Is it possible to put a MP3 in an ogg Container? It would be better todo this than to transcode them (APE tags can be used and source MP3 would still be there for portable player use).

Any special reasons why would you like to use Ogg container?

It's possible to put it into MP4 container, but afaik, there is no legal way to do the same thing with Ogg container.

It is possible using ogg direct show filters, but I doubt that no stand-alone player/hw-player can play it.

its possible with tobias waldvogels ogg directshow muxer, playback works with his splitter filter in any dshow based player