Combining the quality of the same video encoded in two files, CBR/VBR

[NonprofitProphet]

Hello! I'm upscaling a video, but the original source is not great. The final result is pretty good, but I'd like to make the best result possible.

The best source files I can find are two from the same source. One is encoded in CBR with a 3,271 kb/s bitrate, the other is VBR with an average of 3,260 kb/s and a maximum of 8,000 kb/s.

Is it possible to combine these two files into one? Ideally this new file would be a VBR where every frame lower than or equal to 3,271 would be taken from the CBR, and every frame higher from the VBR.

Apologies if I'm misunderstanding how bitrates work, I'm new to this stuff. Thanks for any help!

[johnmeyer]

I'm not sure how such a thing would work, but you might be able to use something like "ClipClop:"

ClipClop v1.27 - Range/Frame Replacement plug - 27 Jul 2021

[killerteengohan]

It's possible, but its way more work and time than you or anyone else will want to put into it. You will have to go through it one frame at a time, find out what every individual frames bitrate is, then write a VERY lengthy and time consuming script and pick which frames from both sources you want to use. It's really not worth the time and effort for that, especially since it sounds like you are using things downloaded from streaming sites and grabbed both CBR and VBR. If there is an easier software out there for doing this, I have never seen any.

Just accept the VBR one, it's most likely set to a constant quality and adjusts bitrate as needed to stay at that quality. Not every frame will need the same amount of bitrate. You are getting too obsessed over a mostly negligible quality difference between the two. The only reason to bother with CBR in my opinion would be if it's bitrate was higher than the VBR in all cases, or over 70% of the time.

[NonprofitProphet]

Very late response, but thanks to both of you for the help.

Killerteengohan, you were spot on. I made a script to do this (its way easier than you think, I just had ffmpeg analyze both videos frame by frame, outputting the higher bitrate frame to PNG, then combining all the frames again at the end, Bard did 90% of the work in seconds) but I can't see any difference in the final result (then again, I can't see the difference for CBR either). It's probably not a very useful tool.
If anyone's curious, I would say only around 5-10% of the final result came from the CBR, interestingly enough, and they would usually occur together in clumps of no more than 2 or 3, but rarely by themselves.
I think there are a few other reasons why this is probably not worth it. To start, it's possible that the lower bitrate frame is actually of higher visual quality. Also, it's possible that the VBR and CBR frames have slightly different images, rather than just bitrates, due to things like compression artifacts, and that switching between the 2 will cause "jumps" that will lower the overall quality of the video. I'm not really sure, though, I'm very new to this stuff.

EDIT: It's too bad the upscalers can't take in multiple sources files to use as extra information about the frame to upscale. I think that might actually achieve what I'm trying to do here. They could probably even utilize videos of the same type (VBR/CBR) at different resolutions, assuming both were compressed from a larger source file. Obviously that's way more complex than what I did, unfortunately