Why does a card-reader fail, when same SDcard works in camera?

While recording my son's soccer-games, some of my cheap cameras just run-thru. Sometimes, the batteries get weak, so the file on SDcard is corrupted ('not closed'), kaputt.

What I noticed:
• using a card-reader, MacOS tells me "no way!", file can not be opened with any software, even copying the file to my harddrives doesn't work.

• but… 
that same 'corrupted' card in the camera DOES playback!
And, when connecting the cam via usb, allows to download and/or import the files to FCPX.-

___________

Has anybody a technologically explanation for that?

Does a camera has some sort-of 'smart operating system', which ignores the standards, and reads out the 'video' anyhow…? Or, perhaps has a not-so-smart operating system… ??

… I'm happy, it 'just works' - just curious…
And it really saved my a** a few times :lol:

Hi Karsten,

When a card inside a camera gets "corrupted" the metadata on the card folder may not contain the headers that are required to automatically recognize and open the card structure outside of the camera.

This does not mean that the video files on the card cannot be read individually, and that's what happens when you connect the camera via USB to your computer: the camera just takes every MOV or MTS video clip inside your card folder and streams them to your system without the system needing to recognize the complete folder structure. It's the same as if you were to copy the card to your system, open the folder structure yourself and import or convert every individual video clip that is inside the folder.

- Ronny

ronny courtens wrote: …  It's the same as if you were to copy the card to your system, open the folder structure yourself and import or convert every individual video clip that is inside the folder.… 

thanks, Ronny, for taking your time to feed my curiosity!

… I tried this, via Finder:
one of my cams uses an .avi container: no Finder-operation (copy, open, play) was possible; same card IN camera, usb-connection = working

the other device uses .mov wrappers - again: no play, no copy from card-reader; from camera: fully functional.

Lucky me, my two other cams using AVCHD have some 'safety'-feature, when card full or battery empty, the actual video gets written… 'til now, no probs with AVCHD…-

BOTH files were visible in Finder, the other, healthy ones on the same card were useable.
Both files did not show the generic QT-icon
Both files were NOT able to be opened via VLC (which usually is my 'can opener', to dig-out 'video' from any file - I have friends sharing video via powerpoint-files! … thinking for a second: no, not 'friends' .... )

so, in my unpublished book "Dirty Workarounds", this method "from inside cam" is really helpful - and I recommended this trick to others, with same issues, with same positive results.

I just want to impress others with my 'understanding', what secret sauce is at work here…  :lol:

.... I was told, in the Windows-world are tools avail, which are able to 'close' such files and/or strain the video out of such corrupted files… I guess, even if an engineer explains it to me, I will not understand it. :silly: