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:
“It is marvelous indeed to watch on television the rings of Saturn close; and to speculate on what we may yet find at galaxy’s edge. But in the process, we have lost the human element; not to mention the high hope of those quaint days when flight would create “one world.” Instead of one world, we have “star wars,” and a future in which dumb dented human toys will drift mindlessly about the cosmos long after our small planet’s dead.”
—Gore Vidal (b. 1925)
“There is no question but that if Jesus Christ, or a great prophet from another religion, were to come back today, he would find it virtually impossible to convince anyone of his credentials ... despite the fact that the vast evangelical machine on American television is predicated on His imminent return among us sinners.”
—Peter Ustinov (b. 1921)
“Television ... helps blur the distinction between framed and unframed reality. Whereas going to the movies necessarily entails leaving one’s ordinary surroundings, soap operas are in fact spatially inseparable from the rest of one’s life. In homes where television is on most of the time, they are also temporally integrated into one’s “real” life and, unlike the experience of going out in the evening to see a show, may not even interrupt its regular flow.”
—Eviatar Zerubavel, U.S. sociologist, educator. The Fine Line: Making Distinctions in Everyday Life, ch. 5, University of Chicago Press (1991)