A method and apparatus for coding video information are disclosed. In one example, the method may involve: identifying one or more prediction modes for a fixed-rate codec, each prediction mode having a rate-distortion cost; and selecting, for a current block, a prediction mode that has the lowest rate-distortion cost from among the one more prediction modes not previously selected. The method may involve: (i) determining whether the selected prediction mode would result in overflow or underflow of a buffer of the fixed-rate codec; and (ii) determining whether the selected prediction mode would result in remaining bits in the slice being insufficient to code remaining blocks of the slice. The method may involve utilizing a fallback mode to code the current block in response to each of the selected one or more prediction modes resulting in at least one of conditions (i) and (ii) being true.