Appeal No. 1999-2018
Application 08/571,204
(2) Option 2 (Mode 2), forward predictive mode; (3) Option 3
(Mode 3), backward predictive mode; (4) Option 4 (Mode 4),
intra mode.
The prediction error in the bidirectionally predictive
mode is based on the "distance" in terms of the normalized
number of frames from a B-picture to a preceding (past) or
succeeding (future) reference frame. The preceding and
succeeding reference frames are a fixed number of frames N
apart. The predicted frame signal X is formed as a weighed
sum of the "preceding independent frame signal" and the
"succeeding independent frame signal." The forward
weighting value is W=(mc-mp)/N, where mc-mp is the
difference between the current frame number mc and the
preceding independent frame number mp (col. 11, lines 1-6).
The backward weighting value is 1-W, which is the same as
the difference between the current frame number and the
succeeding independent frame number divided by N when the
distance between preceding and succeeding independent frame
numbers is N. The "distance" in terms of number of frames
is only used for the bidirectionally predictive mode.
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