Apparatus for processing image on basis of intra prediction mode
Disclosed are a method for decoding a video signal and a device therefore. More particularly, a method for decoding an image based on an intra prediction mode, may comprise the steps of: acquiring a most probable mode (MPM) flag for indicating whether an MPM is applied to a current block, the MPM representing a mode in which an intra prediction mode of the current block is induced from an intra predicted block neighboring the current block; configuring an MPM list, on the basis of whether intra prediction modes of a left neighboring block and an above neighboring block of the current block satisfy predefined conditions, if the MPM is applied to the current block; acquiring an MPM index for indicating, within the MPM list, a specific intra prediction mode; and generating a prediction block for the current block by using the intra prediction mode specified by the MPM index.
1. An apparatus for decoding a video signal, comprising:
a memory configured to store the video signal; and
a processor coupled with the memory,
wherein the processor is configured to:
configure a list based on whether intra prediction modes of left and upper neighboring blocks of a current block meet a predefined condition;
obtain an index indicating an intra prediction mode in the list;
generate prediction samples of the current block based on an intra prediction mode specified by the index;
derive residual samples of the current block; and
generate reconstructed samples of the current block based on the prediction samples and the residual samples,
wherein for configuring of the list, the processor is configured to:
derive the list based on that the intra prediction mode of the left neighboring block and the intra prediction mode of the upper neighboring block are non-angular modes, and
wherein the list comprises a first intra prediction mode a value of which is 18, a second intra prediction mode a value of which is 50, an intra prediction mode having a value of 46 obtained by subtracting 4 from the value of the second intra prediction mode, and an intra prediction mode having a value of 54 obtained by adding 4 to the value of the second intra prediction mode.
2. The apparatus of claim 1 , wherein the left neighboring block is set as a block including a pixel horizontally adjacent to a left lower pixel of the current block, and
wherein the upper neighboring block is set as a block including a pixel vertically adjacent to an upper right pixel of the current block.
3. The apparatus of claim 1 , wherein for configuring of the list, the processor is configured to configure one of a specific number of lists based on four pre-defined conditions.
4. The apparatus of claim 3 , wherein for configuring of the list, the processor is configured to:
configure a first list based on that a first condition is met;
configure a second list based on that a second condition and a third condition are met but the first condition is not met;
configure a third list based on that the second condition and a fourth condition are met but the first condition and the third condition are not met;
configure a fourth list based on that the second condition is met but the first condition, the third condition, and the fourth condition are not met; and
configure a fifth list based on that the first condition and the second condition are not met.
5. The apparatus of claim 4 , wherein the first condition is set as whether the intra prediction modes of the left neighboring block and the upper neighboring block are smaller than, or equal to, a DC mode,
wherein the second condition is set as whether the intra prediction modes of the left neighboring block and the upper neighboring block are not equal to each other,
wherein the third condition is set as whether the intra prediction mode of the left neighboring block or the intra prediction mode of the upper neighboring block is smaller than or equal to the DC mode, and
wherein the fourth condition is set as whether a difference between a maximum mode indicating a mode with a larger mode index value among the intra prediction modes of the left neighboring block and the upper neighboring block and a minimum mode indicating a mode with a smaller mode index value among the intra prediction modes of the left neighboring block and the upper neighboring block is smaller than a predefined value.
6. The apparatus of claim 1 , the processor is further configured to:
obtain a flag informing whether the intra prediction mode of the current block is derived from an intra predicted block around the current block,
wherein the list is configured when the flag informs that the intra prediction mode is to be derived from the intra predicted block around the current block.
7. An apparatus for encoding a video, comprising:
a memory configured to store the video signal; and
a processor coupled with the memory,
wherein the processor is configured to:
configure a list based on whether intra prediction modes of left and upper neighboring blocks of a current block meet a predefined condition;
generate an index indicating an intra prediction mode in the list;
generate prediction samples of the current block based on an intra prediction mode specified by the index; and
generate residual samples of the current block based on the prediction samples,
wherein for configuring of the list, the processor is configured to:
derive the list based on that the intra prediction mode of the left neighboring block and the intra prediction mode of the upper neighboring block are non-angular modes, and
wherein the list comprises a first intra prediction mode a value of which is 18, a second intra prediction mode a value of which is 50, an intra prediction mode having a value of 46 obtained by subtracting 4 from the value of the second intra prediction mode, and an intra prediction mode having a value of 54 obtained by adding 4 to the value of the second intra prediction mode.
8. The apparatus of claim 7 , wherein the left neighboring block is set as a block including a pixel horizontally adjacent to a left lower pixel of the current block, and
wherein the upper neighboring block is set as a block including a pixel vertically adjacent to an upper right pixel of the current block.
9. The apparatus of claim 7 , wherein for configuring of the list, the processor is configured to configure one of a specific number of lists based on four pre-defined conditions.
10. The apparatus of claim 9 , wherein for configuring of the list the processor is configured to:
configure a first list based on that a first condition is met;
configure a second list based on that a second condition and a third condition are met but the first condition is not met;
configure a third list based on that the second condition and a fourth condition are met but the first condition and the third condition are not met;
configure a fourth list based on that the second condition is met but the first condition, the third condition, and the fourth condition are not met; and
configure a fifth list based on that the first condition and the second condition are not met.
11. The apparatus of claim 10 , wherein the first condition is set as whether the intra prediction modes of the left neighboring block and the upper neighboring block are smaller than, or equal to, a DC mode,
wherein the second condition is set as whether the intra prediction modes of the left neighboring block and the upper neighboring block are not equal to each other,
wherein the third condition is set as whether the intra prediction mode of the left neighboring block or the intra prediction mode of the upper neighboring block is smaller than or equal to the DC mode, and
wherein the fourth condition is set as whether a difference between a maximum mode indicating a mode with a larger mode index value among the intra prediction modes of the left neighboring block and the upper neighboring block and a minimum mode indicating a mode with a smaller mode index value among the intra prediction modes of the left neighboring block and the upper neighboring block is smaller than a predefined value.
12. The apparatus of claim 7 , the processor is further configured to:
generate a flag informing whether the intra prediction mode of the current block is derived from an intra predicted block around the current block,
wherein the list is configured when the flag informs that the intra prediction mode is to be derived from the intra predicted block around the current block.
13. A transmitting apparatus of data for image information, comprising
a processor configured to obtain a bitstream for the image; and
a transmitter configured to transmit the data comprising the bitstream,
wherein the processor is configured to:
obtain the bitstream for the image; and
transmit the data comprising the bitstream,
wherein, for obtaining the bitstream, the processor is further configured to:
configure a list based on whether intra prediction modes of left and upper neighboring blocks of a current block meet a predefined condition;
generate an index indicating an intra prediction mode in the list;
generate prediction samples of the current block based on an intra prediction mode specified by the index; and
generate residual samples of the current block based on the prediction samples,
wherein for configuring of the list, the processor is configured to:
derive the list based on that the intra prediction mode of the left neighboring block and the intra prediction mode of the upper neighboring block are non-angular modes, and
wherein the list comprises a first intra prediction mode a value of which is 18, a second intra prediction mode a value of which is 50, an intra prediction mode having a value of 46 obtained by subtracting 4 from the value of the second intra prediction mode, and an intra prediction mode having a value of 54 obtained by adding 4 to the value of the second intra prediction mode.