Method for identifying improper transmission of images in an image-processing device and a corresponding image-processing device

An image-processing device, comprising:

• a transmitter and at least one receiver, which are designed for the digital transmission of an image signal, which comprises a timed sequence of images, wherein an image buffer is assigned to the receiver, into which successfully transmitted images are written, and the image most recently written to the buffer is repeated if a defect in the image transmission process occurs, wherein the image-processing device is configured to superimpose an alternating signal, which alternates at a signal alternation frequency, on the image content of the images before the images are transmitted and before the image buffer, and wherein the signal alternation frequency is greater than or equal to the perception frequency resolvable by the human eye.