Intra prediction in image processing
An intra prediction method and a device using the intra prediction method are provided. The intra prediction method includes the steps of: deriving a current prediction mode as a prediction anode of a current block; constructing neighboring samples of the current block with available reference samples; filtering the available reference samples; and generating predicted samples of the current block on the basis of the filtered available reference samples. The filtering step includes performing the filtering using the available reference sample located in the prediction direction of the current prediction mode and a predetermined number of available reference samples neighboring to the prediction direction of the current prediction mode.
1. An image encoding method using intra prediction, by an encoding apparatus, the method comprising:
determining an intra prediction mode of a current block, wherein the intra prediction mode is determined as a directional prediction mode from intra prediction modes including 33 directional prediction modes and at least one non-directional prediction mode;
deriving neighboring reference samples of the current block;
performing filtering on at least one of the reference samples;
generating a prediction sample of the current block based on a filtered reference sample; and
encoding image information including prediction mode information indicating the intra prediction mode of the current block,
wherein the filtered reference sample is filtered by using a first reference sample located in a prediction direction of the intra prediction mode with regard to a location of the prediction sample and reference samples adjacent to the first reference sample, and
wherein the reference samples adjacent to the first reference sample including a second reference sample located on a right side of the first reference sample and a third reference sample located on a left side of the first reference sample is derived based on a location of the first reference sample.
2. The method of claim 1 , wherein a filtering coefficient for the first reference sample is greater than filtering coefficients for the reference samples adjacent to the first reference sample.
3. The method of claim 1 , wherein the filtered reference sample is filtered by applying a 3-tap filter with a filtering coefficient of [1 2 1] to the first reference sample.
4. The method of claim 1 , wherein the intra prediction mode is a prediction mode having an up-left diagonal prediction direction.
5. The method of claim 1 , wherein the intra prediction mode is a prediction mode having a down-left diagonal prediction direction.
6. The method of claim 1 , wherein it is determined whether the filtering is performed depending on a size and the intra prediction mode of the current block.
7. The method of claim 6 , wherein when it is determined that the filtering is not performed, the prediction sample is generated based on the first reference sample, and
wherein a smoothing process using 2-tap coefficients is performed on the first reference sample.
8. An encoding apparatus, comprising:
a prediction module configured to determine an intra prediction mode of a current block, wherein the intra prediction mode is determined as a directional prediction mode from intra prediction modes including 33 directional prediction modes and at least one non-directional prediction mode, derive neighboring reference samples of the current block, perform filtering on at least one of the reference samples, generate a prediction sample of the current block based on a filtered reference sample; and
an encoding module configured to encode image information including prediction mode information indicating the intra prediction mode of the current block,
wherein the filtered reference sample is filtered by using a first reference sample located in a prediction direction of the intra prediction mode with regard to a location of the prediction sample and reference samples adjacent to the first reference sample, and
wherein the reference samples adjacent to the first reference sample including a second reference sample located on a right side of the first reference sample and a third reference sample located on a left side of the first reference sample is derived based on a location of the first reference sample.
9. A non-transitory computer-readable storage medium storing image information, the image information, when executed, causing a decoding apparatus to perform the following steps:
determining an intra prediction mode of a current block based on the image information, wherein the intra prediction mode is determined as a directional prediction mode from intra prediction modes including 33 directional prediction modes and at least one non-directional prediction mode;
deriving neighboring reference samples of the current block;
performing filtering on at least one of the reference samples;
generating a prediction sample of the current block based on a filtered reference sample;
deriving a residual sample of the current block based on the image information; and
generating a reconstructed picture based on the prediction sample and the residual sample,
wherein the filtered reference sample is filtered by using a first reference sample located in a prediction direction of the intra prediction mode with regard to a location of the prediction sample and reference samples adjacent to the first reference sample, and
wherein the reference samples adjacent to the first reference sample including a second reference sample located on a right side of the first reference sample and a third reference sample located on a left side of the first reference sample is derived based on a location of the first reference sample.