a method of error concealment or correction , suitable for signals such as speech , image and video signals , and particularly for such signals as transmitted over wireless and atm channels . the method has improved stability for large block sizes and bunched errors . it is based on a modification of the discrete fourier transform which is equivalent to a permutation of the fourier coefficients . thus , as with the conventional fourier transform , setting a contiguous set of coefficients equal to zero in the transmitted signal enables error concealment techniques to be used at the receiver . however , with the modified transform , the zeroes are not bunched together in the spectrum , so the instability problems that arise when the conventional fourier transform is used are mollified , and much larger block sizes can be used .