Welcome to Doom9's Forum, THE in-place to be for everyone interested in DVD conversion.

Before you start posting please read the forum rules. By posting to this forum you agree to abide by the rules.

 

Go Back   Doom9's Forum > Video Encoding > (Auto) Gordian Knot

Reply
 
Thread Tools Search this Thread Display Modes
Old 31st July 2023, 05:16   #1  |  Link
orion44
None
 
orion44's Avatar
 
Join Date: Jul 2007
Location: The Background
Posts: 316
How does AutoGK calculate compressibility percentage?

I would like to learn how to do compressibility calculation manually.

From what info I could find on Doom9, AutoGK performs a constant quality pass at Q2 quantizer on 5% of the video,
but I couldn't find the exact formulas that it uses.

How exactly does AutoGK calculate compressibility percentage?
orion44 is offline   Reply With Quote
Old 10th August 2023, 05:26   #2  |  Link
hello_hello
Registered User
 
Join Date: Mar 2011
Posts: 4,938
If I remember correctly it's just a percentage, so if Q2 equals 100% and (based on the sections of video it tests) the total video size at Q2 would be 1000MB, then a file size of 750MB would be 75% quality, which is what it aims for, from memory (or it might be between 70% and 100%). That part would be easy enough to test if you ran a single pass encode at 100% quality and then again at 75% quality (same resolution each time).

What I don't think I've ever known is exactly how it calculates a new resolution after the compression test if need be, when it's in 2 pass auto mode, in order to achieve a 70% to 75% quality. It's possibly a simple formula but I don't know what it is. You could probably ask the same question in the StaxRip thread because StaxRip can (or at least it used to) run a compression test and I think it updates the expected quality when you change the resizing. It's been a while since I've used it.
hello_hello is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +1. The time now is 19:33.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.