Low-frequency non-separable transform design method and device
AssigneeLG Electronics Inc.
InventorsMoonmo KOO, Seunghwan KIM, Jaehyun LIM
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Abstract
According to the disclosure of the present document, a quantization parameter for a quantized transform coefficient present at a DC position within a current block can have the smallest value among quantization parameters which are applied to quantized transform coefficients within the current block, on the basis that an LFNST is applied to the current block. Therefore, coding performance capable of being brought by the LFNST can be maximized within the implementation complexity permitted in forthcoming standards.
Claims15
An image decoding method performed by a decoding apparatus, the method comprising:
- obtaining image information through a bitstream, wherein the image information includes residual information and information related to a quantization parameter;
- deriving quantized transform coefficients for a current block based on the residual information;
- deriving transform coefficients for the current block based on the quantized transform coefficients and the information related to the quantization parameter;
- deriving modified transform coefficients by applying a low-frequency non-separable transform (LFNST) based on the transform coefficients;
- generating residual samples for the current block based on the modified transform coefficients;
- and
- generating reconstructed samples for the current block based on the residual samples,
- wherein based on the LFNST being applied to the current block, a quantization parameter for a quantized transform coefficient present at a DC position in the current block has a smallest value among quantization parameters applied to the quantized transform coefficients in the current block.
An image encoding method performed by an encoding apparatus, the method comprising:
- generating residual samples for a current block;
- deriving transform coefficients based on the residual samples;
- deriving modified transform coefficients by applying an low-frequency non-separable transform (LFNST) to the transform coefficients;
- deriving quantized transform coefficients for the modified transform coefficients based on the modified transform coefficients and a quantization parameter;
- generating information related to the quantization parameter:
- generating residual information based on the quantized transform coefficients;
- and
- encoding image information including the residual information and the information related to the quantization parameter.
- wherein based on the LFNST being applied to the current block, a quantization parameter for a modified transform coefficient present at a DC position in the current block has a smallest value among quantization parameters applied to the modified transform coefficients in the current block.
A transmission method of data for an image, the method comprising:
- obtaining a bitstream for the image, wherein the bitstream is generated based on generating residual samples for a current block, deriving transform coefficients based on the residual samples, deriving modified transform coefficients by applying an low-frequency non-separable transform (LFNST) to the transform coefficients, deriving quantized transform coefficients for the modified transform coefficients based on the modified transform coefficients and a quantization parameter, generating information related to the quantization parameter, generating residual information based on the quantized transform coefficients, and encoding image information including the residual information and the information related to the quantization parameter;
- and
- transmitting the data comprising the bitstream,
- wherein based on the LFNST being applied to the current block, a quantization parameter for a modified transform coefficient present at a DC position in the current block has a smallest value among quantization parameters applied to the modified transform coefficients in the current block.
Dependencies are inferred from the claim text.