AAC is a very expensive format to licence, so we would only do so if there was great demand for it. It probably wouldn't be a free upgrade either, so it would have to wait until such time as we can distribute codecs in a modular fashion.

The issues with VQF (more properly known as TwinVQ) are more involved. The format was developed by NTT and licenced exclusively to Yamaha. The format is proprietry and Yamaha refuse to release specifications - although a few people have reverse engineered it. Given the relatively small demand we have received to support this format, it's almost certainly not worth us risking the legal minefield that would come with it. I believe there is an open VQF project underway for Linux, so maybe someone else could hack up an empeg codec, if and when we provide support for such things.

Rob