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