Video encoding method with intra prediction using checking process for unified reference possibility, video decoding method and device thereof

A video decoding apparatus comprising:

• a parser configured to restore samples by performing entropy decoding on a bit string parsed from a received bitstream;
• an inverse transformer configured to restore samples by performing inverse quantization and inverse transformation on a quantized transformation coefficient from among the restored samples;
• an intra predictor configured to search for a neighboring block restored prior to a current block, determine whether the neighboring block found by the searching is a reference block available for intra prediction of the current block based on a result of checking whether the found neighboring block is a block restored in an intra mode and whether an intra mode of the current block is also a Combined Intra Prediction (CIP) mode in which only blocks pre-restored in the intra mode are referred to, and perform intra prediction on the current block by using sample values of the reference block determined as available for the intra prediction of the current block, to perform the intra prediction on the current block that is in the intra mode from among the samples;
• a motion compensator configured to perform motion compensation on blocks in an inter prediction mode from among the samples;
• and
• a restorer configured to restore an image by using blocks restored by the inter prediction or the intra prediction.

A video encoding apparatus comprising:

• an intra predictor configured to search for a neighboring block restored prior to a current block, determine whether the neighboring block found by the searching is a reference block available for intra prediction of the current block based on a result of checking whether the found neighboring block is a block restored in an intra mode and whether an intra mode of the current block is also a Combined Intra Prediction (CIP) mode in which only blocks pre-restored in the intra mode are referred to, and perform intra prediction on the current block by using sample values of the reference block determined to be available for the intra prediction of the current block, to perform the intra prediction on the current block that is in the intra mode from among blocks of a video;
• an inter predictor configured to perform inter prediction on blocks in an inter prediction mode from among the blocks;
• a transformer and quantizer configured to perform transformation and quantization on a result of performing the intra prediction or the inter prediction;
• and
• an output unit configured to output a bitstream generated by performing entropy encoding on samples including a quantized transformation coefficient generated as a result of the transformation and quantization.

A non-transitory computer-readable recording medium having recorded thereon a program which causes a computer to perform an intra prediction method comprising:

• searching for a neighboring block restored prior to a current block from among blocks of an image;
• checking whether the neighboring block found by the searching is a block restored in an intra mode and whether an intra mode of the current block is also a Combined Intra Prediction (CIP) mode in which only blocks pre-restored in the intra mode are referred to;
• determining based on a checking result of the checking whether the found neighboring block is a reference block available for intra prediction of the current block;
• and
• performing intra prediction on the current block by using sample values of the reference block determined as available for the intra prediction of the current block.