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 Post subject: XRGB Mini + Elgato capture scanline degradation
PostPosted: Mon Mar 14, 2016 7:24 am 


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Joined: 11 Mar 2016
Posts: 37
Location: France
Greetings all,

First of all thanks for sharing all this valuable information on this forum, it helped me a lot in the past. I didn't find any solution for my problem so maybe you guys would have any clue on this.

I'm having a strange issue with my setup, I'm using a Framemeister XRGB Mini unit for video capture purposes.

I tested the Framemeister with that setup:
Console => SCART RGB => XRGB => HDMI => LCD screen

And the image displays properly without problems.

When using that setup:
Console => SCART RGB => XRGB => HDMI => Elgato game Capture HD => Computer

The rendered image looks overall OK except only in the areas where the dominant color is red/purple/pink-ish the scanlines don't look good/are misplaced, making the image look pretty bad whenever big red sprites are displayed.

From left to right: CRT screen photo, XRGB to LCD photo, XRGB + Elgato capture feed - click for full view:

ImageImageImage

Since the problem only occurs when going through the Elgato I believe this is some kind of encoding issue? Did any of you already acknowledge this particular problem?

I was able to mitigate the issue by setting the XRGB HDMI output color range to limited and adjusting the contrast/brightness to get back good black levels but the effect is still visible and some other colors are crushed so I'd like to find another way. I tried to tweak the scanline settings with no luck. Whenever I change the ZOOM setting the scanline settings are compleletely messed up and look very bad so I keep the zoom to default. For some reason when I set the HDMI range to full in the XRGB and HDMI color range setting to "Expanded" in the Elgato I get a red-ish image. So I set Elgato setting to "Standard".

Below are the specific settings of the setup:
Spoiler: show
Consoles are NTSC versions, with RGB Euro SCART outputs

XRGB firmware 2.02 with Euro SCART RGB adapter
Code:
HDMI_OUTPUT: 720_60p
IMAGE_MODE: NATURAL
SCREEN_SET: SMART_X2
COLOR_SET
- BRIGHTNESS: 30
- GAMMA: 8
- BLACK: 2
- SHARPNESS: 1
VISUAL_SET
- AUTO_SCALER: GAME
ZOOM: OFF
SYNC_MODE: OFF
HDMI_SET
- DeepColor: OFF
- OUTPUT_RANGE: FULL
SPECIAL
- A/D_LEVEL: 175
- SCANLINE
-- INT_LINE: 100
-- INT_SMOOTH: 100

Image

Elgato Game Capture HD (standard version, not HD60) software v 2.11.43

- Encoding device is set to software/built-in
- When I set HDMI Color Range to "Expanded" I get a redish image

ImageImage

Any suggestions welcomed :)
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 Post subject: Re: XRGB Mini + Elgato capture scanline degradation
PostPosted: Mon Mar 14, 2016 1:00 pm 


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Joined: 06 Mar 2006
Posts: 11492
Location: Germany
That's caused by the 4:2:0 encoding of your Elgato box, although it still looks a bit weird and I've never seen it to this extend.

4:2:0 means that the first color channel is saved at half resolution and the second one is saved with just a quarter of the luma resolution. Satured reds get fully hit by this.


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 Post subject: Re: XRGB Mini + Elgato capture scanline degradation
PostPosted: Mon Mar 14, 2016 1:16 pm 


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Joined: 11 Mar 2016
Posts: 37
Location: France
Thanks for your fast reply Fudoh, highly appreciated. I suspected it could have been an encoding problem but I wouldn't know the details.

Do you think the effect is very noticeable because some of my XRGB settings are wrong? Do you or anyone here used an Elgato device for capture and encountered/overcomed the issue?

I'm putting the encoding quality to maximum but it's still very noticeable and I don't understand why my image becomes "redish" when I put the HDMI Range of the Elgato to "Extended", shouldn't it be on par with the source?
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 Post subject: Re: XRGB Mini + Elgato capture scanline degradation
PostPosted: Mon Mar 14, 2016 1:22 pm 


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Joined: 06 Mar 2006
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Location: Germany
Quote:
Do you think the effect is very noticeable because some of my XRGB settings are wrong?

no, it's the same on all Youtube 720p videos of the FM running with scanlines. I just checked a few videos.

With 720p you get a 2:1 scanline pattern

like this

0000
0000
xxxx
0000
0000
xxxx
0000
0000
xxxx

With 4:2:0 encoding you get this instead

00
xx
00
00
xx

you see that you actually lose a scanline, that's why the scanlines look further apart on your recorded video.

Quote:
I'm putting the encoding quality to maximum but it's still very noticeable and I don't understand why my image becomes "redish" when I put the HDMI Range of the Elgato to "Extended", shouldn't it be on par with the source?

no idea, but you should use YCbCr output from the Mini anyway and here you never get extended range, but always limited.

I think the only way to capture proper scanlines on red would be to use 1080p with integer scaling. Your capture box only does 30fps this way, but as long as you're using a 4x integer scaling, you would keep all the scanlines intact.


