How to capture 4K while downscaled to 1080p?

[MusclebrahTV]

hey guys!

I have a problem which I can't find a solution for in this forum and never read about it here.

I want to basically record my streams in OBS in 4k!
But to do that I have to have the Base & Output resolution in 4K like this -> https://prnt.sc/vgq1yn !
BUT if you want to stream in high end quality, you obviously want to downscale to FHD for your viewers for 2 reasons: the bitrate Twitch provides is not enough for 4k so thee stream gets pixely and most people dont even have the screens to watch it in the first place.
So this is the normal setting everyone with a 4K monitor should run -> https://prnt.sc/vgq2vs !
This is my recording settings which is pretty optimum for high end stuff -> https://prnt.sc/vgq3nu !

So now here is my problem:
- If I capture in 4k with this settings but base & output equals 4k settings like here https://prnt.sc/vgq1yn its perfect! video saves in 4k, perfect quality.
BUT I want to stream like in the this -> https://prnt.sc/vgq2vs (which I have to cause im a Twitch Livestreamer) that I downscale the output to FHD it effects then my capture and I only get a FHD video instead of 4K.
So is there a way to stream FHD downscaled but capture the image somehow still to 4k? Since in my OBVS preview atleast the picture is still 4k and not downscaled which happens if OBS send the picture to twitch.

Please help!

MusclebrahTV

 

[koala]

To record in 4k and stream in 1080p, you need to set your output resolution to 4k, and in the streaming encoder settings you need to activate "Rescale Output" and enter 1920x1080. Unfortunately, this rescaling is very resource consuming and you might get lags or encoder overload. OBS isn't optimized for this very good.

By the way, don't record with VBR. Disk space is not used in an optimal way. Instead, use CQP and vary the file size with the CQ parameter (start with a value of 20. Lower values mean higher quality but larger file size, higher values mean lower quality but smaller file size. A change of 3 results in about half (resp. double) the file size.

 

[MusclebrahTV]

Oh thats already really good, seems like the only option to do it is to use the rescale output option right?
does it help if I have a high end PC? or which resources are u talking about?
Aree u sure about the VBR stuff?
I talked to alot of other big streamers and they all capture VBR.
I never heard about the "CQP" !

ty for ur responses!

 

[MusclebrahTV]

I have 2 high end PCs (3090s gaming 3080s streaming pc with both i9 10900k 5.1 ghz OC)
if i stream with 2nd pc it should not have any issues to encode it isnt it? thats why I asked koala if the encoding matters only on Hardware if so I have the latest build, also with 970 evo pros where I save the files.

greets