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The basic idea is to write out the signal that came in with the same number of channels as it had when it came in. Things get a bit more complicated when one output block may be derived from more than one input block, each having different numbers of channels. When this happens, the input blocks with fewer channels are upmixed, so as not to lose (or distort) any signal in the block with more channels. HRTFPanner no longer uses exponential decay (with time constant 20ms) for delay changes, but a smoother linear transition during cross-fade time (~45ms). --HG-- rename : content/media/webaudio/DelayProcessor.cpp => content/media/webaudio/DelayBuffer.cpp rename : content/media/webaudio/DelayProcessor.h => content/media/webaudio/DelayBuffer.h extra : rebase_source : 18453d631779cd7d0672b5325e110b107ab4237d
113 lines
3.9 KiB
C++
113 lines
3.9 KiB
C++
/*
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* Copyright (C) 2010, Google Inc. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS'' AND ANY
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* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS BE LIABLE FOR ANY
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* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
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* ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#ifndef HRTFPanner_h
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#define HRTFPanner_h
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#include "FFTConvolver.h"
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#include "DelayBuffer.h"
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namespace mozilla {
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struct AudioChunk;
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}
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namespace WebCore {
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class HRTFDatabaseLoader;
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using mozilla::AudioChunk;
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class HRTFPanner {
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public:
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HRTFPanner(float sampleRate, mozilla::TemporaryRef<HRTFDatabaseLoader> databaseLoader);
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~HRTFPanner();
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// chunk durations must be 128
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void pan(double azimuth, double elevation, const AudioChunk* inputBus, AudioChunk* outputBus);
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void reset();
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size_t fftSize() const { return m_convolverL1.fftSize(); }
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float sampleRate() const { return m_sampleRate; }
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int maxTailFrames() const;
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private:
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// Given an azimuth angle in the range -180 -> +180, returns the corresponding azimuth index for the database,
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// and azimuthBlend which is an interpolation value from 0 -> 1.
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int calculateDesiredAzimuthIndexAndBlend(double azimuth, double& azimuthBlend);
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mozilla::RefPtr<HRTFDatabaseLoader> m_databaseLoader;
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float m_sampleRate;
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// We maintain two sets of convolvers for smooth cross-faded interpolations when
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// then azimuth and elevation are dynamically changing.
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// When the azimuth and elevation are not changing, we simply process with one of the two sets.
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// Initially we use CrossfadeSelection1 corresponding to m_convolverL1 and m_convolverR1.
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// Whenever the azimuth or elevation changes, a crossfade is initiated to transition
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// to the new position. So if we're currently processing with CrossfadeSelection1, then
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// we transition to CrossfadeSelection2 (and vice versa).
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// If we're in the middle of a transition, then we wait until it is complete before
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// initiating a new transition.
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// Selects either the convolver set (m_convolverL1, m_convolverR1) or (m_convolverL2, m_convolverR2).
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enum CrossfadeSelection {
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CrossfadeSelection1,
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CrossfadeSelection2
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};
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CrossfadeSelection m_crossfadeSelection;
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// azimuth/elevation for CrossfadeSelection1.
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int m_azimuthIndex1;
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double m_elevation1;
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// azimuth/elevation for CrossfadeSelection2.
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int m_azimuthIndex2;
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double m_elevation2;
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// A crossfade value 0 <= m_crossfadeX <= 1.
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float m_crossfadeX;
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// Per-sample-frame crossfade value increment.
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float m_crossfadeIncr;
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FFTConvolver m_convolverL1;
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FFTConvolver m_convolverR1;
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FFTConvolver m_convolverL2;
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FFTConvolver m_convolverR2;
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mozilla::DelayBuffer m_delayLine;
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AudioFloatArray m_tempL1;
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AudioFloatArray m_tempR1;
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AudioFloatArray m_tempL2;
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AudioFloatArray m_tempR2;
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};
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} // namespace WebCore
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#endif // HRTFPanner_h
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