Television system for transmitting digitized television pictures form a transmitter to a receiver where different transform coding techniques are selected on the determination of motion

A motion detector, particularly for use in a television system for transmitting television pictures in a digital form, is adapted to partition each picture into pixel blocks, to subject each pixel block to a modified intraframe transform for determining a first coefficient which corresponds to the basic picture having the lowest horizontal and highest vertical frequency, and to determine a plurality of further coefficients which correspond to basic pictures also having the lowest horizontal frequency, but a vertical frequency which is lower than that for the first coefficient. The motion detector signalizes the presence of motion within a pixel block if the first coefficient has a large absolute value, but if simultaneously none of the further coefficients has a sufficiently large absolute value. If the first coefficient has a sufficiently large absolute value, absence of motion is nevertheless signalized if simultaneously one of the further coefficients also has a sufficiently large absolute value