Why is Quicktime trying to change from .MP4 to .Mov?

Question

Having spent months saving clients promotional files from .avi, .mov and may other formats into .MP4 why on earth is Quicktime on Mavericks trying to play tham back as .MOV especially as I charged them for my time in converting the files in the first place. I really dont want to reencode 500GB+ files... HELPPpppp!
Many thanks

Answer 1

There is a slow change for the QuickTime platform coming. Right now the new OS has a built-in library which tries to re-encode your older videos. They are no longer being actively supported by Apple, since the switch is on, with the 64-bit architecture and of course the mobile platforms (all the "iThings" out there..) to make all of the supported file codecs be as efficient as possible for the newer hardware.
The QuickTime PlayerX that comes with your system is trying to reformat - there is NO way to get around it as the instructions are nested down in the libraries for the application - in the QTKit.framework. It's an instruction-set that you can't get out unless you know how to program code. (I think it's in Objective C)
With that as a given, what is left to do is download and use the last available version of QuickTime Player 7 and get the codec packs you need - all of this is the 32-bit code and it's days ARE numbered so fair warning. Here is the quick list I've built as a workaround to keep your files unsullied.
Start with QT 7.6.6. - http://support.apple.com/kb/DL923
Get Perian, and install it. - http://perian.org
then VLC, - http://videolan.org
DivX - http://divx.com - and the
Flip4Mac package from Telestream - http://www.telestream.net/flip4mac/
This is what I've put into my system and so far I've gotten every file to run fine, even my oldest videos.
These are codecs you should see.
In System/Library/QuickTime
     AppleIntermediateCodec.component
     AppleMPEG2Codec.component* (*optional if you've bought it)
     DivX Decoder.component
     Flip4Mac WMV Advanced.component
     Flip4Mac WMV Export.component
     Flip4Mac WMV Import.component
In your Home/Library/QuickTime/
     AC3MovieImport.component
     Perian.component
For AC3 sound that is in most .mkv files, you need the A52Codec.component, here:https://dl.dropboxusercontent.com/u/34821905/A52Codec.component.zip - unzip the file and put the component into the System/Library/Audio/Plug-ins/Components
Go back to your Perian settings and in the Audio Output button, set it to 'Multi Channel Sound' - Ignore the message Perian puts up and select it.
By doing a 'Get Info' on your files and where it says 'Open With' - default them to the QuickTime 7 program. Perian no longer will work with QuickTime Player so you must have QT 7.6.6 and set it so it is the default for all the filetypes you use.
It works perfectly with QT7. So far I've gotten ALL my old videos to play.
.avi, .mov (with the AC3 sound), .wmv, .flv, .mp4 and .m4v. all run fine as do all the older formats.
Good luck!
Deb.