Rate Ceiling on Transport Streams

In certain situations it is desirable to implement a hard limit on a data stream. Perhaps the MPEG transport protocol is being used to carry non real-time data in its elementary streams and this is then being multiplexed in with some rate sensitive real-time video. In such a scenario it may be desirable to put a hard ceiling on the rate of the variable rate data so that it does not inadvertently steal bandwidth from real-time sensitive data and thereby impinge on its quality.

In such a scenario WooshCom's MPA-1212 may be used as a hard ceiling which will implement a hard block against data ever exceeding a user specified rate Rl. The MPA-1212 has 128 pre-programmed rates ranging from as low as 70 Kbps up to 213 Mbps which can be used to implement a rate ceiling. As shown in the Data Rate Limiting Diagram, the stream entering the MPA-1212 is varying in rate over time without any limit on the rates that it can hit. But after running through the MPA-1212 the output stream will be limited to the output data rate which the MPA-1212 is set to, call it Rl. Any data that exceeds that rate (Rl) will be discarded as shown in the output rate diagram.

If the MPA-1212 is placed on the streams which need to be limited in rate before they are multiplexed together with sensitive real-time steams the sensitive streams may be protected from being overrun by the less important stream. In such a scenario the MPA-1212 may be thought of establishing a safety limit on that source.