i suppose as your not watching the playback for pleasure it doesn't really matter which way up it records, just as long as it is recording what is going on behind. as for sd cards i didnt realise there are different write speeds until i had my dash cam, i brought a cheap 32gb card but it was too slow to capture the hd cam data (ok on a lower res though) apparently they have numbers on them for the write speed (
@Redline would know more about this)
Many chips are made in the same foundry - they start out exactly the the same. They're tested and graded which is why you get different card sizes and speeds. HD video has a continuous high data rate up to 7Mbit/s after compression depending on the compression rate applied. The faster the card the better able it is to cope.
There different read/write speeds within the classification. You will find some X10 cards much faster than others. Any x10 card will or should cope with standard HD video. If you go to UHD (also incorrectly known as 4k - it isn't quite) the data rate is upwards of 20Mbit/s, so, the fastest possible cards are needed. Full 4k has four times the data each frame and twice the frame rate of standard HD. Nobody will use 4k in a dashcam but the results are stunning in GoPro.
I get 4 hours of video on to a 32MB card in my dashcam.
They are cheap enough so I only ever buy x10 cards but I swap them around between cameras. I don't want to be fiddly to see if a card is actually fast enough in some of them.
The main thing is to look at the read/write speed even on a x10 card. They are different. Some are still much faster than others. For a dashcam a generic brand should be enough as well as being cheaper. For serious stuff I always go for Sandisk Ultras or Extreme but I do also use cheap cards in my Raspberry Pi. When dumping 10 frames a second of 25M-pixel full frame images using RAW in my camera, that is a colossal amount of data. The faster the card the better to stop buffering after a few frames.
You will find though that they do in fact wear out. The cards only have a finite write capacity - so many write cycles. With continuous writing, as in a dashcam, your are continuously using all the memory and so, after a while, some bits of memory will stop working. The cards themselves actually have more memory than they claim. Faulty bits are automatically swapped out so you don't see it. However, I've had two cards stop working entirely after lots of use. Unless your dashcam gives you a memory card error warning, check them every once in a while or you may find that at the very moment you need it, it doesn't work.
