100FPS video corrupted on export unless speed of clips is changed

I’ve been using Shotcut to build videos from multiple short clips shot at 100FPS (H.264, PAL). The files are from my Sony RX10 iv. I use proxy and export with default settings and without hardware acceleration on Windows 10.

I’ve regularly seen corruption (localized artifacting) in the exports, but I’ve discovered that if I substantially change the speed of a clip it seems to resolve. I slowed some videos to 1/2 or 1/3 the original rate, and then they export cleanly.

What might be causing this problem?

Are you using the correct video mode for this? set at 100fps (not just in the export panel)?
Do the artefacts look like regular low bitrate video? If so maybe try increasing the export quality to something like 65% (crf18).

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Thank you for the response. Please clarify what you mean by “video mode”. If I look at frame rate in the Properties panel for each clip I see 100.000000.

The artifacting is local (not across the entire frame). I don’t believe it’s an overall quality issue. The segments around the problem areas and during the sections without problems are of high quality.

In my research the topic of codecs for Windows came up. Are there any I should have that aren’t bundled with Windows?

You change the video mode via Settings → Video Mode, to see the current active mode click on the little area that says Output (top left corner of timeline) and open the Properties panel.

The default export profile uses H264 (AVC), this is very common and 100% present in Windows.

Thanks again. The Video Mode was set to Automatic. Here are the active mode parameters:

Resolution: 1920 x 1080
Aspect ratio: 16 : 9
Frame rate: 100.000000 fps
Scan mode: Progressive
Colorspace: ITU-R BT.709

My untrained eye spots no issues there. Is it possible that machine performance can result in corruption, or is that just a matter of output speed?

You say default export settings, so I assume that is h264 on your machine. @daniel47 already gave you one possible answer and it involves changing the quality in the codec tab:

  • Enable advanced mode in the export tab.
  • Change interpolation to lanczos.
  • In the codec panel (at the top) change the percentage to 67%, assuming the codec is libx264.

Re-export and see how that goes for you.

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Thank you. I’ve tried that and the outcome was the same. Here’s a couple screen grabs showing the problem. You can see how certain parts of the image are badly pixelated or otherwise distorted.

This might be a problem in your media player handling the frame and data rate. Try playing it in Shotcut. I doubt you need 100 fps. You should try using a video mode with 25 fps.

The problem persists with videos uploaded to YouTube, so I’m reasonably sure it’s not a player issue. My camera was set up for other events, which is why the clips are at 100fps. You’re right that this project doesn’t need that, though. I’ll reduce it and try again. Thanks.

Export at 60fps worked well. Thanks all for the assistance.

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