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+--- Thread: Is it normal for ffmpeg to use 100% cpu? (/thread-11287.html)
Is it normal for ffmpeg to use 100% cpu? - steveaxford - 2018-09-01
When I render a timelapse video my performance monitor shows that cpu busy starts at a low figure (~15%), but then increases to 100% and processing slows, Has anybody else seen this and do you think it's an error?
I have a Dell XPS 8930 with 16GB of RAM.
Note - This was running with MP4 selected. If I select mjpeg, then the cpu stays at around 15% for the whole task and it executes at high speed throughout the task. There appears to be an error with mp4 processing
RE: Is it normal for ffmpeg to use 100% cpu? - Gunther - 2018-09-01
This can be normal depending on your settings and cpu. A high cpu usage normally is desired, since it means rendering will be as fast as it could possibly be.
For best quality, I'd recommend rendering in ProRes.
RE: Is it normal for ffmpeg to use 100% cpu? - steveaxford - 2018-09-01
I think it may be an error as it starts at around 15% cpu. It processes around 100 frames at that % and it then quickly climbs to 100% cpu and the throughput drops by a factor of 3 or 4. This happens with MP4.
With mjpeg or prores the cpu stays at 18% or 30% and the throughput stays high. I'll try some other parameters
RE: Is it normal for ffmpeg to use 100% cpu? - steveaxford - 2018-09-01
I have done some more tests
Using a file of 700 images processed by Lr?LRT using 4k and jpeg.
LRT rendering to video file:
MP4 and 1080p - cpu 40% - elapsed time - 60 sec
MP4 and 4k - cpu 100% - elapsed time - 220 sec *************
mjpeg and 1080p - cpu 15% - elapsed time - 60 sec
mjpeg and 4k - cpu 20% - elapsed time - 60 sec
prores and 1080p - cpu 20% - elapsed time - 60 sec
prores and 4k - cpu 30% - elapsed time 60 sec
It would see that there is a problem with MP4 and 4k only (and maybe MP4 and 1080p is a bit high on cpu).
Is it normal for ffmpeg to use 100% cpu? - Gunther - 2018-09-01
Depending on which settings, framerate, aspect ratio etc. you use for 4k MP4 they might be on the edge of the mp4 specifications, which might lead to strange results.
RE: Is it normal for ffmpeg to use 100% cpu? - steveaxford - 2018-09-02
OK, but 1080p and MP4 should be ok? It uses 40% cpu, where mjpeg or prores uses less than half of this. No big deal as I used MP4 by mistake, but something seems to be wrong in MP4 processing. I use it for internet uploads as it takes much less time, but it can produce lousy results.