From ff018a98e1e38f7735ee316788c8b5c0baf5132f Mon Sep 17 00:00:00 2001
From: Thomas Kolb <cfr34k-git@tkolb.de>
Date: Tue, 16 Feb 2021 22:44:31 +0100
Subject: [PATCH] Initial commit

Start experimenting with Rust. This is a little experimental, but fully
functional real-time FFT program based on the FFTW library.
---
 .gitignore               |   1 +
 Cargo.lock               | 298 +++++++++++++++++++++++++++++++++++++++
 Cargo.toml               |  12 ++
 src/config.rs            |   3 +
 src/main.rs              |  67 +++++++++
 src/signal_processing.rs | 114 +++++++++++++++
 6 files changed, 495 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 Cargo.lock
 create mode 100644 Cargo.toml
 create mode 100644 src/config.rs
 create mode 100644 src/main.rs
 create mode 100644 src/signal_processing.rs

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new file mode 100644
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new file mode 100644
index 0000000..bbe9a81
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diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..2de235c
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,12 @@
+[package]
+name = "musiclight"
+version = "0.1.0"
+authors = ["Thomas Kolb <cfr34k-git@tkolb.de>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+byteorder = "1.4"
+fftw      = { version = "0.6", default-features = false, features = ["system"] }
+mlua      = { version = "0.5", features = ["lua53"] }
diff --git a/src/config.rs b/src/config.rs
new file mode 100644
index 0000000..3370f98
--- /dev/null
+++ b/src/config.rs
@@ -0,0 +1,3 @@
+// definitions for the FFT
+pub const BLOCK_LEN: usize = 512;
+pub const SAMP_RATE: f32   = 48000.0;
diff --git a/src/main.rs b/src/main.rs
new file mode 100644
index 0000000..2f18e15
--- /dev/null
+++ b/src/main.rs
@@ -0,0 +1,67 @@
+// vim: noet
+
+use std::process::exit;
+
+use byteorder::{NativeEndian, ReadBytesExt};
+
+use mlua::Lua;
+
+mod signal_processing;
+mod config;
+
+use crate::signal_processing::SignalProcessing;
+
+fn main()
+{
+	let mut stdin = std::io::stdin();
+
+	// test the mlua crate
+	let lua_state = Lua::new();
+
+	lua_state.globals().set("get_rust_value", lua_state.create_function(|_, ()| {
+		Ok(3)
+	}).unwrap()).unwrap();
+
+	let user_script = std::fs::read_to_string("test.lua").unwrap();
+	lua_state.load(&user_script).exec().unwrap();
+
+	let lua_func_test : mlua::Function = lua_state.globals().get("test").unwrap();
+
+	println!("{}", lua_func_test.call::<_, u32>(123).unwrap());
+
+	let mut sigproc = SignalProcessing::new(config::BLOCK_LEN, config::SAMP_RATE).unwrap();
+
+	println!("Done! Starting main loop…");
+
+	// array for samples directly read from stream
+	let mut samples = [0i16; config::BLOCK_LEN];
+
+	// main loop
+	loop {
+
+		// read a block of samples and exit gracefully on EOF
+		for sample in samples.iter_mut() {
+			let res = stdin.read_i16::<NativeEndian>();
+
+			match res {
+				Ok(s) => *sample = s,
+				Err(e) if e.kind() == std::io::ErrorKind::UnexpectedEof => {
+					println!("End of stream. Exiting.");
+					exit(0);
+				},
+				Err(e) => panic!(e)
+			}
+		}
+
+		sigproc.import_i16_mono(&samples).unwrap();
