Add NullTarget

src/index.ts

@@ -89,7 +89,7 @@ export {
 	getFirstEncodableAudioCodec,
 	getFirstEncodableSubtitleCodec,
 } from './encode';
-export { Target, BufferTarget, StreamTarget, StreamTargetChunk, StreamTargetOptions } from './target';
+export { Target, BufferTarget, StreamTarget, StreamTargetChunk, StreamTargetOptions, NullTarget } from './target';
 export { Rotation, AnyIterable, SetRequired, MaybePromise } from './misc';
 export {
 	Source,

src/target.ts

@@ -6,7 +6,7 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/.
  */
 
-import { BufferTargetWriter, StreamTargetWriter, Writer } from './writer';
+import { BufferTargetWriter, NullTargetWriter, StreamTargetWriter, Writer } from './writer';
 import { Output } from './output';
 
 /**
@@ -104,3 +104,15 @@ export class StreamTarget extends Target {
 		return new StreamTargetWriter(this);
 	}
 }
+
+/**
+ * This target just discards all incoming data. It is useful for when you need an `Output` but extract data from it
+ * differently, for example through format-specific callbacks (`onMoof`, `onMdat`, ...) or encoder events.
+ * @public
+ */
+export class NullTarget extends Target {
+	/** @internal */
+	_createWriter() {
+		return new NullTargetWriter();
+	}
+}

src/writer.ts

@@ -459,3 +459,24 @@ export class StreamTargetWriter extends Writer {
 		return this.writer?.close();
 	}
 }
+
+export class NullTargetWriter extends Writer {
+	private pos = 0;
+
+	write(data: Uint8Array) {
+		this.maybeTrackWrites(data);
+		this.pos += data.byteLength;
+	}
+
+	getPos() {
+		return this.pos;
+	}
+
+	seek(newPos: number) {
+		this.pos = newPos;
+	}
+
+	async flush() {}
+	async finalize() {}
+	async close() {}
+}