Start work on demuxing

src/input-format.ts

@@ -0,0 +1,55 @@
+import { Demuxer } from './demuxer';
+import { Input } from './input';
+import { IsobmffDemuxer } from './isobmff/isobmff-demuxer';
+import { IsobmffReader } from './isobmff/isobmff-reader';
+import { MatroskaDemuxer } from './matroska/matroska-demuxer';
+
+export abstract class InputFormat {
+	/** @internal */
+	abstract _canReadInput(input: Input): Promise<boolean>;
+
+	/** @internal */
+	abstract _createDemuxer(input: Input): Demuxer;
+}
+
+class IsobmffInputFormat extends InputFormat {
+	/** @internal */
+	override async _canReadInput(input: Input) {
+		const sourceSize = await input._reader.getSourceSize();
+		if (sourceSize < 8) {
+			return false;
+		}
+
+		await input._reader.loadRange(4, 8);
+
+		const isobmffReader = new IsobmffReader(input._reader);
+		isobmffReader.pos = 4;
+		const fourCc = isobmffReader.readAscii(4);
+
+		return fourCc === 'ftyp';
+	}
+
+	override _createDemuxer(input: Input) {
+		return new IsobmffDemuxer(input);
+	}
+}
+
+class MatroskaInputFormat extends InputFormat {
+	/** @internal */
+	override async _canReadInput() {
+		return false; // TODO
+	}
+
+	override _createDemuxer(input: Input) {
+		return new MatroskaDemuxer(input);
+	}
+}
+
+export const ISOBMFF = new IsobmffInputFormat();
+export const MP4 = ISOBMFF;
+export const MOV = ISOBMFF;
+export const MATROSKA = new MatroskaInputFormat();
+export const MKV = MATROSKA;
+export const WEBM = MATROSKA;
+
+export const ALL_FORMATS: InputFormat[] = [ISOBMFF, MKV];