Apple has updated their developer notes to include some detailed information regarding AppleTV Export found in QuickTime 7.1.5 last week.

The technical note details why we were getting such strange file sizes while exporting. This note as confirmed (again) that M4V with ACC sstill only allows stereo audio.

Movie Size:
Your exported movie dimensions will be determined by the source movie and source frame rate. The best you can get out of the export is 1280x720 at 24 fps or 960x540 at 30 fps. You won't find anything larger then 720p in an effort to save excessive filesizes as this is AppleTV's maximum output.



Frame Rate:
So now that we know the file size we'll take a peak at the frame rate. Once again your exported movie is based on your source. The export process will always favor maintaining the existing fps. If its less then or equal to 30 fps, it will remain the same. If you are over 30fps the export will adjust this appropriately.

Data Rate:
The datarate has a ceiling of 5MBps, which is once again restricted by your source document. The data rate is based on the most effective destination movie size, after it has been scaled and fps has been adjusted (if necessary) Basically it falls inline like this:

• ≤ 320x240 = 768 kbps
• > 320x24 & ≤ 848x480 = 3000 kbps
• > 848x480 & ≤ 1280x720 5000 kpbs.
  

Additionally, within an encoded movie the data rate may spike up to a maximum of 12 Mbps.

Well I hope that clears up a bit of the file size confusion. So I guess there seems to be a some what rational explanation to all of it?