Elgato 4K X Still Doesn't Work Properly On Apple Silicon Mac And OBS
36The Elgato 4K X has been out for almost a year and it still has issues on Apple Silicon Mac and OBS.
In this video I show two issues with the Elgato 4K X. One issue is that it does not record the correct colour and the other issue is that it does not record using NV12 but uses MJPEG, which causes problems with the picture quality.
Unfortunately, due to the inter-frame and temporal redundancy artefacts with the way YouTube encodes its video streams, the second example showing the quality issues of the Elgato recording were not so obvious. Here's a link to a video that you can download which will show those issues more clearly. https://www.mediafire.com/folder/8l2zyr2somkss/ELAGTO_4K_X_ISSUES
Video Chapters:
00:00 Intro and explanation
10:16 Colour problem
18:32 Picture quality problem
26:00 End summary
Stuff used in this video:
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Acasis no longer make the VC-009Pro UVC. However, it has been replaced with the VC-007Pro, which also records 4K 60FPS. If buying from the Acasis website, use my discount code David15 for 15% off.
Acasis VC-007Pro on the Acasis website https://bit.ly/4jjSEnQ
Acasis VC-007Pro on Amazon https://geni.us/AcasisVC-007Pro
I would just like to clear up some of the things that I said when saying "uncompressed" and codec, as I wasn't super clear in the video and what I said was not totally accurate. When I was talking about ProRes 422 HQ, yes, this is a video codec and I was sometimes using the word "uncompressed" interchangably when talking about ProRes 422 HQ.
I did say near the start of the video that ProRes 422 HQ is a very low compression ratio codec that is also an intra-frame codec. However, later in the video I wasn't as specific when talking about ProRes 422 HQ and started saying uncompressed.
Although ProRes 422 HQ is a visually lossless codec, it is not a true 1:1 sample in the way that uncompressed is. However, as it is an intra-frame codec, intra-frame basically meaning all I frame. It does not have the same issues as the inter-frame variations of codecs such as H.264, H.265, VP9 etc. These inter-frame codecs are what we call a codec that has temporal redundancy, basically, I frame B frame and P frame codecs.
With inter-frame codecs, they use parts of adjacent frames to make up other frames. This helps to reduce the bitrate for these codecs. As a side effect of inter-frame codecs, you will sometimes see mosaic patterning, small squares, when using low bitrates or zooming into the picture. This is something that you don't see when using a low compression ratio intra-frame codec, such as ProRes 422 HQ.
With something like MJPEG, this is a heavily compressed codec. However, it is an intra-frame codec, as in, all I frame. You can think of MJPEG as a sequence of JPEG images. However, while it does not have the same issues as an inter-frame codec, with the mosaic patterns, which some people call "pixelated". Because of the compression method, when using low bitrate variations or zooming into the picture. You will see a similar mosaic, blocky pattern, as you see with inter-frame codecs. This is simply a side effect of the compression.
So when I was showing the zoomed in versions of the Elgato capture and the ProRes 422 HQ capture. Although I was wrong to say "uncompressed" when talking about ProRes 422 HQ. The end result was that the Elgato capture was showing the mosaic pattern, which I'm assuming is MJPEG because MJPEG is part of the UVC standard and Elgato acknowledge that the 4K X uses MJPEG when at 120+FPS in 4K.
Now to be clear about NV12 and MJPEG. MJPEG is a video compression codec and NV12 is a video format. Although NV12 will truncate the incoming video signal's bit depth to 8 Bit and it will truncate/reduce the chroma to 4:2:0. It is not a compression codec. NV12 is essentially uncompressed video at 8 Bit 4:2:0 and it does not apply any compression techniques, temporal or otherwise, that a video codec would.
So when capturing NV12 to a low compression ratio, high bit rate, intra-frame codec, such as ProRes 422 HQ. It will in effect result in a capture that is visually lossless. However, when capturing, or converting, MJPEG to the same ProRes 422 HQ codec. The captured ProRes file will still have the same visual artefacts that are inherent to MJPEG.
This is why zooming into the Elagto capture, even though it was ProRes 422 HQ, still had the mosaic patterning. And because the Acasis ProRes 422 HQ capture was from an NV12 input, this is why it still had definition when zoomed into and it wasn't blocky.
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I’m David Harry. Thank you very much for watching this video, take care and goodbye now.
Cheers,
Dave.
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