Bug Report OBS Potentially Ignoring "709" color space and "Full" color range settings with utvideo (Output mode: Simple, Quality: Lossless)

oblivioncth

New Member
Hi,

I'm not 100% sure if this is truly a bug but at the very least this behavior is not as one would expect. I am trying to record short snippets of footage for later analysis, pixel-by-pixel, so in this use case accuracy is everything and file size/CPU usage is not a concern. Because of this I am using the "Lossless" preset under the simple mode of Output settings. I also have selected Color Space: 709, Color Range: Full, and Color Format: RGB under the Video portion of Advance settings.

If you look at the spec for the utvideo format, at the following link, you will see the FourCC codes that the format uses for each codec it has implemented:
http://umezawa.dyndns.info/archive/utvideo/utvideo-17.4.0-readme.en.html

Given my exact settings, I would expect that the "UtVideo RGB" codec would be used during the render of my recordings; however, the file generated seems to use a completely different codec that doesn't match any of the settings. Any files I record while using these settings have the "ULY4" signature at offset 0x70, which corresponds to "UtVideo YUV444 BT.601" and VLC recognizes the file as using this codec (though it doesn't seem to support decoding it at the moment). I would expect the latter codec to be used if my settings where Color Space: 601, Color Range: Limited (though perhaps this isn't the case), and Color Format: I444, which obviously are not what I am trying to record with. Changing the Color Space setting to 601 just to see if they were perhaps reversed for example has no effect and ULY4 is still used.

The colors in my recordings are ever so slightly different than expected when compared to a screenshot of the same source.

Windows 10 x64
OBS x64 24.0.3
Recording Window based on title, then exe name
Base & Output Resolution: 320x224
FPS: 60
Downscale Filter: Bilinear
 
Last edited:

oblivioncth

New Member
I looked through the log file and nothing there seems to mention the ouput format but here it is anyway:
https://obsproject.com/logs/S0z_iS4wMn4cDMOE

It does note that RGBA is being used even though the menu just shows RGB (which is understandable since I'm sure many discount the alpha even if its being used) so I supposed the expected codec would actually be UtVideo RGBA (ULRA).
 

oblivioncth

New Member
Does no one use this codec? I know lossless video recording is a bit niche and that the primary focus of OBS is streaming, but I figured it would have some presence.
 

Narcogen

Active Member
I don't think this configuration is common at all. Most users are advised to use NV12 and 601 or 709 Partial, not Full, as most end-users displays when used through streaming services do not support this color space, and attempting to use it increases GPU load.
 

DeMoN

Member
I still wonder why 601 is the default color though. It makes absolutely no sense to use the worse color
Partial is correct though.
 
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