Testing Overcranking advice.
 

Could I run this past someone please.

I'm testing my 16gb Transcend cards by overcranking 48fps 720/25p

After 15 mins I got media error message.

Is 15 mins good or bad?
Is it reasonably safe to use this card for 1080/50i recording? (no OC intended btw)
How long do you overcrank the SDHC card, for testing purposes?

I formated the same card and the next overcranking test I preformed the card recorded till full with the same settings and no error message.

Thanks in advance.

As far as I know, overcranking has less to do with the ability of the card to keep up than the bitrate.

Class 2 cards will only record 16mbps at max, Class 4 cards will only record 32mbps, and class 6 cards will only record 48mbps at max.

Some Class 6 cards are better than others, but Transcend's pretty cheap, so I wouldn't push it past 48mbps.

Lowering the bitrate should allow you to record as fast as you want without error.

Thanks Brian,
I don't really intend to OC, just testing if the card is safe to use in the 1080/50i recording mode without errors, I don't want to loosing important wedding clips.

Non overcranked frame rates/sizes are 35mbps (VBR) so they all work equally well (HDV mode is 25mbps).

To test a card's ability to overcrank I do something similar to what you do. I set it to a frame rate and see how long it goes before it errors.

Overcranking effects the bit rate. For example. 720p24/60 is about 87.5mbps.

Brian, many cards outperform their class rating and sometimes there's a difference from one card to another even from the same manufacturer and class rating. The class rating is a minimum the card has mean but may perform much higher (and may not) so one must test the card.

Anthony, 15 minutes is good but I wouldn't consider a card trustworthy at a given overcrank speed unless you could fill the entire card at that frame rate. I'm very cautious though. I've had shoots where I had to do that and the last thing one wants is to be put in a situation where you need 30 minutes of overcrank only to hit the error 15 minutes in. Of course generally overcrank shots are fairly short. I would do several tests to make sure that "15 minutes" doesn't vary.

Overcrank has NOTHING to do with standard shooting. XDCAM is 35mbps (VBR) so frame size/rate isn't relevant to the data rate.
720p25, 1080i50, 720p50, etc ALL ARE 35mbps

Thanks all for your replies.

I might have mislead you all a little.
I don't want to use overcranking on an SDHC card.

Let me start again, I've bought a few 16gb Transcend cards and I want to test them before I use them at my next wedding. I normally put the new cards into my camera (EX3)
format them and record on them till full and if no error message appears I would then use the cards.
But I read that test alone "isn't good enough", you have to overcrank the sdhc card as well, to test it.
So just to correct what i should have asked in the first place.
I don't intend to OC the SDHC cards. I just want to test the card before I record my wedding on it at the 1080/50i format.

So, I overcranked the card at 48fps 720/25p. After 15 mins I got the media error message.
Going by that, is this card faulty or not.

Sorry for not explaining it better in the first place.

I take the easy way out here by just shooting any overcranked footage on the 8Gb SxS that came with the camera then just copying that over to an SDHC in slot B. Yes it takes a few seconds to do that but that isn't an issue for me. The only limit I have then is the size of the 8Gb card. But I don't shoot a ton of overcrank all at once either.

For non overcrank use, testing by recording normally straight through is good enough.
The overcrank test just shows you how much headroom the card has (peak sustained data rate). I've seen cards all over the place with overcranking work just fine at 35mbps.

[QUOTE=Craig Seeman;1172052]For non overcrank use, testing by recording normally straight through is good enough.
QUOTE]

Thanks Craig, so formating the new cards and test record on them till full is as good a way as any, I don't intend to overcrank at anytime.

It's a good test. The other is doing shorter records and occasionally delete clips. Do remember do "cross at the green" though. In other words don't blame the card if you hit record before the write of the previous record hasn't finished.

[QUOTE=Anthony McErlean;1172064]

OK Craig, so test record till full delete a few clips record again and if no errors appear in the VF the card should be OK.

Thanks.

I'm not sure - I've heard reports of (a very few) cards working fine *most* of the time, but then giving a hiccup. The reason seems to have been a below average one working with very little headroom, then one day something is slightly different and the headroom is just not quite enough.

Hence, a test such as Anthony is talking about may be seen as a good thing. It gives an idea of whether the card is just working under those circumstances (though may fail tomorrow) or whether it has a decent safety margin.

And to answers Tonys original question
the answer must be "good, you should be pretty safe to use it for normal speed work".

Thanks David, normal speed (1080/50i) work is all I ask of these SDHC cards. If it dose that and that only I'm more than happy.

So, if 15mins of 48fps is Good before an error message appears, what would be a bad reading,
2mins..5 mins, 7 mins were is the cut off point, When would you say, I don't want to chance that card.

Thanks again.

I'm sorry, I don't know the answer to that question, and I don't think there is an exact answer. You could argue it depends how much headroom is felt to be safe.

I'm not sure it's really that important if you're using many cards, since then it can be seen more a comparison test, not an absolute test. If you've got several cards (all working OK) and they all give similar results when you test them, it gives an idea of what is normal for that make of card. If you then buy another, and it only manages a much poorer result than all the others, I'd be very suspicious of using it for serious work. (Even if it seems OK for normal recording at first, it might be right on the limit.)

Overcrank in the field
 

I don't know if this will help, but I have shot alot of overcrank material to the SDHC cards- all nature/ surf in Australia, Indonesia, South America, California, Hawaii, Mexico and the conditions were extremely harsh.

What I have to come to realize is that each card is extremely picky, I have gotten multiple error reading on the cards in field. The card works fine after, but you must reboot the camera and rebuild the card. The previous data is saved prior to the error.

I have found that I will never get an error reading shooting between 40-44fps, but once I hit 45fps and onward I will start getting errors, my takes are not long 5sec-1min. Luckily I have never had an error read while I was shooting something important, I would be careful with a wedding- as you only get one take- If I am shooting a high profile setup I will shoot all overcrank to SxS cards and all normal speed content to the SDHC cards.

Below is a link to some of the footage shot on the EX3's.

Lost Prophets-trailer 01 on Vimeo

This was all shot on EX3's shooting between 40-60FPS. I would say that you are OK to shoot short takes at 45fps ( I would not go higher) and use the SxS cards for longer record times.

Nate