YouTube closed captioning is easy and free. It does a pretty good job, especially with high quality audio and clearly spoken English. Some video content from the iTunes Store includes alternative audio languages or other accessibility features such as closed captions (CC), subtitles for the. The FCC's rules for closed captioning of Spanish and bilingual English/Spanish programming are important to note as the industry grows.
Captions can also be used by viewers who simply wish to read a transcript along with the program audio. In the United States, the National Captioning Institute noted that English as a foreign or second language ESL learners were the largest group buying decoders in the late s and early s before built-in decoders became a standard feature of US television sets. This suggested that the largest audience of closed captioning was people whose native language was not English. In the United Kingdom, of 7.
In addition, online videos may be treated through digital processing of their audio content by various robotic algorithms robots. Multiple chains of errors are the result. When a video is truly and accurately transcribed, then the closed-captioning publication serves a useful purpose, and the content is available for search engines to index and make available to users on the internet.
Television and video[ edit ] For live programs, spoken words comprising the television program's soundtrack are transcribed by a human operator a speech-to-text reporter using stenotype or stenomask type of machines, whose phonetic output is instantly translated into text by a computer and displayed on the screen.
This technique was developed in the s as an initiative of the BBC 's Ceefax teletext service. Sometimes, the captions of live broadcasts, like news bulletins, sports events, live entertainment shows, and other live shows, fall behind by a few seconds.
This delay is because the machine does not know what the person is going to say next, so after the person on the show says the sentence, the captions appear. Live captioning is also a form of real-time text. Meanwhile, sport events on ESPN are using court reportersusing a special steno keyboard and individually constructed "dictionaries.
For programs that have a mix of pre-prepared and live content, such as news bulletinsa combination of techniques is used. For prerecorded programs, commercials, and home videos, audio is transcribed and captions are prepared, positioned, and timed in advance. For all types of NTSC programming, captions are "encoded" into line 21 of the vertical blanking interval - a part of the TV picture that sits just above the visible portion and is usually unseen.
For ATSC digital television programming, three streams are encoded in the video: Like all teletext fields, teletext captions can't be stored by a standard line VHS recorder due to the lack of field shifting support ; they are available on all professional S-VHS recordings due to all fields being recorded. Recorded Teletext caption fields also suffer from a higher number of caption errors due to increased number of bits and a low SNRespecially on low-bandwidth VHS.
This is why Teletext captions used to be stored separately on floppy disk to the analogue master tape. DVDs have their own system for subtitles and captions, which are digitally inserted in the data stream and decoded on playback into video. For older televisions, a set-top box or other decoder is usually required.
In the US, since the passage of the Television Decoder Circuitry Act, manufacturers of most television receivers sold have been required to include closed captioning display capability. High-definition TV sets, receivers, and tuner cards are also covered, though the technical specifications are different high-definition display screens, as opposed to high-definition TVs, may lack captioning.
Canada has no similar law but receives the same sets as the US in most cases. During transmission, single byte errors can be replaced by a white space which can appear at the beginning of the program. More byte errors during EIA transmission can affect the screen momentarily, by defaulting to a real-time mode such as the "roll up" style, type random letters on screen, and then revert to normal.
Uncorrectable byte errors within the teletext page header will cause whole captions to be dropped. EIA, due to using only two characters per video frame, sends these captions ahead of time storing them in a second buffer awaiting a command to display them; Teletext sends these in real-time. The use of capitalization varies among caption providers. Most caption providers capitalize all words while others such as WGBH and non-US providers prefer to use mixed-case letters.
There are two main styles of line 21 closed captioning: Roll-up or scroll-up or paint-on or scrolling: Real-time words sent in paint-on or scrolling mode appear from left to right, up to one line at a time; when a line is filled in roll-up mode, the whole line scrolls up to make way for a new line, and the line on top is erased.
The lines usually appear at the bottom of the screen, but can actually be placed on any of the 14 screen rows to avoid covering graphics or action. This method is used when captioning video in real-time such as for live events, where a sequential word-by-word captioning process is needed or a pre-made intermediary file isn't available. This method is signaled on EIA by a two-byte caption command or in Teletext by replacing rows for a roll-up effect and duplicating rows for a paint-on effect.
