Fix SourceRef race conditions, fix "source" and "target" getter returning unused instances, add missing validation, make "getDurationFromMetadata" only exist on tracks, fix examples, expand media player to support live playback, change the signatures of some Input APIs

src/segmented-input.ts

@@ -117,10 +117,6 @@ class SegmentedInputDemuxer extends Demuxer {
 		this.segmentedInput = segmentedInput;
 	}
 
-	async getDurationFromMetadata(): Promise<number | null> {
-		throw new Error('Unreachable');
-	}
-
 	async getMetadataTags(): Promise<MetadataTags> {
 		throw new Error('Unreachable');
 	}