Media Servers are used for the purpose of transcoding media streams; for example, in case of WebRTC, it converts audio/video from the WebRTC standard to other codecs understandable by legacy agents.
Media-related operations such as audio/video recording, playback, announcement, and conferencing are handled via the Media Server. Few of the advanced use cases such as Music on Hold, IVR, Video on Demand, and others are also configured through the Media Server logic. Importantly, the Media Server also provides for Media Resource Function (MRF), which processes real-time audio and video media streams and forms a crucial part of the IMS architecture.
To play a simple announcement through the Media Server, the establishment of a SIP session is requested. Similarly, record and playback operations, on part of the Media Server, require the establishment of a SIP session, just as in case of a call.
The call flow for media announcement is depicted in the following...