An apparatus in a video signal transmission system for measuring cable length and compensating for cable loss is described. A number of pilot signals of different frequencies are compressed into one of the three color signals during the vertical sync periods in a time-division manner. The vertical and horizontal sync signals are compressed into the other two color signals. The video signal is transmitted over a cable having at least three pairs of wires, each color signal being transmitted by one pair of wires. A pilot signal converting circuit obtains the levels of the pilot signals transmitted by the cable. A compensation control circuit averages the levels of the multiple pilot signals of different frequencies over a number of vertical sync periods, and generates compensation control signals based on the average level of the pilot signals. The compensation control signals are used to perform video signal compensation.