Sorry. As you said in the beginning mediasource doesn't seem to recognise it. I don't know the softw & whether it is capable of recognising m4a for not. I'd suggest (a) you check the options & preferences as to whether you can enable m4a support. (b) Check any documentation or online help for this product. (c) Go to their site & see if there's any updates. I went to one site which offered updates but I'm not 100% sure it's the same product. So I haven't left a link. Google mediasource