obs-filters: Add noise gate filter

plugins/obs-filters/CMakeLists.txt

@@ -9,6 +9,7 @@ set(obs-filters_SOURCES
 	chroma-key-filter.c
 	color-key-filter.c
 	sharpness-filter.c
+	noise-gate-filter.c
 	mask-filter.c)
 
 add_library(obs-filters MODULE

plugins/obs-filters/data/locale/en-US.ini

@@ -6,6 +6,7 @@ ScrollFilter="Scroll"
 ChromaKeyFilter="Chroma Key"
 ColorKeyFilter="Color Key"
 SharpnessFilter="Sharpen"
+NoiseGate="Noise Gate"
 DelayMs="Delay (milliseconds)"
 Type="Type"
 MaskBlendType.MaskColor="Alpha Mask (Color Channel)"
@@ -42,3 +43,8 @@ Red="Red"
 Green="Green"
 Blue="Blue"
 Magenta="Magenta"
+NoiseGate.OpenThreshold="Open Threshold (db)"
+NoiseGate.CloseThreshold="Close Threshold (db)"
+NoiseGate.AttackTime="Attack Time (milliseconds)"
+NoiseGate.HoldTime="Hold Time (milliseconds)"
+NoiseGate.ReleaseTime="Release Time (milliseconds)"

