Question / Help Question about video frame rate (VFR)

[chummy]

Hello, i'm here to know from some video expertise/guru why OBS Variable Frame Rate recording method differs from MSI afterburner VFR.

Afterburner developer says than VFR will lock recording FPS to ingame FPS, while this really happens in Afterburner recorder, in OBS even a VFR recorded video becomes with a locked FPS without variation.


I made a little footage demonstrations using MPC OSD to show recorded videos performance and show the strange thing happens when in game FPS drop below recording target framerate with Afterburner.

1. Video recorded with Afterburner using Quicksync 60fps, game has high graphics settings which make ingame FPS drop below 60fps.

https://mega.nz/#!dV8QxYzb!nlthTyiDK...2aHFUx1mPwf2cg

In this case you can see than when game keep above 65fps, the recording is steady 59-60fps with no drops, but when ingame FPS get close to 60fps and below then afterburner recording connect the recorded footage to ingame fps.


2. This video is recorded with OBS with same Quicksync 60fps, ingame graphics settings are same to afterburner which will drop below 60fps, but OBS has no compatibility with fraps so cant show ingame FPS, but remember this is same to video 2 settings.

https://mega.nz/#!0ElTmbqb!f7xf9DR0U...Fkmj3g8-G_n0PA

You can see than recorded video stay steady 59-60fps with no drops even in the places where game/afterburner droped below 50 in this settings. Mediainfo show both videos are variable frame rate.

PS: Videos are reencoded with VP9, and all videos was recorded using same Quicksync codec.

If someone can explain why the same Frame rate method works in different way in each software. Shadowplay works sameway to OBS with locked variable framerate.

 

[Boildown]

The developers of OBS kind of hard-coded it to work in CFR mode even if CFR is unchecked:

https://obsproject.com/forum/threads/use-cfr-not-working.18696/#post-96893

Basically all that leaving CFR unchecked does is not put the information in the file that what is to come is constant framerate video. If you actually want VFR, you'd probably have to use an old version of OBS. Not sure how old, you'd have to ask Jim or find it out experimentally.

That said, there's practically no use case for VFR video anyways. Why do you want to record in VFR mode? "Lock recording FPS to ingame FPS" is much less of a good thing than it sounds.

 

[chummy]

I dont want to use, the thing is i just get confused because both encoders were considered VFR by mediainfo but works in different ways, so thanks for information. I prefer constant framerate anyway.