Coefficient coding method, encoder, and decoder

A coefficient encoding method, applied to an encoder and comprising:

• determining a video flag and a position of a last significant coefficient;
• determining a last-significant-coefficient position-reverse flag when the video flag indicates that a video satisfies a preset condition;
• determining coordinate information of the last significant coefficient according to the position of the last significant coefficient and the last-significant-coefficient position-reverse flag;
• determining prefix information of a horizontal coordinate of the last significant coefficient, prefix information of a vertical coordinate of the last significant coefficient, suffix information of the horizontal coordinate of the last significant coefficient, and suffix information of the vertical coordinate of the last significant coefficient according to the coordinate information of the last significant coefficient;
• and
• encoding all coefficients before the position of the last significant coefficient according to a preset scanning order, and signalling bit information obtained by the encoding, the video flag, the prefix information of the horizontal coordinate of the last significant coefficient, the prefix information of the vertical coordinate of the last significant coefficient, the suffix information of the horizontal coordinate of the last significant coefficient, and the suffix information of the vertical coordinate of the last significant coefficient into a bitstream.

An encoder, comprising a processor and a memory storing a computer program which, when executed by the processor, causes the processor to:

• determine a video flag and a position of a last significant coefficient;
• determine a last-significant-coefficient position-reverse flag when the video flag indicates that a video satisfies a preset condition;
• determine coordinate information of the last significant coefficient according to the position of the last significant coefficient and the last-significant-coefficient position-reverse flag;
• determine prefix information of a horizontal coordinate of the last significant coefficient, prefix information of a vertical coordinate of the last significant coefficient, suffix information of the horizontal coordinate of the last significant coefficient, and suffix information of the vertical coordinate of the last significant coefficient according to the coordinate information of the last significant coefficient;
• and
• encode all coefficients before the position of the last significant coefficient according to a preset scanning order, and signal bit information obtained by the encoding, the video flag, the prefix information of the horizontal coordinate of the last significant coefficient, the prefix information of the vertical coordinate of the last significant coefficient, the suffix information of the horizontal coordinate of the last significant coefficient, and the suffix information of the vertical coordinate of the last significant coefficient into a bitstream.

A decoder, comprising a processor and a memory storing a computer program which, when executed by the processor, causes the processor to:

• parse a bitstream to obtain a video flag;
• parse the bitstream to obtain a last-significant-coefficient position-reverse flag when the video flag indicates that a video satisfies a preset condition;
• parse the bitstream to obtain prefix information of a horizontal coordinate of a last significant coefficient, prefix information of a vertical coordinate of the last significant coefficient, suffix information of the horizontal coordinate of the last significant coefficient, and suffix information of the vertical coordinate of the last significant coefficient;
• determine the horizontal coordinate of the last significant coefficient according to the prefix information of the horizontal coordinate of the last significant coefficient and the suffix information of the horizontal coordinate of the last significant coefficient;
• determine the vertical coordinate of the last significant coefficient according to the prefix information of the vertical coordinate of the last significant coefficient and the suffix information of the vertical coordinate of the last significant coefficient;
• and
• determine coordinate information of the last significant coefficient according to the horizontal coordinate of the last significant coefficient and the vertical coordinate of the last significant coefficient;
• determine a position of the last significant coefficient by calculation with the coordinate information of the last significant coefficient when the last-significant-coefficient position-reverse flag indicates that the position of the last significant coefficient is reversed for a current block;
• and
• decode, according to a preset scanning order, all coefficients before the position of the last significant coefficient to determine coefficients of the current block.