channelmix: add simple upmix method

Add a property to select the upmix method. PSD is enabled by default
but a new simple upmixing algorithm is available that duplicates
channels and avoids lowpass filter on the FC and disables widening.

Fixes #861

spa/plugins/audioconvert/channelmix-ops-c.c

@@ -246,6 +246,16 @@ channelmix_f32_2_3p1_c(struct channelmix *mix, void * SPA_RESTRICT dst[],
 		for (i = 0; i < n_dst; i++)
 			memset(d[i], 0, n_samples * sizeof(float));
 	}
+	else if (mix->upmix == CHANNELMIX_UPMIX_SIMPLE) {
+		for (n = 0; n < n_samples; n++) {
+			float c = s[0][n] + s[1][n];
+			d[0][n] = s[0][n] * v0;
+			d[1][n] = s[1][n] * v1;
+			d[2][n] = c * v2;
+			d[3][n] = c;
+		}
+		lr4_process(&mix->lr4[3], d[3], d[3], v3, n_samples);
+	}
 	else if (v0 == 1.0f && v1 == 1.0f) {
 		for (n = 0; n < n_samples; n++) {
 			float c = s[0][n] + s[1][n];
@@ -289,6 +299,18 @@ channelmix_f32_2_5p1_c(struct channelmix *mix, void * SPA_RESTRICT dst[],
 		for (i = 0; i < n_dst; i++)
 			memset(d[i], 0, n_samples * sizeof(float));
 	}
+	else if (mix->upmix == CHANNELMIX_UPMIX_SIMPLE) {
+		for (n = 0; n < n_samples; n++) {
+			float c = s[0][n] + s[1][n];
+			d[0][n] = s[0][n] * v0;
+			d[1][n] = s[1][n] * v1;
+			d[2][n] = c * v2;
+			d[3][n] = c;
+			d[4][n] = s[0][n] * v4;
+			d[5][n] = s[1][n] * v5;
+		}
+		lr4_process(&mix->lr4[3], d[3], d[3], v3, n_samples);
+	}
 	else if (v0 == 1.0f && v1 == 1.0f) {
 		for (n = 0; n < n_samples; n++) {
 			float c = s[0][n] + s[1][n];
@@ -347,6 +369,20 @@ channelmix_f32_2_7p1_c(struct channelmix *mix, void * SPA_RESTRICT dst[],
 		for (i = 0; i < n_dst; i++)
 			memset(d[i], 0, n_samples * sizeof(float));
 	}
+	else if (mix->upmix == CHANNELMIX_UPMIX_SIMPLE) {
+		for (n = 0; n < n_samples; n++) {
+			float c = s[0][n] + s[1][n];
+			d[0][n] = s[0][n] * v0;
+			d[1][n] = s[1][n] * v1;
+			d[2][n] = c * v2;
+			d[3][n] = c;
+			d[4][n] = s[0][n] * v4;
+			d[5][n] = s[1][n] * v5;
+			d[6][n] = s[0][n] * v6;
+			d[7][n] = s[1][n] * v7;
+		}
+		lr4_process(&mix->lr4[3], d[3], d[3], v3, n_samples);
+	}
 	else if (v0 == 1.0f && v1 == 1.0f && v4 == 1.0f && v5 == 1.0f) {
 		for (n = 0; n < n_samples; n++) {
 			float c = s[0][n] + s[1][n];

spa/plugins/audioconvert/channelmix-ops.c

@@ -210,7 +210,8 @@ static int make_matrix(struct channelmix *mix)
 	unassigned = src_mask & ~dst_mask;
 	keep = dst_mask & ~src_mask;
 
