Apple Photos app corrupts images

He says the checksums are different but he doesn’t provide a diff to show how different. It could just be a single flipped bit or something. And that could happen in his own RAM/disk/CPU/router so seems premature to immediately blame Apple.

"I’ve not seen any file corruption when importing to Darktable, so I am convinced this is a problem with the Photos app."

Yes this argument is a bit unconvincing for me. Not saying Apple photos doesn't corrupt his files, but this is not real proper investigating either.

He switched out his laptop.

Yeah, I would have been interested in the diff too.

That said, the article does mention replacing basically all the hardware and still encountering the issue. FWIW, my personal experience with Apple software so far is that the usage expected for Average Joe is well tested and polished. But stepping outside of that, it's "Here be dragons" territory very quickly.

Here you go!

  https://gist.github.com/tenderlove/25853f50ab46a58738ff2cc22d682f2b

I ran both files through xxd then diffed them. I've literally changed every piece of hardware (at no small cost). "premature to immediately blame Apple" seems a bit off.

There's a corrupted photo at the top of the article and the non corrupt version at the bottom, is that not enough?

No, it isn’t. The OP isn’t questioning whether the file changed, but asking what changed to the file, not what changed visibly.

The visible effect shown could be due to a change as small as a single bit flip. It also could be that large parts of the file got overwritten, or that it partially got zeroed. The exact kind of damage can help pinpoint the cause of the problem.

This is the kind of stuff that makes me wish my Binary Diff Tool was already completed, but unfortunately I'm still working on it. Can't tell much what's wrong with the differences in the bytes without knowing what the structure behind it is.

I tried running the file segments through a binary diff with Hex Fiend

As far as I can tell:

- 0x7800 bytes were replaced at file offset 0x00aa0000

- 0x2200 bytes were replaced at file offset 0x00aa8000

I can't tell if the replacement data came from a different part of the file, or somewhere totally different. Race condition somewhere sounds plausible.

gcd(0x2200,0x7800) = 512

So some part of the chain with 512 byte buffer size corrupted the data.

It doesn't look like a memory corruption but if this were my computer I'd run the equivalent of memtest86 on it.

It looks like a filing system corruption to me. Running `diskutil info` on the main harddisk and the sd card might be interesting to see if the block sizes match.

Running a disk tester on the sd card and the main disk might be a good idea too. Here is one I wrote: https://github.com/ncw/stressdisk

It's a shame APFS does nothing to ensure file integrity.