Function extractAv1CodecInfoFromPacket

src/codec_data.ts:1259–1475

(
	packet: Uint8Array,
)

 * into the AV1 bitstream.
 */
export const extractAv1CodecInfoFromPacket = (
	packet: Uint8Array,
): Av1CodecInfo | null => {
	// https://aomediacodec.github.io/av1-spec/av1-spec.pdf

	for (const { type, data } of iterateAv1PacketObus(packet)) {
		if (type !== 1) {
			continue; // 1 == OBU_SEQUENCE_HEADER
		}

		const bitstream = new Bitstream(data);

		// Read sequence header fields
		const seqProfile = bitstream.readBits(3);

		// eslint-disable-next-line @typescript-eslint/no-unused-vars
		const stillPicture = bitstream.readBits(1);

		const reducedStillPictureHeader = bitstream.readBits(1);

		let seqLevel = 0;
		let seqTier = 0;
		let bufferDelayLengthMinus1 = 0;

		if (reducedStillPictureHeader) {
			seqLevel = bitstream.readBits(5);
		} else {
			// Parse timing_info_present_flag
			const timingInfoPresentFlag = bitstream.readBits(1);

			if (timingInfoPresentFlag) {
				// Skip timing info (num_units_in_display_tick, time_scale, equal_picture_interval)
				bitstream.skipBits(32); // num_units_in_display_tick
				bitstream.skipBits(32); // time_scale
				const equalPictureInterval = bitstream.readBits(1);

				if (equalPictureInterval) {
					// Skip num_ticks_per_picture_minus_1 (uvlc)
					// Since this is variable length, we'd need to implement uvlc reading
					// For now, we'll return null as this is rare
					return null;
				}
			}

			// Parse decoder_model_info_present_flag
			const decoderModelInfoPresentFlag = bitstream.readBits(1);

			if (decoderModelInfoPresentFlag) {
				// Store buffer_delay_length_minus_1 instead of just skipping
				bufferDelayLengthMinus1 = bitstream.readBits(5);
				bitstream.skipBits(32); // num_units_in_decoding_tick
				bitstream.skipBits(5); // buffer_removal_time_length_minus_1
				bitstream.skipBits(5); // frame_presentation_time_length_minus_1
			}

			// Parse operating_points_cnt_minus_1
			const operatingPointsCntMinus1 = bitstream.readBits(5);