How to reduce the massive 4k file size??

[RutReturns]

So a quick breakdown of my setup. I use 2 PC's.
Gaming PC:
AMD 7950x3d, 64GB DDR5, Asrock 7900xtx Taichi, 1GB NIC for Network, 2.5GB NIC connected to 2nd PC
OBS is setup and Teleport is configured @ 4k resolution

Recording PC:
AMD 7900x, 64GB DDR5, Nvidia 2070 Super, 3 x NVME SSDs, 2.5GB NIC for network and 2.5GB NIC connected to gaming PC Using CAT8 cable
OBS is setup as:
Recording .mp4
Video Encoder: NVIDIA NVENC HEVC

CQP - 20
Preset P7 :slowest (Best Quality)
Tuning :High quality
MM: 2 passes (full res)
Look ahead off
Psycho tuning on
GPU 0
b Frames 2
Video is set for full 4k @ 60 fps since I am recording gaming

When I record my games, If the game lasts 15 minutes, I am walking away with a 40GB File size.
How can i adjust OBS to get a smaller file size without losing a noticeable amount of clarity and smoothness?
I have watched many people explain "their" setups on YouTube, but none really fit what I am trying to accomplish.

I used to use ShadowPlay to record and I was able to record what appeared to be lossless video @ 4k and the file sizes were about 15GB for a 30 minute game. Since then I have upgraded my video card to the AMD 7900xtx Taichi and the Adrenaline software didn't record a very clear picture to me. This led me to the 2 PC OBS setup I have now. Don't get me wrong, the recordings I get now are absolutely amazing!! They look just as good as the original game itself. I just need to get the file sizes smaller as I only have a 1TB drive for recording video right now.

Any help would be greatly appreciated.

 

[qhobbes]

If you want to control the quality, you need to use CQP. If you want to control the file size, you need to use CBR or VBR.

If you plan on uploading those to YouTube, use the settings from https://support.google.com/youtube/answer/1722171 (you can probably lower the bitrate a bit if you're using HEVC).

I used the lower end of those settings recently (320 for audio) for a 4K SDR recording at 24 FPS and it was 315 MB per minute. That's 4.7 GB for 15 minutes.
The low end of the recommended settings for those HDR 4K 60 FPS settings would be around 9 GB for 15 minutes.

 

[koala]

Gradually increase the CQP value and observe how quality and file size will lower. Find the sweet spot.

 

[RutReturns]

So I changed a few things.
- I swapped from CQP to CBR
- 53000 kbps
- Preset to P4 Medium quality
- Left Tuning on High quality
- Multipass mode @ Two Passes (Quarter Res)

The file was crazy small, 7 minute test game was only like 2GB but the quality was not very good so I set:
- CBR to 68000
- Preset to P7 Best Quality

Left everything else the same. The video became super choppy. I am using NVME drives and the 7 minute file was only 3.8GB. I was watching the network traffic and it never reached 800MBps on the dedicated line so I have no clue what would cause that.

So I changed:
- CBR to 60000
- Preset to P6 Better Quality

Still jumpy. Looks good but unusable footage.

Next change
- CBR back to 68000
- Preset to P5 Slow Good Quality

Finally got a smooth playing video and the 9 minute test game came out to 4.6GB file. That is so much better than the 40 gig files I was getting before. I will do some more testing to see if I can get the quality even better and try to keep this file size at the same time.

The quality using CBR seems just as good as when I was using CQP @ 16. I am really not sure why the CQP is even there when you can use the CBR to get the same quality and a file a fraction of the size.

Thank you guys so much for your help. You really got me on the right path to figuring this out.

 

[qhobbes]

It sounds like there's encoded overload or render lag.

Please post a log with your issue! Here's how...

OBS Studio creates a log file each time you run it which contains very useful diagnostic information. Without a log file, it's much harder for any support volunteers to figure out problems and your post may be ignored. To upload a log file, go to the Help menu > Log Files > Upload Last Log...

obsproject.com

 

[koala]

CBR is inferior to CQP, because it wastes bandwidth with low motion scenes and doesn't have enough bandwidth with high motion scenes.
You didn't realize perhaps that you need to increase the CQ value to decrease quality, so file size is decreased. Try CQ=30 and see how quality and file size will change.

CBR is an internal method to dynamically adjust the CQ value, so always the same bitrate is achieved. If you say bitrate=40000, it's internally increasing the CQ value until the resulting bitrate drops below 40000. This can lead to vey high CQ values, so the result (in high motion scenes) will appear as bloody mess. If you use CQP in the first place, the CQ value is constant, so the quality is constant, and the bitrate dynamically changes according to motion.

So I propose a different approach. For getting the size of your files down to an acceptable level while having the same quality, choose CQP and start with a CQ value of 35. Notice quality and file size. Decrease CQ by 3 to 32. This will about double the file size but increase quality much (CQ change by 3 about doubles/halves file size). Repeat this until you find your sweet spot between file size and video quality.