103 lines
3.9 KiB
C++
103 lines
3.9 KiB
C++
/*
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* Copyright (c) 2013 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 "common_audio/resampler/push_sinc_resampler.h"
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#include <cstring>
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#include "common_audio/include/audio_util.h"
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#include "rtc_base/checks.h"
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namespace webrtc {
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PushSincResampler::PushSincResampler(size_t source_frames,
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size_t destination_frames)
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: resampler_(new SincResampler(source_frames * 1.0 / destination_frames,
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source_frames,
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this)),
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source_ptr_(nullptr),
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source_ptr_int_(nullptr),
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destination_frames_(destination_frames),
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first_pass_(true),
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source_available_(0) {}
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PushSincResampler::~PushSincResampler() {}
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size_t PushSincResampler::Resample(const int16_t* source,
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size_t source_length,
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int16_t* destination,
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size_t destination_capacity) {
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if (!float_buffer_.get())
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float_buffer_.reset(new float[destination_frames_]);
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source_ptr_int_ = source;
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// Pass nullptr as the float source to have Run() read from the int16 source.
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Resample(nullptr, source_length, float_buffer_.get(), destination_frames_);
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FloatS16ToS16(float_buffer_.get(), destination_frames_, destination);
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source_ptr_int_ = nullptr;
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return destination_frames_;
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}
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size_t PushSincResampler::Resample(const float* source,
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size_t source_length,
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float* destination,
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size_t destination_capacity) {
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RTC_CHECK_EQ(source_length, resampler_->request_frames());
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RTC_CHECK_GE(destination_capacity, destination_frames_);
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// Cache the source pointer. Calling Resample() will immediately trigger
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// the Run() callback whereupon we provide the cached value.
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source_ptr_ = source;
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source_available_ = source_length;
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// On the first pass, we call Resample() twice. During the first call, we
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// provide dummy input and discard the output. This is done to prime the
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// SincResampler buffer with the correct delay (half the kernel size), thereby
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// ensuring that all later Resample() calls will only result in one input
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// request through Run().
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//
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// If this wasn't done, SincResampler would call Run() twice on the first
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// pass, and we'd have to introduce an entire `source_frames` of delay, rather
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// than the minimum half kernel.
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//
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// It works out that ChunkSize() is exactly the amount of output we need to
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// request in order to prime the buffer with a single Run() request for
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// `source_frames`.
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if (first_pass_)
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resampler_->Resample(resampler_->ChunkSize(), destination);
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resampler_->Resample(destination_frames_, destination);
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source_ptr_ = nullptr;
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return destination_frames_;
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}
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void PushSincResampler::Run(size_t frames, float* destination) {
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// Ensure we are only asked for the available samples. This would fail if
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// Run() was triggered more than once per Resample() call.
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RTC_CHECK_EQ(source_available_, frames);
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if (first_pass_) {
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// Provide dummy input on the first pass, the output of which will be
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// discarded, as described in Resample().
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std::memset(destination, 0, frames * sizeof(*destination));
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first_pass_ = false;
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return;
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}
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if (source_ptr_) {
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std::memcpy(destination, source_ptr_, frames * sizeof(*destination));
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} else {
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for (size_t i = 0; i < frames; ++i)
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destination[i] = static_cast<float>(source_ptr_int_[i]);
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}
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source_available_ -= frames;
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}
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} // namespace webrtc
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