How close can we get our guitar tone to a given recording?
- Possible to avoid having to model specific guitars and amps? (Might not know what was used anyway; prohibitively expensive and time-consuming.)
- Different approach: use impulse response (many available on web for free), convolve with input to produce output
- NeuralPi example below works in real-time but that requires a lot of work!
- Start with offline, any language and hardware.
- Use dynamic time warping to align guitar input to target recording?
- First do coarse alignment: which section of recording corresponds to input?
- Use source separation to isolate the guitar track in the recording.
- There will be limits imposed by the guitar and amp e.g. no amount of audio processing could make an SSS strat sound like a guitar with humbuckers.
- Port to Rust?! (NeuralPi requires SIMD: only experimental support in Rust.)
- Could real-time performance be improved further by compressing the model?
- Rather than set small weights to zero after training, book suggests using L1-regularization during training to drive as many weights as possible to zero.
- MVP:
- Take any input (existing recording of guitar with clean tone).
- Apply any effect (distortion) using any stack (Python?).
- Save to file and play it back.
- Choose example song and isolate guitar part.
- Record yourself trying to play that same part (short subsection).
- Read links above and see what can be adapted:
- How do they define loss function?
- What are their inputs and outputs?
- Gather more links, summarise here.
- Diagrams
- Data preparation
- Loss function
- Model inference
- Audio interface:
- Choose one
- Get it working (see guitar input in browser/DAW)
- Tuner (see JS Rocks ... can it be improved upon e.g. smoothing, considering harmonics?)
- Parametric EQ
- Pipeline to isolate guitar samples of interest (or see what is available online?)
- RTNeural: A lightweight neural network inferencing engine written in C++. This library was designed with the intention of being used in real-time systems, specifically real-time audio processing.
- Web Audio API
- Librosa Audio and music processing in Python.
- Dynamic Time Warping Align two audio signals in time domain (does it actually modify one or only identify corresponding samples?). Example plot doesn't look very good! Expect much is lost by extracting chroma features. Try instead warping one of the signals and measuring similarity (cross-correlation?) with target, search that way.
Guitar effects and cabinets using Web Audio API.
Uses impulse responses to model well-known amps and the reverb of several different spaces.
NeuralPi is a guitar pedal using neural networks to emulate real amps and pedals on a Raspberry Pi 4.
Raspberry Pi Zero based guitar pedal with real-time effects written in C.
Sadly it looks like it is out of stock and the site has been down for some years!
// CC-by-www.Electrosmash.com Pedl-Pi open-source project
// clean.c effect pedal, the signal is read by the ADC and written again using 2 PWM signals.
#include <stdio.h><br>#include <bcm2835.h>
// Define Input Pins
#define PUSH1 RPI_GPIO_P1_08 //GPIO14
#define PUSH2 RPI_V2_GPIO_P1_38 //GPIO20
#define TOGGLE_SWITCH RPI_V2_GPIO_P1_32 //GPIO12
#define FOOT_SWITCH RPI_GPIO_P1_10 //GPIO15
#define LED RPI_V2_GPIO_P1_36 //GPIO16
uint32_t read_timer=0;
uint32_t input_signal=0;
uint8_t FOOT_SWITCH_val;
uint8_t TOGGLE_SWITCH_val;
uint8_t PUSH1_val;
uint8_t PUSH2_val;
//main program
int main(int argc, char **argv)
{
// Start the BCM2835 Library to access GPIO.
if (!bcm2835_init())
{printf("bcm2835_init failed. Are you running as root??\n"); return 1;}
// Start the SPI BUS.
if (!bcm2835_spi_begin())
{printf("bcm2835_spi_begin failed. Are you running as root??\n"); return 1;}
//define PWM mode
bcm2835_gpio_fsel(18,BCM2835_GPIO_FSEL_ALT5 ); //PWM0 signal on GPIO18
bcm2835_gpio_fsel(13,BCM2835_GPIO_FSEL_ALT0 ); //PWM1 signal on GPIO13
bcm2835_pwm_set_clock(2); // Max clk frequency (19.2MHz/2 = 9.6MHz)
bcm2835_pwm_set_mode(0,1 , 1); //channel 0, markspace mode, PWM enabled.
