the p picture and the prediction pixelblock is then coded for transmission each motion vector may also be transmitted via predictive coding for example a motion vector prediction may be formed using nearby motion vectors in such a case then the difference between the actual motion vector and the motion vector prediction is coded for transmission each b pixelblock uses two motion vectors a first motion vector referencing the aforementioned previous video picture and a second motion vector referencing the future video picture from these two motion vectors two prediction pixelblocks are computed the two predicted pixelblocks are then combined together using some function to form a final predicted pixelblock as above the difference between the actual pixelblock in the b frame picture and the final predicted pixelblock is then encoded for transmission as with p pixelblocks each motion vector mv of a b pixelblock may be transmitted via predictive coding specifically a predicted motion vector is formed using nearby motion vectors then the difference between the actual motion vector and the predicted is coded for transmission however with b pixelblocks the opportunity exists for interpolating motion vectors from motion vectors in the nearest stored picture pixelblock such motion vector interpolation is carried.