Television
Likewise, analog TV signals were transmitted with the black and white luminance part as the main signal, and the color chrominance as the subcarriers. A black and white TV simply ignores the extra information, as it has no decoder for it. To reduce the bandwidth of the color subcarriers, the sampling rate for color information is reduced four-to-one by using half vertical resolution on every other scan line. (This is made possible by the fact that the human eye sees much more detail in contrast than in color.) In addition, only blue and red are transmitted, with green being determined by subtracting the other two from the luminance and taking the remainder. (See: YIQ, YCbCr, YPbPr) Various broadcast television systems use different subcarrier frequencies, in addition to differences in encoding.
For the audio part, MTS uses subcarriers on the video that can also carry three audio channels, including one for stereo (same left-minus-right method as for FM), another for second audio programs (such as descriptive video service for the vision-impaired, and bilingual programs), and yet a third hidden one for the studio to communicate with reporters or technicians in the field (or for a technician or broadcast engineer at a remote transmitter site to talk back to the studio), or any other use a TV station might see fit. (See also NICAM, A2 Stereo.)
In RF-transmitted composite video, subcarriers remain in the baseband signal after main carrier demodulation to be separated in the receiver. The mono audio component of the transmitted signal is in a separate carrier and not integral to the video component. In wired video connections, composite video retains the integrated subcarrier signal structure found in the transmitted baseband signal, while S-Video places the chrominance and luminance subcarriers on separate wires to eliminate subcarrier crosstalk and enhance the signal bandwidth and strength (picture sharpness and brightness).
Read more about this topic: Subcarrier
Famous quotes containing the word television:
“Cultural expectations shade and color the images that parents- to-be form. The baby product ads, showing a woman serenely holding her child, looking blissfully and mysteriously contented, or the television parents, wisely and humorously solving problems, influence parents-to-be.”
—Ellen Galinsky (20th century)
“His [O.J. Simpson’s] supporters lined the freeway to cheer him on Friday and commentators talked about his tragedy. Did those people see the photographs of the crime scene and the great blackening pools of blood seeping into the sidewalk? Did battered women watch all this on television and realize more vividly than ever before that their lives were cheap and their pain inconsequential?”
—Anna Quindlen (b. 1952)
“Laughter on American television has taken the place of the chorus in Greek tragedy.... In other countries, the business of laughing is left to the viewers. Here, their laughter is put on the screen, integrated into the show. It is the screen that is laughing and having a good time. You are simply left alone with your consternation.”
—Jean Baudrillard (b. 1929)