Artifacts in Screen Capture of Streaming Video

[malrey]

Hi all,

I am trying to create a screen capture (using SimpleScreenRecorder and Linux) which includes an online video stream being shown on screen. During the streaming part I get offset-artifacts that are probably somehow caused by the interplay of my screen recorder and the stream web player in my browser. An example of such an artifact is shown in the attached image. It's particularly prevalent when there is much motion in the streaming video (without motion it's of course not so easily visible).
The artifacts are not visible when watching the stream while recording but are quite noticeable in the recorded video afterwards. I already tried doubling the Framerate of my recording (set it to 50, the online stream has 25 fps) but the artifacts still occur with what feels like the same frequency. Any ideas how I might get rid of those? Or remove them afterwards by somehow detecting and filtering them out while converting the captured video?
I don't think it's dependant on the capture software I used (tried another one and had the same problem).


https://forum.videohelp.com/images/imgfiles/aaOoKvSh.jpg

Thanks,
mal

[jagabo]

It's called tearing. It happens when the video frame buffer is being updated as the screen is being captured. The result is a cap that part one frame, part the next. You need to use a player that swaps buffers during vertical refresh (online players often don't do that), and capture software that syncs to that.

[malrey]

Thanks. Knowing what it's called will be a big help looking for further solutions. I have no control (I think) over the player my browser uses to play the video (or the way that player updates its buffers).
Could I maybe record at a high fps and then reencode to a lower one while somehow identifying and filtering all frames with tearing (it should be easy to detect)? I usually use ffmpeg but am not aware of any filters or similar options for removing such artifacts...

Thanks again,
mal

[theewizard]

increasing frame rate/capture rate will NOT help, it might make it worse
the best thing to do, might be
to capture at a lower resolution
DO NOT expand to full screen while playing the stream
capture the video at the stream resolution, NOT expanded play.. full display

[jagabo]

Tearing is an issue gamers often complain about. The graphics drivers usually have a vertical sync setting to prevent it. So check your drivers too.

You might be able to come up with an AviSynth script (for Windows but it works in wine) that only removes torn frames. But I don't know if any specific filter that identifies them.