Image decoding device and image encoding device
View Patent ↗The present invention avoids waste caused by performing both a Secondary Transform and an Adaptive Multiple Core Transform. Provided is a device including: a core transform unit ( 1521 ) that can perform an Adaptive Multiple Core Transform on a Coding Tree Unit; and a Secondary Transform unit ( 1522 ) that can perform, before the Adaptive Multiple Core Transform, a Secondary Transform on at least any one of sub-blocks included in the Coding Tree Unit. The device omits any of the Adaptive Multiple Core Transform and the Secondary Transform in accordance with at least any of a flag associated with the Adaptive Multiple Core Transform and a flag associated with the Secondary Transform, or in accordance with a size of the Coding Tree Unit.
1. An image decoding device configured to decode a picture by using a coding unit into which the picture is split, the device comprising:
a first decoding circuit configured to decode a secondary index specifying whether or not a secondary transform is used;
a second decoding circuit configured to decode a first index;
a first deriving circuit configured to derive a secondary transform matrix based on the secondary index;
a first transform circuit configured to apply the secondary transform to a transform unit included in the coding unit based on the secondary transform matrix;
a second deriving circuit configured to derive vertical and horizontal transform selection indexes based on the first index; and
a second transform circuit configured to apply a core transform to the transform unit based on the vertical and horizontal transform selection indexes,
wherein the second decoding circuit derives the first index equal to 0 in a case where the secondary index specifies that the secondary transform is used.
2. An image decoding method for decoding a picture by using a coding unit into which the picture is split, the method comprising:
decoding a secondary index specifying whether or not a secondary transform is used;
decoding a first index;
deriving a secondary transform matrix based on the secondary index;
applying the secondary transform to a transform unit included in the coding unit based on the secondary transform matrix;
deriving vertical and horizontal transform selection indexes based on the first index; and
applying a core transform to the transform unit based on the vertical and horizontal transform selection indexes,
wherein the first index is derived equal to 0 in a case where the secondary index specifies that the secondary transform is used.