The VideoLAN Forums

Hi,
I recently noticed that red colors in a Big Bang Theory episode are all blocky and very annoying in VLC 1.0.5. The same problems do not appear in WMP12. I do not know if this is a known issue (I tried searching). I made a zip file with 2 screenshots.

bbt_wmp12.png vs. bbt_vlc105.png (see my post below)

It is not the exact same frame but the problem is easily visible. I also apologize for using rapidshare (10 downloads limit) but image sharing sites would recompress the image making the problem undetectable. I would be grateful if someone can reshare them if they have access to a good image hosting site.

Here's the setup I tested this on:

Dell Inspiron 1520.
Windows 7 Ultimate 64-Bit, fully updated.
Nvidia 8400M GS, driver 195.62 / 197.16.

Please, share images via image servicers like imgur. Rapidshare is horrible nowadays.

Do other video output modules work any better?
http://wiki.videolan.org/WindowsFAQ-1.0 ... _output.3F

OK here's photobucket. I tried directx3d, opengl and gdi output modes with no change.


WMP:




VLC:




+ Another example :

Is there some short sample video you could share to us?

I paid attention while watching other videos. And they all reproduce this problem, only in red colors. The distortion is in all shades of red, but the brighter/fuller the red, the worse it gets. It's not some samples that this is happening, but all videos, therefore there's no point to sharing a sample. There is nothing special about the video file that does this it seems.
I tried turning off post-processing, no change.
Any ideas except try and see what happens with the upcoming VLC 1.1 ?

It seems this bothers VLC 1.1.0 also. Thanks for noticing this. I opened trac ticket for this
http://trac.videolan.org/vlc/ticket/3487

Glad to help. VLC belongs to all of us and all should contribute as they can. Is it universal and not my config?

I can replicate the issues with those images if I open them with my VLC so it is at least Win32 level issue.

I found mention of the same problem here:

http://www.cccp-project.net/forums/inde ... pic=3442.0

(Vista, CCCP codec, AMD graphics)

Maybe the problem is not in VLC at all but files with low bitrate encoding. Then I wonder what the WMP codec does to mask the problem..

Here is an explanation from that forum:

"The samples are taken from overlapped pixels and/or a smaller number of samples spread across those pixels and/or samples recorded in a macro block pattern not directly representing each pixel but representing a pattern within the macro block. This unfortunately makes the macro blocks within solid colours and vivid colours very noticeable depending on which encoder is used, the encoder's bit rate, quantisation settings and also any chroma optimisations that are selected at the time of encoding. This macro block encoding also creates the well known halo effect around high contrast content within the scene like logos and sharp edges. When the bit rate falls below a certain threshold it becomes very noticeable."

It isn't bitrate related, since the image files itself can be used to replicate the issue.

True. I didn't think of loading the static image into VLC before.
I tried loading various .jpg's into VLC, and it exhibits the same issue. I also noticed that pictures loaded into VLC have slightly more washed-out, less vibrant colors than when I view them with Windows Photo Viewer. Could this be considered a problem too?

JPEG files can have additional color correction info but AFAIK VLC doesn't support those. It might explain some color issues.

Also if you have NVIDIA display adapter, then try
viewtopic.php?f=14&t=72889&p=240603&hilit=YUV#p240603

The fix on viewtopic.php?f=14&t=72889&p=240603&hilit=YUV#p240603 solved the slight color issue! thanks.
Does disabling hardware YUV>RGB conversion come with a performance penalty though?

Yep, but very minor one.

I see on trac that the issue is still not resolved. I have a tidbit of new information for you. I notice similar pixelation with red colors in flash videos on sites like The Onion too. The problem is not as bad as in VLC with the Onion vidoes, but I assume it's because the videos are way more compressed overall so overall quality is lower.

Check out this video : http://www.theonion.com/video/new-googl ... dir,17470/

0:08 the reporter's red tie
0:57 red rectangle on the very right hand of the screen
1:08 red phone icon on the handheld device

can you see the pixelation?

This is very odd. It must be something to do with either Nvidia drivers, or Windows 7 x64 ? Since we know the problem is not there in WMP, what could VLC and Adobe Flash player have in common?

could VLC and Adobe Flash player have in common?

Overlay or YUV>RGB conversion done via display adapter.

I have "Use hardware YUV>RGB conversions" disabled in VLC, the problem persists. Is this expected?

Deactivate Overlay too.

Tried that already (and again now). Does not solve it.

Then it might be some sort of DirectX or Direct3D driver bug.

Update:
Nvidia drivers 257.21 x64 Windows 7

Problem remains with Output modes "Default", "Windows GDI", "OpenGL", "DirectX3D".

Output mode "DirectX" does not have the problem! However this disables Windows Aero.

Problem is no longer there in VLC 1.1
Except when I take a snapshot in VLC.. "Print Screen" screenshot does not show problem either..

jpg snapshot?

VLC 1.1 default settings (cleared pref's and cache).


Printscreen pasted into photoshop and saved as png (This is how I see it during playback):



Snapshot using VLC's snapshot tool:

ok, does it happen if you use jpg to snapshot?