For more information about the examples, such as how the Python and Mojo files interact with each other, see the Examples Overview

MFCCExample

The energy of each Mel band is visualized in the console as a series of asterisks. Also the energy of each Mel band controls the loudness of a sine tone at center frequency of its band. The result is a frequency-quantized analysis-sinusoidal-resynthesis effect.

Python Code

from mmm_python import *
ma = MMMAudio(128, graph_name="MFCCExample", package_name="examples")
ma.start_audio()

ma.send_int("update_modulus",80) # higher number = slower updates

ma.stop_audio()

Mojo Code

from mmm_audio import *

comptime num_bands: Int = 40
comptime num_coeffs: Int = 13
comptime fft_size: Int = 1024

struct MFCCExample(Movable, Copyable):
    var world: World
    var buffer: Buffer
    var playBuf: Play
    var fftproc: FFTProcess[MFCC,False,WindowType.hann]
    var m: Messenger
    var print_counter: Int
    var update_modulus: Int

    fn __init__(out self, world: World):
        self.world = world
        self.buffer = Buffer.load("resources/Shiverer.wav")
        self.playBuf = Play(self.world)
        p = MFCC(sr=self.world[].sample_rate, num_bands=num_bands, num_coeffs=num_coeffs, min_freq=20.0, max_freq=20000.0, fft_size=fft_size)
        self.fftproc = FFTProcess[MFCC,False,WindowType.hann](self.world,p^, window_size=fft_size, hop_size=fft_size//2)
        self.m = Messenger(self.world)
        self.print_counter = 0
        self.update_modulus = 50

    fn next(mut self) -> MFloat[2]:

        self.m.update(self.update_modulus,"update_modulus")
        flute = self.playBuf.next(self.buffer)

        # do the analysis
        _ = self.fftproc.next(flute)

        # get the results
        if self.world[].top_of_block:
            # print the mel band energies
            if self.print_counter % self.update_modulus == 0:
                string = "\n\n\n\n\n"
                for i in range(num_coeffs):
                    val = self.fftproc.buffered_process.process.process.coeffs[i]
                    string += "Coeff " + String(i) + ": " + String(val) + "\n"

                print(string)
                # print the results
            self.print_counter += 1

        return MFloat[2](flute, flute)