Abstract: Multiple streams of digital video data are partitioned into frames of at least two different lengths, where each frame length is an integer multiple times a minimum frame length. Each frame is written into a series of full cells and one or two partial cells. Each full cell carries the same number of video data bits, while each partial cell carries video data bits and/or other overhead bits which together equal the number of video data bits in one full cell. All of the full cells and partial cells for the frames are sent in a time-multiplexed fashion on a communication channel at a single cell rate. A constraint is imposed whereby the different frame lengths are limited to those where the integer multiple of the minimum frame length, divided by the total number of full and partial cells per frame, is a single ratio; and consequently, the video data bits in all of the video streams occur on the communication channel at the same average bit rate, independent of the different frame lengths.