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Improve Taito Zoom ZSG-2 sound emulation (#3847)
* Improve Taito Zoom ZSG-2 sound emulation zsg2.cpp: implement emphasis filter, this is a noise reduction scheme that amplifies higher frequncies to reduce quantization noise. zsg2.cpp: Add sample interpolation and another adjustable lowpass filter. This seems to be roughly what real hardware does... zsg2.cpp: Improve panning registers and identify DSP output gain registers. * zsg2: minor changes [nw] zsg2: Register 0b appears to be status flags [nw] zsg2: Linear ramping probably makes more sense [nw] * zsg2: slight adjustment of emphasis filter [nw] * zsg2: slight adjustment of emphasis filter #2 [nw] * zsg2: more sober ramping algorithm [nw]
This commit is contained in:
superctr
R. Belmont
parent
c347aec715
commit
9bad37d8cb
@ -1,11 +1,12 @@
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// license:BSD-3-Clause
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// copyright-holders:Olivier Galibert, R. Belmont, hap
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// copyright-holders:Olivier Galibert, R. Belmont, hap, superctr
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/*
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ZOOM ZSG-2 custom wavetable synthesizer
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Written by Olivier Galibert
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MAME conversion by R. Belmont
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Working emulation by The Talentuous Hands Of The Popularious hap
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Improvements by superctr
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---------------------------------------------------------
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Additional notes on the sample format, reverse-engineered
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@ -44,9 +45,9 @@
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---------------------------------------------------------
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TODO:
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- volume/panning is linear? volume slides are too steep
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- most music sounds tinny, probably due to missing DSP?
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- what is reg 0xa/0xc? seems related to volume
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- Filter behavior might not be perfect.
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- Volume ramping probably behaves differently on hardware.
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- hook up DSP, it's used for reverb and chorus effects.
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- identify sample flags
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* bassdrum in shikigam level 1 music is a good hint: it should be one octave
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lower, indicating possible stereo sample, or base octave(like in ymf278)
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@ -57,6 +58,13 @@ TODO:
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#include "emu.h"
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#include "zsg2.h"
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#include <algorithm>
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#include <fstream>
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#include <cmath>
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#define EMPHASIS_CUTOFF_BASE 0x800
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#define EMPHASIS_CUTOFF_SHIFT 1
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#define EMPHASIS_OUTPUT_SHIFT 15
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// device type definition
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DEFINE_DEVICE_TYPE(ZSG2, zsg2_device, "zsg2", "ZOOM ZSG-2")
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@ -74,7 +82,6 @@ zsg2_device::zsg2_device(const machine_config &mconfig, const char *tag, device_
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{
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}
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//-------------------------------------------------
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// device_start - device-specific startup
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//-------------------------------------------------
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@ -85,7 +92,7 @@ void zsg2_device::device_start()
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memset(&m_chan, 0, sizeof(m_chan));
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m_stream = stream_alloc(0, 2, clock() / 768);
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m_stream = stream_alloc(0, 4, clock() / 768);
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m_mem_blocks = m_mem_base.length();
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m_mem_copy = make_unique_clear<uint32_t[]>(m_mem_blocks);
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@ -96,6 +103,13 @@ void zsg2_device::device_start()
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save_pointer(NAME(m_full_samples), (m_mem_blocks * 4 + 4) / sizeof(int16_t));
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save_item(NAME(m_read_address));
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// Generate the output gain table. Assuming -1dB per step for now.
