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obs-studio/plugins/obs-filters/expander-filter.c

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#include <stdint.h>
#include <inttypes.h>
#include <math.h>
#include <obs-module.h>
#include <media-io/audio-math.h>
#include <util/platform.h>
#include <util/circlebuf.h>
#include <util/threading.h>
/* -------------------------------------------------------- */
#define do_log(level, format, ...) \
blog(level, "[expander: '%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
/* -------------------------------------------------------- */
/* clang-format off */
#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 S_DETECTOR "detector"
#define S_PRESETS "presets"
#define MT_ obs_module_text
#define TEXT_RATIO MT_("expander.Ratio")
#define TEXT_THRESHOLD MT_("expander.Threshold")
#define TEXT_ATTACK_TIME MT_("expander.AttackTime")
#define TEXT_RELEASE_TIME MT_("expander.ReleaseTime")
#define TEXT_OUTPUT_GAIN MT_("expander.OutputGain")
#define TEXT_DETECTOR MT_("expander.Detector")
#define TEXT_PEAK MT_("expander.Peak")
#define TEXT_RMS MT_("expander.RMS")
#define TEXT_NONE MT_("expander.None")
#define TEXT_PRESETS MT_("expander.Presets")
#define TEXT_PRESETS_EXP MT_("expander.Presets.Expander")
#define TEXT_PRESETS_GATE MT_("expander.Presets.Gate")
#define MIN_RATIO 1.0f
#define MAX_RATIO 20.0f
#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_RLS_MS 1000
#define MAX_ATK_MS 100
#define DEFAULT_AUDIO_BUF_MS 10
#define MS_IN_S 1000
#define MS_IN_S_F ((float)MS_IN_S)
/* clang-format on */
/* -------------------------------------------------------- */
struct expander_data {
obs_source_t *context;
float *envelope_buf[MAX_AUDIO_CHANNELS];
size_t envelope_buf_len;
float ratio;
float threshold;
float attack_gain;
float release_gain;
float output_gain;
size_t num_channels;
size_t sample_rate;
float envelope[MAX_AUDIO_CHANNELS];
float slope;
int detector;
float runave[MAX_AUDIO_CHANNELS];
bool is_gate;
float *runaverage[MAX_AUDIO_CHANNELS];
size_t runaverage_len;
float *gaindB[MAX_AUDIO_CHANNELS];
size_t gaindB_len;
float gaindB_buf[MAX_AUDIO_CHANNELS];
float *env_in;
size_t env_in_len;
};
enum {
RMS_DETECT,
RMS_STILLWELL_DETECT,
PEAK_DETECT,
NO_DETECT,
};
/* -------------------------------------------------------- */
static void resize_env_buffer(struct expander_data *cd, size_t len)
{
cd->envelope_buf_len = len;
for (int i = 0; i < MAX_AUDIO_CHANNELS; i++)
cd->envelope_buf[i] =
brealloc(cd->envelope_buf[i],
cd->envelope_buf_len * sizeof(float));
}
static void resize_runaverage_buffer(struct expander_data *cd, size_t len)
{
cd->runaverage_len = len;
for (int i = 0; i < MAX_AUDIO_CHANNELS; i++)
cd->runaverage[i] = brealloc(
cd->runaverage[i], cd->runaverage_len * sizeof(float));
}
static void resize_env_in_buffer(struct expander_data *cd, size_t len)
{
cd->env_in_len = len;
cd->env_in = brealloc(cd->env_in, cd->env_in_len * sizeof(float));
}
static void resize_gaindB_buffer(struct expander_data *cd, size_t len)
{
cd->gaindB_len = len;
for (int i = 0; i < MAX_AUDIO_CHANNELS; i++)
cd->gaindB[i] =
brealloc(cd->gaindB[i], cd->gaindB_len * sizeof(float));
}
static inline float gain_coefficient(uint32_t sample_rate, float time)
{
return expf(-1.0f / (sample_rate * time));
}
static const char *expander_name(void *unused)
{
UNUSED_PARAMETER(unused);
return obs_module_text("Expander");
}
static void expander_defaults(obs_data_t *s)
{
const char *presets = obs_data_get_string(s, S_PRESETS);
bool is_expander_preset = true;
if (strcmp(presets, "gate") == 0)
is_expander_preset = false;
obs_data_set_default_string(s, S_PRESETS,
is_expander_preset ? "expander" : "gate");
obs_data_set_default_double(s, S_RATIO,
is_expander_preset ? 2.0 : 10.0);