plugins/obs-filters/noise-gate-filter.c

@@ -0,0 +1,222 @@
+#include <obs-module.h>
+#include <math.h>
+
+#ifdef _MSC_VER
+#include <float.h>
+
+#ifndef finite
+#define finite _finite
+#endif
+
+static inline float fmaxf(float a, float b)
+{
+	return a > b ? a : b;
+}
+
+static inline float fminf(float a, float b)
+{
+	return a < b ? a : b;
+}
+
+#endif
+
+#define do_log(level, format, ...) \
+	blog(level, "[noise gate: '%s'] " format, \
+			obs_source_get_name(ng->context), ##__VA_ARGS__)
+
+#define warn(format, ...)  do_log(LOG_WARNING, format, ##__VA_ARGS__)
+#define info(format, ...)  do_log(LOG_INFO,    format, ##__VA_ARGS__)
+
+#define S_OPEN_THRESHOLD               "open_threshold"
+#define S_CLOSE_THRESHOLD              "close_threshold"
+#define S_ATTACK_TIME                  "attack_time"
+#define S_HOLD_TIME                    "hold_time"
+#define S_RELEASE_TIME                 "release_time"
+
+#define MT_ obs_module_text
+#define TEXT_OPEN_THRESHOLD            MT_("NoiseGate.OpenThreshold")
+#define TEXT_CLOSE_THRESHOLD           MT_("NoiseGate.CloseThreshold")
+#define TEXT_ATTACK_TIME               MT_("NoiseGate.AttackTime")
+#define TEXT_HOLD_TIME                 MT_("NoiseGate.HoldTime")
+#define TEXT_RELEASE_TIME              MT_("NoiseGate.ReleaseTime")
+
+struct noise_gate_data {
+	obs_source_t *context;
+
+	float sample_rate_i;
+	size_t channels;
+
+	float open_threshold;
+	float close_threshold;
+	float decay_rate;
+	float attack_rate;
+	float release_rate;
+	float hold_time;
+
+	bool is_open;
+	float attenuation;
+	float level;
+	float held_time;
+};
+
+#define VOL_MIN -96.0f
+#define VOL_MAX 0.0f
+
+static inline float rms_to_db(float rms)
+{
+	float db = 20.0f * log10f(rms);
+	return finite(db) ? db : VOL_MIN;
+}
+
+static inline float db_to_rms(float db)
+{
+	return powf(10.0f, db / 20.0f);
+}
+
+static const char *noise_gate_name(void)
+{
+	return obs_module_text("NoiseGate");
+}
+
+static void noise_gate_destroy(void *data)
+{
+	struct noise_gate_data *ng = data;
+	bfree(ng);
+}
+
+static inline float ms_to_secf(int ms)
+{
+	return (float)ms / 1000.0f;
+}
+
+static void noise_gate_update(void *data, obs_data_t *s)
+{
+	struct noise_gate_data *ng = data;
+	float open_threshold_db;
+	float close_threshold_db;
+	float sample_rate;
+	int attack_time_ms;
+	int hold_time_ms;
+	int release_time_ms;
+
+	open_threshold_db = (float)obs_data_get_double(s, S_OPEN_THRESHOLD);
+	close_threshold_db = (float)obs_data_get_double(s, S_CLOSE_THRESHOLD);
+	attack_time_ms = (int)obs_data_get_int(s, S_ATTACK_TIME);
+	hold_time_ms = (int)obs_data_get_int(s, S_HOLD_TIME);
+	release_time_ms = (int)obs_data_get_int(s, S_RELEASE_TIME);
+	sample_rate = (float)audio_output_get_sample_rate(obs_get_audio());
+
+	ng->sample_rate_i = 1.0f / sample_rate;
+	ng->channels = audio_output_get_channels(obs_get_audio());
+	ng->open_threshold = db_to_rms(open_threshold_db);
+	ng->close_threshold = db_to_rms(close_threshold_db);
+	ng->attack_rate = 1.0f / (ms_to_secf(attack_time_ms) * sample_rate);
+	ng->release_rate = 1.0f / (ms_to_secf(release_time_ms) * sample_rate);
+
+	const float threshold_diff = ng->open_threshold - ng->close_threshold;
+	const float min_decay_period = (1.0f / 75.0f) * sample_rate;
+
+	ng->decay_rate = threshold_diff / min_decay_period;
+	ng->hold_time = ms_to_secf(hold_time_ms);
+	ng->is_open = false;
+	ng->attenuation = 0.0f;
+	ng->level = 0.0f;
+	ng->held_time = 0.0f;
+}
+
+static void *noise_gate_create(obs_data_t *settings, obs_source_t *filter)
+{
+	struct noise_gate_data *ng = bzalloc(sizeof(*ng));
+	ng->context = filter;
+	noise_gate_update(ng, settings);
+	return ng;
+}
+
+static struct obs_audio_data *noise_gate_filter_audio(void *data,
+		struct obs_audio_data *audio)
+{
+	struct noise_gate_data *ng = data;
+
+	float *adata[2] = {(float*)audio->data[0], (float*)audio->data[1]};
+	const float close_threshold = ng->close_threshold;
+	const float open_threshold = ng->open_threshold;
+	const float sample_rate_i = ng->sample_rate_i;
+	const float release_rate = ng->release_rate;
+	const float attack_rate = ng->attack_rate;
+	const float decay_rate = ng->decay_rate;
+	const float hold_time = ng->hold_time;
+	const size_t channels = ng->channels;
+
+	for (size_t i = 0; i < audio->frames; i++) {
+		float cur_level = (channels == 2)
+			? (fabsf(adata[0][i] + adata[1][i]) * 0.5f)
+			: (fabsf(adata[0][i]) * 0.5f);
+
+		if (cur_level > open_threshold && !ng->is_open) {
+			ng->is_open = true;
+		}
+		if (ng->level < close_threshold && ng->is_open) {
+			ng->held_time = 0.0f;
+			ng->is_open = false;
+		}
+
+		ng->level = fmaxf(ng->level, cur_level) - decay_rate;
+
+		if (ng->is_open) {
+			ng->attenuation = fminf(1.0f,
+					ng->attenuation + attack_rate);
+		} else {
+			ng->held_time += sample_rate_i;
+			if (ng->held_time > hold_time) {
+				ng->attenuation = fmaxf(0.0f,
+						ng->attenuation - release_rate);
+			}
+		}
+
+		for (size_t c = 0; c < channels; c++)
+			adata[c][i] *= ng->attenuation;
+	}
+
+	return audio;
+}
+
+static void noise_gate_defaults(obs_data_t *s)
+{
+	obs_data_set_default_double(s, S_OPEN_THRESHOLD, -26.0f);
+	obs_data_set_default_double(s, S_CLOSE_THRESHOLD, -32.0f);
+	obs_data_set_default_int   (s, S_ATTACK_TIME, 25);
+	obs_data_set_default_int   (s, S_HOLD_TIME, 200);
+	obs_data_set_default_int   (s, S_RELEASE_TIME, 150);
+}
+
+static obs_properties_t *noise_gate_properties(void *data)
+{
+	obs_properties_t *ppts = obs_properties_create();
+
+	obs_properties_add_float_slider(ppts, S_CLOSE_THRESHOLD,
+			TEXT_CLOSE_THRESHOLD, VOL_MIN, VOL_MAX, 1.0f);
+	obs_properties_add_float_slider(ppts, S_OPEN_THRESHOLD,
+			TEXT_OPEN_THRESHOLD, VOL_MIN, VOL_MAX, 1.0f);
+	obs_properties_add_int(ppts, S_ATTACK_TIME, TEXT_ATTACK_TIME,
+			0, 10000, 1);
+	obs_properties_add_int(ppts, S_HOLD_TIME, TEXT_HOLD_TIME,
+			0, 10000, 1);
+	obs_properties_add_int(ppts, S_RELEASE_TIME, TEXT_RELEASE_TIME,
+			0, 10000, 1);
+
+	UNUSED_PARAMETER(data);
+	return ppts;
+}
+
+struct obs_source_info noise_gate_filter = {
+	.id = "noise_gate_filter",
+	.type = OBS_SOURCE_TYPE_FILTER,
+	.output_flags = OBS_SOURCE_AUDIO,
+	.get_name = noise_gate_name,
+	.create = noise_gate_create,
+	.destroy = noise_gate_destroy,
+	.update = noise_gate_update,
+	.filter_audio = noise_gate_filter_audio,
+	.get_defaults = noise_gate_defaults,
+	.get_properties = noise_gate_properties,
+};

plugins/obs-filters/obs-filters.c

@@ -12,6 +12,7 @@ extern struct obs_source_info color_key_filter;
 extern struct obs_source_info sharpness_filter;
 extern struct obs_source_info chroma_key_filter;
 extern struct obs_source_info async_delay_filter;
+extern struct obs_source_info noise_gate_filter;
 
 bool obs_module_load(void)
 {
@@ -23,5 +24,6 @@ bool obs_module_load(void)
 	obs_register_source(&sharpness_filter);
 	obs_register_source(&chroma_key_filter);
 	obs_register_source(&async_delay_filter);
+	obs_register_source(&noise_gate_filter);
 	return true;
 }