/*************************************************************************** * __________ __ ___. * Open \______ \ ____ ____ | | _\_ |__ _______ ___ * Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ / * Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < < * Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \ * \/ \/ \/ \/ \/ * $Id$ * * Copyright (C) 2006 Thom Johansen * * All files in this archive are subject to the GNU General Public License. * See the file COPYING in the source tree root for full license agreement. * * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY * KIND, either express or implied. * ****************************************************************************/ #include #include "config.h" #include "dsp.h" #include "eq.h" #include "replaygain.h" /* Inverse gain of circular cordic rotation in s0.31 format. */ static const long cordic_circular_gain = 0xb2458939; /* 0.607252929 */ /* Table of values of atan(2^-i) in 0.32 format fractions of pi where pi = 0xffffffff / 2 */ static const unsigned long atan_table[] = { 0x1fffffff, /* +0.785398163 (or pi/4) */ 0x12e4051d, /* +0.463647609 */ 0x09fb385b, /* +0.244978663 */ 0x051111d4, /* +0.124354995 */ 0x028b0d43, /* +0.062418810 */ 0x0145d7e1, /* +0.031239833 */ 0x00a2f61e, /* +0.015623729 */ 0x00517c55, /* +0.007812341 */ 0x0028be53, /* +0.003906230 */ 0x00145f2e, /* +0.001953123 */ 0x000a2f98, /* +0.000976562 */ 0x000517cc, /* +0.000488281 */ 0x00028be6, /* +0.000244141 */ 0x000145f3, /* +0.000122070 */ 0x0000a2f9, /* +0.000061035 */ 0x0000517c, /* +0.000030518 */ 0x000028be, /* +0.000015259 */ 0x0000145f, /* +0.000007629 */ 0x00000a2f, /* +0.000003815 */ 0x00000517, /* +0.000001907 */ 0x0000028b, /* +0.000000954 */ 0x00000145, /* +0.000000477 */ 0x000000a2, /* +0.000000238 */ 0x00000051, /* +0.000000119 */ 0x00000028, /* +0.000000060 */ 0x00000014, /* +0.000000030 */ 0x0000000a, /* +0.000000015 */ 0x00000005, /* +0.000000007 */ 0x00000002, /* +0.000000004 */ 0x00000001, /* +0.000000002 */ 0x00000000, /* +0.000000001 */ 0x00000000, /* +0.000000000 */ }; /** * Implements sin and cos using CORDIC rotation. * * @param phase has range from 0 to 0xffffffff, representing 0 and * 2*pi respectively. * @param cos return address for cos * @return sin of phase, value is a signed value from LONG_MIN to LONG_MAX, * representing -1 and 1 respectively. */ static long fsincos(unsigned long phase, long *cos) { int32_t x, x1, y, y1; unsigned long z, z1; int i; /* Setup initial vector */ x = cordic_circular_gain; y = 0; z = phase; /* The phase has to be somewhere between 0..pi for this to work right */ if (z < 0xffffffff / 4) { /* z in first quadrant, z += pi/2 to correct */ x = -x; z += 0xffffffff / 4; } else if (z < 3 * (0xffffffff / 4)) { /* z in third quadrant, z -= pi/2 to correct */ z -= 0xffffffff / 4; } else { /* z in fourth quadrant, z -= 3pi/2 to correct */ x = -x; z -= 3 * (0xffffffff / 4); } /* Each iteration adds roughly 1-bit of extra precision */ for (i = 0; i < 31; i++) { x1 = x >> i; y1 = y >> i; z1 = atan_table[i]; /* Decided which direction to rotate vector. Pivot point is pi/2 */ if (z >= 0xffffffff / 4) { x -= y1; y += x1; z -= z1; } else { x += y1; y -= x1; z += z1; } } *cos = x; return y; } /** * Calculate first order