Methods and apparatuses for encoding and decoding an image or a video using combined intra modes
Methods and apparatuses for video coding are provided where a block is predicted using a combination of two intra prediction modes. A first prediction is generated from a non-directional mode, such as a Planar, Matrix-based Intra Prediction (MIP), or Intra Block Copy (IBC) mode. A second prediction is generated from a directional mode, which may be derived at a decoder from reconstructed neighboring samples without being explicitly signaled, reducing signaling overhead. A final prediction for the block is formed by combining the first and second predictions, for example, through a weighted average. This technique applies to both encoding and decoding processes.
1 . A method, comprising, for at least one block of an image or a video:
decoding an indicator indicating a first intra prediction mode, wherein the first intra prediction mode is one of an intra block copy prediction mode or a matrix-based intra prediction mode,
determining whether the first intra prediction mode is to be combined with a second intra prediction mode for obtaining a prediction of the at least one block,
responsive to determining that the first intra prediction mode is to be combined with a second intra prediction mode, obtaining the second intra prediction mode, and
decoding the at least one block based on a combination of the first intra prediction mode and the second intra prediction mode.
2 . The method of claim 1 , wherein one of the first intra prediction mode or the second intra prediction mode is obtained from among a set of non-directional intra prediction modes, and the other of the first intra prediction mode and the second intra prediction mode is obtained from among a set of directional intra prediction modes.
3 . The method of claim 1 , wherein at least one of the first intra prediction mode or the second intra prediction mode is signaled in a bitstream.
4 . The method of claim 3 , wherein an indicator indicating whether the second intra prediction mode is obtained from a decoder side intra mode derivation or a template based intra mode derivation is signaled in a bitstream.
5 . The method of claim 1 , wherein obtaining the second intra prediction mode comprises deriving the second intra prediction mode from one or more reconstructed samples neighboring the at least one block.
6 . The method of claim 1 , wherein the second intra prediction mode is obtained from at least one of a decoder side intra mode derivation or a template based intra mode derivation.
7 . The method of claim 1 , wherein the determination that the first intra prediction mode is to be combined with the second intra prediction mode is based on an indicator signaled for the at least one block in a bitstream.
8 . The method of claim 1 , wherein the determination that the first intra prediction mode is to be combined with the second intra prediction mode for the at least one block is based on a cost obtained when determining the second intra prediction mode.
9 . A non-transitory computer readable medium storing executable program instructions to cause a computer executing the program instructions to: for at least one block of an image or a video,
decode an indicator indicating a first intra prediction mode, wherein the first intra prediction mode is one of an intra block copy prediction mode or a matrix-based intra prediction mode,
determine whether the first intra prediction mode is to be combined with a second intra prediction mode for obtaining a prediction of the at least one block,
responsive to determining that the first intra prediction mode is to be combined with a second intra prediction mode, obtain the second intra prediction mode, and
decode the at least one block based on a combination of the first intra prediction mode and the second intra prediction mode.
10 . An apparatus comprising one or more processors, wherein the one or more processors is operable to, for at least one block of an image or a video:
decode an indicator indicating a first intra prediction mode, wherein the first intra prediction mode is one of an intra block copy prediction mode or a matrix-based intra prediction mode,
determine whether the first intra prediction mode is to be combined with a second intra prediction mode for obtaining a prediction of the at least one block,
responsive to determining that the first intra prediction mode is to be combined with a second intra prediction mode, obtain the second intra prediction mode, and
decode the at least one block based on a combination of the first intra prediction mode and the second intra prediction mode.
11 . The apparatus according to claim 10 comprising
at least one of (i) an antenna configured to receive a signal, the signal including data representative of the image or the video, (ii) a band limiter configured to limit the signal to a band of frequencies that includes the data representative of the image or video, or (iii) a display configured to display the image or video.
12 . The apparatus of claim 10 , wherein one of the first intra prediction mode or the second intra prediction mode is obtained from among a set of non-directional intra prediction modes, and the other of the first intra prediction mode and the second intra prediction mode is obtained from among a set of directional intra prediction modes.
13 . The apparatus of claim 10 , wherein the second intra prediction mode is obtained from at least one of a decoder side intra mode derivation or a template based intra mode derivation.
14 . The apparatus of claim 10 , wherein determining that the first intra prediction mode is to be combined with the second intra prediction mode is based on an indicator signaled for the at least one block in a bitstream.
15 . The apparatus of claim 10 , wherein determining that the first intra prediction mode is to be combined with the second intra prediction mode for the at least one block is based on a cost obtained when determining the second intra prediction mode.
16 . A method, comprising, for at least one block of an image or a video:
encoding an indicator indicating a first intra prediction mode, wherein the first intra prediction mode is one of an intra block copy prediction mode or a matrix-based intra prediction mode,
determining whether the first intra prediction mode is to be combined with a second intra prediction mode for obtaining a prediction of the at least one block,
responsive to determining that the first intra prediction mode is to be combined with a second intra prediction mode, obtaining the second intra prediction mode, and
encoding the at least one block based on a combination of the first intra prediction mode and the second intra prediction mode.
17 . An apparatus comprising one or more processors, wherein the one or more processors is operable to, for at least one block of an image or a video:
encode an indicator indicating a first intra prediction mode, wherein the first intra prediction mode is one of an intra block copy prediction mode or a matrix-based intra prediction mode,
determine whether the first intra prediction mode is to be combined with a second intra prediction mode for obtaining a prediction of the at least one block,
responsive to determining that the first intra prediction mode is to be combined with a second intra prediction mode, obtain the second intra prediction mode, and
encode the at least one block based on a combination of the first intra prediction mode and the second intra prediction mode.