Appeal No. 2002-1961
Application No. 09/133,430 Page 10
difference signal output from subtracting circuit 104 and a
signal similar to the difference signal is supplied to adding
circuit 117. The difference signal is produced by subtracting
the predictive video signal produced by 121 from the signal
output from block dividing circuit 103 (col. 5, lines 25-34).
As shown in figure 2, a high level for the control signal
causes a refresh operation. When the control signal is at a low
level, the device executes a normal operation (col. 6, lines 1-
9). The refresh period returns to an initial position every
frame (col. 6, lines 31 and 32). Control circuit 107 outputs the
refresh control signal (col. 6, line 33). As shown in the second
frame of figure 4, the refresh area (where intra-frame encoding
is performed) is shifted by the distance S. The refresh area is
shifted every "n" frame (col. 7, lines 3-15).
We find from the disclosure of Owada that the subtracting
circuit 104 calculates difference values between the predictive
signal output from the motion compensating circuit and the signal
of the present frame processed through the block dividing
circuit. We additionally find that when switching circuits 118
and 105 are connected to terminal (a), intra-frame encoding is
being executed, i.e., the signal of the present frame is encoded
and decoded without the above-mentioned subtraction. Thus, we
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