Unfortunately, if the root cause of this issue is that the video files were transferred as ASCII rather than binary, then I'm afraid the damage is irrevocable. The manner in which data is translated from binary to ASCII results in code that cannot be converted back to binary through an automated process. Put as simply as possible, the ASCII conversion process will invariably create some code that is the same as existing code that is native to the original file, and no automated process exists (that I know of) that can discern between the code created by the ASCII conversion versus the native code.