An ATSC tuner works by generating audio and video signals that are picked up from over the air TV broadcasts. ATSC tuners provide the following functions: demodulation, transport stream demultiplexing, decompression, error correction, analog to digital conversion, AV synchronization and media reformatting to fit the specific type of TV screen optimally.
Demodulation means that the signal that is pulled off the airways is transformed into a usable signal that your TV set can use to display quality images and quality sound.
Transport Stream Demultiplexing
In the US, multiple digital signals are combined and then transmitted from one antenna source to create over the air broadcasts. An ATSC receiver then is able to decode the transport stream and display it on your TV set.
Since digital signal that are broadcast over the air are compressed (packed smaller), once they are received by the ATSC tuner, these compressed packets of digital data are then unpacked to their original size or using the proper term decompressed.
Error correction is a technology that is used by the ATSC tuner to make sure that any data that is missing can be corrected. For instance, sometimes interference or a poor quality signal will cause the loss of data information that the ATSC tuner receives, with error correction, the tuner has the ability to perform a number of checks and repair data so that a signal can be viewed on a TV set.
Analog to Digital Conversion
Analog to digital conversion, sometimes called ADC or A to D refers to a technology in which an analog signal is converted into a digital signal. In the context of an ATSC tuner, an analog TV broadcast that is broadcasted over the air is received by the ATSC tuner and converted from its original analog signal to a new digital signal that can be viewed on a digital TV set.
AV synchronization is the coordination of audio and video signals being displayed on your digital TV in proper time. AV synchronization makes sure that your audio sound doesn't lag behind the video that is being displayed on your TV set or vice versa. This technology makes sure that both your audio and video are in synch.
Media reformatting is extremely important because different TV sets format their images significantly different and can use several different technologies. For instance, a standard TV has an interlaced picture; where as a digital TV has a progressive scan picture.
"Interlaced" means that while there are 30 image frames being shown per second on a standard TV, every 1/60th, the TV refreshes only half the images. With progressive scan, the entire image is refreshed 60 times per second. TV's can come in different aspect ratios.
An aspect ratio is the shape of the TV screen. For example, a standard TV is boxy in shape with a 4:3 ratio, while digital TV's come in aspect ratios more in the shape of a 16:9 rectangle.