A first method of transcoding video data is disclosed that generates a motion vector for a macroblock encoded as a dual prime macro block that has a direct motion vector, and differential motion vector for its two fields respectively. A shadow control unit detects write operations to those regions designated for shadowing. The coated substrates are useful in polymer, catalysis, heating and shielding applications. The gastrointestinal device includes an anchor for anchoring the device to the stomach and a flexible sleeve to limit absorption of nutrients in the duodenum.