Decoder and a method therof for improving decoding of image and video signals
AssigneeTelefonaktiebolaget LM Ericsson (publ)
InventorsAndrey Norkin, Kenneth Andersson, Clinton Priddle
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Abstract
A solution according to one or more embodiments of the present invention is to reconstruct image blocks where only the frequency coefficient that is most sensitive to changes of an average value of the residual image block, typically the lowest frequency coefficient, is present with a flat residual image. The other image blocks are reconstructed by applying an inverse spatial 2D transform. Hence, the other image blocks comprise image blocks with multiple coefficients and image blocks with a single coefficient and wherein the single coefficient is not the coefficient determining that is most sensitive to changes of an average value of the residual image block.
Claims12
A method in a decoder for decoding a bit stream representing a residual image block to be added to a predicted image block for obtaining a reconstructed image block, the method comprising:
- receiving the bit stream,
- entropy decoding the received bit stream to identify transform coefficients of different frequencies of a transform block, determining if the transform coefficients comprise a single non-zero coefficient of a lowest frequency that is most sensitive to changes of an average value of the residual image block,
- if the transform coefficients comprise said single non-zero coefficient, generating a residual block with a level depending on a value of the single non-zero coefficient, and
- otherwise if the transform coefficients do not comprise said single non-zero coefficient, generating a residual block by deploying an inverse of the spatial 2 dimension (2D) transform.
A decoder for decoding a bit stream representing a residual image block to be added to a predicted image block for obtaining a reconstructed image block, the decoder comprising:
- a receiving unit configured to receive the bit stream,
- an entropy decoder configured to entropy decode the received bit stream to identify transform coefficients of different frequencies of a transform block,
- a decision module configured to determine if the transform coefficients comprise a single non-zero coefficient of a lowest frequency that is most sensitive to changes of an average value of the residual image block,
- a generator configured to generate a residual block with a level depending on a value of the single non-zero coefficient if the transform coefficients comprise said single non-zero coefficient, and
- an inverse transformer configured to generate a residual block by deploying an inverse of the spatial 2 dimension (2D) transform if the transform coefficients do not comprise said single non-zero coefficient.
Dependencies are inferred from the claim text.