Function transformAnnexBToLengthPrefixed

src/codec_data.ts:951–982

(packetData: Uint8Array)

/** Converts an AVC packet in Annex B format to length-prefixed format. */
export const transformAnnexBToLengthPrefixed = (packetData: Uint8Array) => {
	const NAL_UNIT_LENGTH_SIZE = 4;

	const nalUnits = findNalUnitsInAnnexB(packetData);

	if (nalUnits.length === 0) {
		// If no NAL units were found, it's not valid Annex B data
		return null;
	}

	let totalSize = 0;
	for (const nalUnit of nalUnits) {
		totalSize += NAL_UNIT_LENGTH_SIZE + nalUnit.byteLength;
	}

	const avccData = new Uint8Array(totalSize);
	const dataView = new DataView(avccData.buffer);
	let offset = 0;

	// Write each NAL unit with its length prefix
	for (const nalUnit of nalUnits) {
		const length = nalUnit.byteLength;

		dataView.setUint32(offset, length, false);
		offset += 4;

		avccData.set(nalUnit, offset);
		offset += nalUnit.byteLength;
	}

	return avccData;
};

// https://en.wikipedia.org/wiki/VP9
export const VP9_LEVEL_TABLE = [