audioconvert: Always apply noise when asked

Rename empty.noise -> dither.noise and always add this amount of noise
when > 0. This also adds the noise to silent sounds, not only when
nothing is connected because that would also be a problem when an amp
needs to be kept alive with an non-0 signal.

Rename noise -> dither because we can use this also for dithering later.

See #705

spa/plugins/audioconvert/audioconvert.c

@@ -49,7 +49,7 @@
 #include "fmt-ops.h"
 #include "channelmix-ops.h"
 #include "resample.h"
-#include "noise-ops.h"
+#include "dither-ops.h"
 
 #undef SPA_LOG_TOPIC_DEFAULT
 #define SPA_LOG_TOPIC_DEFAULT log_topic
@@ -93,7 +93,7 @@ struct props {
 	unsigned int resample_quality;
 	unsigned int resample_disabled:1;
 	double rate;
-	uint32_t empty_noise;
+	uint32_t dither_noise;
 };
 
 static void props_reset(struct props *props)
@@ -110,7 +110,7 @@ static void props_reset(struct props *props)
 	props->rate = 1.0;
 	props->resample_quality = RESAMPLE_DEFAULT_QUALITY;
 	props->resample_disabled = false;
-	props->empty_noise = 0;
+	props->dither_noise = 0;
 }
 
 struct buffer {
@@ -212,7 +212,7 @@ struct impl {
 	struct channelmix mix;
 	struct resample resample;
 	struct volume volume;
-	struct noise noise;
+	struct dither dither;
 	double rate_scale;
 
 	uint32_t in_offset;
@@ -612,9 +612,9 @@ static int impl_node_enum_params(void *object, int seq,
 		case 21:
 			param = spa_pod_builder_add_object(&b,
 				SPA_TYPE_OBJECT_PropInfo, id,
-				SPA_PROP_INFO_name, SPA_POD_String("empty.noise"),
-				SPA_PROP_INFO_description, SPA_POD_String("Fill empty buffers with noise"),
-				SPA_PROP_INFO_type, SPA_POD_CHOICE_RANGE_Int(p->empty_noise, 0, 16),
+				SPA_PROP_INFO_name, SPA_POD_String("dither.noise"),
+				SPA_PROP_INFO_description, SPA_POD_String("Add dithering noise"),
+				SPA_PROP_INFO_type, SPA_POD_CHOICE_RANGE_Int(p->dither_noise, 0, 16),
 				SPA_PROP_INFO_params, SPA_POD_Bool(true));
 			break;
 		default:
@@ -683,8 +683,8 @@ static int impl_node_enum_params(void *object, int seq,
 			spa_pod_builder_int(&b, p->resample_quality);
 			spa_pod_builder_string(&b, "resample.disable");
 			spa_pod_builder_bool(&b, p->resample_disabled);
-			spa_pod_builder_string(&b, "empty.noise");
-			spa_pod_builder_int(&b, p->empty_noise);
+			spa_pod_builder_string(&b, "dither.noise");
+			spa_pod_builder_int(&b, p->dither_noise);
 			spa_pod_builder_pop(&b, &f[1]);
 			param = spa_pod_builder_pop(&b, &f[0]);
 			break;
@@ -754,8 +754,8 @@ static int audioconvert_set_param(struct impl *this, const char *k, const char *
 		this->props.resample_quality = atoi(s);
 	else if (spa_streq(k, "resample.disable"))
 		this->props.resample_disabled = spa_atob(s);
-	else if (spa_streq(k, "empty.noise"))
-		spa_atou32(s, &this->props.empty_noise, 0);
+	else if (spa_streq(k, "dither.noise"))
+		spa_atou32(s, &this->props.dither_noise, 0);
 	else
 		return 0;
 	return 1;
@@ -1395,17 +1395,18 @@ static int setup_out_convert(struct impl *this)
 	spa_log_debug(this->log, "%p: got converter features %08x:%08x passthrough:%d", this,
 			this->cpu_flags, out->conv.cpu_flags, out->conv.is_passthrough);
 
