1. A method for decoding a video, the method comprising: obtaining transformed coefficients of a block from a bitstream; generating inverse-quantized transformed coefficients by performing inverse-quantization, wherein the performing inverse-quantization comprises performing a right bit-shifting operation based on a base-2 logarithm of a size of the block, and by performing a first clipping on the transformed coefficients, wherein the first clipping is performed after the performing the inverse-quantization and before performing an inverse transformation comprising a vertical inverse-transformation and a horizontal inverse-transformation; generating sample values by performing the vertical inverse-transformation and a second clipping on the inverse-quantized transformed coefficients; and generating residual values by performing the horizontal inverse-transformation on the sample values, wherein the first clipping is performed for restricting the inverse-quantized transformed coefficients to a range of a first bitdepth, and the second clipping is performed for restricting the sample values to a range of a second bitdepth.