Image decoding apparatus and image coding apparatus
View Patent ↗An image decoding apparatus and an image coding apparatus are implemented that are capable of more efficiently and effectively performing reconstruction of a prediction residual for a TU. An image decoding apparatus ( 1 ) is an image decoding apparatus including: a transforming unit ( 15 ) configured to perform, on a prescribed unit basis, inverse transform of a transform coefficient or a modification transform coefficient by using a transform basis selected from a plurality of the transform bases, in which the plurality of the transform bases include a first transform basis and a second transform basis obtained by performing symmetric transform of the first transform basis.
1. An image decoding apparatus for performing an inverse transform of a transform coefficient on a prescribed unit basis, the image decoding apparatus comprising:
at least one processor; and
a storage device coupled to the at least one processor and storing a program which, when executed by the at least one processor, causes the at least one processor to:
determine whether to apply a secondary transform to the transform coefficient to generate a modification transform coefficient;
apply a core transform to the modification transform coefficient by a first type core transform when the secondary transform is applied to the transform coefficient; and
apply the core transform to the transform coefficient by a second type core transform different from the first type core transform when the secondary transform is not applied to the transform coefficient, wherein:
the second type core transform is selected with reference to a first syntax and a second syntax; and
the first type core transform is selected with reference to the first syntax without reference to the second syntax.
2. The image decoding apparatus according to claim 1 , wherein the second type core transform is a non-separable transform.
3. The image decoding apparatus according to claim 1 , wherein the program, when executed by the at least one processor, further causes the at least one processor to:
receive a flag for the transform coefficient; and
determine, based on the flag, whether to apply the secondary transform to the transform coefficient to generate the modification transform coefficient.
4. The image decoding apparatus according to claim 3 , wherein the flag is identical to the first syntax.
5. The image decoding apparatus according to claim 4 , wherein the first type core transform is a fixed transform independent to the second syntax and the second type core transform is a selective transform in which switching by the second syntax is performed.
6. The image decoding apparatus according to claim 1 , wherein the first type core transform is selected with no reference to the second syntax.
7. An image coding apparatus comprising:
at least one processor; and
a storage device coupled to the at least one processor and storing a program which, when executed by the at least one processor, causes the at least one processor to:
perform an inverse transform of a transform coefficient on a prescribed unit basis;
determine whether to apply a secondary transform to the transform coefficient to generate a modification transform coefficient;
apply a core transform to the modification transform coefficient by a first type core transform when the secondary transform is applied to the transform coefficient; and
apply the core transform to the transform coefficient by a second type core transform different from the first type core transform when the secondary transform is not applied to the transform coefficient, wherein:
the second type core transform is selected with reference to a first syntax and a second syntax; and
the first type core transform is selected with reference to the first syntax without reference to the second syntax.