bcm2835_pwm_set_range(0,64); //channel 0, 64 is max range (6bits): 9.6MHz/64=150KHz PWM freq.
bcm2835_pwm_set_mode(1, 1, 1); //channel 1, markspace mode, PWM enabled.
bcm2835_pwm_set_range(1,64); //channel 0, 64 is max range (6bits): 9.6MHz/64=150KHz PWM freq.
//define SPI bus configuration
bcm2835_spi_setBitOrder(BCM2835_SPI_BIT_ORDER_MSBFIRST); // The default
bcm2835_spi_setDataMode(BCM2835_SPI_MODE0); // The default
bcm2835_spi_setClockDivider(BCM2835_SPI_CLOCK_DIVIDER_64); // 4MHz clock with _64
bcm2835_spi_chipSelect(BCM2835_SPI_CS0); // The default
bcm2835_spi_setChipSelectPolarity(BCM2835_SPI_CS0, LOW); // the default
uint8_t mosi[10] = { 0x01, 0x00, 0x00 }; //12 bit ADC read channel 0.
uint8_t miso[10] = { 0 };
//Define GPIO pins configuration
bcm2835_gpio_fsel(PUSH1, BCM2835_GPIO_FSEL_INPT); //PUSH1 button as input
bcm2835_gpio_fsel(PUSH2, BCM2835_GPIO_FSEL_INPT); //PUSH2 button as input
bcm2835_gpio_fsel(TOGGLE_SWITCH, BCM2835_GPIO_FSEL_INPT); //TOGGLE_SWITCH as input
bcm2835_gpio_fsel(FOOT_SWITCH, BCM2835_GPIO_FSEL_INPT); //FOOT_SWITCH as input
bcm2835_gpio_fsel(LED, BCM2835_GPIO_FSEL_OUTP); //LED as output
bcm2835_gpio_set_pud(PUSH1, BCM2835_GPIO_PUD_UP); //PUSH1 pull-up enabled
bcm2835_gpio_set_pud(PUSH2, BCM2835_GPIO_PUD_UP); //PUSH2 pull-up enabled
bcm2835_gpio_set_pud(TOGGLE_SWITCH, BCM2835_GPIO_PUD_UP); //TOGGLE_SWITCH pull-up enabled
bcm2835_gpio_set_pud(FOOT_SWITCH, BCM2835_GPIO_PUD_UP); //FOOT_SWITCH pull-up enabled
while(1) //Main Loop
{
//Read the PUSH buttons every 50000 times (0.25s) to save resources.
read_timer++;
if (read_timer==50000)
{
read_timer=0;
uint8_t PUSH1_val = bcm2835_gpio_lev(PUSH1);
uint8_t PUSH2_val = bcm2835_gpio_lev(PUSH2);
TOGGLE_SWITCH_val = bcm2835_gpio_lev(TOGGLE_SWITCH);
uint8_t FOOT_SWITCH_val = bcm2835_gpio_lev(FOOT_SWITCH);
bcm2835_gpio_write(LED,!FOOT_SWITCH_val); //light the effect when the footswitch is activated.
}
//read 12 bits ADC
bcm2835_spi_transfernb(mosi, miso, 3);
input_signal = miso[2] + ((miso[1] & 0x0F) << 8);
//**** CLEAN EFFECT ***///
//Nothing to do, the input_signal goes directly to the PWM output.
//generate output PWM signal 6 bits
bcm2835_pwm_set_data(1,input_signal & 0x3F);
bcm2835_pwm_set_data(0,input_signal >> 6);
}
//close all and exit
bcm2835_spi_end();
bcm2835_close();
return 0;
}