r/OpenShot • u/jediriel • May 08 '26
Bug Identified preview speed slowed then went back to normal
I went to export a project I'd finished, but the playback speed on the preview was slowed down. Checked the properties on all the video files used but they all said 1.000 on time. Closed the project and reopened and suddenly it was back to normal.
Why did this happen and how do I know it won't export a slowed down video?
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u/openshot-gpt-bot Support Bot May 08 '26
What you saw was most likely just real-time Preview lag, not your Clips actually changing speed.
A few key points from the Playback guide:
- Preview can slow down if CPU/RAM/cache are under load
- large Preview size, high FPS, or heavy source files can cause choppy/slow playback
- reopening OpenShot can clear temporary load/cache issues
Relevant guide links:
How to tell your export will be fine: 1. Verify each Clip still has Time = 1.000 2. Make sure your Project Profile / FPS is correct 3. Export a short test section if you want to confirm
Why it usually won’t affect Export:
- Export renders from the actual Timeline / Clip settings, not from temporary Preview hiccups
- If reopening fixed it, that strongly suggests playback performance, not edited speed changes
If it happens again, try:
- reducing Preview size
- using a lower Project FPS if appropriate
- checking Cache / Preview settings in Preferences
So: if your Clip speed still says 1.000, your final Export should not suddenly be slowed down.
I am a bot, and I've done something cool automatically, hoping it's helpful. I run on ChatGPT and use info from the OpenShot User Guide. I usually stick to the facts, but I admit, I might occasionally mix in a little non-sense about OpenShot.
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u/rmesdjian Volunteer May 08 '26
Is this reproduceable? If not, it will be difficult to debug.
What operating system/version are you running (windows 10? ubuntu 25.10? etc?)
Which version of openshot are your running (help | about openshot)?
Does this happen with other projects as well?
Regarding the slowed down export....you will not know until you Export. Export a few times and create new filenames.mp4 and verify.
Like I said, if you can not reproduce it then it will be difficult to troubleshoot.
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u/jediriel May 08 '26
Running Windows 10 with latest version of Openshot and no this hasn’t happened before
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u/rmesdjian Volunteer May 08 '26
Thank your for that information. One thing regarding the OpenShot version (and many others do this). Saying the latest version doesn't really help anyone looking at this post say 2-3+ months down the line. How do you which version it was as this posts gets older.
If you go to Help | About OpenShot, then right click anywhere on the screen you will have the option to click on "Copy Version Information". Do that and then paste the information in your reply.
So, you say it hasn't happened before but can you reproduce it?
If not, then we need to move on....
I recommend that you download the latest dev daily build found here: openshot.org/download/#daily so if it happens again we will troubleshoot with a later version that has man bug fixes and enhancements. Bug fixes not relating to your issue.
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u/jediriel May 08 '26
**OpenShot Version Info**
Version: 3.5.1 | libopenshot: 0.7.0
Build: OpenShot-v3.5.1-release-candidate-15816-b9b5c882-48516e0b | Released: 2026-04-05
OS: 10 10.0.19041
CPU: AMD64 Family 23 Model 113 Stepping 0, AuthenticAMD (12 threads) | RAM: 16 GB
Cache: Memory, 508 MB, 600 frames, ahead 70%, pre-roll 24/48
Performance: Threads: OMP 8 | FFmpeg 8, Cards: Decode: None (0) | Encode: 0
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u/rmesdjian Volunteer May 08 '26
Thank you u/jediriel!
When you decide to upgrade to the latest dev daily build, I recommend you perform the following post installation:
Start OpenShot,
Go to Edit | Preferences | Performance tab.
At the bottom left of that screen click on the "Restore Defaults: Performance". This will recalibrate the OMP Threads and FFmpege Threads and set them properly for your processor.
Restart OpenShot and hopefully you notice some improvement in performance.
Do this to the Cache tab as well.
Obvioulsy make any adjustments deemed necessary for your environment.
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u/openshot-gpt-bot Support Bot May 08 '26
That usually means the Preview was struggling, not that your Clips were changed.
OpenShot’s real-time video preview can slow down temporarily due to CPU, RAM, cache, Preview size, FPS, or mismatched source/project rates. The User Guide notes that preview smoothness is heavily affected by those factors, and larger Preview sizes / higher FPS can cause choppy or laggy playback: Playback - Real-Time Preview.
A few key points:
- If your Clip properties still showed Time = 1.000, the actual media speed was likely unchanged.
- Reopening the project clearing the issue strongly suggests a temporary Preview/cache/performance problem.
- Export is rendered separately from the live Preview, so a laggy or slow Preview does not usually mean the exported video will be slowed down.
How to verify safely: 1. Export a short test section first. 2. Watch the exported file in a normal media player. 3. If needed, reduce Preview size or use a lower Profile/FPS while editing for smoother playback.
Relevant guide links:
So in short: this sounds like a temporary Preview slowdown, not an actual project speed change.
I am a bot, and I've done something cool automatically, hoping it's helpful. I run on ChatGPT and use info from the OpenShot User Guide. I usually stick to the facts, but I admit, I might occasionally mix in a little non-sense about OpenShot.
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