What is "crf"?

Discussions related to the 1.36.x series of ZoneMinder
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alabamatoy
Posts: 297
Joined: Sun Jun 05, 2016 2:53 pm

What is "crf"?

Post by alabamatoy » Tue Jun 15, 2021 11:25 pm

New update from 1.32.something to 1.36.4, we are getting a popup that says: "encoder does not work well with out at least a value for crf. Please see the help"

crf does not occur in the documentation according to the readthedocs search. I see where crf is a value in the encoder details of the monitor, but by default its commented out. So I have 2 installs of 1.36.4 with no crf value (or its commented out) and one that is demanding it be set.

Any advice? Im thinking something went off the rails in the upgrade.

ergamus
Posts: 27
Joined: Sat May 29, 2021 10:09 am

Re: What is "crf"?

Post by ergamus » Wed Jun 16, 2021 1:20 pm

Regarding CRF for H.264/H.265:
https://slhck.info/video/2017/02/24/crf-guide.html

Stick with the default values, decrease if the quality loss is noticable, increase otherwise. A lower CRF value will produce a higher quality image (keep in mind when talking about transcoding, you always degrade quality versus the original video stream), at the cost of larger filesizes. If you're transcoding on your CPU, you might need to tweak the CRF value so you're not exceeding the performance capabilities of your hardware.

If you're doing passthrough on your monitors, this has no effect because you're outputting the H.264/H.265 stream from your camera directly to a file.

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