A method and a device for encoding the video level of a pixel of a picture into a subfield code word in a display device using a PWM (Pulse Width Modulation) technology and subfields for displaying video picture. The bits of the subfield code word are computed recursively one after the other from the bit having the most significant weight to the bit having the least significant weight. In determining the state of a bit of the subfield code word, a first threshold and a second threshold is associated with the bit, the second threshold being greater than the first threshold, and the video level to be encoded by this bit and its following bits in the subfield code word are compared to the first and second thresholds. A state is allocated to the bit based on the comparison.