Caption Channels
The Line 21 data stream can consist of data from several data channels multiplexed together. Field 1 has four data channels: two Captions (CC1, CC2) and two Text (T1, T2). Field 2 has five additional data channels: two Captions (CC3, CC4), two Text (T3, T4), and Extended Data Services (XDS). XDS data structure is defined in CEA–608.
As CC1 and CC2 share bandwidth, if there is a lot of data in CC1, there will be little room for CC2 data. Similarly CC3 and CC4 share the second field of line 21. Since some early caption decoders supported only CC1 and CC2, captions in a second language were often placed in CC2. This led to bandwidth problems, however, and the current U.S. Federal Communications Commission (FCC) recommendation is that bilingual programming should have the second caption language in CC3. Many spanish television networks such as Univision and Telemundo, for example, provides English subtitles for many of its Spanish programs in CC3.
Read more about this topic: Closed Captioning
Famous quotes containing the word channels:
“It is worth the while to detect new faculties in man,—he is so much the more divine; and anything that fairly excites our admiration expands us. The Indian, who can find his way so wonderfully in the woods, possesses an intelligence which the white man does not,—and it increases my own capacity, as well as faith, to observe it. I rejoice to find that intelligence flows in other channels than I knew. It redeems for me portions of what seemed brutish before.”
—Henry David Thoreau (1817–1862)
“As every pool reflects the image of the sun, so every thought and thing restores us an image and creature of the supreme Good. The universe is perforated by a million channels for his activity. All things mount and mount.”
—Ralph Waldo Emerson (1803–1882)