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/*
* 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 "webrtc/common_audio/include/audio_util.h"
#include "webrtc/common_audio/resampler/push_sinc_resampler.h"
#include <string.h>
namespace webrtc {
PushSincResampler::PushSincResampler(int source_frames,
int destination_frames)
: resampler_(new SincResampler(source_frames * 1.0 / destination_frames,
source_frames, this)),
float_buffer_(new float[destination_frames]),
source_ptr_(NULL),
destination_frames_(destination_frames),
first_pass_(true),
source_available_(0) {
}
PushSincResampler::~PushSincResampler() {
}
int PushSincResampler::Resample(const int16_t* source,
int source_length,
int16_t* destination,
int destination_capacity) {
assert(source_length == resampler_->request_frames());
assert(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(), float_buffer_.get());
resampler_->Resample(destination_frames_, float_buffer_.get());
for (int i = 0; i < destination_frames_; ++i)
destination[i] = RoundToInt16(ClampInt16(float_buffer_[i]));
source_ptr_ = NULL;
return destination_frames_;
}
void PushSincResampler::Run(int frames, float* destination) {
assert(source_ptr_ != NULL);
// Ensure we are only asked for the available samples. This would fail if
// Run() was triggered more than once per Resample() call.
assert(source_available_ == frames);
if (first_pass_) {
// Provide dummy input on the first pass, the output of which will be
// discarded, as described in Resample().
memset(destination, 0, frames * sizeof(float));
first_pass_ = false;
} else {
for (int i = 0; i < frames; ++i)
destination[i] = static_cast<float>(source_ptr_[i]);
source_available_ -= frames;
}
}
} // namespace webrtc
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