-	this->noise.intensity = (calc_width(&dst_info) * 8) - 1;
-	this->noise.intensity -= SPA_MIN(this->noise.intensity, this->props.empty_noise);
-	this->noise.n_channels = dst_info.info.raw.channels;
-	this->noise.cpu_flags = this->cpu_flags;
+	if (this->props.dither_noise > 0) {
+		this->dither.intensity = (calc_width(&dst_info) * 8) - 1;
+		this->dither.intensity -= SPA_MIN(this->dither.intensity, this->props.dither_noise);
+		this->dither.n_channels = dst_info.info.raw.channels;
+		this->dither.cpu_flags = this->cpu_flags;
 
-	if ((res = noise_init(&this->noise)) < 0)
-		return res;
-
-	spa_log_debug(this->log, "%p: empty noise:%d intensity:%d", this,
-			this->props.empty_noise, this->noise.intensity);
+		if ((res = dither_init(&this->dither)) < 0)
+			return res;
 
+		spa_log_debug(this->log, "%p: dither noise:%d intensity:%d", this,
+				this->props.dither_noise, this->dither.intensity);
+	}
 	return 0;
 }
 
@@ -2472,10 +2473,13 @@ static int impl_node_process(void *object)
 	}
 	this->out_offset += n_samples;
 
-	if (in_empty && this->props.empty_noise > 0) {
+	if (this->props.dither_noise > 0) {
+		in_datas = (const void**)out_datas;
 		if (out_passthrough)
 			out_datas = dst_datas;
-		noise_process(&this->noise, out_datas, n_samples);
+		else
+			out_datas = (void **)this->tmp_datas[(tmp++) & 1];
+		dither_process(&this->dither, out_datas, in_datas, n_samples);
 		in_empty = false;
 	}
 	if (!out_passthrough) {
@@ -2657,6 +2661,8 @@ impl_init(const struct spa_handle_factory *factory,
 	this->mix.rear_delay = 12.0f;
 	this->mix.widen = 0.0f;
 
+	this->dither.log = this->log;
+
 	for (i = 0; info && i < info->n_items; i++) {
 		const char *k = info->items[i].key;
 		const char *s = info->items[i].value;

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

@@ -22,18 +22,21 @@
  * DEALINGS IN THE SOFTWARE.
  */
 
-#include "noise-ops.h"
+#include "dither-ops.h"
 
-void
-noise_f32_c(struct noise *ns, void * SPA_RESTRICT dst[], uint32_t n_samples)
+void dither_f32_c(struct dither *dt, void * SPA_RESTRICT dst[],
+		const void * SPA_RESTRICT src[], uint32_t n_samples)
 {
 	uint32_t i, n;
+	const float **s = (const float**)src;
 	float **d = (float**)dst;
-	const float *t = ns->tab;
-	int tab_idx = ns->tab_idx;
+	const float *t = dt->tab;
+	int tab_idx = dt->tab_idx;
 
-	for (i = 0; i < ns->n_channels; i++)
+	for (i = 0; i < dt->n_channels; i++) {
 		for (n = 0; n < n_samples; n++)
-			d[i][n] = t[tab_idx++ & NOISE_MOD];
-	ns->tab_idx = (tab_idx + 23) & NOISE_MOD;
+			d[i][n] = s[i][n] + t[tab_idx++ & DITHER_MOD];
+		tab_idx += 61;
+	}
+	dt->tab_idx = tab_idx & DITHER_MOD;
 }

spa/plugins/audioconvert/dither-ops.c

@@ -32,52 +32,53 @@
 #include <spa/support/log.h>
 #include <spa/utils/defs.h>
 
-#include "noise-ops.h"
+#include "dither-ops.h"
 
-typedef void (*noise_func_t) (struct noise *ns, void * SPA_RESTRICT dst[], uint32_t n_samples);
+typedef void (*dither_func_t) (struct dither *d, void * SPA_RESTRICT dst[],
+		const void * SPA_RESTRICT src[], uint32_t n_samples);
 
