Hi, I purchased a SanDisk Ultra Class 10 UHS-1 microSD and the MA reports the slow SD card warning.  I tested this card out in my computer:



As you can see it is writing at 26.3 MB/s which equates to 210.4 Mbit/s.  MA 4k/30fps video writes at 100 Mbit/s so this card is capable of more than twice as fast writing than what is required.

MA uSD write speed test routine firmware bug?

Andrew

I got the same error when i used the SanDisk Ultra cards.  Since i had just bought the card, i just took it back and got the extreme.  I have no problems with it.

I've read the requirements and seen the 12.5 MB/s number.  and i know that the SanDisk Ultra is supposed to be capable of close to 30 MB/s write, however what i have come to believe is that 30 MB/s is burst, and not sustained.

A SanDisk Extreme Pro SD card has read speed of 95 MB/s and a write speed of 90 MB/s.  The SanDisk Ultra SD has a read speed of 80MB/s but the write speed is only specified as "10MB/s minimum"

I put the Ultra in my Mavic Air and got the Slow SD Card warning.  I was able to get short videos like the quick shots, and it did well, but for long sustained video, it skipped a bit.  When i put the extreme in i no longer got the error and i haven't had a single problem with video from the aircraft.  i also went as far as to put an extreme in my Note4 to do local caching and such.  It has made a world of difference.  

I'm not sure i answered your question, but that is my experience.

Andrew, you can try to format the SD card via the DJI GO 4 app, do a backup if needed. If it doesn't help, we advise using the recommended SD cards since they have been tested and verified and can ensure the full functions. Please refer to the list below.

3-D Posted at 2018-5-9 15:56
I got the same error when i used the SanDisk Ultra cards.  Since i had just bought the card, i just took it back and got the extreme.  I have no problems with it.

I've read the requirements and seen the 12.5 MB/s number.  and i know that the SanDisk Ultra is supposed to be capable of close to 30 MB/s write, however what i have come to believe is that 30 MB/s is burst, and not sustained.

I believe you hit on problem with brief vs. sustained video.

SD card manufactures often take liberties with speeds.  Marketing their cards with best speeds obtained for their card(s).  
Common one is Read speeds are quoted, because write speeds are usually slower, sometimes a lot slower.
What goes under table is different sized blocks of data (groups of bytes) for reads and writes have different performance speeds.  There are buffers, and caching.  Buffers allowing bursts of write speeds, and caching speeding up repeated reads of same data or data that was written as a block.

There are some SD card tests that will run numerous types of writes and reads, giving speeds of each type, and aggregated speed.  Those kinds of tests will frequently highlight problems with SD cards from manufactures who took liberities with speed ratings.

Hi, Your Sd card needs to be a class 10 U3 to shoot in 4k

I have the same warning with a Samsung EVO card. It needs to be U3 for the warning to go away. The videos are recorded fine though, if you can live with the warning.

Thanks for the suggestions!  This is frustrating, the manual clearly says Class 10 UHS-1 is required, so that is what I bought from a mainstream brand and immediately hit problems.

Regarding the comments about sustained vs burst write speed, the file I wrote to the card was 1.6 GB and I screen shotted the progress dialogue at 75% transfer, i.e. after it had transferred well over 1 GB.  As you can see the data rate graph is very stable at > 210.4 Mbit/s (26 MB/s) after it settles down from a rate actually much faster than that.

I tried formatting the card while it was in the MA, no difference.

I maintain my opinion that this smells of a firmware issue because a card that can clearly sustain 210 Mbit/s should be more than adequate for 100 Mbit/s 4k video.  Either the firmware needs fixing or the manual needs fixing.  DJI, any remarks?

Thanks,

Andrew

I have the same problem with my A6500...
I had to go get the same card (Samsung EVO) but this time branded as U3 before it even let me choose 4K/100Mbps.
In this respect DJI just gives a warning but at least you can select that format and use your card.  The footage at least in my case is OK, despite the warning.
Obviously the devices cannot perform a benchmark to see if the card inserted is capable or not so they rely on the card classification. Yours is class 10/U1 which means at LEAST 10MB/s (sequential write in an empty card) which is just enough...The MA does not know that even though your card is classified as Class 10/U1 it is more capable than that. So it gives you a warning.

