Option to force reencoding of audio in passthrough mode

Hi,
i have the following setup:

Kodi –HDMI–>HDMI audio extractor –HDMI–> Beamer

The HDMI audio extractor only supports AC3 and DTS decoding for multichannel audio (no LPCM) and has NO VOLUME CONTROL.
The audio extractor is connect so my analog 5.1 sound system.

5.1 surround works as expected in AC3/DTS passthrough mode but with this, i cannot change the volume via kodi.
I have to change volume on my sound system which does not have a remote control.

Since kodi is already able to transcode between all audio formats it would be cool if i could force kodi to transcode all audio to AC3 or DTS.
That would allow me to control the volume of my movies via kodi and still get my audio to work with the passthrough mode.

Something similar has already been requested here: http://forum.kodi.tv/showthread.php?tid=211440 but with no real conclusion or answer.