TV tuner card

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.

Variants

TV tuners are available in a number of different interfaces: as PCI-bus expansion card, PCIe (PCI Express) bus or USB devices. Ethernet-connected devices also exist.(HDHomeRun) In addition, some video cards double as TV tuners, notably the ATI All-In-Wonder series. The card contains a tuner and an analog-to-digital converter (collectively known as the analog front end) along with demodulation and interface logic. Some very cheap cards lack an onboard processor and, like a Winmodem, rely on the system's CPU for demodulation.

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

Analog TV tuners: Cheaper models output a raw video stream, suitable for real-time viewing but ideally requiring some sort of compression if it is to be recorded. More expensive models encode the signal to Motion JPEG or 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.

Digital TV tuners: Digital TV is broadcast as an MPEG-2 stream, so no encoder is necessary; instead, the digital cards either provide the whole MPEG transport stream or extract the individual (audio and video) elementary streams.

Hybrid tuners: 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: This is similar to a hybrid tuner, except there are two 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 two separate cards are cost and utilization of expansion slots in the computer. As many regions around the world convert 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 generally do not have hardware encoding due to size and heat constraints.

While most TV tuners are limited to the radio frequencies and video formats used in the country of sale, 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. However, while it is generally possible to flash a card from one analog format to another due to the similarities, it is generally not possible to flash a card from one digital format to another due to differences in decode logic necessary.

Many TV tuners can function as FM radios: this is because there are similarities between broadcast television and FM radio. The FM radio spectrum is close to (or even inside) that used by VHF terrestrial TV broadcasts. And many broadcast television systems around the world use FM audio. So listening to an FM radio station is simply a case of configuring existing hardware.

TV tuner card

Variants

Manufacturers

See also