Drop in Frame Rate with Multiple 4K HAP Videos

1

Hello everyone,

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?

Thanks in advance for your help!

2

Just wanted to add more info after doing a test.

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.

Thanks again!

3

Hi @Dorian_Dev ,

Thanks for posting to our Answerhub!

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:

  1. 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.
  2. 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.

Looking forward to your response.

Best,
Sara