For transmission of an airborne infrared (IR) image sequence from a plane to a receiving earth station and for transmission of moving images in mobile networks the image data rate has to be reduced by a source coding technique, in order to meet the available relatively low channel capacity.
The PCM data rate of a 8 bit infrared image signal with 720 by 288 picture elements (pel) per field and 50 fields per second, corresponding to TV-resolution, amounts a data rate of 83 Mbit/s. For data reduction coding techniques are applied. These coders split each image into blocks, which are then coded by a motion compensating transform coding technique. Using MPEG-2 [1] the PCM data rate of an infrared image sequence can be cut down to 4 Mbit/s without visible distortions. As the capacity of the available transmission channels is less than 0.5 Mbit/s, an additional compression factor of about 8 is required.
In order to achieve the additional compression factor, a so called ROI-based coding technique has been developed, which uses MPEG-4 AVC [2] and focusses the coding on detected regions of interest (ROIs).
[1] ISO/IEC MPEG-2
[2] MPEG-4 AVC
