color bleeding with amd 780g and samsung A656 - AVS Forum
Home Theater Computers > color bleeding with amd 780g and samsung A656
hooaarzt's Avatar hooaarzt 11:17 AM 03-21-2009

I have a HTPC with a gigabyte GA-MA78G-DS3H (amd 780g chipset) hooked up to a samsung LE46A656 LCD TV using a HDMI cable.

Unfortunately, I'm experiencing color bleeding or chroma bleeding on the windows desktop. This is most noticeable on vertical red or blue edges. If I open paint and draw some light red (R=255, G=0, B=0) vertical lines being 1 pixel in width, they do appear as dark red lines on the TV. Horizontal lines appear in light red, except the first pixel (Image how this looks on my TV: Attachment 137426).

As white lines do not suffer from this problem, I assume this has to do something with the pixel format setting in catalyst. There, i have 4 options to set the pixel format:
  • YCbCr 4:2:2 Pixel Format
  • YCbCr 4:4:4 Pixel Format
  • RGB 4:4:4 Pixel Format Studio (Limited RGB)
  • RGB 4:4:4 Pixel Format PC Standard (Full RGB)

After doing a complete reinstall of catalyst 9.3, the pixel format was set to YCbCr 4:2:2. This would explain the chroma bleeding to me, as the chroma signals only have half of the resolution of the luminance signal.
But regardless, which pixel format I select in catalyst, I can't get rid of the problem. I can see no difference between YCbCr 4:2:2 and YCbCr 4:4:4. Between Limited RGB and Full RGB the black and white levels change on the picture displayed on my TV.

Reading the EDID-data of my TV using EnTech's Monitor Asset Manager (sorry, this is my first post, so I'm not allowed to post URLs yet) shows, that it supports YCbCr 4:2:2, YCbCr 4:4:4 and RGB.

As i have set all filters on my TV (100Hz, digital noise reduction, resharpening, etc.) to disabled, the effect can't be the result of a filtering mechanism in the TV. At least not of one, which can be disabled in the OSD.

Now I'm stuck with this problem and have not any clue, how I can force my HTPC and TV to display a full quality 1080p signal as I would have on a PC monitor :-(

I'll hope, one of you has a solution of this problem.

Some additional data of my setup:
  • OS: Windows XP
  • Catalyst version: 9.3 (9.2 had the problem, too)
  • Video mode used: 1080p50 (overscan set to 0% in catalyst control center) (1080p24 and 1080p60 have the problem, too)


lostgoblin's Avatar lostgoblin 01:07 PM 03-29-2009

I have the same color bleeding problem with ATI HD4670 and Samsung LE40A656. It seems to be less noticable after selecting HDMI 2 input renamed to PC. I have also tried all video outputs (VGA/DVI/HDMI) and the result was same.

The problem is noticable even with TV Wiselink function. However, this can be caused by Wiselink display settings.

Maybe there is some filter still enabled in service menu? Did you also try NVIDIA graphic card or another input device?
hooaarzt's Avatar hooaarzt 02:02 PM 04-09-2009

at least someone who notices the same problem. Unluckily you have not solved it either

In the mean time I did some further testing:

I connected the PC to HDMI2 and named the input "PC". If feeding the TV with a 1080p60 signal, it seems to detect a PC signal, as most of the picture settings are disabled or not present at all. But the problem is still there and I can't say, that it is less noticeable.

Like you, I can reproduce this problem using wiselink.

My TV even shows the chroma bleeding, if the PC is connected via the VGA Sub-D 15 connector. On black and white lines, the effect does not appear, so this can't be a synchronization issue.

I tried three PCs in total using different connections, but the TV always showed the chroma bleeding effect:
  • AMD 780g onboard graphics: HDMI
  • AMD 780g onboard graphics: analog VGA
  • Intel G33 onboard grahics: DVI->HDMI cable
  • Intel G33 onboard VGA: analog VGA
  • Intel G965 (notebook) onboard VGA

Last week I made a call on samsung's support and today I had a visit of a technician. He noticed the problem, too and replaced the mainboard of the TV. But that didn't help either. He promised to test another TV of the same model in his repair shop and wil tell me the results. I'll keep you updated about his findings.

I strongly hope, that your TV and mine suffer from a seldom defect and that this is not a general problem of the a656 series. Before purchasing the TV I've read many forums where users have hooked up their PCs to the TV. But I didn't read about the problem we're having.

P.S.: When the technician opened up my TV he noticed a heat sink not being in place. It hang fairly loose on a shield plate of the mainboard but according to the technician it should have been glued on a chip which seems to be the interface to the panel (at the top edge, its printig reads "DNIe pro"). Maybe the chip was damaged due to the missing heatsink? But that sounds like a last hope.
Jackie78's Avatar Jackie78 01:11 PM 03-20-2010
Same problem on my Samsung LE40F86BD, looks like this is tome sort of image optimization done by the TV. Any way to solve this?
Jackie78's Avatar Jackie78 04:48 AM 04-16-2010

just another observation I made on my Samsung TV in "Just Scan" mode: it cuts three rows of pixels on the left side, can anybody confirm that? Just try moving your mouse to the left and look how far you can move it, when I move my mouse to the very left, it is only partially visible
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