Method, apparatus and system for encoding and decoding a transformed block of video samples

A method of encoding a transform block in an image into a bitstream, the method comprising:

• determining a horizontal transform type for the transform block;
• determining a vertical transform type for the transform block;
• encoding the transform block in the image by applying the determined horizontal transform type and the determined vertical transform type to the transform block in the image;
• and
• encoding at least a single truncated unary codeword,
• wherein, in a method of decoding, the horizontal transform type is determined by using the single truncated unary code for the transform block and the vertical transform type is determined by using the single truncated unary code for the transform block,
• wherein the single truncated unary codeword which is used for determining the horizontal transform type in the method of decoding is same as the single truncated unary codeword which is used for determining the vertical transform type in the method of decoding, and
• wherein, by using the single truncated unary codeword, different transform types are determined for the horizontal transform type and the vertical transform type in the method of decoding.

An apparatus configured for decoding a transform block in an image from a bitstream, the apparatus comprising:

• a decoding unit configured to decode at least a single truncated unary codeword from the bitstream;
• and
• a determination unit configured to determine a horizontal transform type and a vertical transform type for the transform block by using the same decoded single truncated unary codeword, wherein a transform type different from the horizontal transform type can be determined by using the same decoded single truncated unary codeword as the vertical transform type, and
• wherein the decoding unit is configured to decode the transform block in the image by applying the determined horizontal transform type and the determined vertical transform type to the transform block in the image.

An apparatus configured for encoding a transform block in an image into a bitstream, the apparatus comprising:

• a determination unit configured to determine a horizontal transform type for the transform block, and to determine a vertical transform type for the transform block;
• and
• an encoding unit configured to encode the transform block in the image by applying the determined horizontal transform type and the determined vertical transform type to the transform block in the image,
• wherein the encoding unit is configured to encode at least a single truncated unary codeword,
• wherein, in apparatus for decoding, the horizontal transform type is determined by using the single truncated unary codeword for the transform block and the vertical transform type is determined by using the single truncated unary codeword for the transform block,
• wherein, by using the single truncated unary codeword, different transform types are determinable for the horizontal transform type and the vertical transform type in the apparatus for decoding.

A non-transitory computer readable medium comprising a computer program comprising instructions that, when the program is executed by a computer, cause the computer to execute a method of decoding a transform block in an image from a bitstream, the method comprising:

• decoding at least a single truncated unary codeword from the bitstream;
• determining, for the transform block, a horizontal transform type by using the decoded single truncated unary codeword and a vertical transform type by using the decoded single truncated unary codeword,
• wherein the decoded single truncated unary codeword which is used for determining the horizontal transform type is same as the decoded single truncated unary codeword which is used for determining the vertical transform type, and
• wherein by using the decoded single truncated unary codeword, different transform types are determinable for the horizontal transform type and the vertical transform type;
• and
• decoding the transform block in the image by applying the determined horizontal transform type and the determined vertical transform type to the transform block in the image.

A non-transitory computer readable medium comprising a computer program comprising instructions that, when the program is executed by a computer, cause the computer to carry out a method of encoding a transform block in an image into a bitstream, the method comprising:

• determining a horizontal transform type for the transform block;
• determining a vertical transform type for the transform block;
• encoding the transform block in the image by applying the determined horizontal transform type and the determined vertical transform type to the transform block in the image;
• and
• encoding at least a single truncated unary codeword,
• wherein, in a method of decoding, the horizontal transform type is determined by using the single truncated unary codeword for the transform block and the vertical transform type is determined by using the single truncated unary codeword for the transform block,
• wherein the single truncated unary codeword which is used for determining the horizontal transform type in the method of decoding is same as the single truncated unary codeword which is used for determining the vertical transform type in the method of decoding, and
• wherein, by using the single truncated unary codeword, different transform types are determinable for the horizontal transform type and the vertical transform type in the method of decoding.