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Slow Sd Card

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UHS Speed Class 1 (U1) cards are rated for a minimum sustained write speed of 10 MBytes/sec (80 Mbit/s) which is not sufficient to accept a real-time stream of 1080p HD recorded video.
UHS Speed Class 3 (U3) cards are rated for a minimum sustained write speed of 30 Mbytes/sec (240 Mbit/s) which is more than enough to accept & store a real-time stream of HD video without dropping frames.
 
Okay so the specs are wrong then? The u1 sd that i ordered has 100mb/s and the sandisk that u recomended has 60mb/s but is a u3, is there something i miss ?
 
Okay so the specs are wrong then? The u1 sd that i ordered has 100mb/s and the sandisk that u recomended has 60mb/s but is a u3, is there something i miss ?
There are quite a few different spec's that are applied to SD cards in regard to the type of data 'bus' they can connect to, and the way that the speed of data transfer for both read and write is specified. What is important about the UHS speed bus specification is the words 'MINUMUM' and 'SUSTAINED' ... While it might be possible for a U1 card to write at 100 Mbit/s for a short burst - that specification may be great for a still shot camera where data is captured 'blam' - then buffered off to storage ... no problem ... But - if you want to continually stream live data into the SD card, then that storage card has to be able to maintain a 'minimum' level of data acquisition, that is higher than the video camera is feeding into it. If you look at maximum data transfer rates, then these are of no use to you as they just imply short-duration 'peaks' ... The important thing - and why I said what I did in post #5 above - is the "minimum sustained write speed". A "UHS Speed Bus 3" (U3) rated card will only start to drop data if you continually exceed 240 Mbit/s data streaming rate ... In other words, you can fire data at it at up to 239 Mbit/s all day, and it will faithfully record it!
The other thing to be careful of - is that data transfer rates are quoted in MB/sec (MegaBytes per second), and Mb/sec (MegaBits per second). 8 bits make a Byte. bits are always small 'b' and Bytes are always big 'B'. So 10 MB/sec is 80 Mb/sec ... I would suggest that your U3 card has a max (peak & unsustained) data transfer rate of 60 MB/s (480 Mb/s).
 
I have the same problem and will be buying the correct sd card tomorrow. I have another issue and wonder if this will fix it. My video is pretty clear but on replays its stutters, and then goes fast to catch up, and even freezes for a second here and there. Would the slow write speed cause that? Thanks
 
I have the same problem and will be buying the correct sd card tomorrow. I have another issue and wonder if this will fix it. My video is pretty clear but on replays its stutters, and then goes fast to catch up, and even freezes for a second here and there. Would the slow write speed cause that? Thanks
Yes it can due to skipping and/or interpolating frames in software wiring to the slower card.
 
I have the same problem and will be buying the correct sd card tomorrow. I have another issue and wonder if this will fix it. My video is pretty clear but on replays its stutters, and then goes fast to catch up, and even freezes for a second here and there. Would the slow write speed cause that? Thanks
That's a pretty good description of a card that's not able to keep up with the video streamed to it!
 
You have your answer, and quite well explained. For anyone else reading this- DJI is serious when they say you have to use a fast card (U3) If they recommend Sandisk Extreme or whatever, get that for your best results and to record your first flight:D
 
Heyho

I just bought a new sd card for my mavic air to capture 2.7k 60fps. My sd Card is rated at 100mb/s read and write and is a class 10 card, but the mavic still says it is to slow. Its this Sd card: https://www.digitec.ch/de/s1/produc...ard-32gb-32gb-class-10-speicherkarte-12240022

Can anyone say what the problem is ?
Hello

I use for 2.7K and 4K

Sandisk Extreme plus up to 4k with no trouble about speed.
" Ultra shows slow but fine for up to 1080p and snapshots

The problem is trying to play on computer / laptop need hardware that runs 4k
The video taken in 4k will playback fine connected through controller to phone/tablet.
Brian
 

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I have a U3 card also indicated as "Slow":
1578853164719.png

The red card works fine, the new grey one (bought is in Switzerland at a respected store in original packaging) shows up as slow.
I formated both cards inside the drone via the DJI Go App. I tested them in the card reader (USB3) on my Win10 computer with large files and got these results (and yes, MByte/s not Mbit/s):

Red: 60 MByte/s write, 70 MByte/s read
Grey: 70 MByte/s write, 90 MByte/s read

I wonder how the card speed is detected by the drone so quickly after inserting the card.
 

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