strange CRF sizes with version 2.6

[tnt]

Hello.

I have been using version 2.5 for a long time and now I gave version 2.6(. a try.

First, I have used 2.5 to reencode 1.6GB 2160p ~50Mbps video with CRF 24 and some custom encoding settings which I am using for a long time. Resulting file was 1290 MB in size.
Once I have tried to do the same CRF 24 using version 2.6, my results were:

• high444 film slow - 1606 MB
• high444 film slower - 1609 MB

As a second test file, I used 1.8GB 2160p ~50Mbps video and version 2.5 gave CRF 24 encode which was 1050 MB big.
Same video was reencoded with version 2.6:

• high444 film slow - 971 MB
• high444 film slower - 991 MB

So, my questions are:

1. How come in the second case version 2.6 gives slightly better results, while in the first case it gave quite a bigger file for the same quality? Are there some additional settings which have to be set/turned on in version 2.6, or combination of high444, film optimization and slow/slower is enough?

2. How come slower encoding method in version 2.6 gives bigger files as the result?

Thx.

[Jan Gruuthuse]

What 4K video source video codec/container are you using in avidemux 2.5. branch (2.5.6)? You only tell half the story.

to reencode 1.6GB 2160p ~50Mbps video with CRF 24

The first important factor is the actual shot footage. (CRF 24 going to approx. HD quality?)

[tnt]

First example has much more movement and needs more bitrate to keep CRF 24 quality.
Second one is less demanding.
Question is why is CRF 24 threated differently in case of Avidemux version 2.5 and 2.6?

[Jan Gruuthuse]

That is easy to answer:
2.5 branch is frame based editor
2.6 branch is time based editor