Abstract: A method of decoding coded image data, preferably coded according to CCITT Recommendsation H. 261, wherein the data stream is continuously monitored for transmission errors by utilizing the residual redundancy of the data stream, and pixel values reconstructed after the detection of a transmission error are not entered into the predicted-image memory until a subsequent starting code word for a frame or field has appeared.

Abstract: A process of frame-to-frame prediction coding in which a frame is broken down into a regular block scanning field of n x n pixels and then prior to each prediction, up to four prediction methods, namely (1) block-by-block displacement vector calculation, (2) object-related displacement vector calculation, (3) nullification of the displacement, and (4) nullification of the prediction, are monitored as to the data rate to be transmitted, and the prediction method that leads to the smallest prediction errors is selected for the transmission.

Abstract: A system for permitting compatible communications among broadband and narrowband picture telephone installations, the bandwidth of a narrowband installation corresponding to the lower portion of the bandwidth of a broadband installation, in which the pictures associated with both types of installations have the same number of lines, the same line scanning frequency and the same frame rate, both the scanning of the subject image and playback are effected with a wave-shaped line scan for playback in a broadband installation, the signals in the transmitting portion of a broadband installation are split into a low frequency component, covering a bandwidth corresponding to that of a narrowband installation, and a high frequency component, and both components transmitted from a broadband installation are recombined in the receiving portion of a further broadband installation receiving the transmitted signals.