4k downscale to 1440p or not

[karlos103]

Hi all
I usually record 4k content at 4k but at a lower bitrate ( Nvidia NVENC AV1 encoder )...i usually use CBR 25,000 but heard should be double that for 4k ...but file size is bigger as expected.
Is it better to downscale to 1440p and keep CBR 25,000 ...so can keep same file size ?
If so ...whats best way to do that ?

Also should i be using CQP or CBR ?
If had faster internet then i wouldnt be asking these question lol .
Any help most appreciated.
Karl

 

[qhobbes]

It depends on your content and your target audience. YouTube recommends 24 Mbps for 60 FPS SDR 1440p content so you're pretty close there. For 4K, it's 53–68 Mbps. See https://support.google.com/youtube/answer/1722171?hl=en#zippy=,bitrate but that's for H264 and you're using AV1.

In 2018, Facebook conducted testing that approximated real-world conditions, and the AV1 reference encoder achieved 34%, 46.2% and 50.3% higher data compression than libvpx-vp9, x264 High profile, and x264 Main profile respectively. Wikipedia, source.

If you need consistent quality, use CQP. If you need consistent file size, use CBR or VBR.

Here https://www.youtube.com/watch?v=KA1sWx0CDys is a demo me recording at VBR 24000 at 1440p with an old H264 hardware encoder. I think the YouTube version is pretty accurate representation of the source material.