-	if (!SPA_FLAG_IS_SET(mix->options, CHANNELMIX_OPTION_UPMIX))
+	if (!SPA_FLAG_IS_SET(mix->options, CHANNELMIX_OPTION_UPMIX) ||
+	    mix->upmix == CHANNELMIX_UPMIX_NONE)
 		keep = 0;
 
 	keep |= FRONT;

spa/plugins/audioconvert/channelmix-ops.h

@@ -26,6 +26,7 @@
 #include <stdio.h>
 
 #include <spa/utils/defs.h>
+#include <spa/utils/string.h>
 #include <spa/param/audio/raw.h>
 
 #undef SPA_LOG_TOPIC_DEFAULT
@@ -61,6 +62,10 @@ struct channelmix {
 #define CHANNELMIX_OPTION_NORMALIZE	(1<<1)		/**< normalize volumes */
 #define CHANNELMIX_OPTION_UPMIX		(1<<2)		/**< do simple upmixing */
 	uint32_t options;
+#define CHANNELMIX_UPMIX_NONE		(0)		/**< disable upmixing */
+#define CHANNELMIX_UPMIX_SIMPLE		(1)		/**< simple upmixing */
+#define CHANNELMIX_UPMIX_PSD		(2)		/**< Passive Surround Decoding upmixing */
+	uint32_t upmix;
 
 	struct spa_log *log;
 
@@ -97,6 +102,26 @@ struct channelmix {
 
 int channelmix_init(struct channelmix *mix);
 
+static const struct channelmix_upmix_info {
+	const char *label;
+	const char *description;
+	uint32_t upmix;
+} channelmix_upmix_info[] = {
+	[CHANNELMIX_UPMIX_NONE] = { "none", "Disabled", CHANNELMIX_UPMIX_NONE },
+	[CHANNELMIX_UPMIX_SIMPLE] = { "simple", "Simple upmixing", CHANNELMIX_UPMIX_SIMPLE },
+	[CHANNELMIX_UPMIX_PSD] = { "psd", "Passive Surround Decoding", CHANNELMIX_UPMIX_PSD }
+};
+
+static inline uint32_t channelmix_upmix_from_label(const char *label)
+{
+	uint32_t i;
+	for (i = 0; i < SPA_N_ELEMENTS(channelmix_upmix_info); i++) {
+		if (spa_streq(channelmix_upmix_info[i].label, label))
+			return channelmix_upmix_info[i].upmix;
+	}
+	return CHANNELMIX_UPMIX_NONE;
+}
+
 #define channelmix_process(mix,...)	(mix)->process(mix, __VA_ARGS__)
 #define channelmix_set_volume(mix,...)	(mix)->set_volume(mix, __VA_ARGS__)
 #define channelmix_free(mix)		(mix)->free(mix)

