Add a default noise floor.

Pretty simple, if the average amplitude is under a certain value clear
out the buffer! The value I chose (.001) was an arbitrary value I got
from printf debugging. I was able to show that this worked pretty well
on the desktop session. Hopefully we'll add this to the settings page at
some point.

gui/src/effects.rs

@@ -10,6 +10,8 @@ use tracing::{error, info};
 use crate::imp;
 
 static DF_MODEL: Asset = asset!("/assets/DeepFilterNet3_ll_onnx.tar.gz");
+// TODO: make this user configurable.
+static DEFAULT_NOISE_FLOOR: f32 = 0.001;
 
 enum DenoisingModelState {
     Nothing,
@@ -76,6 +78,7 @@ pub struct AudioProcessor {
     denoise: bool,
     spawn: imp::SpawnHandle,
     buffer: Vec<f32>,
+    noise_floor: f32,
 }
 
 impl AudioProcessor {
@@ -84,6 +87,7 @@ impl AudioProcessor {
             denoise: false,
             spawn: imp::SpawnHandle::current(),
             buffer: Vec::new(),
+            noise_floor: DEFAULT_NOISE_FLOOR,
         }
     }
 
@@ -92,6 +96,7 @@ impl AudioProcessor {
             denoise: true,
             spawn: imp::SpawnHandle::current(),
             buffer: Vec::new(),
+            noise_floor: DEFAULT_NOISE_FLOOR,
         }
     }
 }
@@ -132,6 +137,16 @@ impl AudioProcessor {
         if include_raw {
             output.extend(audio.iter().step_by(channels).copied());
         }
+
+        // Adds threshoulding to prevent sending audio when things are really quiet.
+        let avg: f32 = if output.is_empty() {
+            0.0
+        } else {
+            output.iter().map(|x| x.abs()).sum::<f32>() / output.len() as f32
+        };
+        if avg < self.noise_floor {
+            output.clear();
+        }
     }
 }