A method and an apparatus for encoding and decoding of digital image/video material

Abstract

The embodiments relate to a method comprising determining a coding mode of a transform block, wherein a transform block comprises a set of transform coefficients; determining a shape of the transform block; determining at least one transform mode for a block based at least partly on said coding mode and said shape of the transform block; applying the determined transform mode to a set of transform coefficients to produce sample values; and adding said sample values to a block of predicted sample values. The embodiments also relate to technical equipment for implementing the method.

1 - 15 . (canceled) 
     
     
         16 . A method, comprising:
 determining a coding mode of a transform block, wherein a transform block comprises a set of transform coefficients;   determining a scan order for the set of transform coefficients;   determining a position of the last non-zero coefficient of the transform block in a selected scan order;   determining a transform mode based on a bitstream signaling, wherein the bitstream signaling is conditioned to the position of the last non-zero coefficient of the transform block in the selected scan order;   applying the determined transform mode to the set of transform coefficients to produce residual sample values.   
     
     
         17 . The method according to  claim 16 , wherein the determined transform mode specifies which transform is applied in a horizontal direction and which transform is applied in a vertical direction. 
     
     
         18 . The method according to  claim 16 , wherein the bitstream signaling of the transform mode is performed when a scan position of the last non-zero transform coefficient is larger than a predefined threshold. 
     
     
         19 . The method according to  claim 16 , wherein the bitstream signaling of the transform mode is performed before encoding or decoding of the set of transform coefficients. 
     
     
         20 . The method according to  claim 19 , wherein encoding or decoding of the set of transform coefficients is performed at least partially based on the signaled transform mode. 
     
     
         21 . The method according to  claim 16 , wherein the transform mode comprises a discrete cosine transforms (DCT) or a discrete sine transforms (DST). 
     
     
         22 . The method according to  claim 16 , wherein determining a the transform mode comprises comparing the width and the height of the transform block. 
     
     
         23 . An apparatus comprising:
 at least one processor; and   at least one non-transitory memory including computer program code; the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to perform:   determine a coding mode of a transform block, wherein a transform block comprises a set of transform coefficients;   determine a scan order for the set of transform coefficients;   determine a position of the last non-zero coefficient of the transform block in a selected scan order;   determine a transform mode based on bitstream signaling, wherein the bitstream signaling is conditioned to the position of the last non-zero coefficient of the transform block in the selected scan order; and   apply the determined transform mode to the set of transform coefficients to produce residual sample values.   
     
     
         24 . The apparatus according to  claim 23 , wherein the determined transform mode specifies which transform is applied in a horizontal direction and which transform is applied in a vertical direction. 
     
     
         25 . The apparatus according to  claim 23 , wherein the bitstream signaling of the transform mode is performed if the scan position of the last non-zero transform coefficient is larger than a predefined threshold. 
     
     
         26 . The apparatus according to  claim 23 , wherein the bitstream signaling of the transform mode is performed before encoding or decoding of the transform coefficients. 
     
     
         27 . The apparatus according to  claim 26 , wherein the apparatus is further caused to perform: encode or decode of the set of transform coefficients at least partially based on the signaled transform mode. 
     
     
         28 . The apparatus according to  claim 23 , wherein the transform mode comprises a discrete cosine transforms (DCT) or a discrete sine transforms (DST). 
     
     
         29 . The apparatus according to  claim 23 , wherein the apparatus further caused to perform: determine a transform mode based on comparing the width and the height of the transform block. 
     
     
         30 . A non-transitory computer readable medium comprising program instructions stored thereon for performing at least the following:
 determining a coding mode of a transform block, wherein a transform block comprises a set of transform coefficients;   determining a scan order for the set of transform coefficients;   determining a position of the last non-zero coefficient of the transform block in selected scan order;   determining a transform mode based on a bitstream signaling, wherein the bitstream signaling is conditioned to the position of the last non-zero coefficient of the transform block in the selected scan order; and   applying the determined transform mode to the set of transform coefficients to produce residual sample values.   
     
     
         31 . The non-transitory computer readable medium according to  claim 30 , wherein the determined transform mode specifies which transform is applied in a horizontal direction and which transform is applied in a vertical direction. 
     
     
         32 . The non-transitory computer readable medium according to  claim 30 , wherein the bitstream signaling of transform mode is performed if the scan position of the last non-zero transform coefficient is larger than a predefined threshold. 
     
     
         33 . The non-transitory computer readable medium according to  claim 30 , wherein the bitstream signaling of the transform mode is performed before encoding or decoding of the transform coefficients. 
     
     
         34 . The non-transitory computer readable medium according to  claim 33 , wherein encoding or decoding of the set of transform coefficients is performed at least partially based on the signaled transform mode. 
     
     
         35 . The non-transitory computer readable medium according to the  claim 30 , wherein the computer program product further caused to perform: determining a transform mode based on comparing the width and the height of the transform block.