A multiplierless letter-box converter for displaying 16:9 images on a 4:3 screen

This paper proposes a simple and efficient realization of letter-box conversion for displaying 16:9 images on a 4:3 screen. Compared to the true 16:9 letter-box display where 4:3 vertical decimation is used, the new method yields 5:3 display aspect ratio (slightly wider than 16:9 in the vertical direction) by using 5:4 vertical decimation, and enables the decimation filter to be implemented exactly and easily without multipliers. An efficient hardware architecture is also shown for implementing the proposed 5:4 decimation; in case of progressive scan, if requires only two m-bit adders and two m-bit 2:1 multiplexers where m is the number of bits (typically 8) per pixel. Experiment shows little visual difference between the proposed letter-box conversion and the true 16:9 display with the 4:3 decimation