DPCM-based encoder, decoder, encoding method and decoding method

An encoding method, comprising the steps of:

• performing a reversible color transform to output a transformed video signal according to an input video signal;
• performing a difference pulse code modulation (DPCM) intra prediction to output a least residual according to the transformed video signal, wherein the least residual is selected from a plurality of residuals generated in correspondence to a plurality of intra prediction direction modes, wherein the prediction direction modes comprise a plurality of linear direction modes and a rotation direction mode;
• performing a quantization operation on the least residual to output a quantization coefficient;
• performing a reversible frequency transform on the quantization coefficient to output a frequency coefficient;
• and
• performing an entropy coding operation to output a compression bit stream according to the frequency coefficient.

A decoder, comprising:

• an entropy decoding module for performing entropy decoding to output a frequency coefficient according to an input compression bit stream;
• an inverse reversible frequency transform module for performing an inverse reversible frequency transform on the frequency coefficient to output a quantization coefficient;
• an inverse quantization module for performing an inverse quantization operation on the quantization coefficient to output a least residual;
• a compensation module for performing a difference pulse code modulation (DPCM) intra compensation to output a transformed video signal according to neighboring compensated video signals and the least residual, wherein the least residual corresponds to one of a plurality of residuals generated by an encoder in a plurality of intra prediction direction modes, wherein the prediction direction modes comprise a plurality of linear direction modes and a rotation direction mode;
• and
• an inverse reversible color transform module for performing an inverse reversible color transform according to the transformed video signal to output an input video signal.

A decoding method, comprising:

• performing entropy decoding to output a frequency coefficient according to an input compression bit stream;
• performing an inverse reversible frequency transform on the frequency coefficient to output a quantization coefficient;
• performing an inverse quantization operation on the quantization coefficient to output a least residual;
• performing an intra compensation to output a transformed video signal according to neighboring compensated video signals and the least residual, wherein the least residual corresponds to one of a plurality of residuals generated by an encoder in a plurality of intra prediction direction modes, wherein the prediction direction modes comprise a plurality of linear direction modes and a rotation direction mode;
• and
• performing an inverse reversible color transform to output an input video signal according to the transformed video signal.