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sound/va_eg.cpp: Fixing subtle bugs. (#13570)

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* Actually take a voltage snapshot when R or C change. This was being attempted, but didn't work because set_target_v would exit early if the target V was not changing. Made the snapshoting more explicit.
* Consider the EG done based on elapsed time, instead of proximity to target value. Some low volume DMX sounds were affected by this.
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m1macrophage 2025-04-08 15:36:19 -07:00 committed by GitHub
parent 1779ca5db6
commit ccb469b9a7
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2 changed files with 30 additions and 20 deletions
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46
src/devices/sound/va_eg.cpp
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@ -5,6 +5,9 @@
#include "va_eg.h"
#include "machine/rescap.h"
// The envelope is considered completed after this many time constants.
static constexpr const float TIME_CONSTANTS_TO_END = 10;
DEFINE_DEVICE_TYPE(VA_RC_EG, va_rc_eg_device, "va_rc_eg", "RC-based Envelope Generator")
va_rc_eg_device::va_rc_eg_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock)
@ -28,7 +31,7 @@ va_rc_eg_device &va_rc_eg_device::set_r(float r)
if (m_stream != nullptr)
m_stream->update();
set_target_v(m_v_end); // Snapshots voltage, using the old `r` value.
snapshot(); // Snapshots voltage using the old `r` value.
m_r = r;
m_rc_inv = 1.0F / (m_r * m_c);
return *this;
@ -42,7 +45,7 @@ va_rc_eg_device &va_rc_eg_device::set_c(float c)
if (m_stream != nullptr)
m_stream->update();
set_target_v(m_v_end); // Snapshots voltage, using the old `c` value.
snapshot(); // Snapshots voltage using the old `c` value.
m_c = c;
m_rc_inv = 1.0F / (m_r * m_c);
return *this;
@ -55,19 +58,8 @@ va_rc_eg_device &va_rc_eg_device::set_target_v(float v)
if (m_stream != nullptr)
m_stream->update();
if (has_running_machine())
{
const attotime now = machine().time();
m_v_start = get_v(now);
m_v_end = v;
m_t_start = now;
}
else
{
m_v_start = 0;
m_v_end = v;
m_t_start = attotime::zero;
}
snapshot();
m_v_end = v;
return *this;
}
@ -79,6 +71,7 @@ va_rc_eg_device &va_rc_eg_device::set_instant_v(float v)
m_v_start = v;
m_v_end = v;
m_t_start = has_running_machine() ? machine().time() : attotime::zero;
m_t_end_approx = m_t_start;
return *this;
}
@ -103,19 +96,16 @@ void va_rc_eg_device::device_start()
save_item(NAME(m_v_start));
save_item(NAME(m_v_end));
save_item(NAME(m_t_start));
save_item(NAME(m_t_end_approx));
}
void va_rc_eg_device::sound_stream_update(sound_stream &stream, const std::vector<read_stream_view> &inputs, std::vector<write_stream_view> &outputs)
{
// The envelope stage will be considered done once the voltage reaches
// within MIN_DELTA of the target.
static constexpr const float MIN_DELTA = 0.0001F;
assert(inputs.size() == 0 && outputs.size() == 1);
write_stream_view &out = outputs[0];
attotime t = out.start_time();
if (fabsf(get_v(t) - m_v_end) < MIN_DELTA)
if (t >= m_t_end_approx)
{
// Avoid expensive get_v() calls if the envelope stage has completed.
out.fill(m_v_end);
@ -127,3 +117,19 @@ void va_rc_eg_device::sound_stream_update(sound_stream &stream, const std::vecto
for (int i = 0; i < n; ++i, t += dt)
out.put(i, get_v(t));
}
void va_rc_eg_device::snapshot()
{
if (has_running_machine())
{
const attotime now = machine().time();
m_v_start = get_v(now);
m_t_start = now;
}
else
{
m_v_start = 0;
m_t_start = attotime::zero;
}
m_t_end_approx = m_t_start + attotime::from_double(TIME_CONSTANTS_TO_END * m_r * m_c);
}

4
src/devices/sound/va_eg.h
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@ -42,6 +42,9 @@ protected:
void sound_stream_update(sound_stream &stream, const std::vector<read_stream_view> &inputs, std::vector<write_stream_view> &outputs) override;
private:
// Takes a snapshot of the current voltage into m_v_start and m_t_start.
void snapshot();
sound_stream *m_stream;
float m_r;
@ -50,6 +53,7 @@ private:
float m_v_start;
float m_v_end;
attotime m_t_start;
attotime m_t_end_approx;
};
DECLARE_DEVICE_TYPE(VA_RC_EG, va_rc_eg_device)