Simplified rule set for deriving motion field
{"Image DocumentName": "Simplified rule set for deriving motion field", "Image ImageDescription": "Macroblocks with no motion vector have the same movement as in the previous image. This is required since there is a small percentage of intra-coded blocks in B- and P-frames that would otherwise have unknown motion. Also, I-frames have no motion at all so this rule will provide a smooth motion field for them. The justification for this is step is that consecutive images are strongly correlated therefore there is a high probability that the motion field has not changed much. When a macroblock has two motion vectors, the one pointing back is reversed and added to the one pointing forward. This step accomplishes both noise reduction (due to the averaging effect) and normalizes vector magnitude (so they span three images in B-frames which is what happens in P-frames). Motion vector magnitude is normalized. If a macroblock in a B-frame only has one motion vector then it has to be multiplied by a factor so its magnitude corresponds to a vector spanning three images. Skipped macroblocks in I-frames have no movement, while in P-frames, they have movement similar to the previous block. This is a rule obtained directly from the MPEG-2 standard.", "Image XResolution": "37", "Image YResolution": "37", "Image ResolutionUnit": "Pixels/Centimeter", "Image Software": "SlidePlayer", "Image YCbCrPositioning": "Centered"}