-static const struct noise_info {
-	noise_func_t process;
+static const struct dither_info {
+	dither_func_t process;
 	uint32_t cpu_flags;
-} noise_table[] =
+} dither_table[] =
 {
-	{ noise_f32_c, 0 },
+	{ dither_f32_c, 0 },
 };
 
 #define MATCH_CPU_FLAGS(a,b)	((a) == 0 || ((a) & (b)) == a)
 
-static const struct noise_info *find_noise_info(uint32_t cpu_flags)
+static const struct dither_info *find_dither_info(uint32_t cpu_flags)
 {
 	size_t i;
-	for (i = 0; i < SPA_N_ELEMENTS(noise_table); i++) {
-		if (!MATCH_CPU_FLAGS(noise_table[i].cpu_flags, cpu_flags))
+	for (i = 0; i < SPA_N_ELEMENTS(dither_table); i++) {
+		if (!MATCH_CPU_FLAGS(dither_table[i].cpu_flags, cpu_flags))
 			continue;
-		return &noise_table[i];
+		return &dither_table[i];
 	}
 	return NULL;
 }
 
-static void impl_noise_free(struct noise *ns)
+static void impl_dither_free(struct dither *d)
 {
-	ns->process = NULL;
+	d->process = NULL;
 }
 
-int noise_init(struct noise *ns)
+int dither_init(struct dither *d)
 {
-	const struct noise_info *info;
+	const struct dither_info *info;
 	size_t i;
 
-	info = find_noise_info(ns->cpu_flags);
+	info = find_dither_info(d->cpu_flags);
 	if (info == NULL)
 		return -ENOTSUP;
 
-	if (ns->intensity >= 64)
+	if (d->intensity >= 64)
 		return -EINVAL;
 
-	for (i = 0; i < SPA_N_ELEMENTS(ns->tab); i++)
-		ns->tab[i] = (drand48() - 0.5) / (UINT64_C(1) << ns->intensity);
+	for (i = 0; i < SPA_N_ELEMENTS(d->tab); i++)
+		d->tab[i] = (drand48() - 0.5) / (UINT64_C(1) << d->intensity);
 
-	ns->free = impl_noise_free;
-	ns->process = info->process;
+	d->free = impl_dither_free;
+	d->process = info->process;
 	return 0;
 }

spa/plugins/audioconvert/dither-ops.h

@@ -26,36 +26,65 @@
 #include <stdio.h>
 
 #include <spa/utils/defs.h>
+#include <spa/utils/string.h>
 #include <spa/param/audio/raw.h>
 
-#define NOISE_SIZE	(1<<8)
-#define NOISE_MOD	(NOISE_SIZE-1)
+#define DITHER_SIZE	(1<<8)
+#define DITHER_MOD	(DITHER_SIZE-1)
 
-struct noise {
+struct dither {
 	uint32_t intensity;
+#define DITHER_METHOD_NONE 		0
+#define DITHER_METHOD_RECTANGULAR 	2
+#define DITHER_METHOD_TRIANGULAR 	3
+#define DITHER_METHOD_SHAPED_5	 	4
+	uint32_t method;
 	uint32_t n_channels;
 	uint32_t cpu_flags;
 
 	struct spa_log *log;
 
-	void (*process) (struct noise *ns, void * SPA_RESTRICT dst[], uint32_t n_samples);
-	void (*free) (struct noise *ns);
+	void (*process) (struct dither *d, void * SPA_RESTRICT dst[],
+			const void * SPA_RESTRICT src[], uint32_t n_samples);
+	void (*free) (struct dither *d);
 
-	float tab[NOISE_SIZE];
+	float tab[DITHER_SIZE];
 	int tab_idx;
 };
 
-int noise_init(struct noise *ns);
+int dither_init(struct dither *d);
 
