Class VideoDecoderPolyfill

src/video_decoder.ts:43–457

 * Corresponds to the WebCodecs VideoDecoder API.
 */
export class VideoDecoderPolyfill extends EventTarget {
	private init: VideoDecoderInit;
	private codecContext: CodecContext | null = null;
	private mutex = new AsyncMutex();
	private frame: Frame;
	private packet: Packet;
	private _decodeQueueSize = 0;
	private currentConfigId = 0;
	private keyChunkRequired = true;
	private pendingFlushResolvers: Array<{ resolve: () => void; reject: (e: unknown) => void }> = [];

	private _state: VideoDecoder['state'] = 'unconfigured';
	/**
	 * The current state of the decode.
	 */
	get state() {
		return this._state;
	}

	/**
	 * The number of pending decode operations.
	 */
	get decodeQueueSize() {
		return this._decodeQueueSize;
	}

	/**
	 * Event handler called when a decode operation completes and leaves the queue.
	 */
	ondequeue: ((this: VideoDecoder, ev: Event) => unknown) | null = null;

	/**
	 * Creates a new VideoDecoder.
	 */
	constructor(init: VideoDecoderInit) {
		super();

		if (!init.output || !init.error) {
			throw new TypeError('VideoDecoderInit requires \'output\' and \'error\' callbacks.');
		}

		this.init = init;
		this.frame = new Frame();
		this.frame.alloc();
		this.packet = new Packet();
		this.packet.alloc();
	}

	private static createCodecContext(config: VideoDecoderConfig) {
		const inferred = inferCodecFromCodecString(config.codec);
		if (!inferred) {
			return null;
		}

		let codec: Codec | null;
		if (inferred === AV_CODEC_ID_AV1 || config.hardwareAcceleration !== 'prefer-hardware') {
			// https://github.com/opencv/opencv/issues/24430
			codec = Codec.findDecoder(inferred);