Coding method and apparatus

A video decoder, comprising:

• an entropy decoding unit, is configured to parse a received bitstream to obtain prediction information of a coding unit (CU);
• obtain a target transform mode of a residual transform unit (TU) when the residual TU is the only residual TU of the CU and a size of the residual TU is less than a size of the CU, wherein the target transform mode specifies a TU partitioning mode of the CU, the position of the residual TU, and a transform type of the residual TU;
• and parse the received bitstream to obtain transform coefficients of the residual TU;
• an inverse quantization processing unit, is configured to apply an inverse quantization to the transform coefficients of the residual TU to obtain dequantized coefficients;
• an inverse transform processing unit, is configured to apply, based on the target transform mode, an inverse transform to the dequantized coefficients to obtain a residual block of the residual TU;
• a prediction processing unit, is configured to obtain a prediction block of the CU based on the prediction information;
• a reconstruction unit, is configured to obtain a video block based on the residual block and the prediction block;
• and
• an output, is configured to output a video sequence, the video sequence including a video frame that includes the video block.