I did a couple of clips for Goldeneye Source
720p 30 frames per second
Same video, upscaled to 4K before uploading. So Youtube thinks its a 4K/30 video.
This clip is 720/60. The game was actually running at 30fps (I capped the framerate at 30), but I set the recording software to capture at 60fps.
And same video, upscaled to 4K/60 before uploading. So, Youtube thinks its a 4K/60 video. But the game was running at 720p/30
Remember, the point here is not to make a 720p video look like a 4K video. The point is to keep our video looking like the source file. In this case, a 720p source. Youtube does not give enough bitrate to a 720p video upload. So we trick youtube by upscaling to 2K or 4K. This assigns more bitrate when youtube processes your video. The net result is that the video on youtube will look more like the 720p source file. 60fps also gets more bitrate Vs. 30fps. If your source file is 30fps, you can frame double before uploading, to gain that extra bitrate. Or you can try to record 60fps to begin with.
If you haven’t read this whole thread: 2K/60 on youtube looks pretty darn good. But still has some noticeable compression issues. 4K/30 and 4K/60 help things further. There are of course still going to be some issues. But they will be further minimized. Its the price you pay for compression. Also note-able is that with a 4K upload, if you select the 2K or 1080p quality setting while watching the video, its going to look better than a video which you uploaded at 2K or 1080p. The extra tier of bitrate for 4K has a trickle down effect to the other, lower quality settings. Here is an example:
720p/60 upload
4K/60 upscaled upload, with 720p/60 quality setting selected
4K/60 upscaled upload, with 4K/60 quality setting:
Note that if you frame double a 30fps video to 60fps: you need to also double the bitrate for that new video you are outputting. So lets say you captured at 1080p/30. Then you make some edits in a program and set the final product to upscale to 2K resolution with 40,000kbps bitrate. and that’s the file you upload to youtube. —If you wanted to do that same video with doubled frames for 60fps, you should output it at 80,000kbps, to achieve the same relative quality, before uploading to youtube. Even though you simply doubled the frames rather than having 60 unique frames----you still have twice the amount of frames to compress. So, you need more bitrate to keep it looking good.
Its the same with capturing video. If you are going to capture at 60fps, you need to double the bitrate of what looks acceptable to you, at 30fps. Otherwise, you will run into a lot more compression issues.
Overall, after all of my comparisons: I recommend upscaling to at least 2K/60. With the extra bitrate assigned by Youtube, you gain a huge amount of clarity compared to 720p and 1080p. 2K/60 Minimizes a lot of mush and artifacts. Especially for brighter scenes, it can look very clean and is similar enough to a 4K/60 upload. Looking overall similar to the source file.
If its mostly darker scenes, I recommend spending the extra processing time to upscale for the 4K/60. It goes a couple of extra steps to help keep detail in dark colors and darkly lit secenes. Especially when there is a hi amount of motion.