shelving filter coefficients. * Note that the filter is not compatible with the eq_filter routine. * @param cutoff a value from 0 to 0x80000000, where 0 represents 0 Hz and * 0x80000000 represents the Nyquist frequency (samplerate/2). * @param ad gain at 0 Hz. s3.27 fixed point. * @param an gain at Nyquist frequency. s3.27 fixed point. * @param c pointer to coefficient storage. The coefs are s0.31 format. */ void filter_bishelf_coefs(unsigned long cutoff, long ad, long an, int32_t *c) { const long one = 1 << 27; long a0, a1; long b0, b1; long s, cs; s = fsincos(cutoff, &cs) >> 4; cs = one + (cs >> 4); /* For max A = 4 (24 dB) */ b0 = FRACMUL_SHL(an, cs, 4) + FRACMUL_SHL(ad, s, 4); b1 = FRACMUL_SHL(ad, s, 4) - FRACMUL_SHL(an, cs, 4); a0 = s + cs; a1 = s - cs; c[0] = DIV64(b0, a0, 31); c[1] = DIV64(b1, a0, 31); c[2] = -DIV64(a1, a0, 31); } /* Coef calculation taken from Audio-EQ-Cookbook.txt by Robert Bristow-Johnson. * Slightly faster calculation can be done by deriving forms which use tan() * instead of cos() and sin(), but the latter are far easier to use when doing * fixed point math, and performance is not a big point in the calculation part. * All the 'a' filter coefficients are negated so we can use only additions * in the filtering equation. */ /** * Calculate second order section peaking filter coefficients. * @param cutoff a value from 0 to 0x80000000, where 0 represents 0 Hz and * 0x80000000 represents the Nyquist frequency (samplerate/2). * @param Q Q factor value multiplied by ten. Lower bound is artificially set * at 0.5. * @param db decibel value multiplied by ten, describing gain/attenuation at * peak freq. * @param c pointer to coefficient storage. Coefficients are s3.28 format. */ void eq_pk_coefs(unsigned long cutoff, unsigned long Q, long db, int32_t *c) { long cs; const long one = 1 << 28; /* s3.28 */ const long A = get_replaygain_int(db*5) << 5; /* 10^(db/40), s2.29 */ const long alpha = fsincos(cutoff, &cs)/(2*Q)*10 >> 1; /* s1.30 */ int32_t a0, a1, a2; /* these are all s3.28 format */ int32_t b0, b1, b2; const long alphadivA = DIV64(alpha, A, 27); /* possible numerical ranges are in comments by each coef */ b0 = one + FRACMUL(alpha, A); /* [1 .. 5] */ b1 = a1 = -2*(cs >> 3); /* [-2 .. 2] */ b2 = one - FRACMUL(alpha, A); /* [-3 .. 1] */ a0 = one + alphadivA; /* [1 .. 5] */ a2 = one - alphadivA; /* [-3 .. 1] */ /* range of this is roughly [0.2 .. 1], but we'll never hit 1 completely */ const long rcp_a0 = DIV64(1, a0, 59); /* s0.31 */ *c++ = FRACMUL(b0, rcp_a0); /* [0.25 .. 4] */ *c++ = FRACMUL(b1, rcp_a0); /* [-2 .. 2] */ *c++ = FRACMUL(b2, rcp_a0); /* [-2.4 .. 1] */ *c++ = FRACMUL(-a1, rcp_a0); /* [-2 .. 2] */ *c++ = FRACMUL(-a2, rcp_a0); /* [-0.6 .. 1] */ } /** * Calculate coefficients for lowshelf filter. Parameters are as for * eq_pk_coefs, but the coefficient format is s5.26 fixed point. */ void eq_ls_coefs(unsigned long cutoff, unsigned long Q, long db, int32_t *c) { long cs; const long one = 1 << 25; /* s6.25 */ const long sqrtA = get_replaygain_int(db*5/2) << 2; /* 10^(db/80), s5.26 */ const long A = FRACMUL_SHL(sqrtA, sqrtA, 8); /* s2.29 */ const long alpha = fsincos(cutoff, &cs)/(2*Q)*10 >> 1; /* s1.30 */ const long ap1 = (A >> 4) + one; const long am1 = (A >> 4) - one; const long twosqrtalpha = 2*FRACMUL(sqrtA, alpha); int32_t a0, a1, a2; /* these are all s6.25 format */ int32_t b0, b1, b2; /* [0.1 .. 