This post was last modified: 2018-09-01, 04:12 by steveaxford.

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

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.

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

This post was last modified: 2018-09-01, 08:49 by steveaxford.

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).

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.

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.