Downscaling and transcoding to ProRes or CineForm at 1080p can convert the RGB 4K data from the GH4′s 4K 100Mbit/s codec to the higher bit depth o f 10bit and color sampling of 4:4:4.
If true, this is a very interesting aspect to this camera. Shoot 4K, 8-bit, 4:2:0. Down-sample to 1080p, 10-bit, 4:4:4 in post. According to Dave Newman (@David_Newman), GoPro's Senior Director of Software Engineering and ex-Cineform CTO, that is exactly what happens.