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 Post subject: Re: XRGB Mini + Elgato capture scanline degradation
PostPosted: Mon Mar 14, 2016 2:12 pm 


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Joined: 11 Mar 2016
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Location: France
Thanks a lot for the input, that makes sense.
Fudoh wrote:
you should use YCbCr output from the Mini anyway and here you never get extended range, but always limited.

I wasn't aware of this! By "use YCbCr output" you mean use a physical DT cable for component output on the XRGB instead of the current HDMI cable or is it a setting of the XRGB I'm not aware of ? If you mean the cable I need to check if I have a component adapter for the Elgato input..

Fudoh wrote:
I think the only way to capture proper scanlines on red would be to use 1080p with integer scaling. Your capture box only does 30fps this way, but as long as you're using a 4x integer scaling, you would keep all the scanlines intact.


I'll see what I can do in 720p since yeah as you said I don't have the HD60 model and I'd like to avoid 30FPS capture if possible.

I'll post my findings once I can check it tomorrow.
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 Post subject: Re: XRGB Mini + Elgato capture scanline degradation
PostPosted: Mon Mar 14, 2016 2:15 pm 


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Location: Germany
Quote:
I wasn't aware of this! By "use YCbCr output" you mean use a physical DT cable for component output on the XRGB instead of the current HDMI cable or is it a setting of the XRGB I'm not aware of ?

YCbCr vs. RGB color space - both when using HDMI of course. On the Mini you have a "force RGB output" option. You should disable it, since your Elgato works best with YCbCr signals.


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 Post subject: Re: XRGB Mini + Elgato capture scanline degradation
PostPosted: Mon Mar 14, 2016 2:28 pm 


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Location: Montréal, Canada
TBH, scanlines aren't great for video use: they ruin motion estimation so they really hurt video compression, and as Fudoh pointed out they're not going to line up well with chroma subsampling.


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 Post subject: Re: XRGB Mini + Elgato capture scanline degradation
PostPosted: Mon Mar 14, 2016 2:41 pm 


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Fudoh wrote:
Quote:
I wasn't aware of this! By "use YCbCr output" you mean use a physical DT cable for component output on the XRGB instead of the current HDMI cable or is it a setting of the XRGB I'm not aware of ?

YCbCr vs. RGB color space - both when using HDMI of course. On the Mini you have a "force RGB output" option. You should disable it, since your Elgato works best with YCbCr signals.

Ah I see. I was wondering what kind of sorcery the XRGB would use to output 1080p60 stream through RCA..

From what I read on the page 2 of my status screen the XRGB is already set to YCbCr output so that's good and now I understand why the Elgato "Extended range" messes up my colors since as you mentionned the range is limited by default in this color space.

Guspaz wrote:
TBH, scanlines aren't great for video use: they ruin motion estimation so they really hurt video compression, and as Fudoh pointed out they're not going to line up well with chroma subsampling.


Yeah you're right, scanlines are very sensitive to image compression though I'd like to keep them if I can since my goal is to share gameplay with a rendering that is as close as possible to the experience I have on my CRT for users watching it on a modern screen. I may end up disabling them if I don't find any satisfying result though.

I'll keep investigating, thanks for your time :D
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 Post subject: Re: XRGB Mini + Elgato capture scanline degradation
PostPosted: Mon Apr 25, 2016 11:45 am 


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Joined: 11 Mar 2016
Posts: 37
Location: France
Small update peeps.

I though a lot about this matter and investigated my options.

Seems like the HD60 pro version of the Elgato still uses the 4:2:0 encoding by default so it wouldn't change anything, though according to this blog post the card can be controlled with XSplit to enhance the encoding quality. That would mean having a better result on my encoded files though I would loose the benefit of the Elgato software that handles buffering and a user firendly interface.

But more importantly, all these efforts would be put to waste if Youtube used 4:2:0 encoding, which is indeed the case.

That means untill Youtube switches to a better encoding my current hardware is already good enough to pull the best quality available.

I tuned the XRGB scanline settings to reduce the effect and added a few tweaks to improve image balance, here's a result of a test with my current settings:

https://www.youtube.com/watch?v=HI_aaxP ... ucu34We4_q

While in motion the encoding defects are not very noticeable and IMHO the picture is gorgeous considering this is from a real hardware and not an emulator :)

If someone's interrested I can share my settings, I'll use this setup to share/stream from now, thanks for the help!
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 Post subject: Re: XRGB Mini + Elgato capture scanline degradation
PostPosted: Mon Apr 25, 2016 12:40 pm 


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Location: Germany
looks good indeed. What bitrate for you use for capturing ? And to which bitrate do you re-encode before uploading (if so).


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 Post subject: Re: XRGB Mini + Elgato capture scanline degradation
PostPosted: Mon Apr 25, 2016 1:50 pm 


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Joined: 11 Mar 2016
Posts: 37
Location: France
Thanks :D

I use the maximum quality available in the Elgato software so I believe it should be around 30 Mbit/sec at 720p60. I uploaded the MP4 output from the software directly without re-encoding them.

If I have to do some further editing i'll mess around encoding it myself, I'll post the results then.
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