A method for interpolating missing samples from existing samples of a composite sampled image or video data, the composite sampled image or video data being formed by combining together two or more sub-sampled images or video data pertaining to one of a plurality of image or video categories in a first block by means of multiplexing, the method comprising: - sampling the composite sampled image or video data to extract one of the two or more sub-sampled images or video data from the composite sampled image or video data, wherein a first set of samples corresponding to the samples of the extracted one of the sub-sampled images or video data is retained, the first set of samples being referred to as the existing samples; - storing the existing samples in an initial block of existing samples of the same category, the initial block comprising half the number of rows in the first block and half the number of columns in the first block; and - applying a transform to the samples of the initial block; characterised in that the method further comprises: - using transform coefficients of the initial block to estimate transform coefficients of a double-sized block, the double-sized block comprising twice the number of rows in the initial block and twice the number of columns in the initial block, and the double-sized block containing the same existing samples of the initial block and the missing samples of the same category of the existing samples, wherein the estimated transform coefficients are to be applied for both the existing samples and the missing samples of the same category of the existing samples; - adjusting the estimated transform coefficients of the double-sized block, in one case the estimated transform coefficients of the double-sized block being adjusted by setting each of the estimated transform coefficients to zero if the estimated transform coefficient is below a corresponding threshold; and - applying an inverse transform to the samples of the double-sized block in order to yield estimates for both the existing samples and the missing samples of the same category of the existing samples, thereby de-multiplexing and upsampling the two or more sub-sampled images to full resolution; wherein the method is performed for shifted overlapping initial blocks such that a different estimate is yielded for each missing sample, and wherein the different estimates are combined in a linear or non-linear manner to yield a final estimate for each missing sample. - sampling the composite sampled image or video data to extract one of the two or more sub-sampled images or video data from the composite sampled image or video data, wherein a first set of samples corresponding to the samples of the extracted one of the sub-sampled images or video data is retained, the first set of samples being referred to as the existing samples; - storing the existing samples in an initial block of existing samples of the same category, the initial block comprising half the number of rows in the first block and half the number of columns in the first block; and - applying a transform to the samples of the initial block; - using transform coefficients of the initial block to estimate transform coefficients of a double-sized block, the double-sized block comprising twice the number of rows in the initial block and twice the number of columns in the initial block, and the double-sized block containing the same existing samples of the initial block and the missing samples of the same category of the existing samples, wherein the estimated transform coefficients are to be applied for both the existing samples and the missing samples of the same category of the existing samples; - adjusting the estimated transform coefficients of the double-sized block, in one case the estimated transform coefficients of the double-sized block being adjusted by setting each of the estimated transform coefficients to zero if the estimated transform coefficient is below a corresponding threshold; and - applying an inverse transform to the samples of the double-sized block in order to yield estimates for both the existing samples and the missing samples of the same category of the existing samples, thereby de-multiplexing and upsampling the two or more sub-sampled images to full resolution;