Patent ID: 6920175

Claim:
A decoder for decoding encoded data wherein identical frames may be obtained even when they are predicted using different reference frames, said decoder comprising: means for forming a prediction block P of a current block of data I using a plurality of motion vectors and a reference frame; means for calculating a plurality of transform coefficients c.sub.pred for said prediction block; means for calculating a plurality of quantized reconstruction coefficients I.sub.rec for said current block of data, wherein I.sub.rec=(c.sub.pred.times.A(QP 1 )+I.sub.err.times.F(QP 1 ,QP 2 )+f.times.2.sup.20)//2.sup.20 where F(QP 1 ,QP 2 )=(2.sup.20.times.A(QP 1 )+0.5.times.A(QP 2 ))//A(QP 2 ); means for dequantizing said plurality of quantized reconstruction image coefficients, creating a plurality of dequantized coefficients d.sub.rec; and means for inverse transforming said plurality of dequantized coefficients.