Technology talk: 2011

These few questions on "Codecs guide" are really very helpful in solving most of the problems facing you in watching videos on your computer, I copied them to my blog for fear of getting deleted

The original link is:
http://www.codecguide.com/faq_display_issues.htm

The video is displayed only in the top half of the screen, upside down, and also doubled.

Solutions:

Use ffdshow to decode Xvid instead of using the Xvid decoder.
Use ffdshow to decode DivX instead of using the DivX decoder.
In Xvid decoder configuration, force Output Colorspace to YV12.
Use DirectVobSub version 2.33 instead of newer versions.
Enable YV12 on the 'Output' page in ffdshow video decoder configuration.
Use Vista's default theme instead of the classic theme.

General solutions to try when the video displayed is all messed up:

In Media Player Classic, go to Options -> Playback -> Output -> DirectShow video, select a different video renderer.
Install a different version of your graphics card driver.

Q:	The video contains one or more weird lines
A:	This may happen with some buggy graphics drivers. A workaround that often helps is to disable usage of the YV12 colorspace. In ffdshow video decoder configuration, on the Output page, uncheck YV12.

Q:	The video plays with the wrong colors
A:	This may happen with some buggy graphics drivers. A workaround that sometimes works is to disable usage of the YV12 colorspace. In ffdshow video decoder configuration, on the Output page, uncheck YV12.

All colors look completely wrong when playing WMV files

If you have an ATi video card, this is caused by the driver trying to accelerate WMV decoding and failing. You need to disable DXVA WMV hardware acceleration.

With newer ATi drivers, this can only be done from the Catalyst Control Center:

Start the Catalyst Control Center.
Click "View -> Advanced View".
Go to "Video -> All Settings".
Scroll down to the bottom.
Uncheck "Windows Media Video Acceleration".
Click "Apply".
Close the CCC and reboot your computer.

If you have an older ATi driver that doesn't use the Catalyst Control Center, you'll find the WMV acceleration setting in the Windows Desktop properties:

Right-click the desktop and click "Properties".
Click the "Settings" tab.
Click the "Advanced" button.
Here, find a checkbox called "WMV9 acceleration" or something like it. Uncheck it.
Click OK, and reboot your computer.

The video plays with black and white colors in Windows Media Player

This problem is usually caused by a bug in the graphics drivers. First try resetting all the drivers settings to their default values. If that doesn't help, then try a different version of the driver, either older or newer.

A workaround that often works:

In WMP menu go to Tools -> Options -> Performance -> Advanced. That brings up the video acceleration settings. There you should see options called "Use overlays" and "Use high quality mode". Change those settings and restart the player.

Video playback is too dark on some files

Adjust the brightness. There are several ways to do that:

Graphics card
Most graphics card drivers allow you to adjust various picture properties such as Brightness, Contrast, Gamma and saturation.
You can access your graphics card control panel via:
Start -> Settings -> Control Panel -> Display -> Settings -> Advanced
Decoding filter
Most video decoding filters have an option to adjust the brightness. For example DivX, Xvid and ffdshow have such an option.
In Media Player Classic the properties of a filter can be accessed via:
MPC menu -> Play -> Filters -> [name of decoder]
In BS.Player the properties of a filter can be accessed via:
Right-click menu -> Options -> Filters -> [name of decoder]
In Windows Media Player it is not possible to access the properties of a filter.
In ZoomPlayer the properties of a filter can be accessed via:
Right-click menu -> Filter Properties -> [name of decoder]
Windows Media Player
1. In WMP, right-click on the title bar of the window or the Now Playing tab
2. In the context menu, select: View -> Enhancements -> Video Settings
Note: If you can't adjust the sliders in Video Settings, then you need to enable the option in WMP to use the video mixing rendering (VMR). To turn on VMR in WMP, do the following:
1. In WMP, right-click on the title bar of the window or the Now Playing tab
2. In the context menu, select: Tools -> Options
3. Click on the Performance tab.
4. Click on the Advanced button.
5. In the Video Acceleration area, enable Use video mixing renderer.