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for (int i = 0; i < 32; i++)
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{
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double val = pow(10, -(31 - i) / 20.) * 65535.;
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gain_tab[i] = val;
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}
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for (int ch = 0; ch < 48; ch++)
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{
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save_item(NAME(m_chan[ch].v), ch);
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@ -107,14 +121,28 @@ void zsg2_device::device_start()
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save_item(NAME(m_chan[ch].end_pos), ch);
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save_item(NAME(m_chan[ch].loop_pos), ch);
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save_item(NAME(m_chan[ch].page), ch);
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save_item(NAME(m_chan[ch].vol), ch);
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save_item(NAME(m_chan[ch].flags), ch);
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save_item(NAME(m_chan[ch].panl), ch);
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save_item(NAME(m_chan[ch].panr), ch);
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save_item(NAME(m_chan[ch].vol_initial), ch);
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save_item(NAME(m_chan[ch].vol_target), ch);
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save_item(NAME(m_chan[ch].emphasis_cutoff), ch);
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save_item(NAME(m_chan[ch].emphasis_cutoff_initial), ch);
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save_item(NAME(m_chan[ch].emphasis_cutoff_target), ch);
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save_item(NAME(m_chan[ch].output_cutoff), ch);
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save_item(NAME(m_chan[ch].output_cutoff_initial), ch);
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save_item(NAME(m_chan[ch].output_cutoff_target), ch);
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save_item(NAME(m_chan[ch].emphasis_filter_state), ch);
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save_item(NAME(m_chan[ch].output_filter_state), ch);
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save_item(NAME(m_chan[ch].output_gain), ch);
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save_item(NAME(m_chan[ch].samples), ch);
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}
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}
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//-------------------------------------------------
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// device_reset - device-specific reset
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//-------------------------------------------------
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@ -148,7 +176,6 @@ void zsg2_device::device_reset()
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#endif
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}
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/******************************************************************************/
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uint32_t zsg2_device::read_memory(uint32_t offset)
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@ -193,6 +220,22 @@ int16_t *zsg2_device::prepare_samples(uint32_t offset)
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return &m_full_samples[offset];
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}
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// Fill the buffer with filtered samples
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void zsg2_device::filter_samples(zchan *ch)
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{
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int16_t *raw_samples = prepare_samples(ch->page | ch->cur_pos);
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ch->samples[0] = ch->samples[4]; // we want to remember the last sample
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for (int i = 0; i < 4; i++)
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{
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ch->samples[i+1] = raw_samples[i];
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// not sure if the filter works exactly this way, however I am pleased
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// with the output for now.
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ch->emphasis_filter_state += (raw_samples[i]-(ch->emphasis_filter_state>>16)) * (EMPHASIS_CUTOFF_BASE - ch->emphasis_cutoff);
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ch->samples[i+1] = (ch->emphasis_filter_state) >> EMPHASIS_OUTPUT_SHIFT;
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}
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}
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//-------------------------------------------------
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// sound_stream_update - handle a stream update
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@ -202,12 +245,15 @@ void zsg2_device::sound_stream_update(sound_stream &stream, stream_sample_t **in
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{
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for (int i = 0; i < samples; i++)
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{
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int32_t mix_l = 0;
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int32_t mix_r = 0;
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int32_t mix[4] = {};
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int ch = 0;
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// loop over all channels
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for (auto & elem : m_chan)
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//auto & elem = m_chan[0];
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{
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ch++;
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if (!elem.is_playing)
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continue;
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@ -226,21 +272,47 @@ void zsg2_device::sound_stream_update(sound_stream &stream, stream_sample_t **in
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continue;
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}
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}
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elem.samples = prepare_samples(elem.page | elem.cur_pos);
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filter_samples(&elem);
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//elem.samples = prepare_samples(elem.page | elem.cur_pos);
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}
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int32_t sample = (elem.samples[elem.step_ptr >> 14 & 3] * elem.vol) >> 16;
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uint8_t sample_pos = elem.step_ptr >> 14 & 3;
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int32_t sample; // = elem.samples[sample_pos];
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mix_l += (sample * elem.panl + sample * (0x1f - elem.panr)) >> 5;
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mix_r += (sample * elem.panr + sample * (0x1f - elem.panl)) >> 5;
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// linear interpolation (hardware certainly does something similar)
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sample = elem.samples[sample_pos];
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sample += ((uint16_t)(elem.step_ptr<<2&0xffff) * (int16_t)(elem.samples[sample_pos+1] - sample))>>16;
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sample = (sample * elem.vol) >> 16;
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// another filter...
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elem.output_filter_state += (sample - (elem.output_filter_state>>16)) * elem.output_cutoff;
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sample = elem.output_filter_state >> 16;
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for(int output=0; output<4; output++)
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{
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int output_gain = elem.output_gain[output] & 0x1f; // left / right
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int32_t output_sample = sample;
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if (elem.output_gain[output] & 0x80) // perhaps ?
