TV Tuning Basics
A TV tuner for a computer does essentially the same thing that the tuner inside your television does: takes the signal sent to you via a RG59 cable or though the air and converts it into a image that can be displayed onto your computer display.
This may seem like a relatively easy task, and in fact, it is. All the TV tuner cards we have seen make use of a a Philips TV tuner module. Shielded in a metal box to prevent interference, popping the top off the TV tuner module shows that unit is fairly simple. The unit contains quite a few filters and such as well as a Philips TDA9800T VIF-PLL demodulator that provides "a monolithic integrated circuit for vision and sound IF signal processing in TV and VTR sets." This chip, which takes the data sent to it by the coaxial source and converts it into data that a video card can use, is the key to the whole TV tuning function.
From here, things get more familiar. The signal decoded by the TDA9800T next passes out of the shielded box and into a sound processor of the manufacturer's choice that translates the coaxial data into sound capable of being processed by a PC. Next, the video portion of the cable input is sent to a decoder chip so that it may be displayed on a monitor. This chip treats the TV signal just as it would treat any other form of input, be it from a DVD player or a camcorder. This provides the final step in the data processing, allowing the cable input to now be displayed onto any display that accepts a VGA or DVI connection.
One of the more difficult parts of bringing TV to the PC is producing software to control it all. All the manufacturers we have seen use different programs to control access to the television channels. Even the most basic programs must include a channel selector (which tells the TDA9800T what frequency to listen to), volume control, screen size selection, and more. Advanced features found in some of these programs enhance the act of TV watching by including functions that allow for time shifting, closed and caption logging, and video recording.
The decision to integrate TV tuner card onto a video card makes a lot of sense since the two interact on the most basic level. The decision to go with a TV tuner video card, however, is a difficult one. Video cards with a built in TV tuners are naturally more expensive than video cards without this feature, making it hard to bite the bullet and get one of these cards if you are unsure if you will use need TV tuning. So how is TV on a PC and is it right for you? Good question.