DCT mode conversions for field/frame coded MPEG video

Several compressed-domain based processing methods such as video downscaling, filtering, inverse motion compensation, etc. have been developed for MPEG compressed digital video. These processing methods assume that the underlying MPEG video was coded in only one mode, namely, frame or field mode. In order to support both frame and field-mode coded video, in this paper, we present a fast algorithm for converting a sequence of DCT blocks in the field mode to a sequence of blocks whose DCT's represent frame-mode coding. A multiplier-free implementation for this algorithm is also developed in this paper. In a typical coding setup, used in MPEG-2, simulations indicate that the image quality degradations resulting from the multiplier-free implementation is around 0.5-1.0 dB; however, a factor of two speedup is obtained compared with a traditional spatial-domain approach.