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/writer.ts

@@ -11,6 +11,8 @@ import { Target } from './target';
 
 export class Writer {
 	target: Target;
+	finalized = false;
+	started = false;
 
 	private pos = 0;
 
@@ -19,7 +21,9 @@ export class Writer {
 	}
 
 	start() {
+		assert(!this.started);
 		this.target._start();
+		this.started = true;
 	}
 
 	ensureMonotonicity() {
@@ -29,6 +33,8 @@ export class Writer {
 
 	/** Writes the given data to the target, at the current position. */
 	write(data: Uint8Array) {
+		assert(this.started && !this.finalized);
+
 		this.maybeTrackWrites(data);
 		this.target._write(data, this.pos);
 		this.pos += data.byteLength;
@@ -46,15 +52,19 @@ export class Writer {
 
 	/** Signals to the writer that it may be time to flush. */
 	async flush() {
+		assert(this.started && !this.finalized);
 		return this.target._flush();
 	}
 
 	/** Called after muxing has finished. */
 	async finalize() {
+		assert(this.started && !this.finalized);
 		assert(this.target._output);
 
 		await this.target._finalize();
 		this.target._output._targets.delete(this.target);
+
+		this.finalized = true;
 	}
 
 	private trackedWrites: Uint8Array | null = null;