-#define noise_process(ns,...)		(ns)->process(ns, __VA_ARGS__)
-#define noise_free(ns)			(ns)->free(ns)
+static const struct dither_method_info {
+	const char *label;
+	const char *description;
+	uint32_t method;
+} dither_method_info[] = {
+	[DITHER_METHOD_NONE] = { "none", "Disabled", DITHER_METHOD_NONE },
+	[DITHER_METHOD_RECTANGULAR] = { "rectangular", "Rectangular dithering", DITHER_METHOD_RECTANGULAR },
+	[DITHER_METHOD_TRIANGULAR] = { "triangular", "Triangular dithering", DITHER_METHOD_TRIANGULAR },
+	[DITHER_METHOD_SHAPED_5] = { "shaped5", "Shaped 5 dithering", DITHER_METHOD_SHAPED_5 }
+};
+
+static inline uint32_t dither_method_from_label(const char *label)
+{
+	uint32_t i;
+	for (i = 0; i < SPA_N_ELEMENTS(dither_method_info); i++) {
+		if (spa_streq(dither_method_info[i].label, label))
+			return dither_method_info[i].method;
+	}
+	return DITHER_METHOD_NONE;
+}
+
+#define dither_process(d,...)		(d)->process(d, __VA_ARGS__)
+#define dither_free(d)			(d)->free(d)
 
 #define DEFINE_FUNCTION(name,arch)			\
-void noise_##name##_##arch(struct noise *ns,		\
+void dither_##name##_##arch(struct dither *d,		\
 		void * SPA_RESTRICT dst[],		\
+		const void * SPA_RESTRICT src[],	\
 		uint32_t n_samples);
 
-#define NOISE_OPS_MAX_ALIGN	16
+#define DITHER_OPS_MAX_ALIGN	16
 
 DEFINE_FUNCTION(f32, c);
 

spa/plugins/audioconvert/meson.build

@@ -95,8 +95,8 @@ audioconvert_lib = static_library('audioconvert',
     'fmt-ops-c.c',
     'volume-ops.c',
     'volume-ops-c.c',
-    'noise-ops.c',
-    'noise-ops-c.c' ],
+    'dither-ops.c',
+    'dither-ops-c.c' ],
   c_args : [ simd_cargs, '-O3'],
   link_with : simd_dependencies,
   include_directories : [configinc],

src/daemon/client-rt.conf.in

@@ -90,5 +90,5 @@ stream.properties = {
     #channelmix.rear-delay = 12.0
     #channelmix.stereo-widen = 0.0
     #channelmix.hilbert-taps = 0
-    #empty.noise = 0
+    #dither.noise = 0
 }

src/daemon/client.conf.in

@@ -80,5 +80,5 @@ stream.properties = {
     #channelmix.rear-delay = 12.0
     #channelmix.stereo-widen = 0.0
     #channelmix.hilbert-taps = 0
-    #empty.noise = 0
+    #dither.noise = 0
 }

src/daemon/minimal.conf.in

@@ -212,7 +212,7 @@ context.objects = [
             #channelmix.stereo-widen = 0.0
             #channelmix.hilbert-taps = 0
             channelmix.disable     = true
-            #empty.noise = 0
+            #dither.noise = 0
             #node.param.Props      = {
             #    params = [
             #        audio.channels 6
@@ -274,7 +274,7 @@ context.objects = [
             #channelmix.stereo-widen = 0.0
             #channelmix.hilbert-taps = 0
             channelmix.disable     = true
-            #empty.noise = 0
+            #dither.noise = 0
             #node.param.Props      = {
             #    params = [
             #        audio.format  S16

src/daemon/pipewire-pulse.conf.in

@@ -66,7 +66,7 @@ stream.properties = {
     #channelmix.rear-delay = 12.0
     #channelmix.stereo-widen = 0.0
     #channelmix.hilbert-taps = 0
-    #empty.noise = 0
+    #dither.noise = 0
 }
 
 pulse.properties = {