Method and apparatus for compensating errors in a transmitted video signal

Claim 1

The A method, for use in a video signal decoding system, for concealing errors in a video signal transmitted in a compressed form, wherein the video signal includes a reconstructed current frame restored based on motion vectors for a current frame and a reconstructed preceding frame, each of the frames being divided into a multiplicity of blocks each of which has N×M pixel values with N and M being positive integers, the method comprising the steps of: (a) detecting a lost block containing errors; (b) providing pixel values of neighboring blocks of the lost block in the reconstructed current frame and motion vectors corresponding thereto; (c) generating a compensation block based on the motion vectors for the neighboring blocks; and (d) providing the compensation block as a substitution block for concealing the lost block; wherein the step (c) includes the steps of: (c1) calculating a mean vector by using the motion vectors for the neighboring blocks and determining a motion variance between the mean vector and each of the motion vectors for the neighboring blocks; (c2) comparing the motion variance with a first and a second predetermined threshold value; and (c3) if the motion variance is smaller than the first predetermined threshold value, producing the compensation block by using a block at a position corresponding to the mean vector of the motion vectors for the neighboring blocks within the reconstructed preceding frame; and wherein the motion variance is determined as: ##EQU5## wherein σ D 2 represents an amplitude variance of the motion vectors for the neighboring blocks; D MVk represents an amplitude of a motion vector corresponding to the kth neighboring block; D MV is a mean value of the amplitudes for the motion vectors for the neighboring blocks; σ.sub.θ 2 represents a direction variance of the motion vectors for the neighboring blocks; θ MVk represents a directional value of a motion vector corresponding to the kth neighboring block; θ MV is a mean value of the directional values of the motion vectors for the neighboring blocks; σ T 2 represents the motion variance of the motion vectors for the neighboring blocks; and P is a positive integer representing the number of the neighboring blocks.

Claim 3

A method, for use in a video signal decoding system, for concealing errors in a video signal transmitted in a compressed form, wherein the video signal includes a reconstructed current frame restored based on motion vectors for a current frame and a reconstructed preceding frame, each of the frames being divided into a multiplicity of blocks each of which has N×M pixel values with N and M being positive integers, the method comprising the steps of: (a) detecting a lost block containing errors; (b) providing pixel values of neighboring blocks of the lost block in the reconstructed current frame and motion vectors corresponding thereto; (c) generating a compensation block based on the motion vectors for the neighboring blocks; and (d) providing the compensation block as a substitution block for concealing the lost block; wherein the step (c) includes the steps of: (c1) calculating a mean vector by using the motion vectors for the neighboring blocks and determining a motion variance between the mean vector and each of the motion vectors for the neighboring blocks; (c2) comparing the motion variance with a first and a second predetermined threshold value; and (c3) if the motion variance is smaller than the first predetermined threshold value, producing the compensation block by using a block at a position corresponding to the mean vector of the motion vectors for the neighboring blocks within the reconstructed preceding frame; and wherein the motion variance is determined as: ##EQU6## wherein σ x 2 represents an x coordinate variance of the motion vectors for the neighboring blocks; x k represents an x coordinate value of a motion vector corresponding to the kth neighboring block; x is a mean value of the x coordinate values of the motion vectors for the neighboring blocks; σ y 2 represents a y coordinate variance of the motion vectors for the neighboring blocks; y k represents a y coordinate value of a motion vector corresponding to the kth neighboring block; y is a mean value of the y coordinate values of the motion vectors for the neighboring blocks; σ T 2 represents the motion variance of the motion vectors for the neighboring blocks; and P is a positive integer representing the number of the neighboring blocks.

Claim 4

A method, for use in a video signal decoding system, for concealing errors in a video signal transmitted in a compressed form, wherein the video signal includes a reconstructed current frame restored based on motion vectors for a current frame and a reconstructed preceding frame, each of the frames being divided into a multiplicity of blocks each of which has N×M pixel values with N and M being positive integers, the method comprising the steps of: (a) detecting a lost block containing errors; (b) providing pixel values of neighboring blocks of the lost block in the reconstructed current frame and motion vectors corresponding thereto; (c) generating a compensation block based on the motion vectors for the neighboring blocks; and (d) providing the compensation block as a substitution block for concealing the lost block; wherein the step (c) includes the steps of: (c1) calculating a mean vector by using the motion vectors for the neighboring blocks and determining a motion variance between the mean vector and each of the motion vectors for the neighboring blocks; (c2) comparing the motion variance with a first and a second predetermined threshold value; and (c3) if the motion variance is smaller than the first predetermined threshold value, producing the compensation block by using a block at a position corresponding to the mean vector of the motion vectors for the neighboring blocks within the reconstructed preceding frame; and wherein the motion variance is determined as: ##EQU6## wherein σ x 2 represents an x coordinate variance of the motion vectors for the neighboring blocks; x k represents an x coordinate value of a motion vector corresponding to the kth neighboring block; x is a mean value of the x coordinate values of the motion vectors for the neighboring blocks; σ y 2 represents a y coordinate variance of the motion vectors for the neighboring blocks; y k represents a y coordinate value of a motion vector corresponding to the kth neighboring block; y is a mean value of the y coordinate values of the motion vectors for the neighboring blocks; σ T 2 represents the motion variance of the motion vectors for the neighboring blocks; and P is a positive integer representing the number of the neighboring blocks.

