Is it possible to determine the final bitrate setting Constant Quality (RF)?

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kdantas
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Joined: Sun Sep 27, 2015 5:03 pm

Is it possible to determine the final bitrate setting Constant Quality (RF)?

Post by kdantas » Thu Nov 08, 2018 2:51 pm

Description of problem or question:

Hi, I have 35 dvds and I want to make the encode with Video Final Bitrate between 1500 to 1700, but using Constant Quality (RF). Is there any way to predict which RF setting to get the Video Bitrate Final between 1500 and 1700 based only on the video file size (minutes)? I tested using the Avg Bitrate (kbps) with 2-Pass Enchanting and Turbo First Pass, but doubled the encode time. Please do not censure me for asking this question. Thanks.


Steps to reproduce the problem (If Applicable):

Handbrake Windows GUI - Constant Quality (RF) Setting


HandBrake version (e.g., 1.0.0):

1.1.2 (2018090500) - 64bit


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

Windows 10 Pro


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JohnAStebbins
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Re: Is it possible to determine the final bitrate setting Constant Quality (RF)?

Post by JohnAStebbins » Thu Nov 08, 2018 3:57 pm

No. The purpose of RF is to use as many or as few bits as it takes to meet a certain quality metric. For some video sources this can be 10 or 20 times what it is for other video sources. I.e. for the same quality, cell animation encodes much smaller than fast action grainy video.

mduell
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Re: Is it possible to determine the final bitrate setting Constant Quality (RF)?

Post by mduell » Thu Nov 08, 2018 8:25 pm

Yes. The prediction process is just as computationally intensive as doing the encode; do the encode, and you have your prediction.

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BradleyS
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Re: Is it possible to determine the final bitrate setting Constant Quality (RF)?

Post by BradleyS » Fri Nov 09, 2018 2:39 pm

:mrgreen:

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BradleyS
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Re: Is it possible to determine the final bitrate setting Constant Quality (RF)?

Post by BradleyS » Fri Nov 09, 2018 2:42 pm

You may approximate the brute force approach by encoding single chapters or small time segments of your source that are typical in picture qualities and motion of the overall source, then do the maths to calculate size for the duration of the encode based on the average bit rate, and accept some margin of error.

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