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/* //device/include/server/AudioFlinger/AudioCoefInterpolator.h
** Copyright 2007, The Android Open Source Project
** Licensed under the Apache License, Version 2.0 (the "License");
** you may not use this file except in compliance with the License.
** You may obtain a copy of the License at
** Unless required by applicable law or agreed to in writing, software
** distributed under the License is distributed on an "AS IS" BASIS,
** See the License for the specific language governing permissions and
** limitations under the License.
#include "AudioCommon.h"
namespace android {
// A helper class for linear interpolation of N-D -> M-D coefficient tables.
// This class provides support for out-of-range indexes.
// Details:
// The purpose is efficient approximation of a N-dimensional vector to
// M-dimensional function. The approximation is based on a table of output
// values on a uniform grid of the input values. Values not on the grid are
// linearly interpolated.
// Access to values are done by specifying input values in table index units,
// having an integer and a fractional part, e.g. retrieving a value from index
// 1.4 will result in linear interpolation between index 1 and index 2.
class AudioCoefInterpolator {
// Constructor.
// nInDims Number of input dimensions (limited to MAX_IN_DIMS).
// inDims An array of size nInDims with the size of the table on each
// respective dimension.
// nOutDims Number of output dimensions (limited to MAX_OUT_DIMS).
// table The coefficient table. Should be of size:
// inDims[0]*inDims[1]*...*inDims[nInDims-1]*nOutDims, where
// func([i,j,k]) = table(i,j,k,:)
AudioCoefInterpolator(size_t nInDims, const size_t inDims[],
size_t nOutDims, const audio_coef_t * table);
// Get the value of the approximated function at a given point.
// intCoord The integer part of the input value. Should be an array of
// size nInDims.
// fracCoord The fractional part of the input value. Should be an array
// of size nInDims. This value is in 32-bit precision.
// out An array for the output value. Should be of size nOutDims.
void getCoef(const int intCoord[], uint32_t fracCoord[], audio_coef_t out[]);
// Maximum allowed number of input dimensions.
static const size_t MAX_IN_DIMS = 8;
// Maximum allowed number of output dimensions.
static const size_t MAX_OUT_DIMS = 8;
// Number of input dimensions.
size_t mNumInDims;
// Number of input dimensions.
size_t mInDims[MAX_IN_DIMS];
// The offset between two consecutive indexes of each dimension. This is in
// fact a cumulative product of mInDims (done in reverse).
size_t mInDimOffsets[MAX_IN_DIMS];
// Number of output dimensions.
size_t mNumOutDims;
// The coefficient table.
const audio_coef_t * mTable;
// A recursive function for getting an interpolated coefficient value.
// The recursion depth is the number of input dimensions.
// At each step, we fetch two interpolated values of the current dimension,
// by two recursive calls to this method for the next dimensions. We then
// linearly interpolate these values over the current dimension.
// index The linear integer index of the value we need to interpolate.
// fracCoord A vector of fractional coordinates for each of the input
// dimensions.
// out Where the output should be written. Needs to be of size
// mNumOutDims.
// dim The input dimensions we are currently interpolating. This
// value will be increased on recursive calls.
void getCoefRecurse(size_t index, const uint32_t fracCoord[],
audio_coef_t out[], size_t dim);
// Scalar interpolation of two data points.
// lo The first data point.
// hi The second data point.
// frac A 32-bit fraction designating the weight of the second point.
static audio_coef_t interp(audio_coef_t lo, audio_coef_t hi, uint32_t frac);