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output_sample = -output_sample;
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mix[output] += (output_sample * gain_tab[output_gain&0x1f]) >> 13;
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}
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// Apply transitions (This is not accurate yet)
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elem.vol = ramp(elem.vol, elem.vol_target);
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elem.output_cutoff = ramp(elem.output_cutoff, elem.output_cutoff_target);
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elem.emphasis_cutoff = ramp(elem.emphasis_cutoff, elem.emphasis_cutoff_target);
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}
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outputs[0][i] = mix_l;
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outputs[1][i] = mix_r;
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ch = 0;
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for(int output=0; output<4; output++)
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outputs[output][i] = mix[output];
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}
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}
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/******************************************************************************/
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void zsg2_device::chan_w(int ch, int reg, uint16_t data)
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@ -275,9 +347,9 @@ void zsg2_device::chan_w(int ch, int reg, uint16_t data)
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case 0x5:
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// lo byte: loop address low
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// hi byte: right panning (high bits always 0)
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// hi byte: right output gain (bypass DSP)
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m_chan[ch].loop_pos = (m_chan[ch].loop_pos & 0xff00) | (data & 0xff);
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m_chan[ch].panr = data >> 8 & 0x1f;
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m_chan[ch].output_gain[1] = data >> 8;
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break;
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case 0x6:
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@ -287,28 +359,52 @@ void zsg2_device::chan_w(int ch, int reg, uint16_t data)
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case 0x7:
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// lo byte: loop address high
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// hi byte: left panning (high bits always 0)
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// hi byte: left output gain (bypass DSP)
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m_chan[ch].loop_pos = (m_chan[ch].loop_pos & 0x00ff) | (data << 8 & 0xff00);
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m_chan[ch].panl = data >> 8 & 0x1f;
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m_chan[ch].output_gain[0] = data >> 8;
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break;
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case 0x8:
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// Filter cutoff (Direct)
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m_chan[ch].output_cutoff_initial = data;
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break;
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case 0x9:
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// no function? always 0
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break;
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case 0xa:
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// volume (Direct)
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m_chan[ch].vol_initial = data;
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break;
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case 0xb:
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// always writes 0
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// this register is read-only
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break;
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case 0xc:
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// filter gain ?
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m_chan[ch].output_cutoff_target = data;
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break;
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case 0xd:
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// hi byte: DSP Chorus volume
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// lo byte: Emphasis filter time constant (direct value)
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m_chan[ch].output_gain[3] = data >> 8;
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m_chan[ch].emphasis_cutoff_initial = expand_reg(data & 0xff);
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break;
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case 0xe:
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// volume
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m_chan[ch].vol = data;
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// volume (Target)
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m_chan[ch].vol_target = data;
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break;
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case 0xf:
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// flags
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m_chan[ch].flags = data;
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// hi byte: DSP Reverb volume
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// lo byte: Emphasis filter time constant
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m_chan[ch].output_gain[2] = data >> 8;
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m_chan[ch].emphasis_cutoff_target = expand_reg(data & 0xff);
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break;
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default:
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@ -322,10 +418,8 @@ uint16_t zsg2_device::chan_r(int ch, int reg)
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{
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switch (reg)
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{
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case 0xb:
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// ?
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return 0;
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case 0xb: // Only later games (taitogn) read this register...
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return m_chan[ch].is_playing << 13;
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default:
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break;
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}
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@ -333,6 +427,38 @@ uint16_t zsg2_device::chan_r(int ch, int reg)
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return m_chan[ch].v[reg];
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}
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// expand 8-bit reg to 16-bit value. This is used for the emphasis filter
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// register. Not sure about how this works, the sound
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// CPU uses a lookup table (stored in gdarius sound cpu ROM at 0x6332) to
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// calculate this value, for now I'm generating an opproximate inverse.
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int16_t zsg2_device::expand_reg(uint8_t val)
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{
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static const signed char frac_tab[16] = {8,9,10,11,12,13,14,15,-15,-14,-13,-12,-11,-10,-9,-8};
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static const unsigned char shift_tab[8] = {1, 2, 3, 4, 5, 6, 7, 8};
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return (frac_tab[val&0x0f] << shift_tab[val>>4])>>EMPHASIS_CUTOFF_SHIFT;
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}
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// ramp registers
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// The CPU does not write often enough to make the transitions always sound
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// smooth, so the sound chip probably helps by smoothing the changes.
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// There are two sets of the volume and filter cutoff registers.
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// At key on, the CPU writes to the "direct" registers, after that it will
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// write to the "target" register instead.
