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GH4 4K Video Maxing Out at 80mbps


Ben Corwin
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Hey guys,

 

So I've noticed that 4K video on the GH4 isn't actually recording at 100mbps (like stated in the specs), but rather maxes out at 80mbps. I'm using a Sandisk 95mb/s 64gb card and I'm wondering if I have to upgrade to the U3 cards everyone is talking about to get that extra 20mbps. Has anyone else run into this issue? Is anyone getting the full 100mbps with their U3 cards?

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Don't think that has to do with the card. More likely the subjects you are filming. Try something with a lot of small details or high iso.

I have one of those new panasonic 16GB cards, when i get my GH4 ill compare it to some other older cards regarding bitrate.

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It's a variable bitrate codec and it probably leaves 20Mbit in reserve for a particularly challenging few frames to avoid corruption.

 

Try a sudden whip pan of a forest of trees at F5.6 or a sudden flare up of the entire frame whilst shooting something with tons of detail in it, that will really push the codec to the limit!

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Thanks for the comments guys.

 

Yeah, that's what I meant by "maxes out" because I did a stress test. It was particularly windy a couple of days ago and I found a tree with small leaves that were all blowing in the wind. I shot the tree handheld and also shot wide. Unfortunately, when I reviewed the clip on my computer at 100% there was most definitely a break down in the image quality with a noticeable amount of micro-blocking. Like I said above, the bit rate still only reached 80mbps, which is unfortunate because it was still micro-blocking. I feel like 20mbps is a lot to throw away considering that several consumer HD video cameras shoot around 20mbps. I'm really not sure what I can do to get that 20mbps back. It's also worth mentioning that I'm shooting at 30fps, so you guys might not see as much micro-blocking with a lower frame rate.

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Fascinating.  Have you tried the 200mbps ALL-I?

 

If it is somehow managing to do 80mbps 4K and produce quality of the samples floating on the net that is pretty amazing.  Still, higher would be better.

 

Well, at least we know it's not a hardware limitation.  

 

What kind of footage are you shooting to test this by the way?  Try to max out the dynamic range going from full black to full white with a steady distribution of luminescence, with as much color variance as possible, and with a sharp lens at F8-F10, with a descent amount of camera shake.  I see that you did a static noise test, but maybe most of the data got compressed into full black or full white.

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Well, at least we know it's not a hardware limitation.  

 

What kind of footage are you shooting to test this by the way?  Try to max out the dynamic range going from full black to full white with a steady distribution of luminescence, with as much color variance as possible, and with a sharp lens at F8-F10, with a descent amount of camera shake.  I see that you did a static noise test, but maybe most of the data got compressed into full black or full white.

 

I'm shooting Cinelike D and used a variable ND filter to shoot at F8 on my Panasonic 14-140mm lens. I also included camera shake in all the shots and it's still not budging off of 80Mbps.

 

Are you getting 100Mbps on your GH4?

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I was very impressed with the cinema 100mb/s 4kc mode compared to the 200mb/s 1080p mode. I brought both into after effects for some color grading, and the 4k footage grades and keys a LOT better than high bitrate 1080p. Macroblocking is way less visible in 4k, but for some reason, the recording time available on my card shows a lot more time remaining when in 4K cine mode than in 1080 200mb/s; nearly double the amount of recording time!
There's something about how 4k compression that just works much more efficiently than 1080p, giving much more color depth and resolution even at lower bitrates.
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