Claim 8

An apparatus, for use in a video signal decoding system, for concealing errors in a video signal transmitted in a compressed form, wherein the video signal includes a reconstructed current frame restored based on motion vectors for a current frame and a reconstructed preceding frame, each of the frames being divided into a multiplicity of blocks each of which has N×M pixel values with N and M being positive integers, which comprises: means for detecting a lost block containing errors to thereby produce position data representing the position of the lost block in the video signal; means for providing pixel values of neighboring blocks of the lost block in the reconstructed current frame and motion vectors corresponding thereto based on the position data; means for calculating a mean vector by using the motion vectors for the neighboring blocks; means for producing a motion-based block based on the mean vector, the position data and pixel values of the reconstructed preceding frame; a block generation means for producing a spatially interpolated block based on the pixel values of the neighboring blocks; and a selection means for choosing either the motion-based block or the spatially interpolated block as a substitution block for correcting the lost block using the mean vector, wherein the block generation means contains: means for detecting, among the neighboring pixels in the upper, left, right and lower neighboring blocks and lying adjacent to the lost block, four neighboring pixels which are located on the same row or column as that of each pixel of the lost block; means for computing each pixel value in the spatially interpolated block by calculating a weighted sum of the four neighboring pixel values as: ##EQU10## wherein W h represents a weight factor; d h represents a distance between a pixel in the lost block and each of the pixels on the vertical and horizontal lines corresponding to the pixel in the lost block; S ij represents an ijth pixel value in the spatially interpolated block; U Nj , L iM , R i1 and D 1j represent Njth, iMth, ilst and ljth pixel values in the upper, left, right and lower neighboring blocks, respectively; h is from 1 to 4; i ranges from 1 to N; and j ranges from 1 to M.

Claim 9

An apparatus, for use in a video signal decoding system, for concealing errors in a video signal transmitted in a compressed form, wherein the video signal includes a reconstructed current frame restored based on motion vectors for a current frame and a reconstructed preceding frame, each of the frames being divided into a multiplicity of blocks each of which has N×M pixel values with N and M being positive integers, which comprises: means for detecting a lost block containing errors to thereby produce position data representing the position of the lost block in the video signal; means for providing pixel values of neighboring blocks of the lost block in the reconstructed current frame and motion vectors corresponding thereto based on the position data; means for calculating a mean vector by using the motion vectors for the neighboring blocks; means for producing a motion-based block based on the mean vector, the position data and pixel values of the reconstructed preceding frame; a block generation means for producing a spatially interpolated block based on the pixel values of the neighboring blocks; and a selection means for choosing either the motion-based block or the spatially interpolated block as a substitution block for correcting the lost block using the mean vector, wherein the block generation means contains: means for detecting, among the neighboring pixels in the upper, left, right and lower neighboring blocks and lying adjacent to the lost block, four neighboring pixels which are located on the same row or column as that of each pixel of the lost block; means for computing each pixel value in the spatially interpolated block by calculating a weighted sum of the four neighboring pixel values as: ##EQU10## wherein W h represents a weight factor; d h represents a distance between a pixel in the lost block and each of the pixels on the vertical and horizontal lines corresponding to the pixel in the lost block; S ij represents an ijth pixel value in the spatially interpolated block; U Nj , L iM , R i1 and D 1j represent Njth, iMth, ilst and ljth pixel values in the upper, left, right and lower neighboring blocks, respectively; h is from 1 to 4; i ranges from 1 to N; and j ranges from 1 to M.

Claim 19

An apparatus, for use in a video signal decoding system, for concealing errors in a video signal transmitted in a compressed form, wherein the video signal includes a reconstructed current frame restored based on motion vectors for a current frame and a reconstructed preceding frame, each of the frames being divided into a multiplicity of blocks each of which has N×M pixel values with N and M being positive integers, which comprises: means for detecting a lost block containing errors to thereby produce position data representing the position of the lost block in the video signal; means for providing pixel values of neighboring blocks of the lost block in the reconstructed current frame and motion vectors corresponding thereto based on the position data; means for calculating a mean vector by using the motion vectors for the neighboring blocks; means for producing a motion-based block substituting the lost block based on the mean vector, the position data and pixel values of the reconstructed preceding frame; a block generation means for producing a spatially interpolated block based on the pixel values of the neighboring blocks; means for calculating a first mean value of all pixel values of the motion-based block; means for ciphering a second mean value of all pixel values of the spatially interpolated block; means for computing a difference between the first and the second mean values by subtracting the first mean value from the second mean value; means for adding the difference to each of the pixel values of the motion-based block to thereby provide an error compensated block; and a selection means for choosing either the error compensated block or the spatially interpolated block as a substitution block for correcting the lost block based on the mean vector.

Claim 20

An apparatus, for use in a video signal decoding system, for concealing errors in a video signal transmitted in a compressed form, wherein the video signal includes a reconstructed current frame restored based on motion vectors for a current frame and a reconstructed preceding frame, each of the frames being divided into a multiplicity of blocks each of which has N×M pixel values with N and M being positive integers, which comprises: means for detecting a lost block containing errors to thereby produce position data representing the position of the lost block in the video signal; means for providing pixel values of neighboring blocks of the lost block in the reconstructed current frame and motion vectors corresponding thereto based on the position data; means for calculating a mean vector by using the motion vectors for the neighboring blocks; means for producing a motion-based block substituting the lost block based on the mean vector, the position data and pixel values of the reconstructed preceding frame; a block generation means for producing a spatially interpolated block based on the pixel values of the neighboring blocks; means for calculating a first mean value of all pixel values of the motion-based block; means for ciphering a second mean value of all pixel values of the spatially interpolated block; means for computing a difference between the first and the second mean values by subtracting the first mean value from the second mean value; means for adding the difference to each of the pixel values of the motion-based block to thereby provide an error compensated block; and a selection means for choosing either the error compensated block or the spatially interpolated block as a substitution block for correcting the lost block based on the mean vector.