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inline int32_t zsg2_device::ramp(int32_t current, int32_t target)
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{
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int32_t difference = abs(target-current);
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difference -= 0x40;
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if(difference < 0)
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return target;
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else if(target < current)
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return target + difference;
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else if(target > current)
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return target - difference;
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return target;
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}
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/******************************************************************************/
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@ -352,7 +478,11 @@ void zsg2_device::control_w(int reg, uint16_t data)
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m_chan[ch].is_playing = true;
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m_chan[ch].cur_pos = m_chan[ch].start_pos;
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m_chan[ch].step_ptr = 0;
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m_chan[ch].samples = prepare_samples(m_chan[ch].page | m_chan[ch].cur_pos);
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m_chan[ch].emphasis_filter_state = 0;
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m_chan[ch].vol = m_chan[ch].vol_initial;
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m_chan[ch].output_cutoff = m_chan[ch].output_cutoff_initial;
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m_chan[ch].emphasis_cutoff = m_chan[ch].emphasis_cutoff_initial;
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filter_samples(&m_chan[ch]);
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}
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}
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break;
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@ -373,8 +503,15 @@ void zsg2_device::control_w(int reg, uint16_t data)
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break;
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}
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case 0x18:
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break;
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// case 0x0c: //These registers are sometimes written to by the CPU. Unknown purpose.
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// break;
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// case 0x0d:
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// break;
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// case 0x10:
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// break;
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// case 0x18:
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// break;
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case 0x1c:
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// rom readback address low (low 2 bits always 0)
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@ -387,6 +524,7 @@ void zsg2_device::control_w(int reg, uint16_t data)
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break;
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default:
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logerror("ZSG2 control %02X = %04X\n", reg, data & 0xffff);
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break;
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}
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}
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@ -414,7 +552,6 @@ uint16_t zsg2_device::control_r(int reg)
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return 0;
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}
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/******************************************************************************/
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WRITE16_MEMBER(zsg2_device::write)
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@ -51,7 +51,6 @@ private:
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{
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uint16_t v[16];
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bool is_playing;
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int16_t *samples;
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uint32_t cur_pos;
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uint32_t step_ptr;
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uint32_t step;
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@ -59,12 +58,29 @@ private:
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uint32_t end_pos;
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uint32_t loop_pos;
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uint32_t page;
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uint16_t vol;
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uint16_t flags;
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uint8_t panl;
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uint8_t panr;
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uint16_t vol_initial;
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uint16_t vol_target;
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int16_t emphasis_cutoff;
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int16_t emphasis_cutoff_initial;
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int16_t emphasis_cutoff_target;
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uint16_t output_cutoff;
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uint16_t output_cutoff_initial;
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uint16_t output_cutoff_target;
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int32_t emphasis_filter_state;
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int32_t output_filter_state;
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// Attenuation for output channels
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uint8_t output_gain[4];
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int16_t samples[5]; // +1 history
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};
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uint16_t gain_tab[256];
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zchan m_chan[48];
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required_region_ptr<uint32_t> m_mem_base;
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@ -83,6 +99,9 @@ private:
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void control_w(int reg, uint16_t data);
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uint16_t control_r(int reg);
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int16_t *prepare_samples(uint32_t offset);
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void filter_samples(zchan *ch);
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int16_t expand_reg(uint8_t val);
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inline int32_t ramp(int32_t current, int32_t target);
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};
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DECLARE_DEVICE_TYPE(ZSG2, zsg2_device)
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@ -187,6 +187,10 @@ MACHINE_CONFIG_START(taito_zoom_device::device_add_mconfig)
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MCFG_ZSG2_ADD("zsg2", XTAL(25'000'000))
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// we assume the parent machine has created lspeaker/rspeaker
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MCFG_SOUND_ROUTE(0, "^lspeaker", 1.0)
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MCFG_SOUND_ROUTE(0, "^lspeaker", 1.0) // bypass DSP
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MCFG_SOUND_ROUTE(1, "^rspeaker", 1.0)
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//MCFG_SOUND_ROUTE(2, "^lspeaker", 1.0) // DSP reverb
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//MCFG_SOUND_ROUTE(3, "^rspeaker", 1.0) // DSP chorus
|
||||
|
||||
MACHINE_CONFIG_END
|
||||
|
||||
Loading…
Reference in New Issue
Block a user