I’m facing a performance issue in Light Act when adding multiple videos to the timeline. I’m using 4K HAP videos, and even though the videos are played sequentially (not in parallel), I’m experiencing a significant drop in frame rate to below 24 fps.
My system specs:
Graphics Card: RTX 4080 Super
Processor: Ryzen 9 7900X3D
RAM: 32 GB
Storage: SSD with a read speed of 3064 MB/s
Output Resolution: projected onto two Epson 4K projectors in 4K
The total length of all videos in the timeline is 7 minutes 30 seconds, and they are played sequentially. I’ve checked system resource usage, and I noticed that my CPU is being used at 100% during playback, while my GPU is using up to 14.5 GB of VRAM out of 16 GB.
Is this normal for this situation, or should my performance be significantly better with this hardware setup? If anyone has suggestions for optimizing performance, I’m all ears. Would switching to an Intel CPU improve performance in this case?
I opened the exact same project on a different machine to compare performance:
Second machine specs:
GPU: RTX 4090
CPU: Intel i7-13700KF
RAM: 64 GB
Everything else is the same — SSD, same 4K HAP videos, same Light Act version…
On that machine, the framerate jumps up to 40–60 fps, while on my own setup (Ryzen 9 7900X3D + RTX 4080 Super), I drop below 24 fps.
One thing I’ve also noticed: the more videos I add to the timeline (even if they’re played one after another), the more the overall framerate drops. Is that an expected behavior, or does it suggest a decoding/load issue building up over time?
At this point I’m mainly trying to understand how to get better framerate. If switching to Intel helps in this context, I’m open to it — or if there’s any setting or optimization I’ve missed, I’d really appreciate your input.
Honestly, we haven’t tested video playback on Ryzen processors. All our testing is done on Intel processors, which are the processors used on all our servers.
That being said, I still have a couple of questions:
What is the fps of the videos you are trying to play? Also, what is your Application framerate set to? You can find this setting under Edit → Project Settings → General → Framerates and syncing.
Have you tried adjusting the ‘chunks’ size for optimization when exporting the HAP videos yet? If not, you might want to look into this, too.
The videos I’m working with are encoded in HAP at 30 fps, and the application framerate is also set to 30. I’ve tried increasing it to 60 fps and even removing the framerate cap altogether, but the performance drop persists under all settings.
Each video has a resolution of 5077×1867. I’ve tested various HAP encoding settings — both single-chunk and multi-chunk (10 chunks), and performance was a little bit better with the multi-chunk versions. I also tried splitting the videos in half, assigning one half to the left projection and the other to the right (resulting in 2538×1867 per video), but that approach actually led to worse performance.
During playback, I noticed that disk read speed peaks at around 5.1 GB/s. Also: the more video files I add sequentially to the timeline, the more the framerate degrades over time — even though the videos are not played in parallel.
For the specific event I was preparing, I managed to work around the issue by tolerating a framerate drop below 30 fps. However, I’d really like to understand what’s causing this so I can achieve better performance in future projects.
Thanks again for your support — I really appreciate any guidance or suggestions you might have!
First, thank you for taking the time to analyze these issues in such detail.
We certainly need to look into this on our end. We plan to do this next week. On the other hand, if you have the will, would it be possible to use a simple video layer instead of the stock Video layer template?
You would basically create a blank layer (by double clicking on the timeline) and then in it create these nodes:
Thank you for jumping in — and for the suggestion!
I just tested the setup you described using a simple video layer with manual nodes instead of the stock Video layer template, and I’m happy to report a big improvement: the playback now runs at around 50 fps, which is a nice step up from what I was getting before. That’s a promising result, and it definitely opens up new possibilities for optimizing future projects.
Thanks again for your support — I really appreciate the quick and helpful guidance!