Video playback is too bright or too dark on almost all files or the colors are all messed up

This is most likely caused by incorrect settings of your graphics card driver. Some versions of the NVIDIA drivers are notorious for messing up their own settings.

Driver settings:

Go to your control panel of your graphics driver. Reset all settings to their default values. Important settings are Brightness, Contrast, Saturation and Gamma.
You can access the graphics driver settings via: Start -> Settings -> Control Panel -> Display -> Settings -> Advanced.
Go to your control panel of your graphics driver. Select the "Color Correction" page. Select "All" in the drop down box called "Apply color changes to:". Then click on the button called "Restore Defaults".
Go to your graphics card control panel. Open the "video and television" options. (You need to be in the advanced view). Select "adjust video color settings", then select "correction". Hit "do not use co lour temperature correction".
If resetting the settings does not help, then find a newer or an older version of the graphics drivers. Uninstall your current drivers, reboot, and install the older ones.

A possible workaround for the problem is to change the video renderer in Media Player Classic. By default it uses the Overlay Mixer (on XP) or EVR CP (on Vista/Seven). If the default renderer you trouble, then change it to either VMR-7 or VMR-9 (renderless). You can find this option via: MPC Options -> Playback -> Output -> DirectShow Video.

In Windows Media Player there also is an option that influences the renderer that is used. In the WMP menu go to Tools -> Options -> Performance -> Advanced. This brings up the video acceleration settings. There you can choose between 'Use overlays' and 'Use high quality mode' (VMR).

Q:	I am unable to play video in full screen
A:	If you are able to videos at their normal resolution, but not in full screen, it means something is wrong in the graphics drivers or its settings. Updating your graphics driver should fix this problem.

Q:	I have troubles displaying RealMedia files on my secondary monitor
A:	Rename your file to .rmvb. Then MPC will use DirectShow instead of the RealMedia framework to play the file.

Q:	When I play the video full-screen, the screen goes black while the audio continues normally.
A:	This problem may occur if you have the WindowBlinds or ObjectDock programs installed. Disable those programs. If you have a NVIDIA graphics card, then you could try to update its drivers.

I don't see the video, just a black screen, but the audio plays ok.

If this problem occurs in Windows Media Player, but only when a subtitle file is present, then you should use DirectVobSub version 2.33 instead of a newer version. This older version of DirectVobSub is included in the K-Lite Mega Codec Pack (as a secondary choice). You must manually select it during installation.
In general, this problem is caused by buggy graphics drivers. Specifically an issue concerning the Overlay. Some solutions and workarounds for this problem:

Go to the control panel of your graphics driver and reset all settings to their defaults. Particularly settings related to "Overlay", "Video Enhancements", "Color Correction", and "Color Controls".
You can access the graphics driver settings via: Start -> Settings -> Control Panel -> Display -> Settings -> Advanced.
Don't use the Overlay video renderer.
If you are using Media Player Classic, then you can configure which video renderer gets used by going to: Options -> Playback -> Output.
Select either VMR-7, VMR-9 (renderless), or Haali renderer.
If you are using Windows Media Player, then you can find the relevant settings by going to: Tools -> Options -> Performance -> Advanced.
Uncheck the box titled "Use overlays".
Update your graphics driver.

Q:	Some videos files look "washed out" and colors are not vivid
A:	This is caused by wrong luminance levels. Solutions can be found here. If luminance levels are wrong, then black is displayed as dark gray and white is displayed as very light gray. Colors look very dull.

What are luminance levels?

Digital video is typically encoded in a YUV format. YUV is a family of color spaces (YV12, YUY2, etc), that encode color information (chroma) separately from brightness information (luma).

There are two standards for the encoding of luma. For standard-definition TV the standard is BT.601. For high-definition TV the standard is BT.709.

Luma values fall in a range. Unfortunately this range is not always the same. There are two commonly used ranges: 0-255 (aka PC levels) and 16-235 (aka TV levels).

When converting a YUV colorspace to RGB, the correct standard (BT.601 or BT.709) must be used and the correct range (TV or PC levels) must be used.

