Video encoding method and apparatus and video decoding method and apparatus

A video encoding method of performing a motion compensated prediction interframe encoding on a video macroblock of a video frame, the method comprising:

• generating a motion vector candidate between the video macroblock and a first reference frame;
• extracting a first reference macroblock corresponding to the motion vector candidate from the first reference frame;
• scaling the motion vector candidate according to a distance between the video frame and at least one second reference frame to generate a scaled motion vector candidate;
• extracting at least one second reference macroblock corresponding to the scaled motion vector candidate from the second reference frame;
• computing a linear sum of the first reference macroblock and the second reference macroblock using weighting factors to generate a predictive macroblock;
• generating a prediction error signal between the predictive macroblock and the video macroblock;
• determining a motion vector based on a magnitude of the prediction error signal;
• and
• encoding the prediction error signal, a first index indicating the first reference frame and the second reference frame, a second index indicating the weighting factors and the motion vector determined.

A video decoding method of performing a motion compensated prediction interframe decoding on an encoded video macroblock, using a plurality of reference frames and a motion vector between the encoded macroblock and at least one reference frame, the method comprising:

• decoding encoded data including a prediction error signal for the encoded video macroblock, a first index indicating a plurality of reference frames, a second index indicating weighting factors used in a linear sum of a plurality of reference macroblocks and the motion vector;
• extracting a plurality of reference macroblocks from the plurality of reference frames according to the decoded motion vector and the decoded first index;
• computing the linear sum of the plurality of reference macroblocks extracted, using the weighting factors indicated by the decoded second index, to generate a predictive macroblock;
• and
• adding the predictive macroblock and the prediction error signal every encoded video macroblock to reconstruct a video picture.

A video decoding method of performing a motion compensated prediction interframe decoding on an encoded video macroblock of an encoded video frame, using a plurality of reference frames and a motion vector between the encoded video macroblock and at least one of the reference frames, the method comprising:

• decoding encoded data including a prediction error signal for the encoded video macroblock, a first index indicating the plurality of reference frames, a second index indicating the number of the encoded video frame, and the motion vector;
• extracting a plurality of reference macroblocks from the plurality of reference frames according to the decoded motion vector and the decoded first index;
• computing a distance between the plurality of reference frames and the encoded video frame according to the decoded second index;
• computing a linear sum of the reference macroblocks, using weighting factors determined according to the calculated distance, to generate a predictive macroblock;
• and
• adding the predictive macroblock and the prediction error signal every encoded video macroblock to reconstruct a video picture.

A video decoding method of performing a motion compensated prediction interframe decoding on an encoded video macroblock of an encoded video frame, using at least one past reference frame and a motion vector between the encoded video macroblock and the past reference frame, the method comprising:

• decoding encoded data including a prediction error signal for the encoded video macroblock, and a first encoded motion vector or a flag indicating a second motion vector of an encoded macroblock of an encoded video frame immediately before the encoded video frame, the encoded macroblock corresponding in position to the video macroblock;
• generating a predictive macroblock using the decoded first motion vector or the second motion vector;
• and
• adding the predictive macroblock and the decoded prediction error signal to decode the video signal.

A video encoding method of performing a motion compensated prediction interframe encoding on a video macroblock, the method comprising:

• selecting at least one reference frame from a plurality of reference frames;
• generating a motion vector between the video macroblock and the selected reference frame;
• skipping the motion compensated prediction interframe encoding with respect to the video macroblock that all prediction error signals to be encoded in the motion compensated prediction interframe encoding are zero, when the motion vector coincides with a prediction vector selected from a plurality of motion vectors obtained with respect to a plurality of macroblocks adjacent to the video macroblock, and at least one reference frame selected with respect to the video macroblock coincides with a reference frame corresponding to the selected prediction vector;
• and
• encoding the number of skipped macroblocks when a next video macroblock is subjected to the motion compensated prediction interframe encoding.

A video encoding method of performing a motion compensated prediction interframe encoding on a video macroblock of a video frame, using at least one first reference frame from a plurality of reference frames and a motion vector between the video macroblock and the first reference frame, the method comprising:

• encoding a prediction error signal obtained by the motion compensated prediction interframe encoding;
• encoding a difference vector between a motion vector used for the motion compensated prediction interframe encoding and a prediction vector selected from a plurality of motion vectors between a plurality of macroblocks adjacent to the video macroblock and a second reference frame;
• and
• encoding a differential value between an index indicating the first reference frame and an index indicating the second reference frame.

A video decoding method of performing a motion compensated prediction interframe decoding on an encoded video macroblock of an encoded video frame, using at least one reference frame selected from a plurality of reference frames and a motion vector between the encoded video macroblock and the selected reference frame, the method comprising:

• decoding coded data including a prediction error signal for the encoded video macroblock generated by a motion compensated prediction interframe encoding, the number of macroblocks skipped immediately before the encoded video macroblock, and an index indicating at least one selected reference frame;
• selecting a prediction vector from a plurality of motion vectors corresponding to a plurality of macroblocks adjacent to the skipped macroblock;
• generating a predictive macroblock according to at least one reference frame for a macroblock corresponding to the selected prediction vector and the prediction vector;
• and
• outputting the predictive macroblock as a decoded picture signal of the skipped macroblock.

A video decoding method of performing a motion compensated prediction interframe decoding on an encoded video macroblock of an encoded video frame, using a motion vector between the encoded video macroblock and at least one first reference frame selected from a plurality of reference frames, the method comprising:

• decoding encoded data including a prediction error signal generated by the motion compensated prediction interframe decoding, a differential vector between the motion vector and a prediction vector selected from a plurality of motion vectors between a plurality of macroblocks adjacent to the encoded video macroblock and a second reference frame, and a differential value between a first index indicating the first reference frame and a second index indicating the second reference frame;
• selecting the prediction vector from the motion vectors corresponding to the plurality of macroblocks;
• adding the selected prediction vector and the decoded differential vector to reproduce the motion vector;
• adding the decoded differential value and an index of a reference frame including a macroblock corresponding to the selected prediction vector to reproduce the first index;
• generating a predictive macroblock according to the reproduced motion vector and the reproduced first index;
• and
• adding the prediction error signal and the generated predictive macroblock to generate a decoded reproduction picture signal of the encoded video macroblock.

A video encoding method of performing a motion compensated prediction interframe encoding on a video macroblock of a video frame, using a plurality of reference frames and a motion vector between the video macroblock and at least one reference frame, the method comprising:

• determining at least one weighting factor from a ratio between an A.C. component value of the video frame and an A.C. component value of the reference frame;
• determining at least one DC offset value from a difference between a DC component value of the video frame and a DC component value of the reference frame;
• computing a linear sum of a plurality of reference blocks extracted from the reference frame using weighting factors;
• adding this linear sum and the DC offset value to generate a prediction block;
• generating a prediction error signal between the prediction block and the video block;
• and
• encoding information items indicating the prediction error signal, the reference frame, the weighting factor, the DC offset value and the motion vector.

A video decoding method of performing a motion compensated prediction interframe decoding on an encoded video block of a video encoded frame, using a plurality of reference frames and a motion vector between the encoded video block and at least one reference frame, the method comprising:

• decoding encoded data including information items indicating a prediction error signal between a prediction block and the encoded video block, the reference frame, weighting factors, a DC offset value and the motion vector, respectively;
• computing a linear sum of the plurality of reference blocks extracted from the reference frame, using the weighting factor;
• adding the DC offset value to the linear sum to generate the prediction block;
• and
• generating a reproduction video signal by means of the prediction error signal and the prediction block.