summaryrefslogtreecommitdiffstatshomepage
path: root/src/emu/sound/flt_rc.c
blob: 5e68cbb5b1bde7668a8644d2eefd657d516306d7 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
#include "sndintrf.h"
#include "streams.h"
#include "flt_rc.h"
#include <math.h>

struct filter_rc_info
{
	sound_stream *	stream;
	int				k;
	int				memory;
	int				type;
};

const flt_rc_config flt_rc_ac_default = {FLT_RC_AC, 10000, 0, 0, CAP_U(1)};


static void filter_rc_update(void *param, stream_sample_t **inputs, stream_sample_t **outputs, int samples)
{
	stream_sample_t *src = inputs[0];
	stream_sample_t *dst = outputs[0];
	struct filter_rc_info *info = param;
	int memory = info->memory;

	switch (info->type)
	{
		case FLT_RC_LOWPASS:
			while (samples--)
			{
				memory += ((*src++ - memory) * info->k) / 0x10000;
				*dst++ = memory;
			}
			break;
		case FLT_RC_HIGHPASS:
		case FLT_RC_AC:
			while (samples--)
			{
				*dst++ = *src - memory;
				memory += ((*src++ - memory) * info->k) / 0x10000;
			}
			break;
	}
	info->memory = memory;
}

static void set_RC_info(struct filter_rc_info *info, int type, double R1, double R2, double R3, double C)
{
	double Req;

	info->type = type;

	switch (info->type)
	{
		case FLT_RC_LOWPASS:
			if (C == 0.0)
			{
				/* filter disabled */
				info->k = 0x10000;
				return;
			}
			Req = (R1 * (R2 + R3)) / (R1 + R2 + R3);
			break;
		case FLT_RC_HIGHPASS:
		case FLT_RC_AC:
			if (C == 0.0)
			{
				/* filter disabled */
				info->k = 0x0;
				info->memory = 0x0;
				return;
			}
			Req = R1;
			break;
		default:
			fatalerror("filter_rc_setRC: Wrong filter type %d\n", info->type);
	}

	/* Cut Frequency = 1/(2*Pi*Req*C) */
	/* k = (1-(EXP(-TIMEDELTA/RC)))    */
	info->k = 0x10000 - 0x10000 * (exp(-1 / (Req * C) / Machine->sample_rate));
}


static void *filter_rc_start(int sndindex, int clock, const void *config)
{
	struct filter_rc_info *info;
	const flt_rc_config *conf = config;

	info = auto_malloc(sizeof(*info));
	memset(info, 0, sizeof(*info));

	info->stream = stream_create(1, 1, Machine->sample_rate, info, filter_rc_update);
	if (conf)
		set_RC_info(info, conf->type, conf->R1, conf->R2, conf->R3, conf->C);
	else
		set_RC_info(info, FLT_RC_LOWPASS, 1, 1, 1, 0);

	return info;
}


void filter_rc_set_RC(int num, int type, double R1, double R2, double R3, double C)
{
	struct filter_rc_info *info = sndti_token(SOUND_FILTER_RC, num);

	if(!info)
		return;

	stream_update(info->stream);

	set_RC_info(info, type, R1, R2, R3, C);

}

/**************************************************************************
 * Generic get_info
 **************************************************************************/

static void filter_rc_set_info(void *token, UINT32 state, sndinfo *info)
{
	switch (state)
	{
		/* no parameters to set */
	}
}


void filter_rc_get_info(void *token, UINT32 state, sndinfo *info)
{
	switch (state)
	{
		/* --- the following bits of info are returned as 64-bit signed integers --- */

		/* --- the following bits of info are returned as pointers to data or functions --- */
		case SNDINFO_PTR_SET_INFO:						info->set_info = filter_rc_set_info;	break;
		case SNDINFO_PTR_START:							info->start = filter_rc_start;			break;
		case SNDINFO_PTR_STOP:							/* Nothing */							break;
		case SNDINFO_PTR_RESET:							/* Nothing */							break;

		/* --- the following bits of info are returned as NULL-terminated strings --- */
		case SNDINFO_STR_NAME:							info->s = "RC Filter";					break;
		case SNDINFO_STR_CORE_FAMILY:					info->s = "Filters";					break;
		case SNDINFO_STR_CORE_VERSION:					info->s = "1.0";						break;
		case SNDINFO_STR_CORE_FILE:						info->s = __FILE__;						break;
		case SNDINFO_STR_CORE_CREDITS:					info->s = "Copyright (c) 2004, The MAME Team"; break;
	}
}