Ben Corwin Posted May 5, 2014 Share Posted May 5, 2014 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? Quote Link to comment Share on other sites More sharing options...
Julian Posted May 5, 2014 Share Posted May 5, 2014 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. Ben Corwin 1 Quote Link to comment Share on other sites More sharing options...
Administrators Andrew Reid Posted May 6, 2014 Administrators Share Posted May 6, 2014 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! Ben Corwin 1 Quote Link to comment Share on other sites More sharing options...
tupp Posted May 6, 2014 Share Posted May 6, 2014 Shoot static on an old TV set. Ben Corwin 1 Quote Link to comment Share on other sites More sharing options...
Ben Corwin Posted May 6, 2014 Author Share Posted May 6, 2014 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. Quote Link to comment Share on other sites More sharing options...
Ben Corwin Posted May 6, 2014 Author Share Posted May 6, 2014 I also turned the noise reduction all the way down to - 5, so there wouldn't be any smoothing of the image. Quote Link to comment Share on other sites More sharing options...
Michael Ma Posted May 7, 2014 Share Posted May 7, 2014 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. Quote Link to comment Share on other sites More sharing options...
Ben Corwin Posted May 7, 2014 Author Share Posted May 7, 2014 Yes, I have. The highest bit rate I've gotten for that setting is just over 170Mbps. I really wish they were all constant bit rates instead of variable..... Quote Link to comment Share on other sites More sharing options...
Nikkor Posted May 7, 2014 Share Posted May 7, 2014 Turn off audio and see if it changes. Julian 1 Quote Link to comment Share on other sites More sharing options...
Ben Corwin Posted May 7, 2014 Author Share Posted May 7, 2014 Turn off audio and see if it changes. Just tried. It didn't work. Still right at 80Mbps. Quote Link to comment Share on other sites More sharing options...
HurtinMinorKey Posted May 7, 2014 Share Posted May 7, 2014 You shooting at 29.97fps? Quote Link to comment Share on other sites More sharing options...
Ben Corwin Posted May 7, 2014 Author Share Posted May 7, 2014 You shooting at 29.97fps? Yes sir. Quote Link to comment Share on other sites More sharing options...
Michael Ma Posted May 8, 2014 Share Posted May 8, 2014 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. Quote Link to comment Share on other sites More sharing options...
aldolega Posted May 8, 2014 Share Posted May 8, 2014 OH HAI BEN Quote Link to comment Share on other sites More sharing options...
Ben Corwin Posted May 8, 2014 Author Share Posted May 8, 2014 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? Quote Link to comment Share on other sites More sharing options...
Ben Corwin Posted May 8, 2014 Author Share Posted May 8, 2014 OH HAI BEN SUP AL! Haha Quote Link to comment Share on other sites More sharing options...
Ben Corwin Posted May 8, 2014 Author Share Posted May 8, 2014 *UPDATE* So I figured out that Quicktime is only averaging the bit rate. When you play the clips in VLC and view the statistics while it plays, there are peaks that get closer to the 100Mbps mark. Julian 1 Quote Link to comment Share on other sites More sharing options...
Giulio Cosmo Calisse Posted May 8, 2014 Share Posted May 8, 2014 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. Ben Corwin 1 Quote Link to comment Share on other sites More sharing options...
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