Implement CMS output filterjnovak/cms-filter

3 files changed, 26 insertions, 4 deletions

diff --git a/src/dosbox.cpp b/src/dosbox.cpp
index 95d7c3169..3244ce36d 100644
--- a/src/dosbox.cpp
+++ b/src/dosbox.cpp
@@ -812,6 +812,11 @@ void DOSBOX_Init() {
 	                  "           Use the filter of this Sound Blaster model.\n"
 	                  "  none:    Don't filter the output.");
 
+	Pstring = secprop->Add_string("cms_filter", when_idle, "on");
+	Pstring->Set_help("Filter for the Sound Blaster CMS output:\n"
+	                  "  on:    Filter the output (default).\n"
+	                  "  none:  Don't filter the output.");
+
 	// Configure Gravis UltraSound emulation
 	GUS_AddConfigSection(control);
 
diff --git a/src/hardware/gameblaster.cpp b/src/hardware/gameblaster.cpp
index 69b5a271d..10537177d 100644
--- a/src/hardware/gameblaster.cpp
+++ b/src/hardware/gameblaster.cpp
@@ -25,7 +25,8 @@
 #include "support.h"
 #include "pic.h"
 
-void GameBlaster::Open(const int port_choice, const std::string_view card_choice)
+void GameBlaster::Open(const int port_choice, const std::string &card_choice,
+                       const std::string &filter_choice)
 {
 	Close();
 	assert(!is_open);
@@ -88,6 +89,18 @@ void GameBlaster::Open(const int port_choice, const std::string_view card_choice
 	                            ChannelFeature::ReverbSend,
 	                            ChannelFeature::ChorusSend});
 
+	if (filter_choice == "on") {
+		channel->ConfigureLowPassFilter(1, 6000);
+		channel->SetLowPassFilter(FilterState::On);
+	} else {
+		if (filter_choice != "off")
+			LOG_WARNING("%s: Invalid filter setting '%s', using off",
+			            CardName(),
+			            filter_choice.c_str());
+
+		channel->SetLowPassFilter(FilterState::Off);
+	}
+
 	channel->RegisterLevelCallBack(level_callback);
 
 	// Calculate rates and ratio based on the mixer's rate
@@ -290,7 +303,9 @@ GameBlaster gameblaster;
 void CMS_Init(Section *configuration)
 {
 	Section_prop *section = static_cast<Section_prop *>(configuration);
-	gameblaster.Open(section->Get_hex("sbbase"), section->Get_string("sbtype"));
+	gameblaster.Open(section->Get_hex("sbbase"),
+	                 section->Get_string("sbtype"),
+	                 section->Get_string("cms_filter"));
 }
 void CMS_ShutDown([[maybe_unused]] Section* sec) {
 	gameblaster.Close();
diff --git a/src/hardware/gameblaster.h b/src/hardware/gameblaster.h
index 3d2462ed1..c64f90cce 100644
--- a/src/hardware/gameblaster.h
+++ b/src/hardware/gameblaster.h
@@ -26,7 +26,7 @@
 #include <array>
 #include <memory>
 #include <queue>
-#include <string_view>
+#include <string>
 #include <vector>
 
 #include "inout.h"
@@ -40,7 +40,9 @@
 
 class GameBlaster {
 public:
-	void Open(const int port_choice, const std::string_view card_choice);
+	void Open(const int port_choice, const std::string &card_choice,
+	          const std::string &filter_choice);
+
 	void Close();
 	~GameBlaster() { Close(); }