Deblocking Filter Mode
This mode is used to remove blocking effects from the 8×8 block edges. This smoothing of block boundaries allows for better prediction. This mode also permits the use of four motion vectors per macroblock and motion vectors that point beyond the edge of the picture
Reference Picture Selection Mode
This mode is used to prevent error propagation by allowing the algorithm to use a picture other than the previous picture to perform prediction. The mode permits the use of a back channel that the decoder uses to inform the encoder about the correct decoding of parts of the picture. If a part of the picture is not correctly decoded, it is not used for prediction. Instead, an alternate frame is selected as the reference frame. The information about which frame was selected as the reference frame is transmitted to the decoder. The number of possible reference frames is limited by the amount of frame memory available