Question / Help Significant frame-rate reduction with OBS running

[Thaumaturge]

Greetings!

I'm attempting to record some gameplay (offline; not streaming) using OBS Multiplatform, but am finding that recording produces a significant drop in frame-rate--from above sixty to just above twenty. This seems to result from simply running OBS; actually recording produces only a slight additional drop in frame-rate.

I've already performed several searches and messed around with various settings, to little avail. It probably doesn't help that I'm not terribly familiar with video, audio, and recording matters, so I may well have missed or mis-applied the advice most relevant to my situation.

I have already disabled the preview, which helped somewhat (I was previously seeing frame-rates of around seventeen or eighteen, as I recall).

Another screen recorder (LoiLo) managed to produce a recording at thirty frames per second with the same game, so the process would seem to be theoretically possible on this machine. (I mainly chose against that recorder because it doesn't seem to be willing to record the cursor.)

My system specs:
Dell Inspiron 15 3000 Series
CPU: Intel Core i7-5500U @2.40GHz (4 CPUs)
Memory: 8GB
GPU: NVidia GeForce 840M (2GB, I think)
(It does appear that there is also an integrated Intel GPU present. As I gather that OBS makes use of the GPU, I tried to have the NVidia Control Panel specify that OBS use the NVidia card, but my settings there don't seem to remain in effect. :/)

My log file should be available here:
https://gist.github.com/52436bf390d38514d93a

(Given a previous log, the Log Analyser only reported that my CPU Usage Preset was set too low. (It's currently on "ultrafast".))

My thanks for any help given!

 

[Thaumaturge]

Sorry to double-post, but I'd like to add a small update:

Subsequent testing suggests that the drop in frame-rate is coming from the "Game Capture" input specifically; if that is removed, the frame-rate recovers significantly. Attempts to use either the monitor or window inputs results in much better frame-rates, but with black output (i.e. the game-screen not being successfully captured).

I also seem to have forgotten to mention (in case these points are at all relevant) that I'm running under Windows 8.1, and that I have a dual-monitor setup. For a short time it seemed that disabling the second monitor might have been the solution to my problem, but further testing suggests that this result was spurious, likely caused by the "Game Capture" input breaking during that experiment--subsequent tests have produced little to no apparent improvement in the frame-rate.

 

[Thaumaturge]

All right, I think that I've solved my problem. Simply put, it seems that my laptop wasn't assigning the game to the NVidia GPU, instead leaving it to the integrated Intel GPU. This was solved by updating my NVidia drivers and then using the NVidia control panel (which now seems to save my settings) to specify that I'd prefer that the NVidia GPU be used.

As a result, the frame-rate seems to have increased sufficiently that even with the drop produced by the Game Capture input I still achieve greater than thirty frames per second, which is acceptable for my purposes, I believe.