Tv Tuner

A TV tuner card is a computer component that allows television signals to be received by a computer. Most TV tuners also function as video capture cards, allowing them to record television programs onto a hard disk.TV tuners are available as PCI-bus expansion card, PCIe (PCI Express) bus or USB devices. The trend is towards USB devices. In addition, some video cards double as TV tuners, notably the ATI All-In-Wonder series. The card contains a receiver, tuner, demodulator, and an analog-to-digital converter for analog TV. Many cards are limited to the radio frequencies and video formats used in the country of sale. However, many TV tuners used in computers use DSP, so a firmware upgrade is often all that's necessary to change the supported video format. Many newer TV tuners have flash memory big enough to hold the firmwares for decoding several different video formats, making it possible to use the tuner in many countries without having to flash the firmware. In addition to the frequency tuner, many include a composite video input. Many TV tuners can function as FM radios: this is because the FM radio spectrum lies between North American television channels 6 and 7, and the DSP can be easily programmed to decode FM.

There are currently four kinds of tuner card on the market:

Cards for analog TV. Cheaper models output raw tuner data, which requires intensive encoding by another device, normally the system CPU. More expensive models encode the signal to MPEG, relieving the main CPU of this load. Many cards also have analog input (composite video or S-Video). and many also provide FM radio reception.
Cards for digital TV, including satellite TV. Digital TV is broadcast as an MPEG stream, so no encoder is necessary; instead, the digital cards must extract the correct PIDs from the transport stream, which requires much less processing power.
Hybrid tuners that handle both analog and digital inputs. A Hybrid tuner has one tuner that can be configured to act as an analog tuner or a digital tuner. Switching in between the systems is fairly easy, but can not be done "on the fly". The card operates as a digital tuner or an analog tuner until reconfigured.
Combo tuners that have both analog and digital tuners on one card. This is similar to a hybrid tuner, except there are 2 separate tuners on the card. One can watch analog while recording digital, or vice versa. The card operated as an analog tuner and a digital tuner. The advantages over 2 separate cards are cost and utilization of expansion slots in the computer. As the US converts from analog to digital broadcasts, these tuners are gaining popularity.
Like the Analog cards, the Hybrid and Combo tuners can have specialized chips on the tuner card to perform the encoding, or leave this task to the CPU. The tuner cards with this 'Hardware Encoding' are generally thought of as being higher quality. The small USB tuner stick have become more popular in 2006 and 2007 and are expected to increase in popularity. These small tuners do not have hardware encoding due to the size constraints.