From 347a95ea8dad026f20566d142d092fabb1e5a45c Mon Sep 17 00:00:00 2001
From: Thomas Kolb <thomas@tkolb.de>
Date: Sun, 27 Jun 2021 22:01:15 +0200
Subject: [PATCH] =?UTF-8?q?Implement=20silence=20detection=20and=20?=
 =?UTF-8?q?=E2=80=9Estandby=E2=80=9C=20mode?=
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---
 src/config.rs            |  3 +++
 src/main.rs              | 16 ++++++++++++++++
 src/signal_processing.rs |  5 +++++
 3 files changed, 24 insertions(+)

diff --git a/src/config.rs b/src/config.rs
index ee44588..f1e4323 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -16,3 +16,6 @@ pub const UDP_SERVER_ADDR: &str = "192.168.23.118:2703";
 
 pub const FPS_ANIMATION: f32 = SAMP_RATE / SAMPLES_PER_UPDATE as f32;
 pub const FPS_LEDS: f32 = 60.0;
+
+// “standby mode” configuration
+pub const STANDBY_MAX_SILENT_SAMPLES: usize = SAMP_RATE as usize;
diff --git a/src/main.rs b/src/main.rs
index 8baf502..bee4f99 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -65,6 +65,9 @@ fn main()
 	// array for samples directly read from stream
 	let mut samples: VecDeque<i16> = VecDeque::with_capacity(config::BLOCK_LEN);
 
+	// counts silent (zero-valued) samples
+	let mut silent_samples: usize = 0;
+
 	// main loop
 	loop {
 
@@ -98,6 +101,19 @@ fn main()
 		{
 			let mut s = sigproc.borrow_mut();
 			s.import_i16_mono_from_iter(samples.iter()).unwrap();
+
+			if s.is_silent() {
+				silent_samples += config::BLOCK_LEN;
+
+				if silent_samples >= config::STANDBY_MAX_SILENT_SAMPLES {
+					// too many silent samples in a row: stop any signal processing until something
+					// else occurs at the input again
+					continue;
+				}
+			} else {
+				silent_samples = 0;
+			}
+
 			s.update_fft().unwrap();
 		}
 
diff --git a/src/signal_processing.rs b/src/signal_processing.rs
index b233082..9ba4a23 100644
--- a/src/signal_processing.rs
+++ b/src/signal_processing.rs
@@ -104,6 +104,11 @@ impl SignalProcessing
 		Ok(())
 	}
 
+	pub fn is_silent(&self) -> bool
+	{
+		return self.fft_input.iter().sum::<f32>() == 0.0;
+	}
+
 	pub fn update_fft(&mut self) -> fftw::error::Result<()>
 	{
 		self.fft_plan.r2c(&mut self.fft_input, &mut self.fft_output)?;