Export the video : CPU usage


I am using (since a few minutes) Shotcut 20.02.17.

I am exporting a MP4 video made from a time-lapse of 250 JPEGs (sky, moving clouds). It works, but the result quality is not so good (blue dithering patterns).

So I tried to increase the 55% quality of “H.264 High Profile” to 75% + Hyper/Lanczos.

Now exporting is very slow, for a 10 seconds movie (estimated 8h30 instead of about 15 seconds at 55% quality).
Global processor peak usage reach only 15% (4-cores processor).
“Parallel” box is ticked.
Why CPU usage is not going to 100% ?


OK, it seems it was just the video length incorrectly defined from the set of pictures. Resulting video is better using libx264 codec (hardware codec un-ticked).

But the low CPU usage is still strange.

Another problem (on my opinion) is that only one task (exporting a video) at a time is performed.

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I also want to use 100% of my CPU. At the moment I barely get 30% CPU. For a 3 minute video with several filters and tracks, it takes 5 minutes which isn’t bad but I have 10 GB RAM remaining and 70% CPU.

How can we force Shotcut to consume it all?

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Try turning on Parallel processing in Export. It is off by default as of v20.04.

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Yes, that worked perfectly - 99% CPU usage. My mouse has trouble moving smoothly. PERFECT!

This is great and saved me 50 seconds. Thank you!!!

I presume you meant 50 MINUTES.

Well, it was a lot faster. For a 3 minute video that took up to 8 minutes and sometimes 6 minutes, it’s now half of that. I’m really happy now.

Thanks for the feedback. We turned it off by default because there are still occasional problems with video artifacts on certain combinations of effects when it is on. We have fixed a number of them over the years, but I finally decided not to expose the beginner and casual users to this risk. Also, there are a number of people who edit against source videos that seek slowly (e.g. H.264 with GOP > 15) and do not use much effects, and parallel processing can make that use case slower by accessing the decoder out-of-order and trigger seeking.

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That makes sense. It’s a wise decision and it only takes 1 click to turn it on.

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