obs-filters: Add audio compression filter

Closes jp9000/obs-studio#799

plugins/obs-filters/CMakeLists.txt

@@ -31,7 +31,8 @@ set(obs-filters_SOURCES
 	sharpness-filter.c
 	gain-filter.c
 	noise-gate-filter.c
-	mask-filter.c)
+	mask-filter.c
+	compressor-filter.c)
 
 add_library(obs-filters MODULE
 	${obs-filters_SOURCES}

plugins/obs-filters/compressor-filter.c

@@ -0,0 +1,230 @@
+#include <stdint.h>
+#include <inttypes.h>
+#include <math.h>
+
+#include <obs-module.h>
+#include <media-io/audio-math.h>
+
+/* -------------------------------------------------------- */
+
+#define do_log(level, format, ...) \
+	blog(level, "[compressor: '%s'] " format, \
+			obs_source_get_name(cd->context), ##__VA_ARGS__)
+
+#define warn(format, ...)  do_log(LOG_WARNING, format, ##__VA_ARGS__)
+#define info(format, ...)  do_log(LOG_INFO,    format, ##__VA_ARGS__)
+
+#ifdef _DEBUG
+#define debug(format, ...) do_log(LOG_DEBUG,   format, ##__VA_ARGS__)
+#else
+#define debug(format, ...)
+#endif
+
+/* -------------------------------------------------------- */
+
+#define S_RATIO                         "ratio"
+#define S_THRESHOLD                     "threshold"
+#define S_ATTACK_TIME                   "attack_time"
+#define S_RELEASE_TIME                  "release_time"
+#define S_OUTPUT_GAIN                   "output_gain"
+
+#define MT_ obs_module_text
+#define TEXT_RATIO                      MT_("Compressor.Ratio")
+#define TEXT_THRESHOLD                  MT_("Compressor.Threshold")
+#define TEXT_ATTACK_TIME                MT_("Compressor.AttackTime")
+#define TEXT_RELEASE_TIME               MT_("Compressor.ReleaseTime")
+#define TEXT_OUTPUT_GAIN                MT_("Compressor.OutputGain")
+
+#define MIN_RATIO                       1.0f
+#define MAX_RATIO                       32.0f
+#define MIN_THRESHOLD_DB                -60.0f
+#define MAX_THRESHOLD_DB                0.0f
+#define MIN_OUTPUT_GAIN_DB              -32.0f
+#define MAX_OUTPUT_GAIN_DB              32.0f
+#define MIN_ATK_RLS_MS                  1
+#define MAX_ATK_RLS_MS                  100
+#define DEFAULT_AUDIO_BUF_MS            10
+
+#define MS_IN_S                         1000
+#define MS_IN_S_F                       ((float)MS_IN_S)
+
+/* -------------------------------------------------------- */
+
+struct compressor_data {
+	obs_source_t *context;
+	float *envelope_buf;
+	size_t envelope_buf_len;
+
+	float ratio;
+	float threshold;
+	float attack_gain;
+	float release_gain;
+	float output_gain;
+
+	size_t num_channels;
+	float envelope;
+	float slope;
+};
+
+/* -------------------------------------------------------- */
+
+static inline void resize_env_buffer(struct compressor_data *cd, size_t len)
+{
+	cd->envelope_buf_len = len;
+	cd->envelope_buf = brealloc(cd->envelope_buf, len * sizeof(float));
+}
+
+static inline float gain_coefficient(uint32_t sample_rate, float time)
+{
+	return (float)exp(-1.0f / (sample_rate * time));
+}
+
+static const char *compressor_name(void *unused)
+{
+	UNUSED_PARAMETER(unused);
+	return obs_module_text("Compressor");
+}
+
+static void compressor_update(void *data, obs_data_t *s)
+{
+	struct compressor_data *cd = data;
+
+	const uint32_t sample_rate =
+		audio_output_get_sample_rate(obs_get_audio());
+	const size_t num_channels =
+		audio_output_get_channels(obs_get_audio());
+	const float attack_time_ms =
+		(float)obs_data_get_int(s, S_ATTACK_TIME);
+	const float release_time_ms =
+		(float)obs_data_get_int(s, S_RELEASE_TIME);
+	const float output_gain_db =
+		(float)obs_data_get_double(s, S_OUTPUT_GAIN);
+
+	if (cd->envelope_buf_len <= 0) {
+		resize_env_buffer(cd,
+				sample_rate * DEFAULT_AUDIO_BUF_MS / MS_IN_S);
+	}
+
+	cd->ratio = (float)obs_data_get_double(s, S_RATIO);
+	cd->threshold = (float)obs_data_get_double(s, S_THRESHOLD);
+	cd->attack_gain = gain_coefficient(sample_rate,
+			attack_time_ms / MS_IN_S_F);
+	cd->release_gain = gain_coefficient(sample_rate,
+			release_time_ms / MS_IN_S_F);
+	cd->output_gain = db_to_mul(output_gain_db);
+	cd->num_channels = num_channels;
+	cd->slope = 1.0f - (1.0f / cd->ratio);
+}
+
+static void *compressor_create(obs_data_t *settings, obs_source_t *filter)
+{
