From 9b4b4d0bf2366ebbbb3cbb14eeb457da9f2658eb Mon Sep 17 00:00:00 2001 From: Thom Johansen Date: Thu, 2 Feb 2006 20:04:02 +0000 Subject: More sane fixed point format for Q parameter. git-svn-id: svn://svn.rockbox.org/rockbox/trunk@8535 a1c6a512-1295-4272-9138-f99709370657 --- apps/eq.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/apps/eq.c b/apps/eq.c index 57c29dc357..17165be541 100644 --- a/apps/eq.c +++ b/apps/eq.c @@ -132,7 +132,7 @@ static long dbtoA(long db) /* Calculate second order section peaking filter coefficients. cutoff is a value from 0 to 0xffffffff, where 0 represents 0 hz and 0xffffffff represents nyquist (samplerate/2). - Q is an unsigned 6.26 fixed point number, lower bound is artificially set + Q is an unsigned 16.16 fixed point number, lower bound is artificially set at 0.5. db is s15.16 fixed point and describes gain/attenuation at peak freq. c is a pointer where the coefs will be stored. @@ -141,7 +141,7 @@ void eq_pk_coefs(unsigned long cutoff, unsigned long Q, long db, long *c) { const long one = 1 << 28; /* s3.28 */ const long A = dbtoA(db); - const long alpha = DIV64(fsin(cutoff), 2*Q, 25); /* s1.30 */ + const long alpha = DIV64(fsin(cutoff), 2*Q, 15); /* s1.30 */ long a0, a1, a2; /* these are all s3.28 format */ long b0, b1, b2; @@ -164,7 +164,7 @@ void eq_ls_coefs(unsigned long cutoff, unsigned long Q, long db, long *c) { const long one = 1 << 24; /* s7.24 */ const long A = dbtoA(db); - const long alpha = DIV64(fsin(cutoff), 2*Q, 25); /* s1.30 */ + const long alpha = DIV64(fsin(cutoff), 2*Q, 15); /* s1.30 */ const long ap1 = (A >> 5) + one; const long am1 = (A >> 5) - one; const long twosqrtalpha = 2*(FRACMUL(fsqrt(A >> 5, 24), alpha) << 1); @@ -191,7 +191,7 @@ void eq_hs_coefs(unsigned long cutoff, unsigned long Q, long db, long *c) { const long one = 1 << 24; /* s7.24 */ const long A = dbtoA(db); - const long alpha = DIV64(fsin(cutoff), 2*Q, 25); /* s1.30 */ + const long alpha = DIV64(fsin(cutoff), 2*Q, 15); /* s1.30 */ const long ap1 = (A >> 5) + one; const long am1 = (A >> 5) - one; const long twosqrtalpha = 2*(FRACMUL(fsqrt(A >> 5, 24), alpha) << 1); -- cgit