"it's not just because it's dark" it is

src/capture.rs

@@ -27,7 +27,8 @@ impl Capture
         // v4l2-ctl -d /dev/video0 --list-formats-ext
         
         let x = x.video_capture (PixFormat::new (1280, 720, PixelFormat::MJPG))?;
-        x.set_frame_interval(linuxvideo::Fract::new(1, 30)).unwrap ();
+        let interval = x.set_frame_interval(linuxvideo::Fract::new(1, 30)).unwrap ();
+        dbg! (interval);
         dbg! (x.format ());
         let size_image = usize::try_from (x.format ().size_image ()).unwrap ();
         let stream = x.into_stream ()?;

src/main.rs

@@ -33,8 +33,9 @@ fn main() -> Result <(), Error>
             
             println! ("Measuring...");
             let start = Instant::now ();
-            for _ in 0..30
+            for i in 0..30
             {
+                dbg! (i);
                 capture.wait_for_frame (&mut buf).unwrap ();
             }
             let stop = Instant::now ();