External TV-Tuners. They are connected between the monitor and the graphics accelerator of your PC. Of course, a solution like that has both: advantages and drawbacks (actually, any solution would have both). The major advantage is the ease of the connection: you don’t have to open the PC case and dig into the components and wires inside it. Also, the external tuner doesn’t need the system itself: all it needs is the monitor. I would also like to add the third important advantage: the external tuner will not be affected by EMI produced by other components of your system and is more sensitive, so it will produce a less distorted image. However, you have to pay for everything in this world, so the external tuner will definitely cost more and will boast fewer features than an internal one. In particular, it will not be able to capture any freeze-frames and to display the picture in a window (only full-screen mode is supported). This way, external tuners cannot be considered fully-fledged computer devices. I would include them among certain types of consumer electronics connected directly to the PC monitor.
Combo-Devices. These devices a kind of TV-tuners, which can also be classified into three groups. These TV-tuners are designed on the same PCB with a graphics accelerator. ATI Company has been offering solutions like that for a long time already (remember the old Rage Pro and Rage II?) Then this company introduced All-in-Wonder 128 on Rage128 chip, and today we all know very well ATI All-in-Wonder 9600/9800. Note that ATI specialists have already spent quite a bit of time to make sure that their Rage chips work fine with MPEG formats. The drawbacks of combo-devices are evident: TV-tuners do not get outdated as quickly as graphics cards. And it will definitely cost you much more to upgrade a combo-video card.
Internal TV-Tuners (Expansion Cards). Internal TV-Tuners are available as PCI add-in cards. These solution transfer decoded video data along a special bus using DirectX libraries. There used to be tuner-cards for ISA slots. However, since the latter bus no longer exists, the cards like that are considered a rare thing today and are no longer manufactured. Just for your information: ISA tuners were considered expansion cards only nominally, as they actually took only the power from their bus, while the data transfer was all performed via a special external connection cable.
The major drawback of any PCI-tuner is a very high workload it puts onto the system CPU and PCI bus, which has to transfer a huge amount of data. The minimal system requirements for a computer equipped with a TV-tuner include at least a Pentium III 500 processor and at least 128MB of RAM.
The sound accompaniment is usually provided by connecting the TV0tuenr to an external linear output port of your PC sound card. The corresponding connection cable is always included with a TV-tuner card. Some tuner models feature an additional connector located right on the PCB. This way the audio data can be transferred via an internal connection through AUX_IN of the sound card. If there is no sound card in your system, you can connect active acoustic sets to the linear out of the TV-tuner.