OpenAL file formats

I've read a few posts on this but haven't found any definitive answers, hoping someone might be able to help. I'm using OpenAL in my app and am converting my sound effects to the correct format.

If I convert my file like this:

/usr/bin/afconvert -f caff -d LEI16 -c 1 bs3.mp3 bs3.caf

the file works fine. If I convert it like this:

/usr/bin/afconvert -f caff -d ima4 -c 1 bs3.mp3 bs3.caf

it doesn't work at all. I'd like to use the ima4 compression as the files are huge without this. Has anyone had any luck getting ima4 to work?

Thanks in advance

Mike