Ant Media Server has been released with a built-in filtering plugin since v220.127.116.11. The Filter Plugin provides users to perform real-time audio and video manipulation on the server side.
The MCU, which allows users to combine video and audio into a single stream for a conference room, is the main application of the filter plugin. Details can be also found on this blog post.
To change the MCU layout or build the filter plugin, please check here.