Merge pull request #8 from faern/add-spectrum-analyze-backpressure-handling

Add backpressure handling between camera and spectrum analyzer

Author: DerFetzer

src/camera.rs

@@ -1,8 +1,8 @@
 use crate::config::ImageConfig;
 use crate::{ThreadId, ThreadResult};
-use flume::{Receiver, Sender};
+use flume::{Receiver, Sender, TrySendError};
 use image::{DynamicImage, GenericImageView, ImageBuffer, Rgb};
-use log::{error, trace};
+use log::{error, trace, warn};
 use nokhwa::CallbackCamera;
 use nokhwa::pixel_format::RgbFormat;
 use nokhwa::utils::{
@@ -180,9 +180,15 @@ impl CameraThread {
                                         cfg.window.size.y as u32,
                                     )
                                     .to_image();
-                                if let Err(e) = window_tx.send(window) {
-                                    error!("Could not send window: {e}");
-                                    return;
+                                match window_tx.try_send(window) {
+                                    Ok(_) => {}
+                                    Err(TrySendError::Full(_)) => {
+                                        warn!("Window buffer full. Dropping frame");
+                                    }
+                                    Err(TrySendError::Disconnected(_)) => {
+                                        error!("Window receiver disconnected. Exiting");
+                                        return;
+                                    }
                                 };
                             }
                             *frame_tx.lock().expect("Mutex poisoned") = Some(frame);

src/main.rs

@@ -9,8 +9,13 @@ fn main() -> eframe::Result {
     init_logging();
 
     let frame = Arc::new(Mutex::new(None));
+
+    // Image buffer holding the last read frame from the camera. Consumed by the GUI to display the camera feed.
     let (frame_tx, frame_rx) = (frame.clone(), frame.clone());
-    let (window_tx, window_rx) = flume::unbounded();
+    // Channel transporting image buffers from the camera thread to the spectrum calculator thread.
+    // This is bounded to provide backpressure handling. If the spectrum calculator is slower than the
+    // framerate of the camera, frames will be dropped instead of filling up the memory.
+    let (window_tx, window_rx) = flume::bounded(5);
     let (spectrum_tx, spectrum_rx) = flume::bounded(1000);
     let (config_tx, config_rx) = flume::unbounded();
     let (result_tx, result_rx) = flume::unbounded();