The above is not always done correctly. It can go wrong with certain combinations of video renderers, video resolutions, and graphics driver settings.
The most common thing to go wrong is that the video renderer outputs TV levels instead of PC levels.

How can I correct wrong luminance levels?

There are several methods for correcting luminance levels. We have listed them below in order of recommendation.
All methods assume that you are outputting the video to a PC monitor or LCD TV, meaning a device that needs full range luminance (0-255).
If you are using an old CRT TV or projector, then read the comments at methods 2 and 3.

Method #1: Adjusting graphics driver settings

NVIDIA

Since version 177.84, the NVIDIA drivers have an option for configuring the luma range. You can find the option here:
NVIDIA Control Panel -> Video & Television -> Adjust video color settings -> Select "With the NVIDIA settings" -> Advanced tab -> Set Dynamic Range to "Full (0-255)".

ATI

The ATI driver requires a Registry tweak. With the tweak applied, the driver will convert TV levels to PC levels for SD resolution video. It already does that by default for HD video.

Several ATI driver tweaks can be found at: avsforum.
The UseBT601CSC setting is the one related to luminance levels.

Note: the above tweak only works with driver version 9.1 and older. ATI removed it in 9.2 and newer.

Method #2: Pixelshader in Media Player Classic

A pixelshader is a small program that runs on your graphics card and processes some graphic data. In this case each frame of your video.

Media Player Classic has a special pixelshader called "16-235 -> 0-255" for converting TV levels to PC levels. This shader only adjusts luma values. Use the [SD] variant of the shader if luminance levels are only wrong for videos with low resolutions. Use the [SD][HD] variants if the levels are always wrong.

Some requirements for the pixelshaders in MPC:

You need to use a compatible video renderer: VMR-7 (renderless), VMR-9 (renderless), or EVR Custom Presenter.
Surface setting must be set to "3D surfaces".
It requires some DirectX components that are not included with a default Windows installation. Run the DirectX Web Installer to get the required DirectX updates.

Method #3: Convert to RGB32 with ffdshow

Forcing ffdshow to output in the RGB32 colorspace can help prevent luminance level issues. Downside of this method is that doing this conversion increases CPU usage.

To force RGB32 output in ffdshow, you should uncheck all colorspaces except RGB32 on the Output page in ffdshow configuration. It is also recommended to enable "High quality YV12 to RGB conversion".
There are additional options on the RGB conversion page. Recent versions of ffdshow will automatically use the correct settings, so you don't need to worry about them.

If you are outputting to a CRT TV or projector (or any other device that expects TV levels as input), then you need to adjust the setting under Output levels on the RGB conversion page. It is configured by default to output to a computer monitor. LCD TVs usually also expect PC levels, just like a computer monitor. Some TVs have an option to choose between Full and Reduced range.

Tip: the Profiles/Presets feature in ffdshow can be used to create different sets of settings. You can even auto-load profiles based on conditions like resolution of video format. You could for example create a profile specifically for HD resolution video, and use the 'standard' profile for low resolution videos.

Method #4: Levels filter in ffdshow video decoder

ffdshow has a special filter for adjusting (luminance) levels. To correct wrong luminance levels for a PC monitor or LCD TV you need to convert to PC levels. To correct wrong levels for a CRT TV, you need to convert to TV levels.

To convert from TV levels to PC levels use 16-235 as input range and 0-255 as output range. To convert from PC levels to TV levels use 0-255 as input range and 16-235 as output range.

Method #5: Monitor settings

Some monitors can be calibrated to assume a certain luminance level as input. Read its manual for the details.

Method #6: Resize in software

If wrong levels occur only with SD video resolutions and not with high resolutions, then another solution would be to resize the video to your screen resolution before sending it to the video renderer. For example ffdshow can be used for resizing the video.

Q:	The video looks too bright when DXVA is used
A:	Go the Catalyst Control Center of your ATI graphics card. Find the option called "Dynamic Contrast" and disable it. It is located under "Avivo Video" -> "All Settings".

Technology talk

Monday, September 26, 2011

Video display issues

Saturday, September 24, 2011

Watch videos in youtube without flash!!

Labels