Thomson apparently brought the new mp3hd format for music the other day. “HD” is apparently the thing we need to have included when a new term is announced. Why does the world need another lossless music format?
It seems they’ve introduced a crafty dual-format thing where they stuff MPEG-4 SLS lossless encoded data in a new id3 XHD3 tag within the mp3 and then stuff a “regular” mp3 as the normal data in there. This way it is supposed to still work fine with existing and older mp3 players. Of course the total size of all id3v2 tags is limited to 256MB, which could be a limiting factor for it.
As usual, you can find a thriving discussion on this topic on hydrogenaudio.
Rockbox should of course be possible to at first use the mp3 parts and if this truly is an existing established lossless codec there’s a chance it might be able to play that part in the future.