Yevano

Ultra HD (commonly known as 4K) is 3840 by 2160 pixels. In the standard 24-bit representation (1 byte for red, green, blue), each pixel is represented by 3 bytes. So an uncompressed frame requires at most 3840*2160*3 bytes to represent, ~24.9MB. Multiply that by 180 frames, and then multiply that by 60 seconds, and you get ~268.7GB. Maybe I'm ignorant of how demos get converted to video, but I don't see how 1 minute of 4K video could possibly equate to upwards of 1-2.5TB. To me, it seems like you could record around 11 minutes before going over 3TB, or perhaps much better if it's possible to convert the demo directly to a codec that does lossless compression (Though this could be where you hit the limitations of what the recording software has to offer. Again, I'm ignorant of what you can actually do with the established software).

Ross, you are my hero.