Support overriding the number of channels in the AudioDriverPulseAudio buffer

doc/classes/ProjectSettings.xml

@@ -402,6 +402,16 @@
 		<member name="audio/driver/output_latency.web" type="int" setter="" getter="" default="50">
 			Safer override for [member audio/driver/output_latency] in the Web platform, to avoid audio issues especially on mobile devices.
 		</member>
+		<member name="audio/driver/override_channel_out" type="int" setter="" getter="" default="0">
+			The channel index to send to the stereo output when [code]override_speaker_channels[/code] has forced there to be a higher number of actual channels.
+		</member>
+		<member name="audio/driver/override_channels" type="bool" setter="" getter="" default="false">
+			If [code]true[/code], the number of output channels will be set by [code]override_speaker_channels[/code] instead of the speaker mode of the output device.
+			Applies only to PulseAudio.
+		</member>
+		<member name="audio/driver/override_speaker_channels" type="int" setter="" getter="" default="8">
+			The number of channels to use when [code]override_channels[/code] is set to [code]true[/code].
+		</member>
 		<member name="audio/general/2d_panning_strength" type="float" setter="" getter="" default="0.5">
 			The base strength of the panning effect for all [AudioStreamPlayer2D] nodes. The panning strength can be further scaled on each Node using [member AudioStreamPlayer2D.panning_strength]. A value of [code]0.0[/code] disables stereo panning entirely, leaving only volume attenuation in place. A value of [code]1.0[/code] completely mutes one of the channels if the sound is located exactly to the left (or right) of the listener.
 			The default value of [code]0.5[/code] is tuned for headphones. When using speakers, you may find lower values to sound better as speakers have a lower stereo separation compared to headphones.

drivers/pulseaudio/audio_driver_pulseaudio.cpp

@@ -175,7 +175,6 @@ Error AudioDriverPulseAudio::detect_channels(bool input) {
 			ERR_PRINT("pa_context_get_sink_info_by_name error");
 		}
 	}
-
 	return OK;
 }
 
@@ -200,23 +199,31 @@ Error AudioDriverPulseAudio::init_output_device() {
 		return err;
 	}
 
-	switch (pa_map.channels) {
+	print_verbose("PulseAudio: detected " + itos(pa_map.channels) + " output channels");
+	pa_channels = pa_map.channels;
+	if (GLOBAL_GET("audio/driver/override_channels") && (pa_map.channels == 2)) {
+		pa_channels = GLOBAL_GET("audio/driver/override_speaker_channels");
+		pa_channel0 = GLOBAL_GET("audio/driver/override_channel_out");
+		print_verbose("PulseAudio: forcing " + itos(pa_channels) + " output channels, but outputting to " + itos(pa_channel0) + "," + itos(pa_channel0 + 1));
+	}
+
+	switch (pa_channels) {
 		case 1: // Mono
 		case 3: // Surround 2.1
 		case 5: // Surround 5.0
 		case 7: // Surround 7.0
-			channels = pa_map.channels + 1;
+			channels = pa_channels + 1;
 			break;
 
 		case 2: // Stereo
 		case 4: // Surround 4.0
 		case 6: // Surround 5.1
 		case 8: // Surround 7.1
-			channels = pa_map.channels;
+			channels = pa_channels;
 			break;
 
 		default:
-			WARN_PRINT("PulseAudio: Unsupported number of output channels: " + itos(pa_map.channels));
+			WARN_PRINT("PulseAudio: Unsupported number of output channels: " + itos(pa_channels));
 			pa_channel_map_init_stereo(&pa_map);
 			channels = 2;
 			break;
@@ -226,7 +233,7 @@ Error AudioDriverPulseAudio::init_output_device() {
 	buffer_frames = closest_power_of_2(tmp_latency * mix_rate / 1000);
 	pa_buffer_size = buffer_frames * pa_map.channels;
 
-	print_verbose("PulseAudio: detected " + itos(pa_map.channels) + " output channels");
+	print_verbose("PulseAudio: reserving " + itos(channels) + " bus channels");
 	print_verbose("PulseAudio: audio buffer frames: " + itos(buffer_frames) + " calculated output latency: " + itos(buffer_frames * 1000 / mix_rate) + "ms");
 
 	pa_sample_spec spec;
@@ -416,11 +423,10 @@ void AudioDriverPulseAudio::thread_func(void *p_udata) {
 					for (unsigned int i = 0; i < ad->pa_buffer_size; i++) {
 						out_ptr[i] = ad->samples_in[i] >> 16;
 					}
-				} else {
+				} else if (ad->channels == ad->pa_map.channels + 1) {
 					// Uneven amount of channels
 					unsigned int in_idx = 0;
 					unsigned int out_idx = 0;
-
 					for (unsigned int i = 0; i < ad->buffer_frames; i++) {
 						for (int j = 0; j < ad->pa_map.channels - 1; j++) {
 							out_ptr[out_idx++] = ad->samples_in[in_idx++] >> 16;
@@ -429,6 +435,17 @@ void AudioDriverPulseAudio::thread_func(void *p_udata) {
 						uint32_t r = ad->samples_in[in_idx++] >> 16;
 						out_ptr[out_idx++] = (l + r) / 2;
 					}
+				} else {
+					// override_channels case
+					unsigned int in_idx = 0;
+					unsigned int out_idx = 0;
+					for (unsigned int i = 0; i < ad->buffer_frames; i++) {
+						in_idx += ad->pa_channel0;
+						for (int j = 0; j < ad->pa_map.channels; j++) {
+							out_ptr[out_idx++] = ad->samples_in[in_idx++] >> 16;
+						}
+						in_idx += ad->channels - ad->pa_map.channels - ad->pa_channel0;
+					}
 				}
 			}
 

drivers/pulseaudio/audio_driver_pulseaudio.h

@@ -54,6 +54,8 @@ class AudioDriverPulseAudio : public AudioDriver {
 	pa_stream *pa_rec_str = nullptr;
 	pa_channel_map pa_map = {};
 	pa_channel_map pa_rec_map = {};
+	unsigned int pa_channels = 2;
+	unsigned int pa_channel0 = 0;
 
 	String output_device_name = "Default";
 	String new_output_device = "Default";

servers/audio_server.cpp

@@ -216,6 +216,9 @@ void AudioDriverManager::initialize(int p_driver) {
 	GLOBAL_DEF_RST("audio/driver/enable_input", false);
 	GLOBAL_DEF_RST(PropertyInfo(Variant::INT, "audio/driver/mix_rate", PROPERTY_HINT_RANGE, "11025,192000,1,or_greater,suffix:Hz"), DEFAULT_MIX_RATE);
 	GLOBAL_DEF_RST(PropertyInfo(Variant::INT, "audio/driver/mix_rate.web", PROPERTY_HINT_RANGE, "0,192000,1,or_greater,suffix:Hz"), 0); // Safer default output_latency for web (use browser default).
+	GLOBAL_DEF_RST("audio/driver/override_channels", false);
+	GLOBAL_DEF_RST(PropertyInfo(Variant::INT, "audio/driver/override_speaker_channels", PROPERTY_HINT_RANGE, "2,8,1"), 8);
+	GLOBAL_DEF(PropertyInfo(Variant::INT, "audio/driver/override_channel_out", PROPERTY_HINT_RANGE, "0,6,1"), 0);
 
 	int failed_driver = -1;