[MEncoder-users] Need help fixing/decoding a recovered h264 file

[Marc MERLIN]

On Fri, Feb 26, 2010 at 07:38:09PM +0100, Reimar Döffinger wrote:
> On Fri, Feb 26, 2010 at 08:29:10AM -0800, Marc MERLIN wrote:
> > This seems to show that I have at least one page of data that is incorrect.
> 
> More precisely you are missing about 288 kB of the header, more specifically
> almost all of the index (at offset 0x8000 there is the mdat atom, that one is
> supposed to be at offset 0x50000).
> I am not aware of a way that would allow recovering
> mov files without a index - which is why I always considered it a really bad
> format, it is very brittle without being very compact.

I see. Thanks much for the analysis, I was trying to figure that out.
I also briefly entertained the hope that I could use the index of my other
file taken in the same conditions, but first that didn't look easy and
second it didn't look like it would work since the header must be different
for each file anyway.

> > I suppose fixing it from here would not be trivial :-/
> 
> Well, the obvious question is: have you tried those undelete tools for FAT?
> FAT contains a lot of redundant information and thus usually allows for rather
> good recovery of "lost" data.

I tried a few, but my understanding is that once the cluster table has been
freed, the only way to recover the files is to find the file header by
scanning all the block on the card, and then figuring out how many blocks to
restore by assuming that they are contiguous (i.e. unfragmented) since on a
camera, my understanding is that everything gets wiped and you start fresh
every time you start recording new pictures on a freshly deleted (but not
reformatted) card.