40] */ b0 = FRACMUL_SHL(A, ap1 - FRACMUL(am1, cs) + twosqrtalpha, 2); /* [-16 .. 63.4] */ b1 = FRACMUL_SHL(A, am1 - FRACMUL(ap1, cs), 3); /* [0 .. 31.7] */ b2 = FRACMUL_SHL(A, ap1 - FRACMUL(am1, cs) - twosqrtalpha, 2); /* [0.5 .. 10] */ a0 = ap1 + FRACMUL(am1, cs) + twosqrtalpha; /* [-16 .. 4] */ a1 = -2*((am1 + FRACMUL(ap1, cs))); /* [0 .. 8] */ a2 = ap1 + FRACMUL(am1, cs) - twosqrtalpha; /* [0.1 .. 1.99] */ const long rcp_a0 = DIV64(1, a0, 55); /* s1.30 */ *c++ = FRACMUL_SHL(b0, rcp_a0, 2); /* [0.06 .. 15.9] */ *c++ = FRACMUL_SHL(b1, rcp_a0, 2); /* [-2 .. 31.7] */ *c++ = FRACMUL_SHL(b2, rcp_a0, 2); /* [0 .. 15.9] */ *c++ = FRACMUL_SHL(-a1, rcp_a0, 2); /* [-2 .. 2] */ *c++ = FRACMUL_SHL(-a2, rcp_a0, 2); /* [0 .. 1] */ } /** * Calculate coefficients for highshelf filter. Parameters are as for * eq_pk_coefs, but the coefficient format is s5.26 fixed point. */ void eq_hs_coefs(unsigned long cutoff, unsigned long Q, long db, int32_t *c) { long cs; const long one = 1 << 25; /* s6.25 */ const long sqrtA = get_replaygain_int(db*5/2) << 2; /* 10^(db/80), s5.26 */ const long A = FRACMUL_SHL(sqrtA, sqrtA, 8); /* s2.29 */ const long alpha = fsincos(cutoff, &cs)/(2*Q)*10 >> 1; /* s1.30 */ const long ap1 = (A >> 4) + one; const long am1 = (A >> 4) - one; const long twosqrtalpha = 2*FRACMUL(sqrtA, alpha); int32_t a0, a1, a2; /* these are all s6.25 format */ int32_t b0, b1, b2; /* [0.1 .. 40] */ b0 = FRACMUL_SHL(A, ap1 + FRACMUL(am1, cs) + twosqrtalpha, 2); /* [-63.5 .. 16] */ b1 = -FRACMUL_SHL(A, am1 + FRACMUL(ap1, cs), 3); /* [0 .. 32] */ b2 = FRACMUL_SHL(A, ap1 + FRACMUL(am1, cs) - twosqrtalpha, 2); /* [0.5 .. 10] */ a0 = ap1 - FRACMUL(am1, cs) + twosqrtalpha; /* [-4 .. 16] */ a1 = 2*((am1 - FRACMUL(ap1, cs))); /* [0 .. 8] */ a2 = ap1 - FRACMUL(am1, cs) - twosqrtalpha; /* [0.1 .. 1.99] */ const long rcp_a0 = DIV64(1, a0, 55); /* s1.30 */ *c++ = FRACMUL_SHL(b0, rcp_a0, 2); /* [0 .. 16] */ *c++ = FRACMUL_SHL(b1, rcp_a0, 2); /* [-31.7 .. 2] */ *c++ = FRACMUL_SHL(b2, rcp_a0, 2); /* [0 .. 16] */ *c++ = FRACMUL_SHL(-a1, rcp_a0, 2); /* [-2 .. 2] */ *c++ = FRACMUL_SHL(-a2, rcp_a0, 2); /* [0 .. 1] */ } /* We realise the filters as a second order direct form 1 structure. Direct * form 1 was chosen because of better numerical properties for fixed point * implementations. */ #if (!defined(CPU_COLDFIRE) && !defined(CPU_ARM)) || defined(SIMULATOR) void eq_filter(int32_t **x, struct eqfilter *f, unsigned num, unsigned channels, unsigned shift) { unsigned c, i; long long acc; /* Direct form 1 filtering code. y[n] = b0*x[i] + b1*x[i - 1] + b2*x[i - 2] + a1*y[i - 1] + a2*y[i - 2], where y[] is output and x[] is input. */ for (c = 0; c < channels; c++) { for (i = 0; i < num; i++) { acc = (long long) x[c][i] * f->coefs[0]; acc += (long long) f->history[c][0] * f->coefs[1]; acc += (long long) f->history[c][1] * f->coefs[2]; acc += (long long) f->history[c][2] * f->coefs[3]; acc += (long long) f->history[c][3] * f->coefs[4]; f->history[c][1] = f->history[c][0]; f->history[c][0] = x[c][i]; f->history[c][3] = f->history[c][2]; x[c][i] = (acc << shift) >> 32; f->history[c][2] = x[c][i]; } } } #endif