Yup use a u3

There are several factors to consider when choosing your SD card.
Be certain the brand is not counterfeit. If you buy from the manufacturer then that will not be an issue. If you buy from a reputable source like Amazon, Check the supplier is the branded manufacturer and not Joe Blogs selling the latest, fastest SD cards. A clue might be how cheap they are. If very cheap, they may be branded rejects. Someone is always prepared to buy them and re-sell them at face value. A branded reject may work quite well for many devices but they were rejected because they failed to achieve the Class standards.
What will you use the SD card for?
If it is only for 4K video recording from your drone then the same brand and Class that came with your drone will be OK.  You can decide on capacity on the basis of the notes below.
If you intend to use the SD card in other devices, like I do, then consider the needs of that device.

Note. Write speed  is 2 numbers. (The slowest value and particularly relevant if you record to the card like in your drone.) A burst speed and is best ignored. Sustained speed is the speed of the card, NOT the device you might have it fitted into.  For example, A Class UHS III (or 3) will not record data (video) any faster than the drone can produce it. Remember, there is circuitry between the drone camera and sd card that limit the speed data can be passed through.  60MB/sec for a mavic pro in 4K

I chose to buy a Sandisk Ultra, 64GB because it was faster than the drone needed and adequate for another device I put it in. It was the fastest around at the time for sensible money.

The write speed is also important when you send your GBs of video to your PC/MAC for processing. A fast read speed saves waiting around for the download to end. This speed is always higher than the write speed. A con by manufactures to fool the unwary.

Lastly, what capacity do you need?
Good drone practice suggests you put in a fresh chip for each flight, so 16 GB will be all you need. If the drone fails, you will still have your earlier epic footage, safe in your pocket.
No, I don't follow that wise practice. Bigger fool me. The card is 64GB and even with 4 batteries, I have never filled a card. I do have several cards in different drones.

I hope this is helpful.

For Mavic Pro and from DJI Q&A

4. What's the Mavic's maximum video bit rate?         

60 Mbps.

5. How long can a video be recorded with a 16G SD card?

When recording 4K or 1080p video at 60fps and 60Mbps: 36 minutes;
When recording 2.7K video at 45Mbps: 48 minutes;
When recording 1080p video at 50/48/30fps and 40Mbps: 52 minutes;
When recording 720p video at 1080p at 25/24fps and 25Mbps: 84 minutes.

DJI Thor Posted at 2018-5-9 18:31
Andrew, you can try to format the SD card via the DJI GO 4 app, do a backup if needed. If it doesn't help, we advise using the recommended SD cards since they have been tested and verified and can ensure the full functions. Please refer to the list below.[view_image]

In reality the actual requirement (for 4K/30) is for a UHS-3 card (U3), this is equivalent to V30 or 30MBs

UHS-1 and Class 10 are 10MBs is only really good for 1080/60 or stills.

The DJI info is slightly misleading as the Class 10 / UHS-1 is the minimum but it does then go on to list recommended high speed cards.

Have a look at this for further info

https://www.sdcard.org/developers/overview/speed_class/

Ridg Posted at 2018-5-10 07:09
In reality the actual requirement (for 4K/30) is for a UHS-3 card (U3), this is equivalent to V30 or 30MBs

UHS-1 and Class 10 are 10MBs is only really good for 1080/60 or stills.

I beg to differ...

"In reality" the only actual requirement for 100Mb/s video (4k, 1080p, 24fps, 30fps etc. etc. are utterly irrelevant) is a card that can sustain a write speed of no less than 12.5MB/s; period.

UHS standards are split quite apart, with UHS-1 requiring only 10MB/s write speeds (below MA's needs) while UHS-3 requiring at least 30MB/s.

In practice, most of the modern U1 cards are somewhere in between.  Because they can not break the 30MB/s sustained write, they are still classified as U1's; yet they can run circles around Air's 12.5MB/s requirement...

PS: By the way, MP only requires 7.5MB/s for it's 4K30; three quarters of what the worst U1 card can provide...

CemAygun Posted at 2018-5-10 07:50
I beg to differ...

"In reality" the only actual requirement for 100Mb/s video (4k, 1080p, 24fps, 30fps etc. etc. are utterly irrelevant) is a card that can sustain a write speed of no less than 12.5MB/s; period.

Yes you're correct in terms of the recording speed but in the absence of a Class 12.5 / UHS1.25 rule of thumb is UHS-3 for 4K; personally I wouldn't rely on a "good" Class 10 / UHS-1 card for 4K recording and if the MA is saying it's too slow would you rely on it?

