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tube: fix oversampling

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the original cascade was missing a first-order filter entirely!
N is incremented so the cascade is only second-order filters
which allows minimal changes to the code.

additionally the output sample is from the last
zero-padding for a slightly better phase response.
This commit is contained in:
Connor Olding 2014-02-11 03:00:41 -08:00
parent 1b1e4353fb
commit 7545689477
2 changed files with 18 additions and 18 deletions
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3
README.md
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@ -37,8 +37,6 @@ white noise generator. loud, full-range, 0dBFS. don't say i didn't warn you.
__crap\_tube (0x50F7BA11)__
static waveshaper with 4x oversampling, sounds kinda like a tube i guess?
be aware that its oversampling currently boosts top-most frequencies by
~2dB before attenuating.
### crap delay test
@ -60,6 +58,7 @@ other targets:
## TODO
* spaces-in-paths support in Makefile
* rename plugins (fix capitalization consistency and such)
* reduce input/output buffers on biquads (shared)
* ease up on the preprocessor ifs

33
crap/tube.h
View file

@ -11,7 +11,7 @@
#define COPYRIGHT "MIT"
#define PARAMETERS 2
#define HIST_SIZE_2 (2 + 2*10)
#define HIST_SIZE_2 (2 + 2*11)
#define HIST_SIZE (HIST_SIZE_2*2)
typedef struct {
@ -67,21 +67,22 @@ static double
oversample(double h[HIST_SIZE_2], double x)
{
/* designed with <https://coewww.rutgers.edu/~orfanidi/hpeq/>
fs = 44100; OS = 4; Gs = -120; f2 = 18248/fs/OS; f2s = 22050/fs/OS;
N = hpeqord(-Inf,0,Gs,-6,2*pi*f2s,2*pi*f2,2) % 20.9971490662433
fs = 44100; OS = 4; Gs = -120; f2 = 18544/fs/OS; f2s = 22050/fs/OS;
N = hpeqord(-Inf,0,Gs,-6,2*pi*f2s,2*pi*f2,2) % 21.9986847697467
*/
double y;
LOWPASS(0, +0.65855672,-0.92949215,-1.56012668,+0.94774797);
LOWPASS(1, +0.61716958,-0.85685555,-1.47099672,+0.84848033);
LOWPASS(2, +0.56959704,-0.76263107,-1.37527450,+0.75183750);
LOWPASS(3, +0.51503506,-0.64652564,-1.27052746,+0.65407194);
LOWPASS(4, +0.45328074,-0.50918096,-1.15569311,+0.55307363);
LOWPASS(5, +0.38524858,-0.35361043,-1.03185791,+0.44874463);
LOWPASS(6, +0.31367929,-0.18703461,-0.90341296,+0.34373693);
LOWPASS(7, +0.24382090,-0.02260789,-0.77918770,+0.24422161);
LOWPASS(8, +0.18353302,+0.12028336,-0.67260228,+0.15995168);
LOWPASS(9, +0.14205849,+0.21898074,-0.59952639,+0.10262410);
BQSHIFT(10);
LOWPASS( 0,+0.68211844,-0.96291784,-1.54972173,+0.95104078);
LOWPASS( 1,+0.64259794,-0.89367078,-1.46615406,+0.85767914);
LOWPASS( 2,+0.59754712,-0.80432534,-1.37570293,+0.76647184);
LOWPASS( 3,+0.54606830,-0.69425498,-1.27603271,+0.67391434);
LOWPASS( 4,+0.48770451,-0.56343052,-1.16582052,+0.57779902);
LOWPASS( 5,+0.42283783,-0.41357065,-1.04538942,+0.47749444);
LOWPASS( 6,+0.35328311,-0.24971266,-0.91771844,+0.37457200);
LOWPASS( 7,+0.28296589,-0.08195448,-0.78962026,+0.27359756);
LOWPASS( 8,+0.21832227,+0.07351444,-0.67243388,+0.18259286);
LOWPASS( 9,+0.16778186,+0.19566401,-0.58109077,+0.11231849);
LOWPASS(10,+0.13979560,+0.26348229,-0.53059324,+0.07366673);
BQSHIFT(11);
return y;
}
@ -101,10 +102,10 @@ process_os(personal *data, double x, int right)
#define doit(SAMP) \
oversample(h1, process_one(4*oversample(h0, SAMP), \
smooth(&data->drive), smooth(&data->wet)))
y = doit(x);
doit(0);
doit(x);
doit(0);
doit(0);
y = doit(0);
#undef doit
return y;