obs_data_set_default_double(s, S_THRESHOLD, -40.0f);
obs_data_set_default_int(s, S_ATTACK_TIME, 10);
obs_data_set_default_int(s, S_RELEASE_TIME,
is_expander_preset ? 50 : 125);
obs_data_set_default_double(s, S_OUTPUT_GAIN, 0.0);
obs_data_set_default_string(s, S_DETECTOR, "RMS");
}
static void expander_update(void *data, obs_data_t *s)
{
struct expander_data *cd = data;
const char *presets = obs_data_get_string(s, S_PRESETS);
if (strcmp(presets, "expander") == 0 && cd->is_gate) {
obs_data_clear(s);
obs_data_set_string(s, S_PRESETS, "expander");
expander_defaults(s);
cd->is_gate = false;
}
if (strcmp(presets, "gate") == 0 && !cd->is_gate) {
obs_data_clear(s);
obs_data_set_string(s, S_PRESETS, "gate");
expander_defaults(s);
cd->is_gate = true;
}
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);
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->sample_rate = sample_rate;
cd->slope = 1.0f - cd->ratio;
const char *detect_mode = obs_data_get_string(s, S_DETECTOR);
if (strcmp(detect_mode, "RMS") == 0)
cd->detector = RMS_DETECT;
if (strcmp(detect_mode, "peak") == 0)
cd->detector = PEAK_DETECT;
size_t sample_len = sample_rate * DEFAULT_AUDIO_BUF_MS / MS_IN_S;
if (cd->envelope_buf_len == 0)
resize_env_buffer(cd, sample_len);
if (cd->runaverage_len == 0)
resize_runaverage_buffer(cd, sample_len);
if (cd->env_in_len == 0)
resize_env_in_buffer(cd, sample_len);
if (cd->gaindB_len == 0)
resize_gaindB_buffer(cd, sample_len);
}
static void *expander_create(obs_data_t *settings, obs_source_t *filter)
{
struct expander_data *cd = bzalloc(sizeof(struct expander_data));
cd->context = filter;
for (int i = 0; i < MAX_AUDIO_CHANNELS; i++) {
cd->runave[i] = 0;
cd->envelope[i] = 0;
cd->gaindB_buf[i] = 0;
}
cd->is_gate = false;
const char *presets = obs_data_get_string(settings, S_PRESETS);
if (strcmp(presets, "gate") == 0)
cd->is_gate = true;
expander_update(cd, settings);
return cd;
}
static void expander_destroy(void *data)
{
struct expander_data *cd = data;
for (int i = 0; i < MAX_AUDIO_CHANNELS; i++) {
bfree(cd->envelope_buf[i]);
bfree(cd->runaverage[i]);
bfree(cd->gaindB[i]);
}
bfree(cd->env_in);
bfree(cd);
}
// detection stage
static void analyze_envelope(struct expander_data *cd, float **samples,
const uint32_t num_samples)
{
if (cd->envelope_buf_len < num_samples)
resize_env_buffer(cd, num_samples);
if (cd->runaverage_len < num_samples)
resize_runaverage_buffer(cd, num_samples);
if (cd->env_in_len < num_samples)
resize_env_in_buffer(cd, num_samples);
// 10 ms RMS window
const float rmscoef = exp2f(-100.0f / cd->sample_rate);
for (int i = 0; i < MAX_AUDIO_CHANNELS; i++) {
memset(cd->envelope_buf[i], 0,
num_samples * sizeof(cd->envelope_buf[i][0]));
memset(cd->runaverage[i], 0,
num_samples * sizeof(cd->runaverage[i][0]));
}
memset(cd->env_in, 0, num_samples * sizeof(cd->env_in[0]));
for (size_t chan = 0; chan < cd->num_channels; ++chan) {
if (!samples[chan])
continue;
float *envelope_buf = cd->envelope_buf[chan];
float *runave = cd->runaverage[chan];
float *env_in = cd->env_in;
if (cd->detector == RMS_DETECT) {
runave[0] =
rmscoef * cd->runave[chan] +
(1 - rmscoef) * powf(samples[chan][0], 2.0f);
env_in[0] = sqrtf(fmaxf(runave[0], 0));
for (uint32_t i = 1; i < num_samples; ++i) {
runave[i] =
rmscoef * runave[i - 1] +
(1 - rmscoef) *
powf(samples[chan][i], 2.0f);
env_in[i] = sqrtf(runave[i]);
}
} else if (cd->detector == PEAK_DETECT) {
for (uint32_t i = 0; i < num_samples; ++i) {
runave[i] = powf(samples[chan][i], 2);
env_in[i] = fabsf(samples[chan][i]);
}
}
cd->runave[chan] = runave[num_samples - 1];
for (uint32_t i = 0; i < num_samples; ++i)
envelope_buf[i] = fmaxf(envelope_buf[i], env_in[i]);
cd->envelope[chan] = cd->envelope_buf[chan][num_samples - 1];
}
}
// gain stage and ballistics in dB domain
