Method of Intra Block Copy Search and Compensation Range

Abstract

A method of IntraBC coding using restricted reference area is disclosed. A reference block is selected from an available ladder-shaped reference area comprising previously processed blocks before the current working block in the current CTU row and previously processed blocks in one or more previous CTU rows. A location of a last previously processed block of a second previous CTU row that is one CTU row farther away from the current CTU row than a first previous CTU row is always in a same vertical location or after a same vertical position of a last previously processed block of the first previous CTU row. The current picture may be partitioned into multiple CTU rows for applying wavefront parallel processing (WPP) on the multiple CTU rows, where the current working block corresponds to a current working block. Similar restrictions may also be applied to slice/tile-based parallel processing.

1 . A method of video encoding using slice-based or tile-based parallel processing for a picture, the method comprising:
 partitioning a current picture into multiple slices or tiles for applying concurrent encoding process on the multiple slices or tiles; and   if an IntraBC mode (Intra-block copy mode) is selected for a current block in a current slice or a current tile:   selecting a reference block from a selected available reference area comprising one or more previously processed blocks before the current block in the current slice or the current tile;   encoding the current block according to the IntraBC mode using the reference block as a predictor; and   generating compressed data corresponding to the current slice or the current tile by applying entropy coding to prediction result of the current block.   
     
     
         2 . The method of  claim 1 , wherein a block location of the reference block relative to the current block is signaled using a block vector (BV). 
     
     
         3 . The method of  claim 2 , wherein if any portion of the reference block pointed by the BV is located outside the current slice or the current tile, the BV is clipped to a clipped BV so that a modified reference block pointed by the clipped BV is located entirely within the current slice or the current tile. 
     
     
         4 . The method of  claim 3 , wherein for the current tile, the BV is clipped in a vertical direction firstly and clipped in a horizontal direction secondly. 
     
     
         5 . The method of  claim 3 , wherein for the current tile, the BV is clipped in a horizontal direction firstly and clipped in a vertical direction secondly. 
     
     
         6 . The method of  claim 3 , wherein for the current slice, the BV is clipped in a vertical direction. 
     
     
         7 . A method of video decoding using slice-based or tile-based parallel processing for a picture, the method comprising:
 receiving a video bitstream associated with multiple slices or tiles partitioned from a current picture and coded concurrently; and   if an IntraBC mode (Intra-block copy mode) is selected for a current block in a current slice or a current tile:   determining a coded block for the current block from the video bitstream;   selecting a reference block from a selected available reference area comprising one or more previously reconstructed blocks before the current block in the current slice or the current tile; and   reconstructing the current block from the coded block according to the IntraBC mode using the reference block as a predictor.   
     
     
         8 . The method of  claim 7 , wherein a block location of the reference block relative to the current block is signaled using a block vector (BV). 
     
     
         9 . The method of  claim 8 , wherein if any portion of the reference block pointed by the BV is located outside the current slice or the current tile, the BV is clipped to a clipped BV so that a modified reference block pointed by the clipped BV is located entirely within the current slice or the current tile. 
     
     
         10 . The method of  claim 9 , wherein for the current tile, the BV is clipped in a vertical direction firstly and clipped in a horizontal direction secondly. 
     
     
         11 . The method of  claim 9 , wherein for the current tile, the BV is clipped in a horizontal direction firstly and clipped in a vertical direction secondly. 
     
     
         12 . The method of  claim 9 , wherein for the current slice, the BV is clipped in a vertical direction. 
     
     
         13 . The method of  claim 7 , wherein if one or more samples of the reference block are not available, one or more padded samples from neighboring available samples are used to replace one or more unavailable samples of the reference block. 
     
     
         14 . The method of  claim 7 , wherein if one or more samples of the reference block are not available, said one or more samples of the reference block that are unavailable or an entire reference block is replaced by a pre-defined value. 
     
     
         15 . The method of  claim 14 , wherein the pre-defined value corresponds to 128. 
     
     
         16 . The method of  claim 14 , wherein reconstructed samples for the current picture are initialized to the pre-defined value before decoding process starts for the current picture, and if one or more samples of the reference block are not available, said one or more samples of the reference block have the pre-defined value. 
     
     
         17 . The method of  claim 16 , wherein the pre-defined value corresponds to 128. 
     
     
         18 . The method of  claim 14 , wherein the pre-defined value is selected from a list of major colors signaled in a high level of the video bitstream. 
     
     
         19 . The method of  claim 18 , wherein the high level of the video bitstream corresponds to a slice level, a picture level or a sequence level. 
     
     
         20 . The method of  claim 18 , wherein the list of major colors is signaled using a number, N corresponding to a size of the list of major colors and followed by N major color values. 
     
     
         21 . The method of  claim 7 , wherein if the current block is in an Inter-slice and one or more samples of the reference block are not available, said one or more samples of the reference block that are unavailable or an entire reference block is replaced by one or more temporal samples or an entire block of a temporal reference block in a reference frame collocated with the current block. 
     
     
         22 . The method of  claim 7 , wherein if the current block is in an Inter-slice and one or more samples of the reference block are not available, said one or more samples of the reference block that are unavailable or an entire reference block is replaced by one or more temporal samples or an entire block of a temporal reference block in a reference frame collocated with the reference block.