1. Method for encoding a video level of a pixel of a picture to be displayed by a display device into a code word called subfield code word, a weight being associated with each bit of the subfield code word, each bit having a state “ON” or “OFF” and causing light emission during an own period, called subfield, of a video frame when its state is “ON”, the duration of the light emission period for said bit being proportional to the weight associated with said bit and wherein 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, characterized in that, for determining the state of a bit of said subfield code word, it comprises the steps of associating (S 1 ) a first threshold and a second threshold with said bit, said second threshold being greater than said first threshold, comparing the video level to be encoded by said bit and the following bits of the subfield code word to the first and second thresholds and: if said video level is equal to or lower than the first threshold (S 2 ), allocating (S 3 ) a state “OFF” to said bit, if said video level is equal to or greater than the second threshold (S 4 ), allocating (S 5 ) a state “ON” to said bit, if said video level is lying between said first threshold and said second threshold (S 6 ), allocating (S 7 ) a state “ON” or “OFF” to said bit according to a predetermined criteria.