It does raise the question what speed is too slow for the MA or does it look for dropped frames, as I've been in a similar situation to the OP and got error messages from the MA and 4K/60 action cams :-/ ?

Ridg Posted at 2018-5-10 08:24
Yes you're correct in terms of the recording speed but in the absence of a Class 12.5 / UHS1.25 rule of thumb is UHS-3 for 4K; personally I wouldn't rely on a "good" Class 10 / UHS-1 card for 4K recording and if the MA is saying it's too slow would you rely on it?

It does raise the question what speed is too slow for the MA or does it look for dropped frames, as I've been in a similar situation to the OP and got error messages from the MA and 4K/60 action cams :-/ ?

Very good point. Honestly I don't know what MA does when the write speed is really an issue. I was hoping it would stop recording with an error like my LX100 does. You either get a perfect video or nothing with that one; no frame dropping tolerated.
This is also how I test my cards, I use them in LX100 (with a size adapter of course) and see if they are up to the task. And when I need to buy a new card, the only thing I trust is good benchmark (like crystal disk mark)...

I get the card too slow error in MA as well, even with a card that has 20MB/s+ write speed and works flawlessly elsewhere. If I am not mistaken I got this error the second the card was inserted, not when recording. So I don't know how MA decides the card is no good. So far MA never stopped recording on me with that card.

Although I have not noticed any problems with the videos so far, I did not "frame peep" for dropped frames, as I just fly for fun at the moment.

Unfortunately I don't have any slow cards left around, so I cannot test what happens when writing actually fails. It would be nice if someone could test that, or a DJI tech clarifies the confusion...

Fingers crossed for stop recording and not frame skipping

I had slow card warning for a while for the Sandisk Ultra U1. Last night the warning didn't come on for the first time n I was able to take 4K videos over a min long. Still best to use U3 cards as U1 sustained 10mb/s write speeds is less than Mavic 4K 12.5mb/s.

You can debate the technical what if's and maybe's and write speeds and read speeds for ever. The bottom line is this thing needs a U3 card to not give warnings about the speed. I also bought the incorrect card the first time round thinking that it would be ok because it had super fast specs.

There's no technical debate.  Manual says class 10 UHS-1 is fine, firmware doesn't like it.  Either the manual or firmware needs fixing.  My class 10 sustains write at 26 MB/s so the correct fix is in the firmware IMHO.

AndrewUK Posted at 2018-5-11 01:31
There's no technical debate.  Manual says class 10 UHS-1 is fine, firmware doesn't like it.  Either the manual or firmware needs fixing.  My class 10 sustains write at 26 MB/s so the correct fix is in the firmware IMHO.

The manual is wrong, plain and simple, for 4K you need a faster card than the U1

Kevjones1959 Posted at 2018-5-11 01:46
The manual is wrong, plain and simple, for 4K you need a faster card than the U1

How can the firmware not be wrong if I have proven my card can sustain 26 MB/s and max 4k bandwidth is 12 MB/s, yet it still shows the "slow SD card" warning?  The numbers stack up, it should work.

AndrewUK Posted at 2018-5-11 02:09
How can the firmware not be wrong if I have proven my card can sustain 26 MB/s and max 4k bandwidth is 12 MB/s, yet it still shows the "slow SD card" warning?  The numbers stack up, it should work.

I agree Andrew but you can forget about them changing the firmware. I just tossed my others cards and bought a U3.

I just have to agree with Andrew and ggeorgis. I got the warning. Instantly got mad because the manual clearly says "Class 10 or UHS-I required" and then I went after what the manual instructed me to do. It doesnt say its the minimum requirement nor detail anything else, just Class 10 UHS-I. What wasnt my surprise when I saw the warning! If it is so, DJI should refund us about the card for a clear mislead information. Period.
But then I decided to test it anyway. And I just recorded several 4K 24fps videos not 30 minutes ago. No warning about skipped frames or the likes, if there would be one. Rushed to play the files on computer to seek for problems and found nothing. The obvious conclusion is that the firmware has something going wrong. Maybe at first it was the supported but then with firmware updates they changed it just to be sure? Dont know. Just know it works flawlessly. Didnt test 4k 30p, maybe there lies the problem (which I doubt couse my files were about 100mbps).

I see people who bought the U3 just whining and not argumenting about that. Why do you say it wont work if you didnt try? We tried. It worked. Simple as that. Dont know what could be beyond that but I just canceled the 2 Sandisk Extremes V30 I ordered sooner today. Gonna stick with the Ultra for now. Lets see  what happens next...