Help on migration from J River Media Center to Songbird

I've been using J River Media Center on the PC for the longest time. I've recently switched to a MAC and I'm looking to export my J River Media Center database into Songbird. I've got a lot of other metadata associated with each MP3 that I hope will not be lost during this migration. Can someone please help? If it means that I'll need to first export to itunes and then to songbird, I'll do it too. I just need some directions and detailed steps. Thanks.