oday (Shenoda). It is the H.320 specification which is most applicable for narrowband time-division multiplexed (TDM) networks (Shenoda). MPEG on the other hand is more suited to broadband packet-oriented networks and it is these networks which maintain end-to-end quality of service (Shenoda). A third type of specification is motion JPEG but this specification, while it is useful in high-quality video such as that utilized in studio program presentation, is of less general interest due to the high amount of bandwidth it consumes (Shenoda). An underlying physical layer and an overlying H.221 framing standard is recommended for ITU-T H.320 (Shenoda). Shenoda also reveals that: “Above framing reside H.230 control signals, the G.7xx suite of digitized-audio protocols, and the H.261 codec standard for digitized video. Data or other information can be multiplexed with video and audio using the H.221 framing standard. H.320 specifies the system reference configuration and basic requirements. It is based on encoding the program elements to fit in a P x 64-kbit/second channel, which can be from 64 kbits/s to 1920 kbits/s. One or more channels are framed to fit standard transmission rates (T1 or E1) using the H.221 framing recommendation. (Shenoda)”.It is the type of system described above by Shenoda which most often finds its utilization in current distance-learning and videoconferencing applications such as that which will be described below. These systems are able to relay reasonable quality video using higher-capacity channels of 1 Mbit/s or more while at the same time having the ability to utilize existing networks (Shenoda). ITU-T recommends H.261 for videocompression in H.320 systems (Shenoda). This recommendation is based on constant video frame frequency sampling and block encoding where there are 625 to 525 lines of video and where “a block is a number of lines with a number of pixels per line” (Shenoda...
