heck out the below info which explains things credits to TX forums
Making Your Own Rips
When ripping your own discs with the latest Xbox Backup Creator v2.9 Build 350 you should have "processing AP2.5" unchecked. This adds an extra hour to each game rip and is not required. This option is only used when topology data is being collected for development purposes.
Remember that angle measurements need to be as accurate as possible. If you rip your own you are using just 1 set of measurements. Your laser may be weak or you may have just one measurement out of hundreds that is out of bounds of the accepted values and your disc will error and you will be flagged for an AP2.5 Failure (See point #3)
FYI the accepted values are -/+ 22 (even though originals rarely go above -/+ 2 with a perfect quality laser - the extra is allowed for those that have a poor quality laser)
The median files that are created are the work of HUNDREDS of dumps per game over many different consoles and many different drives. Then using a complex algorithm millions of individual results are then calculated to give the absolute best timing scenario possible. The median files that are provided give a deviation of -/+ 8 (The original target was 9 - so anything below this is considered awesome).
To give you an idea of what we are talking about here is the deviation data when using the median file on an XGD3 title:
LT3.0 - Liteon - 14699DAE - Forza 4 BU - New Median - Pastebin.com
As you can see the results are superb and rarely go above -/+ 4 with a maximum of 8 in just one instance.
However if you rip your own you may find that some angles will go up to -/+ 100 which is WAY over the -/2 22 threshold and will give you a bad image.
So when ripping your own images, uncheck Process AP2.5, patch with the given median file and then burn. There may be a simple app coded for you to check the deviation values of your own rips in the near future.
Note: The XGD3 Median Topology file covers ALL current XGD3 games. This includes other languages too. There is no need for you to check the profile of your game at this moment in time. If you are 100% certain that the median file does not work with your XGD3 title then you need to rip the original game using the new XBC and test it again. If it then DOES work then you need to report it with the Profile ID of the game and the AP25 topology file (after checking process AP2.5 of course). If you can't do this then dont bother posting about it.
