public int checkID3V2(byte[] b, int off) {
		if (b.length - off < 10)
			return 0;
		if (b[off] != 'I' || b[off + 1] != 'D' || b[off + 2] != '3')
			return 0;

		version = b[off + 3] & 0xff;

		if (version > 2 && (b[off + 5] & 0x40) != 0)
			exheaderSize = 1; // 设置为1表示有扩展头

		haveID3v2Footer = (b[off + 5] & 0x10) != 0;
		int size = synchSafeInt(b, off + 6);
		size += 10; // ID3 header:10-byte
		return size;
	}