99 lines
4.4 KiB
C++
99 lines
4.4 KiB
C++
/* //device/include/server/AudioFlinger/AudioCoefInterpolator.h
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**
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** Copyright 2007, The Android Open Source Project
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**
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** Licensed under the Apache License, Version 2.0 (the "License");
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** you may not use this file except in compliance with the License.
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** You may obtain a copy of the License at
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**
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** http://www.apache.org/licenses/LICENSE-2.0
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**
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** Unless required by applicable law or agreed to in writing, software
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** distributed under the License is distributed on an "AS IS" BASIS,
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** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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** See the License for the specific language governing permissions and
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** limitations under the License.
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*/
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#ifndef ANDROID_AUDIO_COEF_INTERPOLATOR_H
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#define ANDROID_AUDIO_COEF_INTERPOLATOR_H
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#include "AudioCommon.h"
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namespace android {
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// A helper class for linear interpolation of N-D -> M-D coefficient tables.
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// This class provides support for out-of-range indexes.
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// Details:
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// The purpose is efficient approximation of a N-dimensional vector to
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// M-dimensional function. The approximation is based on a table of output
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// values on a uniform grid of the input values. Values not on the grid are
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// linearly interpolated.
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// Access to values are done by specifying input values in table index units,
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// having an integer and a fractional part, e.g. retrieving a value from index
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// 1.4 will result in linear interpolation between index 1 and index 2.
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class AudioCoefInterpolator {
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public:
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// Constructor.
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// nInDims Number of input dimensions (limited to MAX_IN_DIMS).
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// inDims An array of size nInDims with the size of the table on each
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// respective dimension.
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// nOutDims Number of output dimensions (limited to MAX_OUT_DIMS).
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// table The coefficient table. Should be of size:
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// inDims[0]*inDims[1]*...*inDims[nInDims-1]*nOutDims, where
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// func([i,j,k]) = table(i,j,k,:)
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AudioCoefInterpolator(size_t nInDims, const size_t inDims[],
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size_t nOutDims, const audio_coef_t * table);
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// Get the value of the approximated function at a given point.
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// intCoord The integer part of the input value. Should be an array of
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// size nInDims.
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// fracCoord The fractional part of the input value. Should be an array
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// of size nInDims. This value is in 32-bit precision.
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// out An array for the output value. Should be of size nOutDims.
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void getCoef(const int intCoord[], uint32_t fracCoord[], audio_coef_t out[]);
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private:
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// Maximum allowed number of input dimensions.
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static const size_t MAX_IN_DIMS = 8;
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// Maximum allowed number of output dimensions.
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static const size_t MAX_OUT_DIMS = 8;
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// Number of input dimensions.
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size_t mNumInDims;
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// Number of input dimensions.
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size_t mInDims[MAX_IN_DIMS];
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// The offset between two consecutive indexes of each dimension. This is in
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// fact a cumulative product of mInDims (done in reverse).
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size_t mInDimOffsets[MAX_IN_DIMS];
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// Number of output dimensions.
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size_t mNumOutDims;
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// The coefficient table.
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const audio_coef_t * mTable;
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// A recursive function for getting an interpolated coefficient value.
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// The recursion depth is the number of input dimensions.
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// At each step, we fetch two interpolated values of the current dimension,
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// by two recursive calls to this method for the next dimensions. We then
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// linearly interpolate these values over the current dimension.
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// index The linear integer index of the value we need to interpolate.
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// fracCoord A vector of fractional coordinates for each of the input
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// dimensions.
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// out Where the output should be written. Needs to be of size
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// mNumOutDims.
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// dim The input dimensions we are currently interpolating. This
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// value will be increased on recursive calls.
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void getCoefRecurse(size_t index, const uint32_t fracCoord[],
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audio_coef_t out[], size_t dim);
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// Scalar interpolation of two data points.
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// lo The first data point.
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// hi The second data point.
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// frac A 32-bit fraction designating the weight of the second point.
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static audio_coef_t interp(audio_coef_t lo, audio_coef_t hi, uint32_t frac);
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};
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}
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#endif // ANDROID_AUDIO_COEF_INTERPOLATOR_H
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