diff --git a/lib/filters.c b/lib/filters.c index efa173f..fca4ed6 100644 --- a/lib/filters.c +++ b/lib/filters.c @@ -121,7 +121,22 @@ float voltage_to_power_db(float linear) { return 10.0f * log10f(fmaxf(linear, 1e-10f)); // Avoid log(0) } -void init_compressor(Compressor *compressor, float threshold, float ratio, float knee, float makeup_gain, float attack, float release, float rmsTime, float sample_rate) { +static float compute_gain_reduction(float input_db, float threshold, float ratio, float knee) { + float gain_reduction = 0.0f; + + if (knee > 0.0f && input_db > (threshold - knee / 2.0f) && input_db < (threshold + knee / 2.0f)) { + float knee_range = input_db - (threshold - knee / 2.0f); + float knee_factor = knee_range * knee_range / (2.0f * knee); + gain_reduction = (ratio - 1.0f) * knee_factor / ratio; + } else if (input_db > threshold) { + gain_reduction = (threshold - input_db) * (1.0f - 1.0f / ratio); + } + + return gain_reduction; +} + +void init_compressor(Compressor *compressor, float threshold, float ratio, float knee, + float makeup_gain, float attack, float release, float rmsTime, float sample_rate) { compressor->threshold = threshold; compressor->ratio = ratio; compressor->knee = knee; @@ -134,78 +149,54 @@ void init_compressor(Compressor *compressor, float threshold, float ratio, float compressor->rmsTime = rmsTime; } -float rms_compress(Compressor *compressor, float sample) { - sample *= voltage_db_to_voltage(compressor->makeup_gain); - float env; - float rmsAlpha = 1.0f - exp(-1.0f / (compressor->rmsTime * compressor->sample_rate)); - compressor->rmsEnv = (1.0f - rmsAlpha) * compressor->rmsEnv + rmsAlpha * (sample * sample); - env = sqrtf(compressor->rmsEnv); - - float input_db = voltage_to_voltage_db(env); - - float targetBoost = 0.0f; - if(input_db < compressor->threshold) { - if(compressor->knee > 0.0f) { - float delta = compressor->threshold - input_db; - if(delta < compressor->knee / 2.0f) { - targetBoost = (1.0f - 1.0f / compressor->ratio) * (delta * delta) / compressor->knee; - } else { - targetBoost = (1.0f - 1.0f / compressor->ratio) * delta; - } - } else { - targetBoost = (1.0f - 1.0f / compressor->ratio) * (compressor->threshold - input_db); - } - } else { - targetBoost = 0.0f; - } - - float coeff; - if(targetBoost > compressor->gainReduction) { - coeff = expf(-1.0f / (compressor->attack * compressor->sample_rate)); - } else { - coeff = expf(-1.0f / (compressor->release * compressor->sample_rate)); - } - compressor->gainReduction = coeff * compressor->gainReduction + (1.0f - coeff) * targetBoost; - - float gain = voltage_db_to_voltage(compressor->gainReduction); - return (sample * gain); -} - float peak_compress(Compressor *compressor, float sample) { - float env = fabsf(sample*voltage_db_to_voltage(compressor->makeup_gain)); - - float input_db = voltage_to_voltage_db(env); - - float targetBoost = 0.0f; - if(input_db < compressor->threshold) { - if(compressor->knee > 0.0f) { - float delta = compressor->threshold - input_db; - if(delta < compressor->knee / 2.0f) { - targetBoost = (1.0f - 1.0f / compressor->ratio) * (delta * delta) / compressor->knee; - } else { - targetBoost = (1.0f - 1.0f / compressor->ratio) * delta; - } - } else { - targetBoost = (1.0f - 1.0f / compressor->ratio) * (compressor->threshold - input_db); - } - } else { - targetBoost = 0.0f; - } - - float coeff; - if(targetBoost > compressor->gainReduction) { - coeff = expf(-1.0f / (compressor->attack * compressor->sample_rate)); - } else { - coeff = expf(-1.0f / (compressor->release * compressor->sample_rate)); - } - compressor->gainReduction = coeff * compressor->gainReduction + (1.0f - coeff) * targetBoost; - - float gain = voltage_db_to_voltage(compressor->gainReduction); - return (sample * gain); + float input_level_db = linear_to_db(fabsf(sample)); + + float desired_gain_reduction = compute_gain_reduction(input_level_db, + compressor->threshold, + compressor->ratio, + compressor->knee); + + float attack_coef = expf(-1.0f / (compressor->sample_rate * compressor->attack)); + float release_coef = expf(-1.0f / (compressor->sample_rate * compressor->release)); + + float coef = (fabsf(desired_gain_reduction) > fabsf(compressor->gainReduction)) ? attack_coef : release_coef; + + compressor->gainReduction = desired_gain_reduction + coef * (compressor->gainReduction - desired_gain_reduction); + + float gain = db_to_linear(compressor->gainReduction + compressor->makeup_gain); + + return sample * gain; } +float rms_compress(Compressor *compressor, float sample) { + float rms_coef = expf(-1.0f / (compressor->sample_rate * compressor->rmsTime)); + float squared_input = sample * sample; + + compressor->rmsEnv = squared_input + rms_coef * (compressor->rmsEnv - squared_input); + + float input_level_db = linear_to_db(sqrtf(fmaxf(compressor->rmsEnv, 1e-9f))); + + float desired_gain_reduction = compute_gain_reduction(input_level_db, + compressor->threshold, + compressor->ratio, + compressor->knee); + + float attack_coef = expf(-1.0f / (compressor->sample_rate * compressor->attack)); + float release_coef = expf(-1.0f / (compressor->sample_rate * compressor->release)); + + float coef = (fabsf(desired_gain_reduction) > fabsf(compressor->gainReduction)) ? attack_coef : release_coef; + + compressor->gainReduction = desired_gain_reduction + coef * (compressor->gainReduction - desired_gain_reduction); + + float gain = db_to_linear(compressor->gainReduction + compressor->makeup_gain); + + return sample * gain; +} -void init_compressor_stereo(StereoCompressor *compressor, float threshold, float ratio, float knee, float makeup_gain, float attack, float release, float rmsTime, float sample_rate) { +void init_compressor_stereo(StereoCompressor *compressor, float threshold, float ratio, + float knee, float makeup_gain, float attack, float release, + float rmsTime, float sample_rate) { compressor->threshold = threshold; compressor->ratio = ratio; compressor->knee = knee; @@ -219,117 +210,55 @@ void init_compressor_stereo(StereoCompressor *compressor, float threshold, float compressor->rmsTime = rmsTime; } -float rms_compress_stereo(StereoCompressor *compressor, float l, float r, float *output_r) { - l *= voltage_db_to_voltage(compressor->makeup_gain); - r *= voltage_db_to_voltage(compressor->makeup_gain); - float env_l; - float env_r; - float rmsAlpha = 1.0f - exp(-1.0f / (compressor->rmsTime * compressor->sample_rate)); - compressor->rmsEnv = (1.0f - rmsAlpha) * compressor->rmsEnv + rmsAlpha * (l * l); - compressor->rmsEnv2 = (1.0f - rmsAlpha) * compressor->rmsEnv2 + rmsAlpha * (r * r); - env_l = sqrtf(compressor->rmsEnv); - env_r = sqrtf(compressor->rmsEnv2); - - float input_db_l = voltage_to_voltage_db(env_l); - float input_db_r = voltage_to_voltage_db(env_r); - - float targetBoost_l = 0.0f; - if(input_db_l < compressor->threshold) { - if(compressor->knee > 0.0f) { - float delta = compressor->threshold - input_db_l; - if(delta < compressor->knee / 2.0f) { - targetBoost_l = (1.0f - 1.0f / compressor->ratio) * (delta * delta) / compressor->knee; - } else { - targetBoost_l = (1.0f - 1.0f / compressor->ratio) * delta; - } - } else { - targetBoost_l = (1.0f - 1.0f / compressor->ratio) * (compressor->threshold - input_db_l); - } - } else { - targetBoost_l = 0.0f; - } - - float targetBoost_r = 0.0f; - if(input_db_r < compressor->threshold) { - if(compressor->knee > 0.0f) { - float delta = compressor->threshold - input_db_r; - if(delta < compressor->knee / 2.0f) { - targetBoost_r = (1.0f - 1.0f / compressor->ratio) * (delta * delta) / compressor->knee; - } else { - targetBoost_r = (1.0f - 1.0f / compressor->ratio) * delta; - } - } else { - targetBoost_r = (1.0f - 1.0f / compressor->ratio) * (compressor->threshold - input_db_r); - } - } else { - targetBoost_r = 0.0f; - } - - float shared_target_boost = (targetBoost_l > targetBoost_r) ? targetBoost_l : targetBoost_r; - - float coeff; - if(shared_target_boost > compressor->gainReduction) { - coeff = expf(-1.0f / (compressor->attack * compressor->sample_rate)); - } else { - coeff = expf(-1.0f / (compressor->release * compressor->sample_rate)); - } - compressor->gainReduction = coeff * compressor->gainReduction + (1.0f - coeff) * shared_target_boost; - - float gain = voltage_db_to_voltage(compressor->gainReduction); - *output_r = (r * gain); - return (l * gain); -} - float peak_compress_stereo(StereoCompressor *compressor, float l, float r, float *output_r) { - float env_l = fabsf(l*voltage_db_to_voltage(compressor->makeup_gain)); - float env_r = fabsf(r*voltage_db_to_voltage(compressor->makeup_gain)); - - float input_db_l = voltage_to_voltage_db(env_l); - float input_db_r = voltage_to_voltage_db(env_r); - - float targetBoost_l = 0.0f; - if(input_db_l < compressor->threshold) { - if(compressor->knee > 0.0f) { - float delta = compressor->threshold - input_db_l; - if(delta < compressor->knee / 2.0f) { - targetBoost_l = (1.0f - 1.0f / compressor->ratio) * (delta * delta) / compressor->knee; - } else { - targetBoost_l = (1.0f - 1.0f / compressor->ratio) * delta; - } - } else { - targetBoost_l = (1.0f - 1.0f / compressor->ratio) * (compressor->threshold - input_db_l); - } - } else { - targetBoost_l = 0.0f; - } - - float targetBoost_r = 0.0f; - if(input_db_r < compressor->threshold) { - if(compressor->knee > 0.0f) { - float delta = compressor->threshold - input_db_r; - if(delta < compressor->knee / 2.0f) { - targetBoost_r = (1.0f - 1.0f / compressor->ratio) * (delta * delta) / compressor->knee; - } else { - targetBoost_r = (1.0f - 1.0f / compressor->ratio) * delta; - } - } else { - targetBoost_r = (1.0f - 1.0f / compressor->ratio) * (compressor->threshold - input_db_r); - } - } else { - targetBoost_r = 0.0f; - } - - float shared_target_boost = (targetBoost_l > targetBoost_r) ? targetBoost_l : targetBoost_r; - - float coeff; - if(shared_target_boost > compressor->gainReduction) { - coeff = expf(-1.0f / (compressor->attack * compressor->sample_rate)); - } else { - coeff = expf(-1.0f / (compressor->release * compressor->sample_rate)); - } - compressor->gainReduction = coeff * compressor->gainReduction + (1.0f - coeff) * shared_target_boost; - - float gain = voltage_db_to_voltage(compressor->gainReduction); - *output_r = (r * gain); - return (l*gain); + float max_level = fmaxf(fabsf(l), fabsf(r)); + + float input_level_db = linear_to_db(max_level); + + float desired_gain_reduction = compute_gain_reduction(input_level_db, + compressor->threshold, + compressor->ratio, + compressor->knee); + + float attack_coef = expf(-1.0f / (compressor->sample_rate * compressor->attack)); + float release_coef = expf(-1.0f / (compressor->sample_rate * compressor->release)); + + float coef = (fabsf(desired_gain_reduction) > fabsf(compressor->gainReduction)) ? attack_coef : release_coef; + + compressor->gainReduction = desired_gain_reduction + coef * (compressor->gainReduction - desired_gain_reduction); + + float gain = db_to_linear(compressor->gainReduction + compressor->makeup_gain); + + *output_r = r * gain; + return l * gain; } + +float rms_compress_stereo(StereoCompressor *compressor, float l, float r, float *output_r) { + float rms_coef = expf(-1.0f / (compressor->sample_rate * compressor->rmsTime)); + float squared_input1 = l * l; + float squared_input2 = r * r; + + compressor->rmsEnv = squared_input1 + rms_coef * (compressor->rmsEnv - squared_input1); + compressor->rmsEnv2 = squared_input2 + rms_coef * (compressor->rmsEnv2 - squared_input2); + + float max_rms = fmaxf(compressor->rmsEnv, compressor->rmsEnv2); + + float input_level_db = linear_to_db(sqrtf(fmaxf(max_rms, 1e-9f))); + + float desired_gain_reduction = compute_gain_reduction(input_level_db, + compressor->threshold, + compressor->ratio, + compressor->knee); + + float attack_coef = expf(-1.0f / (compressor->sample_rate * compressor->attack)); + float release_coef = expf(-1.0f / (compressor->sample_rate * compressor->release)); + + float coef = (fabsf(desired_gain_reduction) > fabsf(compressor->gainReduction)) ? attack_coef : release_coef; + + compressor->gainReduction = desired_gain_reduction + coef * (compressor->gainReduction - desired_gain_reduction); + + float gain = db_to_linear(compressor->gainReduction + compressor->makeup_gain); + + *output_r = r * gain; + return l * gain; +} \ No newline at end of file