Well, welcome to version two of the thread. Do you have any details on why a card that consistently writes at 41MB/s could not handle a 7.5MB/s bitrate?
There is something wrong with the card? It's not a good benchmark? The findings are wrong. Lot's of reason I could just right but unless I know more about the question, all I an say is what I know. The P4 writes at 60mb/s which is 7.5MB/s or 75mb/s.
Here are the Phantom's camera specs:
As you an see, MAX VIDEO BIT RATE is 60Mbps (small b means bit instead of bits large B which means Byte).
So in order to have a card that writes 60Mb/s or 7.5MB/s (It's a 1:8 ratio so 60/8 = 7.5MB/s...This is the simple way to figure out what MB you need from Mb) or you can use a calculator or an online converter, the card needs to write at an average of 41MBp/s or 328mb/s. So the answer to your question is 41MB/s and above should be able to handle 7.5MBs (or 60mb/s, the stated spec of the speed of the camera writing by the P4 very easily). If I'm not mistaken that is 328mbs when we need 60mbs.
Of course marketing might just put what it comes in at. It also might have a buffer where it holds some video and maybe needs a little less speed on the card (not sure) also, it encodes with a hardware encoder to H264 as soon as it hits the chip so I don't know if that slows it down. If you look at this BlackMagic Resolve Color Corrector Speed Test you can see the results of my card that is currently in there and see that it will do different formats at different speeds. Also, if I change the card to a different one, the brand, the speed, and a bunch of other factors will change these numbers. Read only matters once you're writing to the computer and who cares unless you're talking about an SSD striped array of drives but when it comes to this, it's mostly aboutt the write speed.
See the calculator below shows that at 41Mb/s = 328mb/s (the P4 needs 60mb/s...sorry for the repetition, just trying to beat this in)
Here is a Black Magic test of my Lexar 633x that comes with the P4 and the latest P3s. I am writing at an average of 68.2 which is
For comparison, I took a grab of the speed of one of my internal SSD striped for performance speed tests. Look at the difference.
Check out what the performance does as the resolutions and formats increase.
So the answer to your question Mike, as to why 41.5MB/S can't handle 60mb/s is I have no idea. Something is missing. This gets a little convoluted to me when I try to look at it as a whole actually so I apologize in advance if I wrote anything wrong here, but I tried to the best of my ability.