| 摘要 |
<p>PCT No. PCT/GB89/01483 Sec. 371 Date Jul. 23, 1991 Sec. 102(e) Date Jul. 23, 1991 PCT Filed Dec. 12, 1989 PCT Pub. No. WO90/07246 PCT Pub. Date Jun. 28, 1990.A predictive coder, e.g., a hybrid DCT interframe predictive video decoder, reduces the tendency of long-term bias error in the decoded difference signal to accumulate in a predictor (7) by periodically alternating the polarity of the bias error relative to the contents of the predictor. Inverse discrete cosine transform (IDCT) stage (6) in a receiver is bracketed by switchable invertors (9a,9b) which, when operating, invert the signal into IDCT stage (6) and then reinvert the signal, plus error, out of IDCT stage (6), thereby inverting the error relative to the difference signal. Control means (10), e.g., a pseudo-random number generator, switches the invertors (9a,9b) in and out periodically such that, over several frames, each block spends an equal amount of time in "normal" and "inverted" modes.</p> |
