In this paper, we present a joint source-channel decoding technique based on exact MAP estimation for data encoded by CABAC (Context-based Adaptive Binary Arithmetic Coding) in standards like H.264/AVC. Soft decoding is put at work using an improved sequential decoding technique, achieving a trade-off between complexity and efficiency of the proposed algorithms. Error detection is realized by exploiting the binarization scheme and redundancy left in the code string, so that CABAC compression efficiency is preserved and no additional redundancy is compulsory.