UI: improve aspect ratio handling

As written in the changelog: Live streams formerly worked around a
Firefox pixel aspect ratio bug by forcing all videos to 16:9, which
dramatically distorted 9:16 camera views. Playback didn't, so anamorphic
videos looked correct on Chrome but slightly stretched on Firefox. Now
both live streams and playback are fully correct on all browsers.

server/db/Cargo.toml

@@ -29,6 +29,7 @@ libpasta = "0.1.2"
 log = "0.4"
 mylog = { git = "https://github.com/scottlamb/mylog" }
 nix = "0.22.0"
+num-rational = { version = "0.4.0", default-features = false, features = ["std"] }
 odds = { version = "0.4.0", features = ["std-vec"] }
 parking_lot = { version = "0.11.1", features = [] }
 pretty-hex = "0.2.1"

server/db/db.rs

@@ -135,6 +135,16 @@ pub struct VideoSampleEntry {
     pub pasp_v_spacing: u16,
 }
 
+impl VideoSampleEntry {
+    /// Returns the aspect ratio as a minimized ratio.
+    pub fn aspect(&self) -> num_rational::Ratio<u32> {
+        num_rational::Ratio::new(
+            u32::from(self.width) * u32::from(self.pasp_h_spacing),
+            u32::from(self.height) * u32::from(self.pasp_v_spacing),
+        )
+    }
+}
+
 #[derive(PartialEq, Eq)]
 pub struct VideoSampleEntryToInsert {
     pub data: Vec<u8>,