1. A Context-based Adaptive Binary Arithmetic Coding (CABAC) decoding apparatus, comprising: an initialization module for initializing a plurality of context variables; a storage module coupled to said initialization module for storing the context variables; an arithmetic decoding module coupled to said storage module for performing arithmetic decoding of a syntax element according to the context variables, so as to output a decoded syntax element and an update signal; and an update module coupled to said arithmetic decoding module and said storage module for updating at least one of the context variables in said storage module according to the update signal received from said arithmetic decoding module; wherein said initialization module pre-initializes at least one of the context variables before a bit stream ready.