Method and apparatus for encoding/decoding image using transform skip flag

A method of decoding, based on loss coding, a video signal having a current block to be decoded with a decoding apparatus, comprising:

• obtaining, from the video signal, residual coefficients relating to the current block, the residual coefficients including first residual coefficients relating to luma components of the current block and second residual coefficients relating to chroma components of the current block;
• obtaining, from the video signal,
• a first transform skip flag relating to the luma components and a second transform skip flag relating to the chroma components;
• performing an inverse-quantization on the first residual coefficients and the second residual coefficients of the current block;
• obtaining residual samples of the current block by selectively performing an inverse-transform for first inverse-quantized residual coefficients resulting from the inverse quantization of the first residual coefficients and second inverse-quantized residual coefficients resulting from the inverse-quantization of the second residual coefficients,
• wherein the first transform skip flag specifies whether the inverse-transform is performed or skipped on the first inverse-quantized residual coefficients resulting from the inverse-quantization of the first residual coefficients, and the second transform skip flag specifies whether the inverse-transform is performed or skipped on the second inverse-quantized residual coefficients resulting from the inverse-quantization of the second residual coefficients, and
• wherein whether to perform or skip the inverse-transform on the second inverse-quantized residual coefficients is determined independently of whether to perform or skip the inverse-transform on the first inverse-quantized residual coefficients;
• determining a prediction mode of the current block based on prediction mode information, the prediction mode information specifying whether the current block is an inter-coded block or an intra-coded block;
• obtaining prediction samples of the current block based on the prediction mode of the current block;
• reconstructing the current block by using the residual samples and the prediction samples;
• and
• applying a deblocking filter to reconstructed samples of the current block.