Two more bits of precision for shelving EQ filters and some comment updates. Tested quite thoroughly, but as always with audio related commits: mind your ears.
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@11265 a1c6a512-1295-4272-9138-f99709370657
This commit is contained in:
Thom Johansen
parent
2f3dafa81c
commit
48b4ac3745
2 changed files with 74 additions and 55 deletions
127
apps/eq.c
127
apps/eq.c
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@ -34,7 +34,7 @@
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#define DIV64(x, y, z) (long)(((long long)(x) << (z))/(y))
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/* This macro requires the EMAC unit to be in fractional mode
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when the coef generator routines are called. If this can't be guaranteeed,
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when the coef generator routines are called. If this can't be guaranteed,
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then add "&& 0" below. This will use a slower coef calculation on Coldfire.
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*/
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#if defined(CPU_COLDFIRE) && !defined(SIMULATOR)
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@ -188,12 +188,12 @@ static long dbtoA(long db)
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}
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/* Calculate first order shelving filter coefficients.
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cutoff is a value from 0 to 0x80000000, where 0 represents 0 hz and
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0x80000000 represents nyquist (samplerate/2).
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ad is gain at 0 hz, and an is gain at Nyquist frequency. Both are s3.27
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format.
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c is a pointer where the coefs will be stored. The coefs are s0.31 format.
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Note that the filter is not compatible with the eq_filter routine.
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* Note that the filter is not compatible with the eq_filter routine.
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* @param cutoff a value from 0 to 0x80000000, where 0 represents 0 Hz and
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* 0x80000000 represents the Nyquist frequency (samplerate/2).
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* @param ad gain at 0 Hz. s3.27 fixed point.
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* @param an gain at Nyquist frequency. s3.27 fixed point.
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* @param c pointer to coefficient storage. The coefs are s0.31 format.
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*/
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void filter_bishelf_coefs(unsigned long cutoff, long ad, long an, int32_t *c)
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{
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@ -215,13 +215,14 @@ void filter_bishelf_coefs(unsigned long cutoff, long ad, long an, int32_t *c)
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c[2] = -DIV64(a1, a0, 31);
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}
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/* Calculate second order section peaking filter coefficients.
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cutoff is a value from 0 to 0x80000000, where 0 represents 0 hz and
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0x80000000 represents nyquist (samplerate/2).
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Q is an unsigned 16.16 fixed point number, lower bound is artificially set
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at 0.5.
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db is s15.16 fixed point and describes gain/attenuation at peak freq.
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c is a pointer where the coefs will be stored.
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/**
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* Calculate second order section peaking filter coefficients.
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* @param cutoff a value from 0 to 0x80000000, where 0 represents 0 Hz and
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* 0x80000000 represents the Nyquist frequency (samplerate/2).
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* @param Q 16.16 fixed point value describing Q factor. Lower bound
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* is artificially set at 0.5.
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* @param db s15.16 fixed point value describing gain/attenuation at peak freq.
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* @param c pointer to coefficient storage. Coefficients are s3.28 format.
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*/
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void eq_pk_coefs(unsigned long cutoff, unsigned long Q, long db, int32_t *c)
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{
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@ -232,72 +233,90 @@ void eq_pk_coefs(unsigned long cutoff, unsigned long Q, long db, int32_t *c)
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int32_t a0, a1, a2; /* these are all s3.28 format */
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int32_t b0, b1, b2;
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/* possible numerical ranges listed after each coef */
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b0 = one + FRACMUL(alpha, A); /* [1.25..5] */
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b1 = a1 = -2*(cc >> 3); /* [-2..2] */
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b2 = one - FRACMUL(alpha, A); /* [-3..0.75] */
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a0 = one + DIV64(alpha, A, 27); /* [1.25..5] */
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a2 = one - DIV64(alpha, A, 27); /* [-3..0.75] */
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/* possible numerical ranges are in comments by each coef */
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b0 = one + FRACMUL(alpha, A); /* [1 .. 5] */
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b1 = a1 = -2*(cc >> 3); /* [-2 .. 2] */
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b2 = one - FRACMUL(alpha, A); /* [-3 .. 1] */
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a0 = one + DIV64(alpha, A, 27); /* [1 .. 5] */
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a2 = one - DIV64(alpha, A, 27); /* [-3 .. 1] */
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c[0] = DIV64(b0, a0, 28);
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c[1] = DIV64(b1, a0, 28);
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c[2] = DIV64(b2, a0, 28);
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c[3] = DIV64(-a1, a0, 28);
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c[4] = DIV64(-a2, a0, 28);
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c[0] = DIV64(b0, a0, 28); /* [0.25 .. 4] */
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c[1] = DIV64(b1, a0, 28); /* [-2 .. 2] */
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c[2] = DIV64(b2, a0, 28); /* [-2.4 .. 1] */
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c[3] = DIV64(-a1, a0, 28); /* [-2 .. 2] */
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c[4] = DIV64(-a2, a0, 28); /* [-0.6 .. 1] */
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}
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/* Calculate coefficients for lowshelf filter */
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/**
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* Calculate coefficients for lowshelf filter. Parameters are as for
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* eq_pk_coefs, but the coefficient format is s5.26 fixed point.
