isomp4: take track id from the media source

symphonia-format-isomp4/src/demuxer.rs

@@ -235,7 +235,7 @@ impl<'s> IsoMp4Reader<'s> {
         }
 
         // Instantiate a `TrackState` for each track in the media.
-        let track_states = (0..moov.traks.len()).map(TrackState::new).collect::<Vec<TrackState>>();
+        let track_states = moov.traks.iter().map(|trak| TrackState::new(trak.tkhd.id as usize)).collect::<Vec<TrackState>>();
 
         // Instantiate a `Track` for all track states above.
         let tracks = track_states