Abstract: An MPEG digital video decoder system, method and computer program product are presented for monitoring decoding of an encoded digital video signal for one or more predefined illegal conditions. Error detection logic is coupled to the variable length (VLC) decoder, inverse quantizer (IQ), inverse discrete cosine transformer (IDCT) and motion compensator (MC) of the decoder for detecting an illegal condition within at least one of the VLC decoder, IQ, IDCT and MC during decoding of the encoded digital video signal. The monitored illegal conditions can include a VLC/IQ control error, an IQ level overrun, and IQ/IDCT buffer error, an MC idle error and an MC macroblock start error. Error signals are reported to a central error register which is monitored periodically by the decoder's control processor. The control processor initiates recovery within the decoder system prior to stoppage of the system due to the illegal condition.

Abstract: A method of and apparatus for identifying a Dual Prime motion estimation best match and generating motion vectors pertaining thereto for inter-picture video compression in a motion picture having images of F.sub.1 and F.sub.2 parities. The Dual Prime method of motion estimation described herein includes a method of generating motion vectors. The motion vectors point from a macroblock in a current field to a macroblock in a past field for inter-picture video compression in a motion picture having images of F.sub.1 and F.sub.2 parities. The first step in the method is defining a macroblock in a parity field of the current picture. Next, the preceding field of the same or opposite parity is searched to find a first best match macroblock in the preceding field. Once a best match macroblock is found, a vector is formed from the current macroblock in the current parity field to the first best match macroblock in the preceding parity field.

Abstract: Disclosed is a method of forming a bidirectionally coded picture, i.e., a B frame, from two reference pictures, e.g. I or P frame pictures. The method utilizes a single memory fetch of each reference picture, and interpolation of the estimated motion of each picture. This is accomplished by identifying a full pixel closest match from three full pixel boundary searches, calculating half pixel reference picture data therefrom, interpolating the half pixels to form bidirectionally coded pictures, and finding the closest match at the half pixel boundary. The intermediate results are stored in an 18.times.18.times.11 bit buffer holding a 7 bit partial sum for each pixel, said partial sum formed by adding the six most significant bits of corresponding I and P frame pixels. In this buffer four bits of each word in the buffer are the two Least Significant Bits of the corresponding I and P frame pixels.