Samsung patents video compression method for faster image decoding

1. An image decoding method, comprising: obtaining at least one coding unit including a current block by hierarchically splitting a current image based on split type information, determining, when a current prediction mode of the current block is an intra mode, a first sample value of an upper left reference sample of the current block by identifying a first availability of the upper left reference sample of the current block; sequentially searching, for remaining reference samples of at least one reference line from a plurality of reference lines, except for the upper left reference sample, the plurality of reference lines comprising a left reference line of the current block, an upper reference line of the current block, and a right reference line of the current block; determining second sample values of the remaining reference samples of the current block by identifying a second availability of the searched remaining reference samples; performing intra prediction on the current block to obtain a prediction block of the current block, based on the first sample value of the upper left reference sample of the current block and the second sample values of the remaining reference samples of the current block; and obtaining a reconstruction block of the current block based on the prediction block of the current block, wherein the determining of the first sample value of the upper left reference sample of the current block comprises: determining, when the upper left reference sample is not available, a first value obtained based on a sample bit depth as the first sample value of the upper left reference sample without searching for available reference samples neighboring the upper left reference sample, wherein the determining of the second sample values of the remaining reference samples of the current block comprises: determining, when a current reference sample in a current search location is not available, a second value obtained based on a sample value of a reference sample in a previous search location as a current sample value of the current reference sample in the current search location, wherein a first search direction of the upper reference line is a right direction relative to the upper left reference sample, wherein a second search direction of the left reference line is a first lower direction relative to the upper left reference sample, wherein a third search direction of the right reference line is a second lower direction relative to an upper right reference sample of the current block, wherein when a coordinate value of an upper left corner sample of the current block is (0,0), a x-axis coordinate value of the upper right reference sample of the current block is a width of the current block, and a y-axis coordinate value of the upper right reference sample of the current block is −1, wherein the split type information indicates one of a plurality of split types including a quad split, a binary split and a tri split, and wherein when the intra prediction on the current block is performed by using only a reference sample reconstructed in the intra mode and a prediction mode of a reference block including the current reference sample corresponds to an inter mode, it is determined that the current reference sample is not available.