[*] refactor video editor

Author: heng30

lib/video-editor/src/tracks/track.rs

@@ -14,9 +14,10 @@ use std::{path::Path, sync::Arc, time::Duration};
 pub struct TrackPriority(u8);
 
 impl TrackPriority {
-    pub const SUBTITLE: TrackPriority = TrackPriority(0);
+    pub const SUBTITLE: TrackPriority = TrackPriority(0); // highest (topmost)
     pub const OVERLAY: TrackPriority = TrackPriority(1);
-    pub const VIDEO_AUDIO: TrackPriority = TrackPriority(2);
+    pub const VIDEO: TrackPriority = TrackPriority(1); // same as overlay, can swap
+    pub const AUDIO: TrackPriority = TrackPriority(2); // lowest (bottommost)
 }
 
 #[derive(Debug, Clone)]
@@ -961,7 +962,8 @@ impl Track {
         match self {
             Track::Subtitle(_) => TrackPriority::SUBTITLE,
             Track::Overlay(_) => TrackPriority::OVERLAY,
-            Track::Video(_) | Track::Audio(_) => TrackPriority::VIDEO_AUDIO,
+            Track::Video(_) => TrackPriority::VIDEO,
+            Track::Audio(_) => TrackPriority::AUDIO,
         }
     }