Export process and video size

[Carlton]

Hi all,

My original video is 4K-30 fps and it’s size is 2,42 Go.
I do no modification at all, not a single cut, not a transition, strictly nothing. I just export the video with the same settings than the original : 3840 x 2160 (i.e 4K), and 30 fps.
It turns out that my output video size is 518 Mo.

How come while I didn’t change the resolution neither the fps?
While I put the original vs the edited next to each other, I cannot see any visual loss of quality while the size has shrunk for 5 times less --> What in the video have been reduced / compressed?

Can anyone explain what is the process behind exporting?
I read on other topics that Codec has something to do with it but I didn’t get it clear. The one set by default here is libx264, quality = 55% (crf = 23) ,GOP = 150 . I kinda guess the 55% quality means something, but again visually I cannot see any difference ( 45% quality loss would be very much noticed I suppose).

Some clarification would be much apreciated.
Thanks in advance.
Regards

[Elusien]

There are various reasons how this could happen, see:

Video export file size smaller then original

Hi, I am joining two videos together in SHOTCUT. Each video is 30min long (12GB in size). When I export my compiled video the exported size is not 2x 12GB (24GB), but 6,83GB only. As pertaining the video quality it seems there is no loss (exported in 4K). Should not the exported file be 24GB? Am I doing something wrong? Thank you for any help or explanantion.

Download mediainfo (MediaInfo - Download), open both files (original and exported) on it, click on menu item View->Text take a screenshot and post it so we can compare the properties.

[kagsundaram]

@Carlton

How come while I didn’t change the resolution neither the fps?
While I put the original vs the edited next to each other, I cannot see any visual loss of quality while the size has shrunk for 5 times less → What in the video have been reduced / compressed?

Welcome to the Forum, @Carlton, you have asked a simple question whose answer is, alas, not simple at all.

I was about to refer you to an explanatory thread which contains this…

GOP, B Frames and Codec Threads - What Do They Mean?

A GOP (Group Of Pictuires) always starts with an I-frame (Intra frame). An I-frame contains all the information needed to produce the picture for that frame, it does not depend on the contents of any other frame. If the GOP consists of only I-frames it would emulate an old cinematographic spool of tape, where e.g. damage to one frame would not affect any other frame. The GOP can also contain zero or more B-frames (Bi-directional frame). B-frames consist of information that describes the chan…

…summary; however, I see that the author of that response has arrived ahead of me.