The upcoming mpd 0.22 version has a new ffmpeg plugin, maybe it will do the trick.
Code:
ver 0.22 (not yet released)
* protocol
- "findadd"/"searchadd"/"searchaddpl" support the "sort" and
"window" parameters
* input
- ffmpeg: allow partial reads
* filter
- ffmpeg: new plugin based on FFmpeg's libavfilter library
- hdcd: new plugin based on FFmpeg's "af_hdcd" for HDCD playback