Just to explain the result you got : there are two different things that data recovery softwares can find, either the actual contents
of files, or indexes
of files, which kinda work like an address book, telling the system (or the recording device) where the contents of each file are located. When a file is deleted, the index is updated but not deleted: it just says to the system (or the recording device) that those sectors where that file used to be are now free, and can therefore be used to record other files – which is what happens obviously when the memory card is used later on. But since the indexes of those former files are still there (until they get overwritten themselves), a data recovery software can very well display the correct names, sizes and timestamps of deleted files, even though the actual data has been overwritten, which is irreversible; then what is exported is actually a random portion of a new file, it doesn't have a valid header (the begining of the file does not contain the informations required to identify a video file as such) and that's why no media player can read them. When a file is accidentally deleted, there's a good chance of recovering it, but only if no further data is written on the device.
Recuva, a very good free recovery software, assesses the condition of the files it detects, then indicates if a file has been overwritten, and by which other file.
Perhaps you would still have a shot at recovering those files from the hard drive, if it has a lot of free space and hasn't been used too much since the deletion... It could happen that the begining of the file is fine, but the end has been overwritten, in this case, for most MP4 files, they won't be readable anyway, because there's an index area at the end of the file which is required by media players to make sense of the stream of data; but in that case there's a possibility to salvage what's left with a software like Grau Video Repair
. Again, for this to work the header has to be valid (in hexadecimal view you should see “ftyp” in the middle of the first line for a MP4 file) and a significant portion of the original file should not be overwritten, so this won't work for sure with that "C0001.mp4" file.
And don't do the stupid thing, which is to attempt to recover a file from a device (a memory card or HDD or whatever) on that same device, because you can't control where the recovered file will be written and there's a high probability of destroying it in the process. I tried to help someone who had done just that (or more accurately, she had handed the card over to a friend working with computers who supposedly knew what he was doing, and it turned out that he did not), but it was too late. She thought that she had copied that one file with the others when she deleted the whole folder, but must have missed it in the mouse selection. To prevent that from happening ever again, I advised her to use a duplicate file remover, to make sure that the files deleted from the memory card have actually been copied to the computer, and flawlessly copied (matching CRC32 or MD5).