Provided is a signal processing method for processing a bitstream, an information storage medium including the bitstream, an encoding apparatus, and a decoding apparatus. The signal processing method includes: receiving a bitstream including additional information; extracting first information which is information associated with extraction of the additional information and is included in at least one of additional bitstream information, a skip field, and auxiliary data bits, which are included in the bitstream; and extracting and decoding the additional information by using the first information.