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https://github.com/themattrosen/cute_dsp

Utility library for cute_sound.
https://github.com/themattrosen/cute_dsp

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Utility library for cute_sound.

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README 

        
# cute_dsp



cute_dsp is a C API for various DSP effects suitable for video games and

meant to interface directly with the cute_sound library created by Randy Gaul.

The scope of cute_dsp will eventually include:



* Lowpass filter

* Highpass filter

* White noise injection

* Lowpass filtering with resonances

* Wind noise presets for resonant filters

* Realtime reverb

* Echo filter

* Randomization settings

* Filter presets



## Implemented Features



### Lowpass Filtering

Uses a second order Butterworth filter with a 6dB per octave rolloff, with added resonance. 



### Highpass Filtering

Uses a second order Butterworth filter with a 6dB per octave rolloff, converted from the lowpass filter equation, without resonance.



### Echo Filtering

Uses two ring buffers for delay of input and output samples. There are three designable parameters:

 

* Delay time

* Mix factor (echo loudness)

* Feedback factor (amount that echoes feedback into themselves)



### Noise Generator

Generates white noise and adds to a signal. The signal path of cute_dsp allows this white noise to be fed into other filters in the signal chain. The white noise is generated using a xorshift128 PRNG. 



## Usage

cute_dsp must be used concurrently with cute_sound. 

  

To set up cute_dsp, `#include "cute_dsp.h"` somewhere below your include for cute_sound.h.

Above the include to cute_dsp, there must be one place where you `#define CUTE_DSP_IMPLEMENTATION`.

  

### cd_context_t

After creating your `cs_context_t` cute sound context, you will need to create a cute_dsp context.



```cpp

cs_context_t* sound_context = cs_make_context(...);



cd_context_def_t dsp_context_definition; // statically create dsp context



// set the max number of mixers

dsp_context_definition.playing_pool_count = num_elements_in_playing_pool;



// set dsp sampling rate

dsp_context_definition.sampling_rate = (float)frequency;



// set which filters you would like to use and some optional parameters

dsp_context_definition.use_highpass = 1;

dsp_context_definition.use_lowpass = 1;

dsp_context_definition.use_echo = 0;

dsp_context_definition.use_noise = 1;

dsp_context_definition.echo_max_delay_s = 0.f;

dsp_context_definition.rand_seed = 2;



// allocate the context

cd_context_t* dsp_context = cd_make_context(dsp_context_definition);



//...



// at the end of the application, after shutting down the sound context, release the dsp context

cs_shutdown_context(sound_context);

cd_release_context(&dsp_context);

```

For each sound played using cute_sound, there will be a copy of each filter you've enabled added as a cute_sound plugin. However, the filter will by default set its internal values such that the effect of the filter is not audible. I.e. if you've enabled lowpass filters in `cd_context_def_t`, then each sound played using cute_sound will have an instance of a lowpass filter. That lowpass filter will have its cutoff frequency at 20kHz, therefore negating its effect.

  

### cd_lowpass_t/cd_highpass_t

To modify the cutoff frequencies of the lowpass/highpass filters:

```cpp

void cd_set_lowpass_cutoff(cs_playing_sound_t* playing_sound, float cutoff_in_hz);

void cd_set_lowpass_resonance(cs_playing_sound_t* playing_sound, float resonance);

void cd_set_highpass_cutoff(cs_playing_sound_t* playing_sound, float cutoff_in_hz);



float cd_get_lowpass_cutoff(const cs_playing_sound_t* playing_sound);

float cd_get_lowpass_resonance(const cs_playing_sound_t* playing_sound);

float cd_get_highpass_cutoff(const cs_playing_sound_t* playing_sound);

```

Cutoff frequency is limited to the range of frequencies able to be heard by humans, [20, 20,000] Hz.

Resonance is limited to the range of [0, 1].



### cd_echo_t

To modify the parameters of the echo filter:

```cpp

void cd_set_echo_delay(cs_playing_sound_t* playing_sound, float t);

void cd_set_echo_mix(cs_playing_sound_t* playing_sound, float a);

void cd_set_echo_feedback(cs_playing_sound_t* playing_sound, float b);



float cd_get_echo_delay(const cs_playing_sound_t* playing_sound);

float cd_get_echo_mix(const cs_playing_sound_t* playing_sound);

float cd_get_echo_feedback(const cs_playing_sound_t* playing_sound);

float cd_get_echo_max_delay(const cs_playing_sound_t* playing_sound);

```



### cd_noise_t

To modify the parameters of the noise generator:

```cpp

void cd_set_noise_amplitude_db(cs_playing_sound_t* playing_sound, float db);

void cd_set_noise_amplitude_gain(cs_playing_sound_t* playing_sound, float gain);



float cd_get_noise_amplitude_db(const cs_playing_sound_t* playing_sound);

float cd_get_noise_amplitude_gain(const cs_playing_sound_t* playing_sound);

```