I'm using a third party utility to RTP audio files over my local network. The audio files are typically MP3/WAVE/PCM. I need to RTP one of these audio files to a multicast address but need to have the volume gradually increase over 5-10 seconds as its heard at the endpoint. Since the gradual fade-in happens dynamically depending on scenario I'm hoping to be able to use FFMPEG or another similar utility to do it on the fly and pipe the resulting audio stream into my RTP utiltiy.
Any help with how to do this using FFMPEG or similar would be appreciate.