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/*
* Copyright (C) 2011 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:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. 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.
* 3. Neither the name of Apple Computer, Inc. ("Apple") 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 APPLE AND ITS 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 APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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#ifndef THIRD_PARTY_BLINK_RENDERER_PLATFORM_AUDIO_SINC_RESAMPLER_H_
#define THIRD_PARTY_BLINK_RENDERER_PLATFORM_AUDIO_SINC_RESAMPLER_H_
#include "base/macros.h"
#include "third_party/blink/renderer/platform/audio/audio_array.h"
#include "third_party/blink/renderer/platform/audio/audio_source_provider.h"
#include "third_party/blink/renderer/platform/platform_export.h"
#include "third_party/blink/renderer/platform/wtf/allocator.h"
namespace blink {
// SincResampler is a high-quality sample-rate converter.
class PLATFORM_EXPORT SincResampler {
USING_FAST_MALLOC(SincResampler);
public:
// scaleFactor == sourceSampleRate / destinationSampleRate
// kernelSize can be adjusted for quality (higher is better)
// numberOfKernelOffsets is used for interpolation and is the number of
// sub-sample kernel shifts.
SincResampler(double scale_factor,
unsigned kernel_size = 32,
unsigned number_of_kernel_offsets = 32);
// Processes numberOfSourceFrames from source to produce numberOfSourceFrames
// / scaleFactor frames in destination.
void Process(const float* source,
float* destination,
unsigned number_of_source_frames);
// Process with input source callback function for streaming applications.
void Process(AudioSourceProvider*,
float* destination,
uint32_t frames_to_process);
protected:
void InitializeKernel();
void ConsumeSource(float* buffer, unsigned number_of_source_frames);
double scale_factor_;
unsigned kernel_size_;
unsigned number_of_kernel_offsets_;
// m_kernelStorage has m_numberOfKernelOffsets kernels back-to-back, each of
// size m_kernelSize. The kernel offsets are sub-sample shifts of a windowed
// sinc() shifted from 0.0 to 1.0 sample.
AudioFloatArray kernel_storage_;
// m_virtualSourceIndex is an index on the source input buffer with sub-sample
// precision. It must be double precision to avoid drift.
double virtual_source_index_;
// This is the number of destination frames we generate per processing pass on
// the buffer.
unsigned block_size_;
// Source is copied into this buffer for each processing pass.
AudioFloatArray input_buffer_;
const float* source_;
unsigned source_frames_available_;
// m_sourceProvider is used to provide the audio input stream to the
// resampler.
AudioSourceProvider* source_provider_;
// The buffer is primed once at the very beginning of processing.
bool is_buffer_primed_;
private:
DISALLOW_COPY_AND_ASSIGN(SincResampler);
};
} // namespace blink
#endif // THIRD_PARTY_BLINK_RENDERER_PLATFORM_AUDIO_SINC_RESAMPLER_H_