Method and apparatus for processing/transmitting bit stream, and method and apparatus for receiving/processing bit stream

The present invention relates to a method and apparatus for scalable encoding / decoding of audio data, such as the BSAC (Bit Sliced ​​Arithmetic Coding), the payload of the audio data and the extended data, and relocating grouped according to their importance, and some of these discard the group, it can preferentially transmit the expansion data to play a more important role than the upper layers of the audio data to the original sound reproduced by transmitting the rest of the group.