No short-desc as we have them in the element details.
Also keep things (Makefile.am and sections.txt) sorted.
Reword ambigous returns. No text after since please.
/**
* SECTION:element-rtpdtmfmux
- * @short_description: mixes RTP DTMF streams into other RTP streams
* @see_also: rtpdtmfsrc, dtmfsrc
*
* The RTPDTMFMuxer mixes/muxes RTP DTMF stream(s) into other RTP
/**
* SECTION:element-rtpmux
- * @short_description: Muxer that takes one or several RTP streams
- * and muxes them to a single rtp stream.
*
* The rtp muxer takes multiple RTP streams having the same clock-rate and
* muxes into a single stream with a single SSRC.