Trouble exporting SD video

I’ve searched this forum for help on this but no luck. I’ve been cutting short clips from HD and SD MKV files. I’ve had no issues with the HD clips but the SD clips wind up being jerky after export. Other than resolution I’m using basically the same settings in both cases. The MKV originals are flawless. On playback the exported SD video makes a slight jump every second or so which suggests a frame rate issue to me. I’m using the latest version of Shotcut. I’m using the H. 264 High Profile preset but have tried numerous other presets and custom combinations, too numerous to list, all with the same result. Maybe some one can suggest some options to enter under the Other tab

Mixing source media with different original frames rates are you?

No I’m not combining the clips just exporting them individually

OK, so are you exporting the clips using their original frame rate?

Yes but I’ve tried several other frame rates as well

You should only use the original frame rate for best results. If you choose a lower fps then frames obviously need to be dropped from the original footage.
Can you tell us more about the source video?

The original MKVs were ripped from my DVD and Blu Ray movie library using MakeMKV. The clips are for testing purposes before editing and re~encoding a few movies to make them more family friendly

Playback is on a Chrome box running Libeelec Kodi

I’m using a Dell Precision M6500 to do the editing

And at what frame rate is the original source SD video?

They’re 29.97 for mostly

And you’re exporting at 29.97 fps?.

Yes. I’ve always made sure of that.

Are you able to supply a short clip from & of the original source?

Can you try to unpack Mkv content and use original material ?

You can use that :

Thanks for all the suggestions, guys, but I solved my own problem. I processed the original MKV file with Handbrake in order to encode it as an MP4. When I imported the video into Shotcut as an MP4 instead of an MKV, I was able to edit it and re-encode it with Shotcut with no jerkiness in the final export. I’m still not understanding why this problem affects only 720x480 videos, and not HD. So in the future I’ll probably rip the original material from the DVDs directly with Handbrake before importing into Shotcut.

Not sure what Handbrake does (if it re encode the video, but if it does you have a quality loss), you should consider MKVExtract as it doesn’t re encode (so no loss with doble re encode steps, but just one).

edit :

Actually I realized that later so converted the MKV container to MP4 without encoding with FFmpeg and that has solved the problem. The final render from Shotcut looks great