spa/plugins/audioconvert/channelmix.c

@@ -546,6 +546,31 @@ static int impl_node_enum_params(void *object, int seq,
 					this->mix.hilbert_taps, 0, MAX_TAPS),
 				SPA_PROP_INFO_params, SPA_POD_Bool(true));
 			break;
+		case 17:
+		{
+			struct spa_pod_frame f[2];
+			uint32_t i;
+			spa_pod_builder_push_object(&b, &f[0],
+				SPA_TYPE_OBJECT_PropInfo, id);
+			spa_pod_builder_add(&b,
+				SPA_PROP_INFO_name, SPA_POD_String("channelmix.upmix-method"),
+				SPA_PROP_INFO_description, SPA_POD_String("Upmix Method to use"),
+				SPA_PROP_INFO_type, SPA_POD_String(
+					channelmix_upmix_info[this->mix.upmix].label),
+				0);
+			spa_pod_builder_prop(&b, SPA_PROP_INFO_labels, 0);
+			spa_pod_builder_push_struct(&b, &f[1]);
+			for (i = 0; i < SPA_N_ELEMENTS(channelmix_upmix_info); i++) {
+				spa_pod_builder_string(&b, channelmix_upmix_info[i].label);
+				spa_pod_builder_string(&b, channelmix_upmix_info[i].description);
+			}
+			spa_pod_builder_pop(&b, &f[1]);
+			spa_pod_builder_add(&b,
+				SPA_PROP_INFO_params, SPA_POD_Bool(true),
+				0);
+			param = spa_pod_builder_pop(&b, &f[0]);
+			break;
+		}
 		default:
 			return 0;
 		}
@@ -605,6 +630,8 @@ static int impl_node_enum_params(void *object, int seq,
 			spa_pod_builder_float(&b, this->mix.widen);
 			spa_pod_builder_string(&b, "channelmix.hilbert-taps");
 			spa_pod_builder_int(&b, this->mix.hilbert_taps);
+			spa_pod_builder_string(&b, "channelmix.upmix-method");
+			spa_pod_builder_string(&b, channelmix_upmix_info[this->mix.upmix].label);
 			spa_pod_builder_pop(&b, &f[1]);
 			param = spa_pod_builder_pop(&b, &f[0]);
 			break;
@@ -648,6 +675,8 @@ static int channelmix_set_param(struct impl *this, const char *k, const char *s)
 		spa_atof(s, &this->mix.widen);
 	else if (spa_streq(k, "channelmix.hilbert-taps"))
 		spa_atou32(s, &this->mix.hilbert_taps, 0);
+	else if (spa_streq(k, "channelmix.upmix-method"))
+		this->mix.upmix = channelmix_upmix_from_label(s);
 	else
 		return 0;
 	return 1;
@@ -1625,6 +1654,7 @@ impl_init(const struct spa_handle_factory *factory,
 	props_reset(&this->props);
 
 	this->mix.options = CHANNELMIX_OPTION_UPMIX;
+	this->mix.upmix = CHANNELMIX_UPMIX_PSD;
 	this->mix.log = this->log;
 	this->mix.lfe_cutoff = 120.0f;
 	this->mix.fc_cutoff = 6000.0f;

src/daemon/client-rt.conf.in

@@ -84,6 +84,7 @@ stream.properties = {
     #channelmix.normalize  = false
     #channelmix.mix-lfe    = true
     #channelmix.upmix      = true
+    #channelmix.upmix-method = psd  # none, simple
     #channelmix.lfe-cutoff = 120
     #channelmix.fc-cutoff  = 6000
     #channelmix.rear-delay = 12.0

src/daemon/client.conf.in

@@ -74,6 +74,7 @@ stream.properties = {
     #channelmix.normalize  = false
     #channelmix.mix-lfe    = false
     #channelmix.upmix      = true
+    #channelmix.upmix-method = psd  # none, simple
     #channelmix.lfe-cutoff = 120
     #channelmix.fc-cutoff  = 6000
     #channelmix.rear-delay = 12.0

src/daemon/minimal.conf.in

@@ -205,6 +205,7 @@ context.objects = [
             #channelmix.normalize   = false
             #channelmix.mix-lfe     = false
             #channelmix.upmix       = true
+            #channelmix.upmix-method = psd  # none, simple
             #channelmix.lfe-cutoff  = 120
             #channelmix.fc-cutoff   = 6000
             #channelmix.rear-delay  = 12.0
@@ -264,6 +265,7 @@ context.objects = [
             #channelmix.normalize  = false
             #channelmix.mix-lfe    = false
             #channelmix.upmix      = true
+            #channelmix.upmix-method = psd  # none, simple
             #channelmix.lfe-cutoff = 120
             #channelmix.fc-cutoff  = 6000
             #channelmix.rear-delay = 12.0

src/daemon/pipewire-pulse.conf.in

@@ -60,6 +60,7 @@ stream.properties = {
     #channelmix.normalize  = false
     #channelmix.mix-lfe    = false
     #channelmix.upmix      = true
+    #channelmix.upmix-method = psd  # none, simple
     #channelmix.lfe-cutoff = 120
     #channelmix.fc-cutoff  = 6000
     #channelmix.rear-delay = 12.0