Transcoding is the process in which one file, either a media file or object, is converted from one format to another. In telecommunications, transcoding is performed when a request is made for a specific document or file and is received by a gateway or proxy server, which then converts it using the appropriate annotation needed for the client. With the help of transcoding and a media gateway, networks are able to be connected to each other with the use of different transmissions and coding techniques.
Media Gateways are used for transcoding media between PSTN and IP networks
Ribbon's Media gateways are used for transcoding media between PSTN and IP networks.