Corruption
When an AVI file is downloaded from multiple users the data is sometimes corrupt.
This happens because a duplicate of the file has been created and then altered.
This "fake AVI" is exactly the same length as the "real AVI" and named similarly
but the contents are no longer genuine.
|
For example, user A has a file which is 100% real. User B creates a file which is obviously 0%
real. When user C downloads this file approximately half the data is downloaded from user A
and half from user B (due to the technique of downloading from multiple users). User C now has
a file which is only 50% real! Now user D tries to download the file and gets roughly a third
of user A's file (100% real), a third of user B's file (0% real) and a third of user C's file
(which is only 50% real)! Soon 50 users have the file but each copy is
infected except for the first one. More often there is more than one "real avi" but if only
one copy is fake then this slowly infects the downloads of new users.
Even though a better player or codec may appear to help the problem
(due to the way the player or codec handles errors)
no player or codec can play what isn't real!
|
 |
Repair
To repair an AVI, all the "fake" data needs to be replaced with "real" data.
There are two ways that this can be achieved:
Reference
|
AVImedic compares the file with a second download of the same AVI,
determines which parts of the first (master) file are fake and patches them with any
available real data in the second (reference) file.
The resulting repaired master file may now be perfect or it may still be corrupt
(but considerably less so than either the original master file or the reference file).
If all the errors are not repaired, AVImedic can use a second reference file,
compare it to the partially repaired master file and repair even more errors!
The master file can be re-created perfectly by repeating this process
(depending on the quality of the downloaded reference files it may take as little as one
reference download to achieve the desired results or,
in the case of a heavily corrupt master file,
a number of reference downloads may be required).
|
 |
Patch
|
Alternatively, someone with the same AVI can create a patch containing only the
required real data. This saves download time as downloading the entire AVI is not really
necessary (as only certain parts are needed).
The patch can optionally contain all the data required or only parts of it depending on
the size of the patch and the bandwidth available to the patch creator and user.
|
 |
| 