Question / Help Some CRF questions

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Boom123

Member
Hello,
I have some questions regarding CRF, I am currently using veryfast as the preset with a CRF of 14. Only doing local recordings not streaming. Gameplay being captured at 480p (old retro shmups), but output resolution of OBS is 1080p 60fps, using Lanczos.

1. In this thread (http://www.tomshardware.co.uk/answers/id-2870384/obs-settings-recording-1080p.html), a user states that CRF=15 is low quality. Any truth to this? (since the CRF range is from 0-51, I thought 15 is quite a good number, especially when the OBS guides recommend a range of 15-25: https://obsproject.com/forum/resour...lity-recording-and-multiple-audio-tracks.221/)

2. Since the outputted video is being upscaled (from 480p to 1080p), will I need to compensate for this with more CRF than CRF 14?

3. If I had to lower the CRF value further than 14 (example 10), will this just increase the bitrate and file size, or also use up more CPU usage? (I'm currently using 60% - 70% CPU usage while playing and recording).

Thanks in advance for any advice :D
 
BK-Morpheus

BK-Morpheus

Active Member
CRF is not directly related to the resolution, so you don't need to compensate anything.
In my opinion, compression artifacts can be more visible at lower resolutions, so I can live with slightly higher CRF values for higher resolutions.

CRF 15 should result in very good quality.
I often record with CRF17 or even CRF18 at 720p and it looks good.

About your question on CPU impact: Higher bitrates increase CPU load slightly. So increasing quality from 15 to 10 will cause higher CPU load, but this impact is not as heavy as changing encoding presets (for example switching from very fast to faster preset will have a higher impact on CPU usage).
 
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Boom123

Member
Thank you for such a prompt reply BK-Morpheus. So I'm fine with my current CRF 14 setting and should just ignore that Tom's Hardware post?

Yes CRF 14 is very nice quality, it's almost identical to the game in my opinion (very slight, almost unnoticeable differences which I only notice if I'm trying really hard to find), that is why I was a bit baffled when I read the post about CRF=15 being low quality and wished to confirm it.

Well if I'm seeing it 'almost identical' to the game with CRF 14, if I lower this further, will I just be getting bigger file sizes and more bitrate, but the differences won't be noticeable to the human eye? (In other words just wasting space and CPU usage?) Or will it actually be a noticeable improvement?
 
BK-Morpheus

BK-Morpheus

Active Member
Yes, in my opinion CRF values below 15 are not necessary or in other words they will result in bigger files with higher CPU usage, but you might not even see a difference at all.
 
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