Hauppauge WinTV USB, Инструкция по установке и справочник

Страница: 38 / 55

How WinTV Works
How WinTV displays Video-in-a-Window
To display live video on your PC monitor, the WinTV boards use a tech-
nique called PCI Push . With this technique, the live video is digitized
by the WinTV
board and then moved over the PCI bus into the
memory of your VGA display adapter. Here are the steps in getting
live TV onto your VGA screen:
- the TV Tuner is controlled by software to tune to a specified TV
channel. It takes a modulated television broadcast signal and turns
it into
demodulated video and audio signals.
- the demodulated video from the TV tuner goes into the 848,
871 or 881 Video Digitizer chip , where it is converted into a
digital form using YUV 4:2:2 sampling. This is a high quality sam-
pling format which results in resolution equivalent to 24-bits of RGB
per video pixel.
- the demodulated audio goes into an on-board audio switcher.
WinTV ’s audio switcher can receive audio from the TV tuner or the
Audio Input Jacks (Left, Right) . The output of this audio switcher
goes to both the Audio Out Jack ( Line Out ) and the CD-audio
passthrough connector for connection to a sound card.
- the Video Digitizer chip is also a PCI-bus Master device.
After the video pixels are digitized, it “pushes” them over the PCI
bus into the memory of your PC’s VGA display adapter. It does this
without requiring your PC’s processor to do any work, therefore live
video can be displayed in a window on your VGA screen without
slowing down your PC.
Video Overlay mode of operation
Live TV can be displayed on your VGA screen by using either the
Video
Overlay
or the
Primary Surface
mode. The mode which is used is
dependent upon your PC’s hardware and software. If your VGA has
enough display memory to hold the digitized video image, then WinTV’s
Video Digitizer “pushes” YUV 4:2:2 video pixels for temporary storage
into an off-screen part of the VGA memory called a Secondary Surface.
This method is called Video Overlay. The VGA display adapter will then
convert the video image from YUV 4:2:2 into RGB video and continu-
6-1