+		sigproc.update_fft().unwrap();
+
+		let energy_bass   = sigproc.get_energy_in_band(   0.0,  400.0);
+		let energy_mid    = sigproc.get_energy_in_band( 400.0, 4000.0);
+		let energy_treble = sigproc.get_energy_in_band(4000.0, config::SAMP_RATE/2.0);
+
+		// dump the output
+		println!("Bass: {:8.2} – Mid: {:8.2} – Treble: {:8.2}", energy_bass, energy_mid, energy_treble);
+	}
+
+}
diff --git a/src/signal_processing.rs b/src/signal_processing.rs
new file mode 100644
index 0000000..3d946c3
--- /dev/null
+++ b/src/signal_processing.rs
@@ -0,0 +1,114 @@
+// vim: noet
+
+use fftw::array::AlignedVec;
+use fftw::plan::*;
+use fftw::types::*;
+use std::f32::consts::PI;
+
+pub struct SignalProcessing
+{
+	samp_rate: f32,
+
+	fft_window: Vec<f32>,
+
+	fft_input: AlignedVec<f32>,
+	fft_output: AlignedVec<c32>,
+
+	fft_plan: R2CPlan32,
+
+	fft_absolute: Vec<f32>,
+}
+
+impl SignalProcessing
+{
+	fn hann_window(block_size: usize) -> Vec<f32>
+	{
+		let mut window = vec![0.0; block_size];
+
+		for i in 0..block_size {
+			window[i] = (PI * (i as f32) / (block_size as f32)).sin().powi(2);
+		}
+
+		window
+	}
+
+	pub fn new(block_size: usize, samp_rate: f32) -> fftw::error::Result<SignalProcessing>
+	{
+		let freq_domain_size = block_size/2 + 1;
+
+		let s = SignalProcessing {
+			samp_rate: samp_rate,
+			fft_window: SignalProcessing::hann_window(block_size),
+			fft_input:  AlignedVec::new(block_size),
+			fft_output: AlignedVec::new(freq_domain_size),
+			fft_plan:   R2CPlan::aligned(&[block_size], Flag::MEASURE)?,
+
+			fft_absolute: vec![0.0; freq_domain_size],
+		};
+
+		Ok(s)
+	}
+
+	fn apply_window(&mut self)
+	{
+		self.fft_input.iter_mut()
+		              .zip(self.fft_window.iter())
+		              .for_each(|(s, w)| *s *= w);
+	}
+
+	pub fn import_i16_stereo(&mut self, data: &[i16]) -> std::result::Result<(), &str>
+	{
+		if data.len() != 2*self.fft_input.len() {
+			return Err("Stereo data length does not match 2x the FFT input length.");
+		}
+
+		data.chunks_exact(2)
+			.map(|channels| (channels[0] as f32 + channels[1] as f32) / 2.0 / 32768.0)
+			.zip(self.fft_input.iter_mut())
+			.for_each(|(c, t)| *t = c);
+
+		self.apply_window();
+
+		Ok(())
+	}
+
+	pub fn import_i16_mono(&mut self, data: &[i16]) -> std::result::Result<(), &str>
+	{
+		if data.len() != self.fft_input.len() {
+			return Err("Mono data length does not match the FFT input length.");
+		}
+
+		data.iter()
+			.map(|&sample| (sample as f32) / 32768.0)
+			.zip(self.fft_input.iter_mut())
+			.for_each(|(c, t)| *t = c);
+
+		self.apply_window();
+
+		Ok(())
+	}
+
+	pub fn update_fft(&mut self) -> fftw::error::Result<()>
+	{
+		self.fft_plan.r2c(&mut self.fft_input, &mut self.fft_output)?;
+
+		for (i, abs_sample) in self.fft_absolute.iter_mut().enumerate() {
+			*abs_sample = self.fft_output[i].norm();
+		}
+
+		Ok(())
+	}
+
+	fn freq_to_idx(&self, freq: f32) -> usize
+	{
+		(freq * (self.fft_input.len() as f32) / self.samp_rate) as usize
+	}
+
+	pub fn get_energy_in_band(&self, freq_start: f32, freq_end: f32) -> f32
+	{
+		let start_bin = self.freq_to_idx(freq_start);
+		let end_bin = self.freq_to_idx(freq_end);
+
+		self.fft_absolute[start_bin ..= end_bin].iter().sum()
+	}
+}