Abstract: The invention discloses a method for coding a video image on a pixel block basis in a transmission system including at least one transmitter and one receiver, where the video image is in one of several possible display formats. The method comprises:(a) defining a first image display format that encompasses each of the several image display formats;(b) dividing the first image format into pixel blocks;(c) assigning labels to the first image format blocks so that they can be individually addressed;(d) selecting a second image display format for the video image that is encompassed by the first image display format; and(e) coding the video image with reference to the individual addresses of the first image format block.A method of decoding transmissions coded by the disclosed coding method is also presented.The invention is applicable to videophones and television transmission systems.

Abstract: A demodulator is provided comprising: a sampler for sampling the signal to be demodulated at a rate equal to four times a frequency F' situated in the frequency band of the signal; a device for determining the position, in a reference frame Oxy, of the rotating vector associated with the signal to be demodulated, by calculating the arc tangent of a ratio R=(y'(t)/x'(t)) between a value x'(t) of a signal sample and an average y'(t) effected on the values x'(t-1/4F') and x'(t+1/4F') of the signal samples; and means for determining an estimation of the frequency variation between two times separated by (1/F'), by comparing the position of the rotating vector at these times.