# The playback is very slow
Once Node Video has created the RAM preview, you'll usually get real-time performance on a second play-through.
How to improve preview speed
- High resolution videos(>=4K) will hurt the preview speed
- High bitrate videos(>=40000 kb/s) will also hurt the preview speed
- You can use "Prefetch" to boost the previewing speed. Please refer to Use Prefetch to Edit Fast
- Recommend FPS not to exceed 30
Check if advanced features are used
- Optical flow will hurt the Previewing & Exporting speed greatly
- Too many effects will also reduce the preview speed
- Time remapping that have reverse playback will also be very lagging
Most crashes are caused by insufficient memory. We will keep optimizing this problem.
- Try replace the high resolution videos in your project with lower ones
- Try reduce your export resolution.
- Try reduce the overlapped layer count
Be care of the **Optical Flow**
This feature is the killer feature of NodeVideo but it does not support on most of the devices and causes crash!
# There are Loss of Video Quality after Export
Please refer to Improving Video Export Quality
# I can't open my project
Please export the project as a .zip file and send it to email@example.com. We will fix and solve the problem for you.
# I can't import video
Please send this video to firstname.lastname@example.org to help us solve the problem. You can also try to export the video with other apps and try again.
# No sound when playing video
Please make sure the mute switch is off and the volume is turned up on your device.
# Only a single layer can be previewed
Please change the Preview Render Mode to All Layers in the project setting.
# Optical flow not working(crash, noise, etc.)
It is most likely your device does not support it. We'll continue to work hard on this feature.
# How to lock the landscape & portrait mode
Please lock your device orientation.
Feel free to send a mail to contact@nodevideo if you have any question. We are glad to help.