Image transmission devices and systems

摘要

An image transmission device, which prevents a time delay from occurring in compressed video data transmitted to the receiving side through a line activated at a low data transfer rate, includes a camera (21) placed on the transmitting side which images an object to be monitored. A compressor (22) receives the video signal (SVi) from the camera (21) to produce compressed video data (DV). This data (DV) is transmitted to the receiving side through a line (40). On the receiving side, an expander (31) receives the data (DV) to obtain a video signal (SVr). A monitor (32) displays an image based on the video signal (SVr). When a supervisor operates a man-machine interface (33) on the receiving side, a control signal (PTC) for a pan tilter (23) is obtained. The control signal (PTC) is transmitted to the transmitting side through the line (40). According to the operation of the man-machine interface (33), the direction of imaging of the camera (21) on the transmitting side is changed. While the screen greatly varies when the imaging direction of the camera (21) is in a changed state, the rate of compression of data by the compressor (22) on the transmitting side is controlled so as to increase, thereby restraining an increase in the amount of the data. Thus, a time delay in the compressed video data (DV) transmitted to the receiving side is prevented.