This tool seems to be what I was looking for, but it does not work with the AVM Fritz Repeater N/G: it is listed in the “Stream to” menue as AVM FRITZ!MediaRenderer, but there is no sound, when I choose it. I already tried it as MP3 and as PCM stream in the settings of SWYH.
The MediaRenderer and loudspeaker work: I tried them with the Android Player “Bubble uPNP”
Anyone any idea?