Yes, I can play wav files with gstreamer, just not mp3 files.
I could convert the mp3 files to wav files as you suggest, it would allow me to keep going with my project, but in the long term I was intending to have a lot of music stored on the edison to play through a bluetooth speaker, so the MP3 compression would allow me to store more music.
I noticed AlexT has a load of gstreamer plugins in his repo http://repo.opkg.net/edison/repo/core2-32/ but I haven't had chance to explore this yet.
as far as I can see AlexT only has the gstreamer "good" plugins and not the "ugly" ones (GStreamer Ugly Plugins 1.0 Plugins Reference Manual: GStreamer Ugly Plugins 1.0 Plugins Reference Manual) which would cover mp3.
Check gstreamer manual (http://gstreamer.freedesktop.org/data/doc/gstreamer/head/manual/manual.pdf) on the differences:
- gstreamer: the core package
- gst-plugins-base: an essential exemplary set of elements
- gst-plugins-good: a set of good-quality plug-ins under LGPL
- gst-plugins-ugly: a set of good-quality plug-ins that might pose distribution problems
- gst-plugins-bad: a set of plug-ins that need more quality
- gst-libav: a set of plug-ins that wrap libav for decoding and encoding
so you may check whether you can use a mp3 decoder out of the "ugly" plugins. Alternatively, there is also the Fluendo mp3 gstreamer decoder plugin you may want to check: Index of /gstreamer/src/gst-fluendo-mp3