[OnePlus 8 Pro  Themes, Apps, and Mods] alem972:
Disclaimer: I'm on ox 13.1.0.580 build and I use the stock camera app only for video.

I'm not interested in video filters so i disabled them (but if you want you can keep them).

To open FeatureEditorActivity i use termux with the above command (as stated in post comments):

su -c am start -n com.oneplus.camera/com.oneplus.camera.FeatureEditorActivity

It's quite some time i have changed the above settings and the video part of the camera app is working flawlessly for me.

[Warning] Lots of parameters MUST be bool type, to check you exactly write the value without spaces or capital letters. what value is saved need to be like this:

View attachment 6025147

[Logging] First of all, we can disable lots of logging stuff dev have left behind and only slow down the app:

(default true) Profiling.Camera.OpenCamera false

(default true) Profiling.Camera.StartPreview false

(default true) Profiling.Camera2Core.AbortCaptures false

(default true) Profiling.ComponentManager.ComponentCreation false

(default true) Profiling.MediaSavingTaskPerformance false

(default true) Tracing.CameraCore.GLPreviewOutput false

(default true) Tracing.ActionPanel.EnablingState false

(default true) Tracing.ActionPanel.ItemIcon false

(default true) Tracing.ActionPanel.Items false

(default true) Tracing.CamCorder.GLVideoOutput false

(default true) Tracing.Image.Releasing false

(default true) Tracing.Image.ReleasingByGC false

(default true) Tracing.ViewFinder.CameraPreviewCapture false

(default true) Tracing.ZoomCamera.EnablingState false

(default true) Tracing.MediaSavingTaskState false

(default true) Dump.Touch3AControl.Touch3aROI false

(default true) Dump.GestureDetector.HandleRegistration false

(default true) Dump.OPRtbMultiFrameCamera.MultiPictureYuvData false

(default true) Dump.OPRtbMultiFrameCamera.PictureCaptureResult false

[Video quality] Before my current oneplus 8 Pro, i had a oneplus 6. Amazing phone with excellent video capabilities even compared to oneplus 8 pro stock settings, the old one seems to record better quality video. Infact oneplus 6 4k30fps HEVC video bitrates are around 50mbps, oneplus 8 pro was only 26😖.

So to fix this we can change this parameters:

(default 40000000) Camcorder.HevcBitrate4K60Fps 55000000

(default 26000000) Camcorder.HevcBitrate4K30Fps 45000000

Obviously with quality increase we see also video size increase. If you want smaller video files you can set lower parameters.

I don't record video in x264 or 1080p but if you want you can change the corresponding bitrates changing this properties:

Camcorder.H264Bitrate4K30fps

Camcorder.H264Bitrate4K60fps

Camcorder.H264Bitrate1080P30Fps

Camcorder.H264Bitrate1080P60Fps

and so on....

[Video zoom] I discovered (also thanks to the msg in this thread) that i can change max zoom levels.

you can set whatever value you want, but past a certain value nothing change. This are the max:

(default 8) VideoCaptureMode.LimitMaxZoom4K60Fps 8.0

(default 10) VideoCaptureMode.LimitMaxZoom 15.0

[Filters] I don't use filters on video, so to disable them:

(Default true) OPFilterCameralmpl.EnableAppVideoFilter false

(Default true) VideoCaptureMode.IsFilterEnabled false

(Default false) VideoCaptureMode.Disable1080P60FPSFilter true

(Default false) VideoCaptureMode.Disable4K60FPSFilter true

(Default false) VideoCaptureMode.Disable4KFilter true

(Default false) VideoCaptureMode.DisableNightFilter true

[Misc] Some other parametrs i found useful or increased speed/stability of video recording:

(default 3000) Camcorder.timeoutPrepareRecorder 2000

(default false) ZoomControl.EnableZoomAnimation true

(default false) ObjectTracking.isEnabled true

(default true) DocumentScanning.EnabledByDefault false

(default true) Thumbnailicon.EnableQuickSharing false

(default false) CaptureModesPanel.EnableSettingsButton true

(default false) TimeLapseCaptureMode.EnableSpeedRationActionItem true

to not make this post tooo long i didn't explay one by one, but if anyone interested i can explain them later.

So if anyone has other parameters that are working or want to test i can try and provide feedback