#include "emu.h" #include "flt_rc.h" const flt_rc_config flt_rc_ac_default = {FLT_RC_AC, 10000, 0, 0, CAP_U(1)}; // device type definition const device_type FILTER_RC = &device_creator; //************************************************************************** // LIVE DEVICE //************************************************************************** //------------------------------------------------- // qsound_device - constructor //------------------------------------------------- filter_rc_device::filter_rc_device(const machine_config &mconfig, const char *tag, device_t *owner, UINT32 clock) : device_t(mconfig, FILTER_RC, "RC Filter", tag, owner, clock), device_sound_interface(mconfig, *this), m_stream(NULL), m_k(0), m_memory(0), m_type(0) { } //------------------------------------------------- // device_start - device-specific startup //------------------------------------------------- void filter_rc_device::device_start() { const flt_rc_config *conf = (const flt_rc_config *)static_config(); m_stream = stream_alloc(1, 1, machine().sample_rate()); if (conf) set_RC_info(conf->type, conf->R1, conf->R2, conf->R3, conf->C); else set_RC_info(FLT_RC_LOWPASS, 1, 1, 1, 0); } //------------------------------------------------- // sound_stream_update - handle a stream update //------------------------------------------------- void filter_rc_device::sound_stream_update(sound_stream &stream, stream_sample_t **inputs, stream_sample_t **outputs, int samples) { stream_sample_t *src = inputs[0]; stream_sample_t *dst = outputs[0]; int memory = m_memory; switch (m_type) { case FLT_RC_LOWPASS: while (samples--) { memory += ((*src++ - memory) * m_k) / 0x10000; *dst++ = memory; } break; case FLT_RC_HIGHPASS: case FLT_RC_AC: while (samples--) { *dst++ = *src - memory; memory += ((*src++ - memory) * m_k) / 0x10000; } break; } m_memory = memory; } void filter_rc_device::set_RC_info(int type, double R1, double R2, double R3, double C) { double Req; m_type = type; switch (m_type) { case FLT_RC_LOWPASS: if (C == 0.0) { /* filter disabled */ m_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 */ m_k = 0x0; m_memory = 0x0; return; } Req = R1; break; default: fatalerror("filter_rc_setRC: Wrong filter type %d\n", m_type); } /* Cut Frequency = 1/(2*Pi*Req*C) */ /* k = (1-(EXP(-TIMEDELTA/RC))) */ m_k = 0x10000 - 0x10000 * (exp(-1 / (Req * C) / machine().sample_rate())); } void filter_rc_device::filter_rc_set_RC(int type, double R1, double R2, double R3, double C) { m_stream->update(); set_RC_info(type, R1, R2, R3, C); }