File Protection

M

Michael Olsen

Veteran
I did some reading elsewhere today that got me thinking about how different cameras protect files on media in the event of some sort of catastrophic failure (e.g., power loss, media removal).

In the event of power loss (simply out of power, or battery physically removed) or media removal (SD pulled out), what happens when the camera is rolling? Is the file closed out and the footage safe except for a few frames? Or is the whole clip lost? Or just part?

I doubt this is anything that has been tested extensively. Given the preproduction state of the cameras, it may still be under development. But I would be curious to know.

And yes, I know. Just check the battery levels and, if I'm really concerned, gaff tap everything into place. This is pretty much just to satisfy my curiosity.
 
On the HVX 200 when you use restore clip after power dies - it would appear to restore right up to the last frame, or very close. But you need to run restore clip before you offload.
 
heavyG said:
On the HVX 200 when you use restore clip after power dies - it would appear to restore right up to the last frame, or very close. But you need to run restore clip before you offload.
Click to expand...

That's definitely good to hear. It definitely leads to me to continue to ask about the AF-100, though. I wonder if there will be a significant difference between P2 and SD in terms of file fidelity.
 
heavyG said:
On the HVX 200 when you use restore clip after power dies - it would appear to restore right up to the last frame, or very close. But you need to run restore clip before you offload.
Click to expand...

P2 is designed to close out the file system every two seconds. It's not the camera that does that, it's the actual recording media. The P2 card has a microprocessor on it and it's what creates and manages the file system, and every two seconds it closes/finalizes the file, so if you encounter a power-out or ejection issue, the worst you'll ever lose is two seconds of footage.

I wonder if there will be a significant difference between P2 and SD in terms of file fidelity.
Click to expand...
Well, surely there will be a difference, but as to what degree, we don't know because the AF100 is new and untested. However, I can answer in terms of the other AVCCAM cameras, which is that they work the same way Robert described for the XDCAMs. If you yank the power out, you'll have an incomplete clip and the next time you power on, the camera will go into a "restore media" function. I've never had it fail, but I'd imagine there are scenarios where it could, I guess.

Another potential area where you could get an incomplete file would be if the battery dies during recording. However, the AVCCAM cameras use a new battery that relays exact battery charge state to the camera, so the camera knows exactly how much juice the battery has, and knows when the battery is about to die. I tested this repeatedly, and in every case that I tried, a battery running out had no effect on the finalized recording; having the battery die resulted in perfectly normal footage. The camera "knows" when the battery is about to die, and shuts down the recording first and finalizes the recording before the battery power gives out.

The bigger danger would be in doing something that could actually damage the card itself -- such as ejecting a card while it's being accessed. P2 cards are engineered to prevent that as a potential source of damage, but SD/SDHC/SDXC cards aren't. If you eject a card from a computer or camera while it's being written to or read from, there's a real danger that the card itself might be damaged or destroyed. So, don't do that. Always make sure that the card is not being accessed before ejecting it. On the Panasonic AVCCAMs, they've engineered a door system to help prevent that; when you open the card door it automatically stops recording and playback. The act of opening the door tells the camera to stop accessing the card. But it's not absolutely instantaneous, especially when recording -- there might be a second or so as the card finalizes its recording. For playback, it's instant; for recording there's obviously a delay of a little bit (maybe half a second, to finish a GoP). If you're foolish and are in an insane rush to open that door and grab a card as quickly as possible, you may very well end up ejecting that card while it's being written to, which will at the minimum result in an incomplete file, and at the worst it may damage the card. So, don't do that. Slow down. Wait two full seconds before ejecting the card, and you should never have a problem.

As for using cheap media which develops write errors or fails on you as you're using it -- I think you're on your own at that point. My advice is to only use the very best media at all times. In my testing and research, I think the premium brands are the SanDisk Extreme, Lexar Gold, and Panasonic Gold. Forget everything else, don't trust your footage to some cheap no-name card off ebay, and really -- do you care if you saved ten bucks on the card cost, if the card itself fails on you?

And, furthermore -- don't buy brand-name cards off cheapo ebay auctions. There are knockoff/fake cards out there. Don't risk it. Buy high-quality best-brand-name cards from authorized resellers. There's nothing more important than the footage you're making, and nothing so foolish as trying to save a couple of dollars on the card you're recording to.
 
All good advice, Barry.

I think the importance of good media is often over-looked in rush to save a little bit of money.

It's good to know that even if one does everything right and something somehow manages to go wrong, there is some data recovery ability there.
 
bad experience Sandisk

bad experience Sandisk

personally i had two erors with SD cards that failed while downloading.
one time the footage lost.
both were with Sandisk extreme 16G class 6.
I have also 3 Trancend class 6 16G and recorded hundreds of times without any problem
 
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