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Diffstat (limited to 'third_party/libwebrtc/common_audio/resampler/push_sinc_resampler.cc')
-rw-r--r-- | third_party/libwebrtc/common_audio/resampler/push_sinc_resampler.cc | 102 |
1 files changed, 102 insertions, 0 deletions
diff --git a/third_party/libwebrtc/common_audio/resampler/push_sinc_resampler.cc b/third_party/libwebrtc/common_audio/resampler/push_sinc_resampler.cc new file mode 100644 index 0000000000..d4b7eed026 --- /dev/null +++ b/third_party/libwebrtc/common_audio/resampler/push_sinc_resampler.cc @@ -0,0 +1,102 @@ +/* + * Copyright (c) 2013 The WebRTC project authors. All Rights Reserved. + * + * Use of this source code is governed by a BSD-style license + * that can be found in the LICENSE file in the root of the source + * tree. An additional intellectual property rights grant can be found + * in the file PATENTS. All contributing project authors may + * be found in the AUTHORS file in the root of the source tree. + */ + +#include "common_audio/resampler/push_sinc_resampler.h" + +#include <cstring> + +#include "common_audio/include/audio_util.h" +#include "rtc_base/checks.h" + +namespace webrtc { + +PushSincResampler::PushSincResampler(size_t source_frames, + size_t destination_frames) + : resampler_(new SincResampler(source_frames * 1.0 / destination_frames, + source_frames, + this)), + source_ptr_(nullptr), + source_ptr_int_(nullptr), + destination_frames_(destination_frames), + first_pass_(true), + source_available_(0) {} + +PushSincResampler::~PushSincResampler() {} + +size_t PushSincResampler::Resample(const int16_t* source, + size_t source_length, + int16_t* destination, + size_t destination_capacity) { + if (!float_buffer_.get()) + float_buffer_.reset(new float[destination_frames_]); + + source_ptr_int_ = source; + // Pass nullptr as the float source to have Run() read from the int16 source. + Resample(nullptr, source_length, float_buffer_.get(), destination_frames_); + FloatS16ToS16(float_buffer_.get(), destination_frames_, destination); + source_ptr_int_ = nullptr; + return destination_frames_; +} + +size_t PushSincResampler::Resample(const float* source, + size_t source_length, + float* destination, + size_t destination_capacity) { + RTC_CHECK_EQ(source_length, resampler_->request_frames()); + RTC_CHECK_GE(destination_capacity, destination_frames_); + // Cache the source pointer. Calling Resample() will immediately trigger + // the Run() callback whereupon we provide the cached value. + source_ptr_ = source; + source_available_ = source_length; + + // On the first pass, we call Resample() twice. During the first call, we + // provide dummy input and discard the output. This is done to prime the + // SincResampler buffer with the correct delay (half the kernel size), thereby + // ensuring that all later Resample() calls will only result in one input + // request through Run(). + // + // If this wasn't done, SincResampler would call Run() twice on the first + // pass, and we'd have to introduce an entire `source_frames` of delay, rather + // than the minimum half kernel. + // + // It works out that ChunkSize() is exactly the amount of output we need to + // request in order to prime the buffer with a single Run() request for + // `source_frames`. + if (first_pass_) + resampler_->Resample(resampler_->ChunkSize(), destination); + + resampler_->Resample(destination_frames_, destination); + source_ptr_ = nullptr; + return destination_frames_; +} + +void PushSincResampler::Run(size_t frames, float* destination) { + // Ensure we are only asked for the available samples. This would fail if + // Run() was triggered more than once per Resample() call. + RTC_CHECK_EQ(source_available_, frames); + + if (first_pass_) { + // Provide dummy input on the first pass, the output of which will be + // discarded, as described in Resample(). + std::memset(destination, 0, frames * sizeof(*destination)); + first_pass_ = false; + return; + } + + if (source_ptr_) { + std::memcpy(destination, source_ptr_, frames * sizeof(*destination)); + } else { + for (size_t i = 0; i < frames; ++i) + destination[i] = static_cast<float>(source_ptr_int_[i]); + } + source_available_ -= frames; +} + +} // namespace webrtc |