Does BRAW not scale linearly in constant quality?

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Zak Ray

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Does BRAW not scale linearly in constant quality?

PostThu May 23, 2024 11:48 pm

I was under the impression that BRAW scales normally, e.g. shooting in 4K is 4x the amount of data as HD. But according to the Ursa Cine calculator, thats not quite the case; it seems 9K and 12K get a boost in data rate in Q1 and Q0.

Here’s what I was able to figure out using normalized* data from the calculator. For a linearly scaled format, every result would be roughly the same at each setting.

Q0
12K: 22.47 MB/s
9K: 22.84
8K: 13.37
4K: 13.55

Q1
12K: 11.68
9K: 11.82
8K: 8.27
4K: 8.38

Q3
12K: 5.50
9K: 5.49
8K: 5.51
4K: 5.59

Q5
12K: 4.11
9K: 4.12
8K: 4.14
4K: 4.27

*I factor in the difference between the real resolution/FPS and an arbitrary one (I chose 1080p30) to get the numbers comparable/normalized. Obviously feel free to take issue if you think the methodology is flawed.

Could someone confirm or deny these findings?

EDIT: I just did the same test with numbers from the Ursa Mini Pro 12K manual and it seems even more inconsistent, though granted the manual doesn't specify which aspect ratio it means for "4K", "8K" etc, so I assumed DCI:

Q0
12K: 23.49
8K: 32.94
6K: 24.08
4K: 62.50

Q1
12K: 20.06
8K: 21.44
6K: 20.06
4K: 47.78

Q3
12K: 14.25
8K: 14.61
6K: 14.44
4K: 38.61

Q5
12K: 8.19
8K: 12.69
6K: 8.39
4K: 31.11
Last edited by Zak Ray on Fri May 24, 2024 2:07 pm, edited 1 time in total.
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Howard Roll

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Re: Does BRAW not scale linearly in constant quality?

PostFri May 24, 2024 12:26 am

Wouldn’t “linear” scaling be a function of constant bitrate? Constant quality implies (to me) a perceptual threshhold.

Good Luck
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Zak Ray

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Re: Does BRAW not scale linearly in constant quality?

PostFri May 24, 2024 12:36 am

Yes but surely the calculator assumes the same "scene" being captured at all resolutions.
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rick.lang

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Re: Does BRAW not scale linearly in constant quality?

PostFri May 24, 2024 11:55 am

I would wait until the URSA Cine 12K is received by customers before coming to any conclusions. When a customer has the shipping general release of the camera and an updated Camera Setup, please post the estimated recording times for a typical scene using identical media. We know those estimates are just a guideline and the actual recording times vary considerably depending upon the actual scene data, but I think those estimates on an identical scene are the best measuring stick for now.
Rick Lang
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Zak Ray

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Re: Does BRAW not scale linearly in constant quality?

PostFri May 24, 2024 2:12 pm

Thanks Rick, I actually took a look at the Ursa Mini Pro 12K manual and found the numbers there to be confusing as well; it seems like 4K is getting a big boost across the board, while 8K gets a small boost at Q0 and Q5.

I have Pockets at home, I'll run the numbers for those soon and verify.

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