Adds Super Game Module support for the ColecoVision.

Components/AY38910/AY38910.cpp

@@ -108,7 +108,6 @@ void AY38910::get_samples(std::size_t number_of_samples, int16_t *target) {
 		}
 
 		evaluate_output_volume();
-		printf("%d ", output_volume_);
 
 		for(int ic = 0; ic < 8 && c < number_of_samples; ic++) {
 			target[c] = output_volume_;
@@ -157,6 +156,11 @@ void AY38910::evaluate_output_volume() {
 	);
 }
 
+bool AY38910::is_zero_level() {
+	// Confirm that the AY is trivially at the zero level if all three volume controls are set to fixed zero.
+	return output_registers_[0x8] == 0 && output_registers_[0x9] == 0 && output_registers_[0xa] == 0;
+}
+
 // MARK: - Register manipulation
 
 void AY38910::select_register(uint8_t r) {

Components/AY38910/AY38910.hpp

@@ -85,6 +85,7 @@ class AY38910: public ::Outputs::Speaker::SampleSource {
 
 		// to satisfy ::Outputs::Speaker (included via ::Outputs::Filter; not for public consumption
 		void get_samples(std::size_t number_of_samples, int16_t *target);
+		bool is_zero_level();
 
 	private:
 		Concurrency::DeferringAsyncTaskQueue &task_queue_;

Components/KonamiSCC/KonamiSCC.cpp

@@ -15,12 +15,12 @@ using namespace Konami;
 SCC::SCC(Concurrency::DeferringAsyncTaskQueue &task_queue) :
 	task_queue_(task_queue) {}
 
-bool SCC::is_silent() {
+bool SCC::is_zero_level() {
 	return !(channel_enable_ & 0x1f);
 }
 
 void SCC::get_samples(std::size_t number_of_samples, std::int16_t *target) {
-	if(is_silent()) {
+	if(is_zero_level()) {
 		std::memset(target, 0, sizeof(std::int16_t) * number_of_samples);
 		return;
 	}

Components/KonamiSCC/KonamiSCC.hpp

@@ -27,7 +27,7 @@ class SCC: public ::Outputs::Speaker::SampleSource {
 		SCC(Concurrency::DeferringAsyncTaskQueue &task_queue);
 
 		/// As per ::SampleSource; provides a broadphase test for silence.
-		bool is_silent();
+		bool is_zero_level();
 
 		/// As per ::SampleSource; provides audio output.
 		void get_samples(std::size_t number_of_samples, std::int16_t *target);

Components/SN76489/SN76489.cpp

@@ -82,6 +82,10 @@ void SN76489::set_register(uint8_t value) {
 	});
 }
 
+bool SN76489::is_zero_level() {
+	return channels_[0].volume == 0xf && channels_[1].volume == 0xf && channels_[2].volume == 0xf && channels_[3].volume == 0xf;
+}
+
 void SN76489::evaluate_output_volume() {
 	output_volume_ = static_cast<int16_t>(
 		channels_[0].level * volumes_[channels_[0].volume] +

Components/SN76489/SN76489.hpp

@@ -30,6 +30,7 @@ class SN76489: public Outputs::Speaker::SampleSource {
 
 		// As per SampleSource.
 		void get_samples(std::size_t number_of_samples, std::int16_t *target);
+		bool is_zero_level();
 
 	private:
 		int master_divider_ = 0;