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4k or 1080 bitrate

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Derek Charles
4k or 1080 bitrate
on Oct 31, 2019 at 7:26:06 am

My computer lags when editing my 4k footage, so I just edit on a 1080 timeline and render out 1080 file to work with before the editing even takes place...- I do this because shooting in 4k to 1080 is sharper than just shooting 1080 - However what about color correction/grading and adjusting overall dynamic range? Am I better off doing that with the original 4k file with the higher original bit rate at 100 Mbps XAVC S? Or is it no different from the now rendered workable 1080 mp4 file with max 22Mbps and average 12Mbps?


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Craig Seeman
Re: 4k or 1080 bitrate
on Oct 31, 2019 at 2:39:56 pm

Do not ever recompress and H.264 source to a lower quality H.264 file for a post-production workflow. Your workflow is major wrong for post.

Transcode to Apple ProRes if you need an easy to playback file.
Alternately DNXHR can work.



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Derek Charles
Re: 4k or 1080 bitrate
on Oct 31, 2019 at 5:21:37 pm

How so? I cant tell a difference - and as far as work "flow" I'd say it saves me a considerable amount of time with the edit - I know bit rate helps with things like fast movement - (less artifacts) but I've been told in this forum that 22Mbps is plenty enough for regular edits


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Craig Seeman
Re: 4k or 1080 bitrate
on Oct 31, 2019 at 8:29:11 pm

It's not simply about the bit rate. It's compressing a compressed source. You're amplifying noise and losing chroma information.



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Derek Charles
Re: 4k or 1080 bitrate
on Oct 31, 2019 at 8:41:28 pm

Forgive me if I'm lacking the terminology of chroma and noise, but how is my tone curve and color adjustments affected within the editing latitude?


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Craig Seeman
Re: 4k or 1080 bitrate
on Oct 31, 2019 at 9:24:00 pm

Less chroma information means artifacts or banding depending on what you're adjusting.
Noise generally increases because encoding removes "like, constant" data and leaves random data (noise).



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Derek Charles
Re: 4k or 1080 bitrate
on Nov 1, 2019 at 12:09:20 am

Not saying you're not correct... but I've taken before and after screengrabs and pixel peeped all the way in and can't see a difference...in color, sharpness, and motion doesn't macro block or ghost or breakup - That being said going back to the 22Mbps is plenty? Even from coming from the 100 Mbps - when originally filmed


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Chris Wright
Re: 4k or 1080 bitrate
on Nov 1, 2019 at 5:57:06 am

i'm not going to say immediately you're wrong. in fact, if you're pixel peeping and don't see much changing, I can't really argue with that as there are some forms of h.264 that can do 4:2:2, 10 bit, but most is 4:2:0, 8 bit so even if your eyes can't see any loss, the computer can. It won't be able to green screen key as well or composite high contrast areas.

theoretically, a high bitrate h.264 4:2:2 is no worse than any other DCT encoding codec. And there's even a 100% lossless 4:2:0 h.264 variant that is as big as uncompressed.

continuing from my initial guess, your eyes can't see the damage, but if you don't need to key, heavy color correct, and only need a 1 generation copy and export, and it makes you happy, then that's fine too. it's not wrong if it works, I just wanted to make you aware of possible problems down the road.


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