revert trimmed file to origianl length

There's no such thing as a one minute 5.3 gigabyte .mov file.
What was the original source of the file? An iMovie Project?
Do you still have the original iMovie files?
QT 7 Pro allows multiple "undo" but only while editing. Once you save the file is changed and reflects the new size. Save as creates a new file and leaves the original untouched.
By your profile you are still using QT 6.

So you've edited the .mov file that was inside your iMovie Project.
It is a reference movie and only points to the other files inside the iMovie Project folder.
You'll need to re-create the iMovie Project. You can make a new Project and drag all of the originals (from the other folder). This should assemble all of the originals but you may have to edit the transitions again.
What you want are all of the .dv files that made up your original.

I can confirm there are things such as 9GB / 5min Quicktime Files. I also trimmed and accidentally saved (pure Quicktime dv file - no iMovie) the thing - the filesize remained the same. So the video data must still be somewhere. There is absolutely no hint on the internet available how to get back to the original material.

Does anybody have a clue?

These discussion are peer to peer and no Apple employees respond to any post.
Any chance your source was in .mpg format?
Normally QT Pro can't edit but there are some exceptions. If you do edit an .mpg file the timeline will show just your trim but the file size doesn't change.

I created a small 1000K movie file as a test file. I duplicated the file in Finder. Get Info shows that both files are identical in size. I opened one of them in QuickTime Player Pro and trimmed, then saved.

The original file was 1,023,299 Bytes. The trimmed file was 1,026,211 Bytes.

I opened the two files in HexEdit and compared them.

The original file began with:
00 00 00 20 66 74 79 70 71 74 20 20 20 05 03 00 ... ftypqt ...
71 74 20 20 00 00 00 00 00 00 00 00 00 00 00 00 qt ............
00 00 0B 34 6D 6F 6F 76 00 00 00 6C 6D 76 68 64 ...4moov...lmvhd

The duplicate showed:
00 00 00 20 66 74 79 70 71 74 20 20 20 05 03 00 ....ftypqt......
71 74 20 20 00 00 00 00 00 00 00 00 00 00 00 00 qt..............
00 00 0b 34 66 72 65 65 00 00 00 6c 6d 76 68 64 ...4free...lmvhd

The only difference being that 4moov became 4free. I changed 4free back to 4moov and then searched to the end of the file for other differences - the only other difference was additional, new information appended to the end of the duplicate file.

The original file ended with:
DB F8 DB 6F E3 6D BF 8D B6 FE 36 DB F8 DB 6F E3 ...o.m....6...0.
6D BF 7F m..

I went to the very bottom of the duplicate file and then scrolled up until I found where the original file had ended. It was identical to the data above but of course there was more data after what is shown above. I deleted everything after what is shown above and saved the file. HexEdit made a backup copy automatically, just in case.

I then double-clicked the freshly saved, edited version of the duplicated and trimmed movie and voila... no trim, the whole file plays.

HexEdit is here:
http://www.ifd.com/productinfo.php/productsid/87?osCsid=deac9ffcb6cb8cd131747a95e18ae15f

Tell Apple what you think about QuickTime here:
http://www.apple.com/quicktime/feedback/

EDIT: Update, I just did the same procedure again, this time changing free to moov and NOT deleting anything or changing anything else - and the whole file plays, no trim. 🙂

Hmm,

I'm trying to get this to work with a 3.5Gb file.and then a 35Gb file.

Only thing, I cannot get hexedit to open even the 3.5Gb file?

Any thoughts (apart from the wrong forum!)