[RUST/HOUND] WavWriter 구조체 : write_sample 메소드를 사용해 삼각파(triangle wave) WAV 파일 생성하기

■ WavWriter 구조체의 write_sample 메소드를 사용해 삼각파(triangle wave)의 WAV 파일을 생성하는 방법을 보여준다.

▶ Cargo.toml


[package]
name = "test_project"
version = "0.1.0"
edition = "2021"

[dependencies]
hound = "3.4.0"

[package]

name = "test_project"

version = "0.1.0"

edition = "2021"

[dependencies]

hound = "3.4.0"

▶ src/main.rs


use std::fs;
use std::io;

use hound;

const SAMPLE_RATE : f32 = 44100.0;

fn main()
{
    let wav_spec : hound::WavSpec = hound::WavSpec
    {
        channels        : 1,
        sample_rate     : SAMPLE_RATE as u32,
        bits_per_sample : 32,
        sample_format   : hound::SampleFormat::Float,
    };

    let mut wav_writer : hound::WavWriter<io::BufWriter<fs::File>> = hound::WavWriter::create("d:/tri.wav", wav_spec).unwrap();

    let mut wave_vector : Vec<f32> = vec![];

    let bpm : usize = 120;

    [60, 64, 67, 64, 60, 64, 67, 72].iter().for_each
    (
        |scale: &i32|
        {
            wave_vector.extend(get_triangle_wave_vector(*scale, calculate_note_length(bpm, 8), 0.5));
        }
    );

    for wave in wave_vector.into_iter()
    {
        wav_writer.write_sample(wave).unwrap();
    }
}

// scale : 음계, 예) 60(도), 64(미), 67(솔)
fn get_frequency(scale : i32) -> f32
{
    return 440.0 * 2.0f32.powf((scale - 69) as f32 / 12.0);
}

// bpm  : 분당 박자, beats per minute
// note : 음표 예) 4(4분 음표)
fn calculate_note_length(bpm : usize, note : usize) -> usize
{
    return ((4.0 / note as f32) * (60.0 / bpm as f32) * SAMPLE_RATE) as usize;
}

// scale       : 음계, 예) 60(도), 64(미), 67(솔)
// note_length : 음표 길이 (샘플 수)
// gain        : 출력
fn get_triangle_wave_vector(scale : i32, note_length : usize, gain : f32) -> Vec<f32>
{
    let frequency : f32 = get_frequency(scale);

    let interval : f32 = SAMPLE_RATE / frequency;

    let mut wave_vector : Vec<f32> = vec![0.0; note_length];

    let half_interval : f32 = interval / 2.0;

    for i in 0..note_length
    {
        let temporary_value : f32 = i as f32 / half_interval;

        let mut value : f32 = 2.0 * (temporary_value % 1.0) - 1.0;

        let is_climbing : bool = temporary_value.floor() as usize % 2 == 0;

        value = if is_climbing { value } else { -value };

        wave_vector[i] = value;
    }

    return wave_vector.into_iter().map(|value : f32| (value * gain) as f32).collect();
}

use std::fs;

use std::io;

use hound;

const SAMPLE_RATE : f32 = 44100.0;

fn main()

{

let wav_spec : hound::WavSpec = hound::WavSpec

{

channels : 1,

sample_rate : SAMPLE_RATE as u32,

bits_per_sample : 32,

sample_format : hound::SampleFormat::Float,

};

let mut wav_writer : hound::WavWriter<io::BufWriter<fs::File>> = hound::WavWriter::create("d:/tri.wav", wav_spec).unwrap();

let mut wave_vector : Vec<f32> = vec![];

let bpm : usize = 120;

[60, 64, 67, 64, 60, 64, 67, 72].iter().for_each

(

|scale: &i32|

{

wave_vector.extend(get_triangle_wave_vector(*scale, calculate_note_length(bpm, 8), 0.5));

}

);

for wave in wave_vector.into_iter()

{

wav_writer.write_sample(wave).unwrap();

}

// scale : 음계, 예) 60(도), 64(미), 67(솔)

fn get_frequency(scale : i32) -> f32

{

return 440.0 * 2.0f32.powf((scale - 69) as f32 / 12.0);

}

// bpm : 분당 박자, beats per minute

// note : 음표 예) 4(4분 음표)

fn calculate_note_length(bpm : usize, note : usize) -> usize

{

return ((4.0 / note as f32) * (60.0 / bpm as f32) * SAMPLE_RATE) as usize;

}

// scale : 음계, 예) 60(도), 64(미), 67(솔)

// note_length : 음표 길이 (샘플 수)

// gain : 출력

fn get_triangle_wave_vector(scale : i32, note_length : usize, gain : f32) -> Vec<f32>

{

let frequency : f32 = get_frequency(scale);

let interval : f32 = SAMPLE_RATE / frequency;

let mut wave_vector : Vec<f32> = vec![0.0; note_length];

let half_interval : f32 = interval / 2.0;

for i in 0..note_length

{

let temporary_value : f32 = i as f32 / half_interval;

let mut value : f32 = 2.0 * (temporary_value % 1.0) - 1.0;

let is_climbing : bool = temporary_value.floor() as usize % 2 == 0;

value = if is_climbing { value } else { -value };

wave_vector[i] = value;

}

return wave_vector.into_iter().map(|value : f32| (value * gain) as f32).collect();

}

test_project.zip