ISO MPEG4 + subs?

[Demi-god]

As I recall, it's possible to mux subtitles into an MPEG-2 stream. Is that possible with ISO MPEG-4(quicktime) format? And if it is, what would I need to do so?

[DeXT]

AFAIK there is no "MPEG-4 subtitle" format, the same way there is no MPEG-2 subtitle. In DVDs you'll find DVD subtitles and in SVCDs you'll find a different format (actually two, CVD & Philips subtitles). None of these are defined in the MPEG-2 specs and they are just propietary extensions to the MPEG-2 format (since you can multiplex almost anything you want inside a MPEG stream, provided you have a compatible player).

So the answer could be, you surely CAN multiplex several subtitle formats inside a MP4 stream but this won't be standard and you'll have to find a player which support this (and there is not such player yet). You cannot do it the same way as with OGG media because currently there is no MP4 splitter DSF. However, Envivio is about to release the first MP4 DSF for WMP.

I'm sure that when they release the HD-DVD specs (with MPEG-4 support) a standard subtitle format will be released, too. But we will have to wait some time for this.