commit 20cac4cb6046c1b7f275b2bc619df4a1b075805e
Author: Albin Chaboissier <chalbin73@gmail.com>
Date:   Wed Sep 17 20:33:25 2025 +0200

    initial commit

diff --git a/.gitignore b/.gitignore
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--- /dev/null
+++ b/.gitignore
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+/target
diff --git a/Cargo.lock b/Cargo.lock
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+++ b/Cargo.lock
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+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 4
+
+[[package]]
+name = "hound"
+version = "3.5.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "62adaabb884c94955b19907d60019f4e145d091c75345379e70d1ee696f7854f"
+
+[[package]]
+name = "rdsp"
+version = "0.1.0"
+dependencies = [
+ "hound",
+]
diff --git a/Cargo.toml b/Cargo.toml
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+++ b/Cargo.toml
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+[package]
+name = "rdsp"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+hound = "3.5.1"
diff --git a/a.jpg b/a.jpg
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diff --git a/sine.wav b/sine.wav
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diff --git a/src/main.rs b/src/main.rs
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+++ b/src/main.rs
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+use std::{
+    f32::consts::PI,
+    fs::File,
+    io::Read,
+    ops::{Add, Div, Mul, Sub},
+};
+
+fn map<T>(input: T, in_min: T, in_max: T, out_min: T, out_max: T) -> T
+where
+    T: Clone + Add<Output = T> + Mul<Output = T> + Sub<Output = T> + Div<Output = T>,
+{
+    ((input - in_min.clone()) / (in_max - in_min)) * (out_max - out_min.clone()) + out_min
+}
+
+struct Nco {
+    // Phase of NCO
+    theta: u32,  // 0 <=> 0, 0xFFFFFFFF <=> 2pi
+    dtheta: u32, // Dtheta = freq : f = dtheta/dt
+}
+
+impl Nco {
+    pub fn new(freq: f32) -> Self {
+        let mut nco = Nco {
+            theta: 0,
+            dtheta: 0,
+        };
+        nco.set_frequency(freq);
+        nco
+    }
+
+    // Sets freq, freq in radian per sample
+    pub fn set_frequency(&mut self, freq: f32) {
+        if freq < 0.0 {
+            self.dtheta = map(2. * PI - freq, 0., 2. * PI, 0., 0xFFFFFFFFu32 as f32).floor() as u32;
+        } else {
+            self.dtheta = map(freq, 0., 2. * PI, 0., 0xFFFFFFFFu32 as f32).floor() as u32;
+        }
+    }
+
+    // Adjusts freq, freq in radian per sample
+    pub fn adjust_frequency(&mut self, freq_off: f32) {
+        self.set_frequency(self.get_frequency() + freq_off);
+    }
+
+    pub fn get_frequency(&self) -> f32 {
+        map(self.dtheta as f32, 0., 0xFFFFFFFFu32 as f32, 0., 2. * PI)
+    }
+
+    pub fn step(&mut self) {
+        let bef = self.theta;
+        self.theta = self.theta.overflowing_add(self.dtheta).0;
+        println!("{}", bef.overflowing_sub(self.theta).0);
+    }
+
+    pub fn step_n(&mut self, n: u32) {
+        self.theta = self
+            .theta
+            .overflowing_add(self.dtheta.overflowing_mul(n).0)
+            .0;
+    }
+
+    pub fn sin(&self) -> f32 {
+        map(self.theta as f32, 0., 0xFFFFFFFFu32 as f32, 0., 2. * PI).sin()
+    }
+
+    pub fn cos(&self) -> f32 {
+        map(self.theta as f32, 0., 0xFFFFFFFFu32 as f32, 0., 2. * PI).cos()
+    }
+}
+
+struct BFSKMod<'a, T: Iterator<Item = bool>> {
+    samples_per_bit: u32,
+    bandwidth: f32,
+    bit_stream: &'a mut T,
+
+    // State
+    oscillator: Nco,
+    sample_index: u32,
+}
+
+impl<'a, T> BFSKMod<'a, T>
+where
+    T: Iterator<Item = bool>,
+{
+    pub fn new(samples_per_bit: u32, bandwidth: f32, bit_stream: &'a mut T) -> Self {
+        BFSKMod {
+            samples_per_bit,
+            bandwidth,
+            oscillator: Nco::new(0.0),
+            bit_stream,
+            sample_index: samples_per_bit,
+        }
+    }
+
+    pub fn step_modulate(&mut self) -> Option<f32> {
+        if self.sample_index == self.samples_per_bit {
+            self.sample_index = 0;
+            let bit = self.bit_stream.next()?;
+
+            let frequency = if bit { self.bandwidth } else { -self.bandwidth };
+            self.oscillator.set_frequency(frequency);
+        }
+
+        self.sample_index += 1;
+        self.oscillator.step();
+        Some(self.oscillator.sin())
+    }
+}
+
+fn main() {
+    let sample_rate = 44100;
+    let mut frequency = 500.0; //HZ
+
+    /*
+    let path = "a.jpg";
+    let file = File::open(path).unwrap();
+    let mut bit_stream = file.bytes().flat_map(|byte| {
+        let byte = byte.unwrap();
+        [
+            byte & 1 == 1,
+            (byte >> 1) & 1 == 1,
+            (byte >> 2) & 1 == 1,
+            (byte >> 3) & 1 == 1,
+            (byte >> 4) & 1 == 1,
+            (byte >> 5) & 1 == 1,
+            (byte >> 6) & 1 == 1,
+            (byte >> 7) & 1 == 1,
+        ]
+    });
+    */
+
+    let mut bit_stream = (0..22000).map(|_| false).chain((0..22000).map(|_| false));
+
+    let mut bfsk = BFSKMod::new(
+        20,
+        2. * PI * (frequency / sample_rate as f32),
+        &mut bit_stream,
+    );
+
+    let spec = hound::WavSpec {
+        channels: 1,
+        sample_rate,
+        bits_per_sample: 16,
+        sample_format: hound::SampleFormat::Int,
+    };
+    let mut writer = hound::WavWriter::create("sine.wav", spec).unwrap();
+
+    while let Some(sample) = bfsk.step_modulate() {
+        let amplitude = i16::MAX as f32;
+        writer.write_sample((amplitude * sample) as i16).unwrap();
+    }
+}