b2a373eb64
Simply extends the current isqrt() to be able to do fractional bits and improves the initial estimate using clz(). iqrt() itself is no more and is equivalent to fp_sqrt(x, 0). The original also had a small bug where the guess comparision should have been >=, not >. Uses no large integer math or division and is very accurate (simply returns a truncated fraction). Change-Id: I2ae26e6505df1770dc01e56220f7385369f90ae9
120 lines
4.3 KiB
C
120 lines
4.3 KiB
C
/***************************************************************************
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* __________ __ ___.
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* Open \______ \ ____ ____ | | _\_ |__ _______ ___
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* Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ /
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* Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < <
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* Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \
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* \/ \/ \/ \/ \/
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* $Id$
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*
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* Copyright (C) 2006 Jens Arnold
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*
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* Fixed point library for plugins
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
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* KIND, either express or implied.
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*
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****************************************************************************/
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/** FIXED POINT MATH ROUTINES - USAGE
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*
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* - x and y arguments are fixed point integers
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* - fracbits is the number of fractional bits in the argument(s)
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* - functions return long fixed point integers with the specified number
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* of fractional bits unless otherwise specified
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*
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* Multiply two fixed point numbers:
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* fp_mul(x, y, fracbits)
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*
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* Divide two fixed point numbers:
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* fp_div(x, y, fracbits)
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*
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* Calculate sin and cos of an angle:
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* fp_sincos(phase, *cos)
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* where phase is a 32 bit unsigned integer with 0 representing 0
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* and 0xFFFFFFFF representing 2*pi, and *cos is the address to
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* a long signed integer. Value returned is a long signed integer
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* from -0x80000000 to 0x7fffffff, representing -1 to 1 respectively.
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* That is, value is a fixed point integer with 31 fractional bits.
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*
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* Take square root of a fixed point number:
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* fp_sqrt(x, fracbits)
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*
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* Calculate sin or cos of an angle (very fast, from a table):
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* fp14_sin(angle)
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* fp14_cos(angle)
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* where angle is a non-fixed point integer in degrees. Value
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* returned is a fixed point integer with 14 fractional bits.
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*
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* Calculate the exponential of a fixed point integer
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* fp16_exp(x)
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* where x and the value returned are fixed point integers
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* with 16 fractional bits.
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*
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* Calculate the natural log of a positive fixed point integer
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* fp16_log(x)
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* where x and the value returned are fixed point integers
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* with 16 fractional bits.
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*
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* Calculate decibel equivalent of a gain factor:
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* fp_decibels(factor, fracbits)
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* where fracbits is in the range 12 to 22 (higher is better),
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* and factor is a positive fixed point integer.
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*
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* Calculate factor equivalent of a decibel value:
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* fp_factor(decibels, fracbits)
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* where fracbits is in the range 12 to 22 (lower is better),
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* and decibels is a fixed point integer.
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*/
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#ifndef FIXEDPOINT_H
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#define FIXEDPOINT_H
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#define fp_mul(x, y, z) (long)((((long long)(x)) * ((long long)(y))) >> (z))
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#define fp_div(x, y, z) (long)((((long long)(x)) << (z)) / ((long long)(y)))
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long fp_sincos(unsigned long phase, long *cos);
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long fp_sqrt(long a, unsigned int fracbits);
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long fp14_cos(int val);
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long fp14_sin(int val);
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long fp16_log(int x);
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long fp16_exp(int x);
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/* fast unsigned multiplication (16x16bit->32bit or 32x32bit->32bit,
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* whichever is faster for the architecture) */
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#ifdef CPU_ARM
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#define FMULU(a, b) ((uint32_t) (((uint32_t) (a)) * ((uint32_t) (b))))
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#else /* SH1, coldfire */
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#define FMULU(a, b) ((uint32_t) (((uint16_t) (a)) * ((uint16_t) (b))))
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#endif
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/** MODIFIED FROM replaygain.c */
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#define FP_INF (0x7fffffff)
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#define FP_NEGINF -(0x7fffffff)
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/** FIXED POINT EXP10
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* Return 10^x as FP integer. Argument is FP integer.
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*/
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long fp_exp10(long x, unsigned int fracbits);
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/** FIXED POINT LOG10
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* Return log10(x) as FP integer. Argument is FP integer.
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*/
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long fp_log10(long n, unsigned int fracbits);
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/* fracbits in range 12 - 22 work well. Higher is better for
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* calculating dB, lower is better for calculating factor.
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*/
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/** CONVERT FACTOR TO DECIBELS */
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long fp_decibels(unsigned long factor, unsigned int fracbits);
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/** CONVERT DECIBELS TO FACTOR */
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long fp_factor(long decibels, unsigned int fracbits);
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#endif /* FIXEDPOINT_H */
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