Honestly, I can’t find anything on the Apple site. All they want to do is sell me things. I’ve spent hours trying to search, and trying to click Google hits that point back to Apple, but I keep ending up in the iTunes store or some other ad selling something else of theirs, be it Quicktime Pro or an AppleTv or an iPhone.
The fact remains that DTS asked Apple to reserve the names of the streams, so that if someone comes along and wants to extract DTS tracks from an .mp4, the names won’t be being used by some other schmuck who wanted to call their stream “DTS.” That in and of itself doesn’t signify any official “recognition” from Apple. They’ve just processed the registration requests. But they also could have said “No, nobody ever will be sticking tracks named ‘DTS’ in so there’s no need to reserve the names.”
The DTS entry listings are readily available from the mp4ra.org, along with all the other registered codecs and types.
AppleTV take 2 seems to support AC3 within .mp4, from what I’ve read elsewhere, and from the fact that Apple sells/rents .m4v files with AC3 5.1 audio in them.
I’m not about to pay the ISO’s prices to buy a copy of the specs, just to satisfy my own curiousity, but that would probably be worthless anyways, as it would describe MPEG-4 audio, not private stream audio within .mp4 containers. The spec itself isn’t required to define all private streams that may be inserted.
The fact is that any player is required to ignore any private streams it doesn’t understand, from what I can read of the MPEG-4 Book. Private streams can’t be “banned” from a specific container, per se. Many players have been able to pull VOBSUB out of .mp4, as a private stream… I believe Nero’s player has been pulling VOBSUB out of .mp4 for some time, despite subs not being nominally in the original MPEG-4 specs, because they fall under the “other” in the specs by being a private stream.
So, there’s no legal or technical reason why I can’t put AC3 or DTS into an .mp4 file, and there’s no legal or technical reason the WDTV can’t pull them back out. That it doesn’t is another matter. But it’s not that it “can’t”. And whether Apple wants me and WD doing it or not is irrelevant.
I’d wager that the real reason WD isn’t pulling DTS out of .mp4 files has nothing to do with Apple saying it’s a no-no, and everything to do with the fact that nobody’s putting DTS into .mp4 files because nothing else will pull it out either.