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*/
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void eq_ls_coefs(unsigned long cutoff, unsigned long Q, long db, int32_t *c)
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{
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long cs;
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const long one = 1 << 24; /* s7.24 */
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const long one = 1 << 25; /* s6.25 */
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const long A = dbtoA(db);
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const long alpha = DIV64(fsincos(cutoff, &cs), 2*Q, 15); /* s1.30 */
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const long ap1 = (A >> 5) + one;
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const long am1 = (A >> 5) - one;
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const long twosqrtalpha = 2*(FRACMUL(fsqrt(A >> 5, 24), alpha) << 1);
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int32_t a0, a1, a2; /* these are all s7.24 format */
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const long ap1 = (A >> 4) + one;
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const long am1 = (A >> 4) - one;
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const long twosqrtalpha = 2*FRACMUL(fsqrt(A >> 3, 26), alpha);
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int32_t a0, a1, a2; /* these are all s6.25 format */
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int32_t b0, b1, b2;
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/* [0.1 .. 40] */
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b0 = FRACMUL(A, ap1 - FRACMUL(am1, cs) + twosqrtalpha) << 2;
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b1 = FRACMUL(A, am1 - FRACMUL(ap1, cs)) << 3;
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b2 = FRACMUL(A, ap1 - FRACMUL(am1, cs) - twosqrtalpha) << 2;
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a0 = ap1 + FRACMUL(am1, cs) + twosqrtalpha;
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a1 = -2*((am1 + FRACMUL(ap1, cs)));
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/* [-16 .. 63.4] */
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b1 = FRACMUL(A, am1 - FRACMUL(ap1, cs)) << 3;
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/* [0 .. 31.7] */
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b2 = FRACMUL(A, ap1 - FRACMUL(am1, cs) - twosqrtalpha) << 2;
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/* [0.5 .. 10] */
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a0 = ap1 + FRACMUL(am1, cs) + twosqrtalpha;
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/* [-16 .. 4] */
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a1 = -2*((am1 + FRACMUL(ap1, cs)));
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/* [0 .. 8] */
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a2 = ap1 + FRACMUL(am1, cs) - twosqrtalpha;
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c[0] = DIV64(b0, a0, 24);
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c[1] = DIV64(b1, a0, 24);
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c[2] = DIV64(b2, a0, 24);
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c[3] = DIV64(-a1, a0, 24);
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c[4] = DIV64(-a2, a0, 24);
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c[0] = DIV64(b0, a0, 26); /* [0.06 .. 15.9] */
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c[1] = DIV64(b1, a0, 26); /* [-2 .. 31.7] */
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c[2] = DIV64(b2, a0, 26); /* [0 .. 15.9] */
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c[3] = DIV64(-a1, a0, 26); /* [-2 .. 2] */
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c[4] = DIV64(-a2, a0, 26); /* [0 .. 1] */
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}
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/* Calculate coefficients for highshelf filter */
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/**
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* Calculate coefficients for highshelf filter. Parameters are as for
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* eq_pk_coefs, but the coefficient format is s5.26 fixed point.
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*/
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void eq_hs_coefs(unsigned long cutoff, unsigned long Q, long db, int32_t *c)
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{
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long cs;
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const long one = 1 << 24; /* s7.24 */
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const long A = dbtoA(db);
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const long alpha = DIV64(fsincos(cutoff, &cs), 2*Q, 15); /* s1.30 */
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const long ap1 = (A >> 5) + one;
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const long am1 = (A >> 5) - one;
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const long twosqrtalpha = 2*(FRACMUL(fsqrt(A >> 5, 24), alpha) << 1);
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int32_t a0, a1, a2; /* these are all s7.24 format */
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const int one = 1 << 25; /* s6.25 */
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const int A = dbtoA(db);
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const int alpha = DIV64(fsincos(cutoff, &cs), 2*Q, 15); /* s1.30 */
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const int ap1 = (A >> 4) + one;
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const int am1 = (A >> 4) - one;
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const int twosqrtalpha = 2*FRACMUL(fsqrt(A >> 3, 26), alpha);
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int32_t a0, a1, a2; /* these are all s6.25 format */
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int32_t b0, b1, b2;
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/* [0.1 .. 40] */
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b0 = FRACMUL(A, ap1 + FRACMUL(am1, cs) + twosqrtalpha) << 2;
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/* [-63.5 .. 16] */
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b1 = -FRACMUL(A, am1 + FRACMUL(ap1, cs)) << 3;
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/* [0 .. 32] */
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b2 = FRACMUL(A, ap1 + FRACMUL(am1, cs) - twosqrtalpha) << 2;
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/* [0.5 .. 10] */
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a0 = ap1 - FRACMUL(am1, cs) + twosqrtalpha;
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/* [-4 .. 16] */
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a1 = 2*((am1 - FRACMUL(ap1, cs)));
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/* [0 .. 8] */
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a2 = ap1 - FRACMUL(am1, cs) - twosqrtalpha;
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c[0] = DIV64(b0, a0, 24);
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c[1] = DIV64(b1, a0, 24);
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c[2] = DIV64(b2, a0, 24);
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c[3] = DIV64(-a1, a0, 24);
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c[4] = DIV64(-a2, a0, 24);
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c[0] = DIV64(b0, a0, 26); /* [0 .. 16] */
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c[1] = DIV64(b1, a0, 26); /* [-31.7 .. 2] */
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c[2] = DIV64(b2, a0, 26); /* [0 .. 16] */
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c[3] = DIV64(-a1, a0, 26); /* [-2 .. 2] */
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c[4] = DIV64(-a2, a0, 26); /* [0 .. 1] */
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}
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#if (!defined(CPU_COLDFIRE) && !defined(CPU_ARM)) || defined(SIMULATOR)
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@ -26,7 +26,7 @@
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and need to be changed when they change.
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*/
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#define EQ_PEAK_SHIFT 4
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#define EQ_SHELF_SHIFT 8
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#define EQ_SHELF_SHIFT 6
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struct eqfilter {
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int32_t coefs[5]; /* Order is b0, b1, b2, a1, a2 */
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