change 8580 filter curve range

Author: ruby-R53

CHANGELOG.md

@@ -1,3 +1,13 @@
+May 1st, 2025:
+- The filter curve value for the 6581 chip still ranges from
+  -2.0 to 2.0. However, for the 8580 it now ranges from 0.0
+  to 1.0.
+  - This is because anything beyond the 0.0-1.0 range breaks
+    that chip's sound. So it's kinda useless to leave it that
+	way.
+  - I've actually wanting to do this for a while, but only now
+    I figured out how to do so x)
+
 April 28, 2025:
 - C++17 is now the minimum version required for C64play to
   compile.

doc/c64play.pod

@@ -179,12 +179,14 @@ which is the default.
 =item B<--curve=>I<< <num> >>
 
 Sets the filter curve on the reSIDfp emulation engine. Ranges
-from -2.0 ("light") to 2.0 ("dark"). Defaults to 0.5.
+from -2.0 ("light") to 2.0 ("dark") for the 6581 chip and from
+0.0 to 1.0 for the 8580 one. Defaults to 0.5 on both.
 
 =item B<--range=>I<< <num> >>
 
 For libsidplayfp v2.7.0 and higher. Controls the filter range
-value for the 6581 chip under the reSIDfp emulation.
+value for the 6581 chip under the reSIDfp emulation. Same
+default as above.
 
 =item B<--no-audio>
 

src/player.cpp

@@ -390,43 +390,61 @@ bool ConsolePlayer::createSidEmu(SIDEMUS emu, const SidTuneInfo *tuneInfo) {
 			rs->combinedWaveformsStrength(m_combinedWaveformsStrength);
 #endif
 
+			bool is6581 = (
+				(m_engCfg.defaultSidModel == SidConfig::MOS6581)
+			    && (m_engCfg.forceSidModel ||
+				   (tuneInfo->sidModel(0) != SidTuneInfo::SIDMODEL_8580))
+				|| (tuneInfo->sidModel(0) == SidTuneInfo::SIDMODEL_6581)
+			);
+
 #ifdef FEAT_FILTER_RANGE
 			// 6581 filter range control
-			if (m_frange.has_value()) {
-				m_filter.filterRange6581 = m_frange.value();
-			}
+			if (is6581) {
+				if (m_frange.has_value()) {
+					m_filter.filterRange6581 = m_frange.value();
+				}
 
-			if ((m_filter.filterRange6581 < 0.0) || (m_filter.filterRange6581 > 1.0)) {
-				cerr << "Invalid 6581 filter range: " << m_filter.filterRange6581 << endl;
-				exit(EXIT_FAILURE);
-			}
+				if ((m_filter.filterRange6581 < 0.0)
+				    || (m_filter.filterRange6581 > 1.0)) {
+					cerr << "Invalid 6581 filter range: "
+					     << m_filter.filterRange6581 << endl;
 
-			rs->filter6581Range(m_filter.filterRange6581);
+					exit(EXIT_FAILURE);
+				}
+
+				rs->filter6581Range(m_filter.filterRange6581);
 #endif
 
-			// 6581 filter curve control
-			if (m_fcurve.has_value()) {
-				m_filter.filterCurve6581 = m_fcurve.value();
-			}
+				// 6581 filter curve control
+				if (m_fcurve.has_value()) {
+					m_filter.filterCurve6581 = m_fcurve.value();
+				}
 
-			if ((m_filter.filterCurve6581 < -2.0) || (m_filter.filterCurve6581 > 2.0)) {
-				cerr << "Invalid 6581 filter curve: " << m_filter.filterCurve6581 << endl;
-				exit(EXIT_FAILURE);
-			}
+				if ((m_filter.filterCurve6581 < -2.0)
+				    || (m_filter.filterCurve6581 > 2.0)) {
+					cerr << "Invalid 6581 filter curve: "
+					     << m_filter.filterCurve6581 << endl;
 
-			rs->filter6581Curve(m_filter.filterCurve6581);
+					exit(EXIT_FAILURE);
+				}
 
-			// 8580 filter curve control
-			if (m_fcurve.has_value()) {
-				m_filter.filterCurve8580 = m_fcurve.value();
-			}
+				rs->filter6581Curve(m_filter.filterCurve6581);
+			} else {
+				// 8580 filter curve control
+				if (m_fcurve.has_value()) {
+					m_filter.filterCurve8580 = m_fcurve.value();
+				}
 
-			if ((m_filter.filterCurve8580 < -2.0) || (m_filter.filterCurve8580 > 2.0)) {
-				cerr << "Invalid 8580 filter curve: " << m_filter.filterCurve8580 << endl;
-				exit(EXIT_FAILURE);
-			}
+				if ((m_filter.filterCurve8580 < 0.0)
+				    || (m_filter.filterCurve8580 > 1.0)) {
+					cerr << "Invalid 8580 filter curve: "
+					     << m_filter.filterCurve8580 << endl;
 
-			rs->filter8580Curve(m_filter.filterCurve8580);
+					exit(EXIT_FAILURE);
+				}
+
+				rs->filter8580Curve(m_filter.filterCurve8580);
+			}
 		}
 
 		catch (std::bad_alloc const &ba) {}