I believe what they are saying is the YUV curve is altered in real time (dynamically) which as you say is scary. I have no idea whether they also change the knee and slope setting dynamically and push the knee point down but that wouldn't surprise me either"Dynamically adapted"? Those are some scary words for video. I'm guessing this only relates to the DNG and photo performance.
OK, for those of you who wanted to know, I have just got an answer back from R&D.......
Quote: "We set the native ISO to 100, which is slightly higher than the standard ISO 100. The video is YUV420 8bit with a tone curve dynamically adapte to the scene. You won't get 12.8 fstops from a normal video. You can compare the DNG of X5 and GH4, to see the difference of the dynamic range. Then you can get the DR of GH4 in DXOMark"
I hope that helps and answers peoples questions (although it is a bit 'Chinglish')
this is true, however I worked with the Panasonic engineers for the original debut of the GH4 (made the video) and they told me native ISO was 400. I believe some Panasonic rep reported 800 as native ISO when it first came out and that got around a bit. Not sure if that was true.'best' ISO <> 'native ISO'. Native ISO will normally be the speed with most DR, not the least noise - and they won't be the same.