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84 lines
3.4 KiB
84 lines
3.4 KiB
/* From https://github.com/chipaudette/OpenAudio_ArduinoLibrary */
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/*
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AudioEffectCompressor
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Created: Chip Audette, Dec 2016 - Jan 2017
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Purpose; Apply dynamic range compression to the audio stream.
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Assumes floating-point data.
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This processes a single stream fo audio data (ie, it is mono)
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MIT License. use at your own risk.
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*/
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#ifndef _COMPRESSOR_H
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#define _COMPRESSOR_H
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#include <arm_math.h> //ARM DSP extensions. https://www.keil.com/pack/doc/CMSIS/DSP/html/index.html
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#include "synth.h"
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class Compressor
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{
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public:
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//constructor
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Compressor(const float32_t sample_rate_Hz);
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void doCompression(float32_t *audio_block, uint16_t len);
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void setDefaultValues(const float32_t sample_rate_Hz);
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void setPreGain(float32_t g);
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void setPreGain_dB(float32_t gain_dB);
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void setCompressionRatio(float32_t cr);
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void setAttack_sec(float32_t a, float32_t fs_Hz);
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void setRelease_sec(float32_t r, float32_t fs_Hz);
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void setLevelTimeConst_sec(float32_t t_sec, float32_t fs_Hz);
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void setThresh_dBFS(float32_t val);
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void enableHPFilter(boolean flag);
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float32_t getPreGain_dB(void);
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float32_t getAttack_sec(void);
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float32_t getRelease_sec(void);
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float32_t getLevelTimeConst_sec(void);
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float32_t getThresh_dBFS(void);
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float32_t getCompressionRatio(void);
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float32_t getCurrentLevel_dBFS(void);
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float32_t getCurrentGain_dB(void);
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protected:
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void calcAudioLevel_dB(float32_t *wav_block, float32_t *level_dB_block, uint16_t len);
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void calcGain(float32_t *audio_level_dB_block, float32_t *gain_block,uint16_t len);
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void calcInstantaneousTargetGain(float32_t *audio_level_dB_block, float32_t *inst_targ_gain_dB_block, uint16_t len);
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void calcSmoothedGain_dB(float32_t *inst_targ_gain_dB_block, float32_t *gain_dB_block, uint16_t len);
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void resetStates(void);
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void setHPFilterCoeff_N2IIR_Matlab(float32_t b[], float32_t a[]);
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//state-related variables
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float32_t *inputQueueArray_f32[1]; //memory pointer for the input to this module
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float32_t prev_level_lp_pow = 1.0;
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float32_t prev_gain_dB = 0.0; //last gain^2 used
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//HP filter state-related variables
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arm_biquad_casd_df1_inst_f32 hp_filt_struct;
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static const uint8_t hp_nstages = 1;
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float32_t hp_coeff[5 * hp_nstages] = {1.0, 0.0, 0.0, 0.0, 0.0}; //no filtering. actual filter coeff set later
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float32_t hp_state[4 * hp_nstages];
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void setHPFilterCoeff(void);
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//private parameters related to gain calculation
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float32_t attack_const, release_const, level_lp_const; //used in calcGain(). set by setAttack_sec() and setRelease_sec();
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float32_t comp_ratio_const, thresh_pow_FS_wCR; //used in calcGain(); set in updateThresholdAndCompRatioConstants()
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void updateThresholdAndCompRatioConstants(void);
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//settings
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float32_t attack_sec, release_sec, level_lp_sec;
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float32_t thresh_dBFS = 0.0; //threshold for compression, relative to digital full scale
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float32_t thresh_pow_FS = 1.0f; //same as above, but not in dB
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void setThreshPow(float32_t t_pow);
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float32_t comp_ratio = 1.0; //compression ratio
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float32_t pre_gain = -1.0; //gain to apply before the compression. negative value disables
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boolean use_HP_prefilter;
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};
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// Accelerate the powf(10.0,x) function
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static float32_t pow10f(float32_t x);
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// Accelerate the log10f(x) function?
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static float32_t log10f_approx(float32_t x);
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static float32_t log2f_approx(float32_t X);
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#endif
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