Dropout-Like Looking Frame

[Benni Katz]

Hey All!
Today I came across a strange problem I saw for the first time
with my EX1.
A friend and I did a timelapse test inside a car using the EX Slow Shutter 32.
The clip duration is about 28 minutes. As we previewed it from camera with 15x speed everything looked normal.
At home, after we imported this clip from card (btw.: Kensington + Sandisk Ultra II 16gb) into Premiere Pro CS3 we got this frame at a certain point:

http://l3ech.m5t.de/Unbenannt-2.jpg

We used Sony Clip Browser 2.0 and Exported MXF for NLE

Moreover Premiere always crashes when playing it.

Any ideas what could have caused this?

[Ted OMalley]

Looks suspiciously like Kermit the Frog, to me.

I've done quite a bit of time lapse, including slow shutter, with SDHC as well, but I've not seen this problem. I suppose you can't just edit around it, right?

[Dave Morrison]

What was the subject matter? Was the car moving/bouncing? Did this green frame last more than a frame or two? Just trying to get some more info before offering my own useless opinion! ;-)

[Benni Katz]

First of all I should point out that we didnt do Interval Recording, but captured all with 25 frames in 1080p25.
I just took a look at the clip and saw that there were several more corrupt frames in it, not as bad as the one (really only 1 frame) I already posted, but still strange. I´ll be posting some more of them soon, but premiere crashed again. So its also pretty hard to cut this part out of the clip.

The car wasnt moving during that period. There were only some cars passing by in front of the camera.

[Alister Chapman]

Duff SD card? There seem to be a few people having issues with the Ultra II cards.

[Benni Katz]

Yes, really seems to be the SD Card.
Did a test with the original 8gig SxS card and it worked without any problem

[Vincent Oliver]

Bad sectors on the card. On a hard drive these can be marked, but won't work on a SD card which is being formatted on a regular basis.

Chuck the card in the bin.

[Alister Chapman]

With flash memory you should just delete the material rather than format the card. This way instead of always using the data cells at the beginning of the card the whole card will get used as files that are marked as "deleted" don't get written over until the card is totally full. This helps increase the reliability of the card. Also you should always keep any cards in an insulated or static safe container. Just consider what might be happening to a card in a pocket when you pull off a sweater creating lots of static electricity. A further consideration is that while there is no direct evidence of the X-ray scanners used to check carry-on damaging flash memory, flash memory can be erased by high powered x-rays. Hold baggage is often subject to much higher powered X-ray machines than the ones used for carry on. According to Kingston the USPS use special radiation scanning and this is known to damage flash cards, so best to avoid USPS.

[Brooks Graham]

Great tips Alister, except one item: most/all modern flash devices automatically manage memory block re-use through what they call "wear-leveling". There is a mapping process of logical blocks (the addresses your computer uses) to physical blocks (the actual addresses on the physical device) and flash cards make sure that most blocks, if not all, get the same amount of erase cycles over time. Also, flash cards, like all modern spinning rust mechanisms (hard drives), automatically map out blocks which become bad over time but IIRC do that at block the block erase operation. Nothing at the host level needs to be involved in that.

It is possible that in this case, a block became bad *after* the write occurred and could not be corrected with ECC (error correction) and introduced corruption in the MPEG structures inside the file. A SWAG on my part, however.

[Alister Chapman]

Thanks for the additional information Graham. You'll still improve card life by not formatting it and deleting the clips instead as this will force the whole card to be used before starting again.

[Vincent Oliver]

Think of formatting as a clean sweep of a memory card, deleting just removes headers to each file, the data is still present on the card - until it is written over.

I am sure that Alister is right about X-Ray machines, I have never tested these to any degree, other than never having lost any still images through camera gear going through the X-Ray. Regarding card holders, Jessops sell a rugged SD card holder for about £7.00, this will hold 8 cards and is well protected against dust etc. They also sell a CF holder with the same design, this holds 4 CF cards.

[Benni Katz]

Thanks for all the input.
I´ll definatly be regarding it in future.
Theres still one thing thats confusing me:
I took the SD card with the corrupt footage again and copied it onto another system which is pretty much the opposite to mine. (XP instead of Vista,Amd instead of Intel CPU,Nvidia GPU instead of ATI, but with both I used Premiere Pro CS3) and with this second system there werent any problems.

[Alister Chapman]

The thing is that if you don't format the card and delete the clips instead the next time you use the card the space that you have not written to yet will get used before the deleted clips (headers removed, marked as deleted in TOC, whatever) are written over. Doing this ensures the whole card gets used. There is no need to format flash memory as it is not going to get unreasonably fragmented. By not formatting you can also keep all your camera settings saved on your cards and you can name your cards so you don't end up with a load of "untitled" cards.

Benni, if the problem has gone away using a different computer perhaps you have an issue with your computer or card reader and not the card.

[Matt San]

ive had the same thing today too - except it lasted a few seconds.

I think mine was due to a static electric shock I had when I touched the cam - It seemed to corrupt the clip as it was recording.

I walked across a room and went to pic the cam up and got a mild shock - it didnt stop recording just dropped a few frames

So be warned!

[Benni Katz]

Interesting, Matt
An electric shock could be the reason for my problem aswell, as the often changed things in camera.
So if we get such a dropout different system seem to handle this problem different