+	struct compressor_data *cd = bzalloc(sizeof(struct compressor_data));
+	cd->context = filter;
+	compressor_update(cd, settings);
+	return cd;
+}
+
+static void compressor_destroy(void *data)
+{
+	struct compressor_data *cd = data;
+	bfree(cd->envelope_buf);
+	bfree(cd);
+}
+
+static inline void analyze_envelope(struct compressor_data *cd,
+	const float **samples, const uint32_t num_samples)
+{
+	if (cd->envelope_buf_len < num_samples) {
+		resize_env_buffer(cd, num_samples);
+	}
+
+	memset(cd->envelope_buf, 0, num_samples * sizeof(cd->envelope_buf[0]));
+	for (size_t chan = 0; chan < cd->num_channels; ++chan) {
+		if (samples[chan]) {
+			float env = cd->envelope;
+			for (uint32_t i = 0; i < num_samples; ++i) {
+				const float env_in = fabsf(samples[chan][i]);
+				if (env < env_in) {
+					env = env_in + cd->attack_gain *
+						(env - env_in);
+				} else {
+					env = env_in + cd->release_gain *
+						(env - env_in);
+				}
+				cd->envelope_buf[i] = fmaxf(
+						cd->envelope_buf[i], env);
+			}
+		}
+	}
+	cd->envelope = cd->envelope_buf[num_samples - 1];
+}
+
+static inline void process_compression(const struct compressor_data *cd,
+	float **samples, uint32_t num_samples)
+{
+	for (size_t i = 0; i < num_samples; ++i) {
+		const float env_db = mul_to_db(cd->envelope_buf[i]);
+		float gain = cd->slope * (cd->threshold - env_db);
+		gain = db_to_mul(fminf(0, gain));
+
+		for (size_t c = 0; c < cd->num_channels; ++c) {
+			if (samples[c]) {
+				samples[c][i] *= gain * cd->output_gain;
+			}
+		}
+	}
+}
+
+static struct obs_audio_data *compressor_filter_audio(void *data,
+	struct obs_audio_data *audio)
+{
+	struct compressor_data *cd = data;
+	const uint32_t num_samples = audio->frames;
+	float **samples = (float**)audio->data;
+
+	analyze_envelope(cd, samples, num_samples);
+	process_compression(cd, samples, num_samples);
+
+	return audio;
+}
+
+static void compressor_defaults(obs_data_t *s)
+{
+	obs_data_set_default_double(s, S_RATIO, 10.0f);
+	obs_data_set_default_double(s, S_THRESHOLD, -18.0f);
+	obs_data_set_default_int(s, S_ATTACK_TIME, 6);
+	obs_data_set_default_int(s, S_RELEASE_TIME, 60);
+	obs_data_set_default_double(s, S_OUTPUT_GAIN, 0.0f);
+}
+
+static obs_properties_t *compressor_properties(void *data)
+{
+	obs_properties_t *props = obs_properties_create();
+
+	obs_properties_add_float_slider(props, S_RATIO,
+		TEXT_RATIO, MIN_RATIO, MAX_RATIO, 0.5f);
+	obs_properties_add_float_slider(props, S_THRESHOLD,
+		TEXT_THRESHOLD, MIN_THRESHOLD_DB, MAX_THRESHOLD_DB, 0.1f);
+	obs_properties_add_int_slider(props, S_ATTACK_TIME,
+		TEXT_ATTACK_TIME, MIN_ATK_RLS_MS, MAX_ATK_RLS_MS, 1);
+	obs_properties_add_int_slider(props, S_RELEASE_TIME,
+		TEXT_RELEASE_TIME, MIN_ATK_RLS_MS, MAX_ATK_RLS_MS, 1);
+	obs_properties_add_float_slider(props, S_OUTPUT_GAIN,
+		TEXT_OUTPUT_GAIN, MIN_OUTPUT_GAIN_DB, MAX_OUTPUT_GAIN_DB, 0.1f);
+
+	UNUSED_PARAMETER(data);
+	return props;
+}
+
+struct obs_source_info compressor_filter = {
+	.id = "compressor_filter",
+	.type = OBS_SOURCE_TYPE_FILTER,
+	.output_flags = OBS_SOURCE_AUDIO,
+	.get_name = compressor_name,
+	.create = compressor_create,
+	.destroy = compressor_destroy,
+	.update = compressor_update,
+	.filter_audio = compressor_filter_audio,
+	.get_defaults = compressor_defaults,
+	.get_properties = compressor_properties,
+};

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

@@ -66,3 +66,9 @@ NoiseSuppress.SuppressLevel="Suppression Level (dB)"
 Saturation="Saturation"
 HueShift="Hue Shift"
 Amount="Amount"
+Compressor="Compressor"
+Compressor.Ratio="Ratio (X:1)"
+Compressor.Threshold="Threshold (dB)"
+Compressor.AttackTime="Attack (ms)"
+Compressor.ReleaseTime="Release (ms)"
+Compressor.OutputGain="Output Gain (dB)"

plugins/obs-filters/obs-filters.c

@@ -20,6 +20,7 @@ extern struct obs_source_info async_delay_filter;
 extern struct obs_source_info noise_suppress_filter;
 #endif
 extern struct obs_source_info noise_gate_filter;
+extern struct obs_source_info compressor_filter;
 
 bool obs_module_load(void)
 {
@@ -38,5 +39,6 @@ bool obs_module_load(void)
 	obs_register_source(&noise_suppress_filter);
 #endif
 	obs_register_source(&noise_gate_filter);
+	obs_register_source(&compressor_filter);
 	return true;
 }