Compression problem, frame size inversely related to file size?

Forum|Forum|5 years ago
December 31, 2020
2 replies
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I have compressed a long string of 4k video hoping to create a file close to 1GB in H.264. When I compress it at 960x480, at medium resolution, I get a 2.67GB file. Strangely, when I compress the same sequence to a 640x360 fram size at medium resolution, I get a 5.86GB file. This makes no sense to me.

It could be that my resolution is changing as I muck with the frame size setting and add a time code window, but I don't see why it would be twice a big a file. Am I doing something wrong? Should I compress to a format other than H.264? Is there a way to keep the resolution the same, because every time I change it, the frame size reverts to the original size, which is 4k?

Thanks!

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Correct answer R Neil Haugen

File size is mostly determined by bitrate times the length of the video. The framesize only sets how sharp things are in the image. The bitrate sets the file size as far as bytes.

Neil

R Neil HaugenCorrect answer

Legend

File size is mostly determined by bitrate times the length of the video. The framesize only sets how sharp things are in the image. The bitrate sets the file size as far as bytes.

Neil

Everyone's mileage always varies ...

M

Michael Grenadier

Legend

Neil, are you saying that a 4k file with the same compression settings will be the same size as a 720 file?

M

Michael Grenadier

Legend

ah, but I mainly just use the vimeo or youtube presets for web delivery which will have different bitrates for different pixel dimensions... So that's why I never had this "aha" moment. If I'm outputting for full rez archival purposes, I use the appropriate flavor of prores and again that doesn't enter in to it... but thanks for setting the record straight...

and this is one of the main reasons why I find monitoring this forum
so valuable. Although I know alot and pretty much everything I need
to know to work, I do have some areas I do not know as thoroughly as I
might. Right now, I'm going thru
"Premiere Pro 2020 Essential Training" on Linkedin Learning wherever I
have a few spare minutes. Gotta say I know at least 90% of it, and
have some serious issues with some of the workflow choices (and have
found some mistakes), but everyonceinawhile I discover something very
useful. So thanks Neil, Ann and all the other heavy hitters here.

M

Michael Grenadier

Legend

what do you mean by "medium resolution?" Resolution usually refers to pixel dimensions (at least I think it does). do you mean bit-rate or quality?" Try working with one of the h264 presets (such as those for youtube) to start with and then adjust the parameters if necessary...

L

Loch PhillippsAuthor

Known Participant

Yes, my bad. I meant quality.

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