Data speed not fast enough at 200Mbps on Transend SDXC Class 10 speed 3 cards ?

Categories: 4K filming 8 Comments

Transcend_SDU3-1-4K-v2

While shooting at the weekend with my 2 GH4’s I got an error message twice (same camera) using Transend SDXC Class 10 speed 3 cards telling me that “RECORDING HAS STOPPED  DUE TO THE REC SPEED NOT KEEPING UP” this was filming at 1920 x 1080 50p at 200 Mbps.

This only happened twice out of about 100 shots so my question is why and is it a bug, or a faulty card.

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8 comments on this post

  1. Yemi says:

    Hey there Philip,

    Having spoken to Samsung a couple of times prior to buying my own GH4 – it would appear the 128GB card is NOT compatible with the camera. Now, this may or may not be the cause of your error message… but the highest capacity is 64GB… apparently! Best, Yemi

  2. Jonathon W says:

    It does say on the cards their maximum read and write speeds which are nowhere near fast enough for 200Mbps.

  3. Frank B says:

    Not something I want to hear! I’m buying a GH4 soon. This is not good. Please keep testing

  4. Peter Loughran says:

    Jonathan W. …bytes not bits!
    The figures quoted on the card are the maximum (claimed) ‘Burst Speeds’ the card is capable of and are in MBps (Megabytes per second) not Mbps (Megabits per second) which are 8 times smaller (8 bits in a byte).
    So R95 MBps (Read speed in Megabytes per second) would equal 760Mbps and W60 MBps (Write speed in Megabytes per second) would equal 480 Mbps.
    (My 64GB Transcend ‘U3’ card has R95.W60MB/s on the label [not R95.W85MB/s] like the 128GB version pictured above).
    The ‘U3’ classification means the card should be capable of a SUSTAINED WRITE SPEED of 30MBps which is 240Mbps and therefore should be more than enough for the GH4s maximum of 200Mbps.
    I have tested the Write/Read speeds, on the 64GB Transcend card, using Blackmagicdesign ‘Disk Speed Test’ (with the card in a Lexar USB 3.0 card reader) and obtained consistent write speeds of ~58MBps (464Mbps) and consistent read speeds of ~82MBps (656Mbps) …not far off the claimed ‘Burst Speed’ figures on the label so would seem to suggest the card is plenty fast enough (unless something odd is going on when extended recording times are tried?).
    I have been using the 64GB Transcend card in my GH4, without any problem so far, but have not tried any extended periods of recording at the 200Mbps settings (Full HD 200Mbps All-I) …partly because the 4K (which only uses the 100Mbps IPB codec) gives a much better quality image (even when editing to Full HD) and also because I’ve yet to see any quality advantage (in Full HD shooting when I often want the 50fps which is not available in 4K …damnit!) of the 200Mbps All-I over the same subjects shot at 100Mbps IPB (or even 50Mbps IPB).
    That may be because my test subjects have been fairly static so I need to find a consistent fast moving subject to test and compare the different codecs under greater image motion stress.
    I have heard it said (by people who know more about these things than I do) that an All-I codec needs to be AT LEAST twice the data rate of the equivalent IPB codec in order to look as good. If that is true then there may be no advantage to shooting at 200Mbps (and [usually] producing bigger files to store and work with) in the GH4 if the 100Mbps IPB codec is just as good?
    That claim seems to be supported by my experience with the GH3, in which the 72Mbps All-I codec gives WORSE image quality than the 50Mbps IPB codec when shooting exactly the same subjects and settings …the video has a pixel-level ‘fizz’ with the All-I which is much less obvious when using the IPB and results in a cleaner image.

  5. nobbystylus says:

    I have to say the fact that the Transcend cards are so much cheaper than the Sandisk or the Kingston ones made me think that they might be too good to be true. I’m sticking to 4k shooting at the moment.

  6. Jim McAdory says:

    I have been following the card discussions found on the web since the GH4 started shipping in the U.S. at the end of April. I saw similar reports on the U3 Transcend card ( both 128gb and the 64gb versions ) but also found other reports of no issues with the card (even 2+ hour recordings on the 128gb card). I decided to try one when my camera arrived in mid-May and have been using the Transcend 128gb U3 card for a couple of weeks with no problems so far. I have recorded 4K, 100Mb & 200Mb settings at 24, 30 & 60fps settings.

    I also have older Transcend 600x 64gb cards that I have used in the GH4 with success for 4K, 100Mb HD and 200Mb HD. Most of my shots have been pretty short, under 2 minutes but I have only had 1 card speed error and only when using an older card.

    In all cases I formatted the card in the GH4 before shooting.

    I used the 600x cards and slower Sandisk cards on the GH2 with the Flowmotion hack at the 100mb rate and got occasional write speed errors (maybe 1 out of 100 shots). Typically the error happened in the first few seconds of recording. After the error I would press record again and without fail there would not be another error and the recording would be fine. The same thing happened when I had the single error with the GH4.

    I even tested an older Sandisk card rated at 45Mb/s and it works ok at all of the 4K & HD 100Mbps settings. I have had about the same write speed error rate on this card as the Transcend with the GH2.

    Also the write speed of an SD card is expressed in megaBytes (MB/s) where the rate on the camera is expressed in megaBits (Mbps). The upper/lower case “b” indicates bits and the upper is bytes. The Transcend U3 card is rated at 60 megabytes per second which indicate it can handle 480 megabits per second which is more than twice as fast as the camera spec of 200Mbps so card speed should not be the issue.

  7. Dan says:

    Slightly differenet question, but do any of you know if there is a way to have the GH4 not span the clips on the SDXC cards? I shot an hour long interview with a musician and ended up with a new clip being made every 7 minutes. I didn’t appear to lose any frames when the new clips were being made, except on one, so not a huge problem, but still kind of a pain.
    Any ideas?

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