Patent ID: 8571337

Claim:
An encoding method for carrying out frame-based encoding processing of an interlaced image, the encoding method comprising: a frequency conversion step of converting the interlaced image to coefficients of frequency domain having predetermined frequency ranges in a vertical direction and a horizontal direction, respectively; and a weighting step of weighting the coefficients of frequency domain for each frequency band; wherein: in the weighting step, a weighting factor used for weighting a coefficient of a frequency band exceeding a predetermined frequency in the vertical direction is substantially equal to or larger than a weighting factor used or weighting the coefficient in the frequency band exceeding the predetermined frequency in the horizontal direction; the coefficients of frequency domain are weighted in accordance with a visual frequency characteristic for each frequency band, and the weighting factor used for weighting a coefficient of a frequency band exceeding a predetermined frequency in the vertical direction is substantially equal to or larger than the weighting factor used for weighting the coefficient exceeding the predetermined frequency in the horizontal direction determined in accordance with the visual frequency characteristic; and the weighting factor used for weighting a coefficient of a frequency band exceeding the predetermined frequency in the vertical direction is determined in accordance with a modified visual frequency characteristic obtained by flipping a visual frequency characteristic applied to a frequency equal to or smaller than the predetermined frequency in the vertical direction so that the modified visual frequency characteristic is symmetrical with respect to the predetermined frequency in the vertical direction.