * x) +
a2 * fdlibm::cos(kTwoPiDouble * 2.0 * x);
// Window the sinc() function.
(*kernel)[i] = sinc * window;
}
return kernel;
}
} // namespace
UpSampler::UpSampler(unsigned input_block_size)
: input_block_size_(input_block_size),
temp_buffer_(input_block_size),
input_buffer_(input_block_size * 2) {
std::unique_ptr<AudioFloatArray> convolution_kernel =
MakeKernel(kDefaultKernelSize);
if (input_block_size_ <= 128) {
// If the input block size is small enough, use direct convolution because
// it is faster than FFT convolution for such input block sizes.
direct_convolver_ = std::make_unique<DirectConvolver>(
input_block_size_, std::move(convolution_kernel));
} else {
// Otherwise, use FFT convolution because it is faster than direct
// convolution for large input block sizes.
simple_fft_convolver_ = std::make_unique<SimpleFFTConvolver>(
input_block_size_, std::move(convolution_kernel));
}
}
void UpSampler::Process(const float* source_p,
float* dest_p,
uint32_t source_frames_to_process) {
const size_t convolution_kernel_size =
direct_convolver_ ? direct_convolver_->ConvolutionKernelSize()
: simple_fft_convolver_->ConvolutionKernelSize();
DCHECK_EQ(source_frames_to_process, input_block_size_);
DCHECK_EQ(source_frames_to_process, temp_buffer_.size());
size_t half_size = convolution_kernel_size / 2;
DCHECK_EQ(input_buffer_.size(), source_frames_to_process * 2);
DCHECK_LE(half_size, source_frames_to_process);
// Copy source samples to 2nd half of input buffer.
float* input_p = input_buffer_.Data() + source_frames_to_process;
memcpy(input_p, source_p, sizeof(float) * source_frames_to_process);
// Copy even sample-frames 0,2,4,6... (delayed by the linear phase delay)
// directly into destP.
for (unsigned i = 0; i < source_frames_to_process; ++i) {
dest_p[i * 2] = *((input_p - half_size) + i);
}
// Compute odd sample-frames 1,3,5,7...
float* odd_samples_p = temp_buffer_.Data();
if (direct_convolver_) {
direct_convolver_->Process(source_p, odd_samples_p,
source_frames_to_process);
} else {
simple_fft_convolver_->Process(source_p, odd_samples_p,
source_frames_to_process);
}
for (unsigned i = 0; i < source_frames_to_process; ++i) {
dest_p[i * 2 + 1] = odd_samples_p[i];
}
// Copy 2nd half of input buffer to 1st half.
memcpy(input_buffer_.Data(), input_p,
sizeof(float) * source_frames_to_process);
}
void UpSampler::Reset() {
if (direct_convolver_) {
direct_convolver_->Reset();
}
if (simple_fft_convolver_) {
simple_fft_convolver_->Reset();
}
input_buffer_.Zero();
}
size_t UpSampler::LatencyFrames() const {
const size_t convolution_kernel_size =
direct_convolver_ ? direct_convolver_->ConvolutionKernelSize()
: simple_fft_convolver_->ConvolutionKernelSize();
// Divide by two since this is a linear phase kernel and the delay is at the
// center of the kernel.
return convolution_kernel_size / 2;
}
} // namespace blink
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