static inline void process_expansion(struct expander_data *cd, float **samples,
uint32_t num_samples)
{
const float attack_gain = cd->attack_gain;
const float release_gain = cd->release_gain;
if (cd->gaindB_len < num_samples)
resize_gaindB_buffer(cd, num_samples);
for (int i = 0; i < MAX_AUDIO_CHANNELS; i++)
memset(cd->gaindB[i], 0,
num_samples * sizeof(cd->gaindB[i][0]));
for (size_t chan = 0; chan < cd->num_channels; chan++) {
for (size_t i = 0; i < num_samples; ++i) {
// gain stage of expansion
float env_db = mul_to_db(cd->envelope_buf[chan][i]);
float gain =
cd->threshold - env_db > 0.0f
? fmaxf(cd->slope * (cd->threshold -
env_db),
-60.0f)
: 0.0f;
// ballistics (attack/release)
if (i > 0) {
if (gain > cd->gaindB[chan][i - 1])
cd->gaindB[chan][i] =
attack_gain *
cd->gaindB[chan][i - 1] +
(1.0f - attack_gain) * gain;
else
cd->gaindB[chan][i] =
release_gain *
cd->gaindB[chan][i - 1] +
(1.0f - release_gain) * gain;
} else {
if (gain > cd->gaindB_buf[chan])
cd->gaindB[chan][i] =
attack_gain *
cd->gaindB_buf[chan] +
(1.0f - attack_gain) * gain;
else
cd->gaindB[chan][i] =
release_gain *
cd->gaindB_buf[chan] +
(1.0f - release_gain) * gain;
}
gain = db_to_mul(fminf(0, cd->gaindB[chan][i]));
if (samples[chan])
samples[chan][i] *= gain * cd->output_gain;
}
cd->gaindB_buf[chan] = cd->gaindB[chan][num_samples - 1];
}
}
static struct obs_audio_data *
expander_filter_audio(void *data, struct obs_audio_data *audio)
{
struct expander_data *cd = data;
const uint32_t num_samples = audio->frames;
if (num_samples == 0)
return audio;
float **samples = (float **)audio->data;
analyze_envelope(cd, samples, num_samples);
process_expansion(cd, samples, num_samples);
return audio;
}
static bool presets_changed(obs_properties_t *props, obs_property_t *prop,
obs_data_t *settings)
{
UNUSED_PARAMETER(props);
UNUSED_PARAMETER(prop);
UNUSED_PARAMETER(settings);
return true;
}
static obs_properties_t *expander_properties(void *data)
{
obs_properties_t *props = obs_properties_create();
obs_property_t *p;
obs_property_t *presets = obs_properties_add_list(
props, S_PRESETS, TEXT_PRESETS, OBS_COMBO_TYPE_LIST,
OBS_COMBO_FORMAT_STRING);
obs_property_list_add_string(presets, TEXT_PRESETS_EXP, "expander");
obs_property_list_add_string(presets, TEXT_PRESETS_GATE, "gate");
obs_property_set_modified_callback(presets, presets_changed);
p = obs_properties_add_float_slider(props, S_RATIO, TEXT_RATIO,
MIN_RATIO, MAX_RATIO, 0.1);
obs_property_float_set_suffix(p, ":1");
p = obs_properties_add_float_slider(props, S_THRESHOLD, TEXT_THRESHOLD,
MIN_THRESHOLD_DB, MAX_THRESHOLD_DB,
0.1);
obs_property_float_set_suffix(p, " dB");
p = obs_properties_add_int_slider(props, S_ATTACK_TIME,
TEXT_ATTACK_TIME, MIN_ATK_RLS_MS,
MAX_ATK_MS, 1);
obs_property_int_set_suffix(p, " ms");
p = obs_properties_add_int_slider(props, S_RELEASE_TIME,
TEXT_RELEASE_TIME, MIN_ATK_RLS_MS,
MAX_RLS_MS, 1);
obs_property_int_set_suffix(p, " ms");
p = obs_properties_add_float_slider(props, S_OUTPUT_GAIN,
TEXT_OUTPUT_GAIN,
MIN_OUTPUT_GAIN_DB,
MAX_OUTPUT_GAIN_DB, 0.1);
obs_property_float_set_suffix(p, " dB");
obs_property_t *detect = obs_properties_add_list(
props, S_DETECTOR, TEXT_DETECTOR, OBS_COMBO_TYPE_LIST,
OBS_COMBO_FORMAT_STRING);
obs_property_list_add_string(detect, TEXT_RMS, "RMS");
obs_property_list_add_string(detect, TEXT_PEAK, "peak");
UNUSED_PARAMETER(data);
return props;
}
struct obs_source_info expander_filter = {
.id = "expander_filter",
.type = OBS_SOURCE_TYPE_FILTER,
.output_flags = OBS_SOURCE_AUDIO,
.get_name = expander_name,
.create = expander_create,
.destroy = expander_destroy,
.update = expander_update,
.filter_audio = expander_filter_audio,
.get_defaults = expander_defaults,
.get_properties = expander_properties,
};
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