Ursa 12K at 4K - bad frame sizes?

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spectecjr

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Ursa 12K at 4K - bad frame sizes?

PostTue Oct 19, 2021 5:40 am

Hey there;
I've been testing out recording footage at different resolutions, and I've been getting some weird vertical squashing in the viewfinder and when I import the footage into Resolve. (Using a normal, spherical lens).

From the BMD website for the 12K, the supported frame resolutions are:

Shooting Resolutions

12,288 x 6480 (12K DCI)

11,520 x 6480 (12K 16:9)

12,288 x 5112 (12K 2.4:1)

7680 x 6408 (12K Anamorphic)

8192 x 4320 (8K DCI)

7680 x 4320 (8K 16:9)

8192 x 3408 (8K 2.4:1)

5120 x 4272 (8K Anamorphic)

6144 x 3240 (6K Super16)

4096 x 2160 (4K Super16)

4096 x 2160 (4K DCI)

3840 x 2160 (4K 16:9)

4096 x 1704 (4K 2.4:1)

2560 x 2136 (4K Anamorphic)

If I record footage in each of the 4K recording modes, and then examine them using MediaInfo, I get the following discrepancies:

4K DCI - should be 4096x2160, is 4112 x 2168, reported aspect ratio 16:9

4K 16:9 - should be 3840x2160, is 3856x2168, reported aspect ratio: 16:9

4K 2.4:1 - should be 4096x1704, is 4112x1712, reported aspect ratio: 16:9

4K Anamorphic 6:5 - should be 2560x2136, is 2576x2144, reported aspect ratio: 16:9

4K Super 16 - should be 4096x2160, is 4128x2176, reported aspect ratio is 16:9.

This seems all off, and the camera has the latest firmware settings. Is anyone else running into this?
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Ben Price

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Re: Ursa 12K at 4K - bad frame sizes?

PostThu Oct 21, 2021 7:53 am

I've not seen that with mine. Although, I did just shoot a project where all of the footage somehow ended up being interpreted at a different pixel aspect ratio upon import. (Simple fix, but annoying.)

For comparison, here's a link to sample shots I took back in April 2021 (testing dual card recording) at the min/max frame rate for every resolution option except Super 16.

https://www.dropbox.com/sh/ep05n4fndehb ... tdWIa?dl=0
URSA 12K, DR Studio 17, SmartView 4K, SmartScope Duo 4K, VideoAssist 4K, Decklink 4K Extreme, Hyperdeck Shuttle II, MacPro (cylinder) 10.15.7, 128GB RAM, 12-core, D500, 12TB RAID5 USB, 36TB RAID5 mini-SAS
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Jeffrey D Mathias

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Re: Ursa 12K at 4K - bad frame sizes?

PostThu Oct 21, 2021 8:30 am

Please check your settings, second page in the Monitor/All settings. There is a de-squeeze that should be off unless required.
AMD Threadripper 1950x 16-core 3.4 GHz
96 GB Crucial DDR4 2666 ECC UDIMM RAM
AsRock Fatal1ty x399 motherboard
AMD FirePro W8100 GPU & AMD Radeon Pro WX 8200 GPU
Windows 10 Pro 64-bit version 2004, build 19041.1165
DeckLink Mini Monitor 4K
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Howard Roll

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Re: Ursa 12K at 4K - bad frame sizes?

PostThu Oct 21, 2021 1:38 pm

Braw pixels are debayered using the value of neighbor pixels. If you don’t overshoot, then all the border pixels will be derived from incomplete samples. If I recall the largest filter kernel the 12k uses is a 7X7 matrix. That means one would need a minumum of 3 additional pixels added to each edge.

I’d imagine the crop would be handled in the SDK for both the Braw Player and Resolve. In either event the difference in aspect ratio is only 8 pixels, is that even detectable at 4K? The difference in aspect ratio is 1.777 vs 1.778, one-thousandth. Any noticeable distortion is something else.

Good Luck

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