1/* 2 * Copyright (C) 2010, Google Inc. All rights reserved. 3 * 4 * Redistribution and use in source and binary forms, with or without 5 * modification, are permitted provided that the following conditions 6 * are met: 7 * 1. Redistributions of source code must retain the above copyright 8 * notice, this list of conditions and the following disclaimer. 9 * 2. Redistributions in binary form must reproduce the above copyright 10 * notice, this list of conditions and the following disclaimer in the 11 * documentation and/or other materials provided with the distribution. 12 * 13 * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS'' AND ANY 14 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 15 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 16 * DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS BE LIABLE FOR ANY 17 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 18 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 19 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON 20 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 21 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 22 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 23 */ 24 25#ifndef AudioResamplerKernel_h 26#define AudioResamplerKernel_h 27 28#include "platform/PlatformExport.h" 29#include "platform/audio/AudioArray.h" 30 31namespace blink { 32 33class AudioResampler; 34 35// AudioResamplerKernel does resampling on a single mono channel. 36// It uses a simple linear interpolation for good performance. 37 38class PLATFORM_EXPORT AudioResamplerKernel { 39public: 40 AudioResamplerKernel(AudioResampler*); 41 42 // getSourcePointer() should be called each time before process() is called. 43 // Given a number of frames to process (for subsequent call to process()), it returns a pointer and numberOfSourceFramesNeeded 44 // where sample data should be copied. This sample data provides the input to the resampler when process() is called. 45 // framesToProcess must be less than or equal to MaxFramesToProcess. 46 float* getSourcePointer(size_t framesToProcess, size_t* numberOfSourceFramesNeeded); 47 48 // process() resamples framesToProcess frames from the source into destination. 49 // Each call to process() must be preceded by a call to getSourcePointer() so that source input may be supplied. 50 // framesToProcess must be less than or equal to MaxFramesToProcess. 51 void process(float* destination, size_t framesToProcess); 52 53 // Resets the processing state. 54 void reset(); 55 56 static const size_t MaxFramesToProcess; 57 58private: 59 double rate() const; 60 61 AudioResampler* m_resampler; 62 AudioFloatArray m_sourceBuffer; 63 64 // This is a (floating point) read index on the input stream. 65 double m_virtualReadIndex; 66 67 // We need to have continuity from one call of process() to the next. 68 // m_lastValues stores the last two sample values from the last call to process(). 69 // m_fillIndex represents how many buffered samples we have which can be as many as 2. 70 // For the first call to process() (or after reset()) there will be no buffered samples. 71 float m_lastValues[2]; 72 unsigned m_fillIndex; 73}; 74 75} // namespace blink 76 77#endif // AudioResamplerKernel_h 78