Method and Apparatus for Processing an Audio Signal

A method of processing an audio signal, comprising the steps of:

• extracting an ancillary signal for generating the audio signal, an extension signal included in the ancillary signal, and header identification information indicating whether a header is included in the ancillary signal from a received bit stream;
• if the header is not included in the ancillary signal according to the header identification information, skipping decoding of the extension signal or not using a result of the decoding based on previously extracted length information for the header;
• and
• generating the audio signal using the ancillary signal.

An apparatus for processing an audio signal, comprising:

• a signal extracting unit extracting an ancillary signal for generating the audio signal, an extension signal included in the ancillary signal, and header identification information indicating whether a header is included in the ancillary signal from a received bit stream;
• an extension signal length reading unit reading length information of the extension signal from the header if the header is included in the ancillary signal according to the header identification information;
• a selective decoding unit skipping decoding of the extension signal or not using a result of the decoding based on the length information;
• and
• an upmixing unit generating the audio signal using the ancillary signal.