Video encoding method with bit depth adjustment for fixed-point conversion and apparatus therefor, and video decoding method and apparatus therefor
Provided are a video encoding method of adjusting a range of encoded output data to adjust a bit depth during restoring of encoded samples, and a video decoding method of substantially preventing overflow from occurring in output data in operations of a decoding process. The video decoding method includes parsing and restoring quantized transformation coefficients in units of blocks of an image from a received bitstream, restoring transformation coefficients by performing inverse quantization on the quantized transformation coefficients, and restoring samples by performing one-dimensional (1D) inverse transformation and inverse scaling on the quantized transformation coefficients. At least one from among the transformation coefficients and the samples has a predetermined bit depth or less.
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 includes performing a 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 including at least one of a vertical inverse-transformation and a horizontal inverse-transformation;
generating inverse-transformed coefficients by performing the vertical inverse-transformation on the inverse-quantized transformed coefficients;
generating sample values by performing a scaling and a second clipping on the inverse-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 corresponding to a first bitdepth,
the second clipping is performed for restricting the sample values to a range corresponding to a second bitdepth, and
the scaling is performed before the second clipping and comprises a bit shift operation to the right by N bits.
2. The method of claim 1 , wherein the first bitdepth is equal to 16 bits.
3. The method of claim 1 , wherein the second bitdepth is equal to 16 bits.
4. The method of claim 1 , wherein N is equal to 7.