&kdetv; gebruikt een pluginsysteem zodat het gebruiksvriendelijk en flexibel is. Er zijn verschilende plugintypen, b.v. Video input, On-screen-display, Mixers en afbeeldingfilters. Waneer u &kdetv; voor het eerst start, ga dan naar het configuratiemenu om de benodige plugins te laden voor uw hardware. Erg belangrijk is dat u de juiste videoplugins gebruikt om te verkomen dat u niet tevreden bent over &kdetv;. Lees het gedeelte over de video-plugins voor meer informatie.

# Video Device Names

On most Linux systems, you will notice two kinds of device names in the device list:

- video4linux - XVideo port <some_number>

  These are the devices provided by the XVIDEO plugin. For more information about this plugin's capabilities, refer to XVIDEO Plugin.

- <Your video card's name> Video4Linux (/dev/videoX)

  These are the devices provided by the Video4Linux plugin. For more information about this plugin's capabilities, refer to Video4Linux Plugin.

# XVIDEO Plugin

To find out whether you are using a XVIDEO plugin device, look here: Video Device Names

How does it work?

The plugin uses the X-Server to display video. It cooperates with an X-Server module that provides video playback (the "v4l" module, a video4linux to XVIDEO bridge). The v4l bridge provides very CPU efficient video playback because the video image is directly copied from the grabber card into the video memory. On most modern hardware, the graphics card will scale the image to the desired size. Some hardware even deinterlaces the image (the author of these lines uses a Radeon 9500 card with the open-source XFree drivers, this combination provides deinterlacing). Since the v4l bridge works in on the XFree server side, it can provide overlay video display without corrupting the screen, as opposed to the Video4Linux plugin overlay mode.

What features does it provide?

- Low CPU usage

- Depending on the hardware, a quite good picture quality

What features does it NOT provide? Why?

- Image filtering. The images are directly transferred to the graphics card, there is no possibility to manipulate them in between.

- Snapshots. Reason: see above.

- Overscan. Reason: see above.

- Audio mode selection. This feature is not exposed by the XVIDEO XFree interface.

- Channel scanning without having the VBI decoder running. The feature to determine signal strength is not exposed by the XVIDEO XFree interface.

- Image scaling on some very old hardware (e.g. NVIDIA Riva 128).

# Video4Linux Plugin

To find out whether you are using a Video4Linux plugin device, look here: Video Device Names

How does it work?

This plugin has two operation modes:

- Overlay

  It works in Overlay mode when you check the Use overlay if possible checkbox. In this mode, the TV image is directly transferred into the graphics card. Since the video window can only be updated AFTER it has been moved or resized (&kdetv; is an XFree client) you will notice display corruption and heavy flicker whenever you move or resize the window. This is necessary to repaint the desktop regions that were corrupted by the video stream. This mode uses almost no CPU resources, but should only be used as a fallback if nothing else works.

  What features does it provide?

  - Low CPU usage

  - Snapshots.

  - Audio mode selection.

  - Channel scanning without having the VBI decoder running.

  What features does it NOT provide? Why?

  - Image filtering. The images are directly transferred to the graphics card, there is no possibility to manipulate them in between.

  - Overscan. Reason: see above.

  - Image scaling. Most TV hardware (bt8X8 chips) does not support it.

- Grab and Display

  This mode is active when the Use overlay if possible checkbox is NOT checked. An image is grabbed from the TV card and stored in a local buffer. This buffer can be manipulated in arbitrary ways (deinterlacing, overscan, other filters) and is then being displayed using different methods (see below). This is the most flexible way, but also the most CPU intensive way &kdetv; offers.

  Tell me more about the different display modes

  - XVIDEO (with or without shared memory)

    The image is handed over to the graphics card in YUV422 format. Depending on the driver, the graphics card or the CPU scale, the image is transformed to RGB with the display's color depth and displayed. This is the fastest and most flexible way &kdetv; provides. It is strongly recommended that you use this mode since it is the only mode that exposes all of &kdetv;'s features. The usage of shared memory MAY yield a small performance benefit.

  - OpenGL

    The image is handed over to the graphics card in RGB format as a texture for a polygon. If you have OpenGL hardware acceleration, the picture is scaled to the desired output size by the graphics card, which causes a very low CPU usage. The drawback of this view mode is that the OpenGL view mode seems to be unstable. Also, all good deinterlacers use the YUV422 image format, which would cause additional conversions that would nullify the hardware acceleration effect.

  - X11 (with or without shared memory)

    The image is displayed using standard XFree mechanisms. This is VERY slow and does not provide image scaling. Use it as a fallback if nothing else works. Since the video image is grabbed in RGB format, all good deinterlacers will not work. The usage of shared memory MAY yield a small performance benefit.

  Framerate selection

  The plugins provide the option of selecting between full and half framerate. Full framerate is only useful in conjunction with one of the "good" DScaler deinterlacers since they create a new image from the two most recent fields. Full framerate provides "smoother" movement.

  What features does it provide (assuming XVIDEO display mode is used)?

  - Best picture quality;

  - Image filtering in arbitrary ways, for example deinterlacing;

  - Snapshots;

  - Overscan;

  - Audio mode selection;

  - Channel scanning without having the VBI decoder running.

  What features does it NOT provide? Why?

  That depends on the display mode. See above. When using XVIDEO mode, all &kdetv; features are available.

# Mixer Plugins

&kdetv; currently ships two mixer plugins (OSS and ALSA). These should work on all platforms &kdetv; supports. Read the FAQ when you have trouble adjusting the volume.