Constant Rate Factor vs. Constant Framerate and other video controls

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Nekoninda
Posts: 2
Joined: Tue Feb 04, 2020 3:06 pm

Constant Rate Factor vs. Constant Framerate and other video controls

Post by Nekoninda »

Description of problem or question:

In 'Adjusting quality' of the 1.3.0 Documentation, it says 'Most of HandBrake’s official Presets use the x264 or x265 video encoders with a Constant Rate Factor, sometimes abbreviated CRF or simply RF.' However, the video screenshot shown below this statement shows the same thing that I see in version 1.3.1 of Handbrake: a control setting labeled 'Quality' with two options, 1) 'Constant Quality' and 2) 'Average Bitrate'; and a separate control setting for 'Framerate (FPS), with choices for 1) 'Peak Framerate (VFR)' or 2) 'Constant Framerate'. There is nothing on the Handbrake video screen that says 'Constant Rate Factor' nor 'CRF'. There is a slider labeled 'RF' as part of the 'Constant Quality' option.

The mismatch in the terminology between the documentation and the Handbrake screen is confusing, made worse by the fact that most of these control options are not mentioned in the 'Adjusting quality' documentation. The documentation doesn't mention either of these controls by the names that appear on the Handbrake screen, nor does it cover their two alternatives. It only mentions the RF slider that is part of the 'Constant Quality' option. It would be very helpful, if the documentation explained these two controls, each with its two options, and how/why to use them (in addition to the discussion of the RF slider that the documentation currently contains).

I would be grateful if anyone could give a more detailed explanation of these controls and how to use them, as a response to this message.

Thank you.

Steps to reproduce the problem (If Applicable):
Launch Handbrake, select 'Fast 1080p30' preset (or many other presets), click on Video button to see video settings

HandBrake version (e.g., 1.0.0):
1.3.1

Operating system and version (e.g., Ubuntu 16.04 LTS, macOS 10.13 High Sierra, Windows 10 Creators Update):
macOS 10.14.6

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BradleyS
Moderator
Posts: 1766
Joined: Thu Aug 09, 2007 12:16 pm

Re: Constant Rate Factor vs. Constant Framerate and other video controls

Post by BradleyS »

The section of the documentation you're referring to is focused on the most common encoding workflow, and most of those controls shouldn't be changed. We plan to add more advanced fine tuning information in another section down the road.

I'm sure someone will be happy to explain the frame rate and quality controls more deeply here shortly.

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JohnAStebbins
HandBrake Team
Posts: 5505
Joined: Sat Feb 09, 2008 7:21 pm

Re: Constant Rate Factor vs. Constant Framerate and other video controls

Post by JohnAStebbins »

There is nothing on the Handbrake video screen that says 'Constant Rate Factor' nor 'CRF'.
The documentation is describing the units of measure used by either x264 or x265 for their quality setting, i.e. CRF. Other encoders use different units of measure, e.g. QP, or CQ. So the units of measure change as you change encoders, and are shown next to the current value on the slider. But the name of the slider remains constant.

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