АУДИО И ВИДЕО

Фрэнк Вёлькель,  18 апреля 2000 Страница:   1 2 3 4 5 6 7 8

How is a TV Card designed and how does it work?

All TV cards - whether designed for analog or digital signals - have the same basic architecture. The figure below shows a simple TV card with a PCI interface for analog TV signal reception. A central group of components constitute the actual wideband tuner, which is located under the metal cover for effective shielding purposes. The tuner plays a very important role by transforming the high-frequency (HF) signals of the antenna input into FBAS signals. The real core of the card is the A/D converter chip, which transforms the analog FBAS signals from the tuner output into digital YUV signals. In addition, the A/D converter chip handles the rescaling of the PAL/NTSC television image to fit the PC's digital resolution. Most of the video chips (A/D converters) available on the market today from Conexant/Brooktree both filter horizontally and vertically too during the rescaling of the television picture. This fact alone is the main reason why most TV cards yield excellent picture quality. The digital picture information is sent directly to the graphics board via the PCI bus using DMA transfers (Direct Memory Access) and therefore hardly increases the processor's workload. Having said that, a data stream of 25 to 30 MB per second is actually present on the bus. Apart from the A/D converter, all TV cards incorporate a simple audio circuit which provides sound for loudspeaker connections.

Basic design of a TV card: the TV tuner is hidden under the metal shielding cover. The core of the card is the A/D converter chip which transforms the FBAS signal of the tuner into a digital YUV signal.

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Brief Introduction Introduction - What do TV Cards offer? Classification - Which Cards Are on Offer on the Market? How is a TV Card designed and how does it work? Audio and Video Connections Taking a Look at our Test Candidates Features Table General Hardware Requirements Summary  Обсуждение в Клубе Экспертов THG