Apparatus and method for coding/decoding image selectively using discrete cosine/sine transform
Disclosed is a data transmission system that transmits data by using a relay. The relay selects a transmission terminal from among a plurality of terminals accessing a base station. A base station transmits base station data to the relay during a first time slot, and the transmission terminal transmits terminal data to the relay. The relay transmits terminal data to the base station during a second time slot, and transmits base station data to the transmission terminal.
1. An apparatus for decoding an image, the apparatus comprising:
an input for receiving a coded image comprising blocks; and a processor to decode an image block, wherein the processor:
determines, based on a coded block pattern (CBP) value, whether or not transform coefficients of the image block include at least one non-zero transform coefficient;
in response to the CBP value indicating that the transform coefficients of the image block include at least one non-zero transform coefficient,
obtains the transform coefficients and a first flag bit for the image block by entropy-decoding an input bitstream;
dequantizes the transform coefficients of the image block to generate dequantized transform coefficients for the image block;
determines, based on the first flag bit, whether neither of a first inverse-transform based on a discrete cosine transform (DCT) and a second inverse-transform based on a discrete sine transform (DST) is to be performed on the dequantized transform coefficients for the image block;
determines, based on a second flag bit, a selected inverse-transform with respect to the image block, the selected inverse-transform being one of the first inverse-transform based on the discrete cosine transform (DCT) or the second inverse-transform based on the discrete sine transform (DST);
generates a residual image for the image block by performing the selected inverse-transform on the dequantized transform coefficients for the image block; and
reconstructs the image block by adding the residual image and a prediction image for the image block,
wherein the determining the selected inverse-transform based on the second flag bit is performed both when the transform coefficients of the image block are determined to include at least one non-zero transform coefficient based on the CBP value and when it is determined that one of the first inverse-transform and the second inverse-transform is to be performed based on the first flag bit.
2. The apparatus of claim 1 , wherein the second flag bit is signaled by a unit of a macroblock.
3. The apparatus of claim 2 , wherein the first flag bit is signaled by a unit of a slice.