This allows for real-time caption line editing. A still frame showing simulated closed captioning in the pop-on style Pop-on or pop-up or block: A caption appears on any of the 14 screen rows as a complete sentence, which can be followed by additional captions. This method is used when captions come from an intermediary file such as the Scenarist or EBU STL file formats for pre-taped television and film programming, commonly produced at captioning facilities.
This method of captioning can be aided by digital scripts or voice recognition software, and if used for live events, would require a video delay to avoid a large delay in the captions' appearance on-screen, which occurs with Teletext-encoded live subtitles. I got the machine ready. US other provider example: Sometimes appended with the speaker's name in alternate case, followed by a colon.
Styles of syntax that are used by various captioning producers: Capitals indicate main on-screen dialogue and the name of the speaker. Legacy EIA home caption decoder fonts had no descenders on lowercase letters. Outside North America, capitals with background coloration indicate a song title or sound effect description. Outside North America, capitals with black or no background coloration indicates when a word is stressed or emphasized. Descenders indicate background sound description and off-screen dialogue.
Words in italics indicate when a word is stressed or emphasized and when real world names are quoted. Italics and bold type are only supported by EIA Some North American providers use this for narrated dialogue. Text coloration indicates captioning credits and sponsorship. Some Teletext countries use coloration to indicate when a word is stressed or emphasized.
Coloration is limited to white, green, blue, cyan, red, yellow and magenta. UK order of use for text is white, green, cyan, yellow; and backgrounds is black, red, blue, magenta, white. US order of use for text is white, yellow, cyan, green; and backgrounds is black, blue, red, magenta, white. Square brackets or parentheses indicate a song title or sound effect description. Parentheses indicate speaker's vocal pitch e.
Outside North America, parentheses indicate a silent on-screen action. A pair of eighth notes is used to bracket a line of lyrics to indicate singing.
A pair of eighth notes on a line of no text are used during a section of instrumental music. Outside North America, a single number sign is used on a line of lyrics to indicate singing. An additional musical notation character is appended to the end of the last line of lyrics to indicate the song's end.
Technical aspects[ edit ] There were many shortcomings in the original Line 21 specification from a typographic standpoint, since, for example, it lacked many of the characters required for captioning in languages other than English. Since that time, the core Line 21 character set has been expanded to include quite a few more characters, handling most requirements for languages common in North and South America such as FrenchSpanishand Portuguesethough those extended characters are not required in all decoders and are thus unreliable in everyday use.
The problem has been almost eliminated with a market specific full set of Western European characters and a private adopted Norpak extension for South Korean and Japanese markets.
The full EIA standard for digital television has worldwide character set support, but there has been little use of it due to EBU Teletext dominating DVB countries, which has its own extended character sets. Captions are often edited to make them easier to read and to reduce the amount of text displayed onscreen. This editing can be very minor, with only a few occasional unimportant missed lines, to severe, where virtually every line spoken by the actors is condensed.
The measure used to guide this editing is words per minute, commonly varying from todepending on the type of program. Offensive words are also captioned, but if the program is censored for TV broadcast, the broadcaster might not have arranged for the captioning to be edited or censored also. The "TV Guardian", a television set-top boxis available to parents who wish to censor offensive language of programs-the video signal is fed into the box and if it detects an offensive word in the captioning, the audio signal is bleeped or muted for that period of time.
Caption channels[ edit ] A bug touting CC1 and CC3 captions on Telemundo The Line 21 data stream can consist of data from several data channels multiplexed together. Odd field 1 can have four data channels: Even field 2 can have five additional data channels: As CC1 and CC2 share bandwidth, if there is a lot of data in CC1, there will be little room for CC2 data and is generally only used for the primary audio captions.
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Similarly, CC3 and CC4 share the second even field of line This led to bandwidth problems, and the U. Many Spanish television networks such as Univision and Telemundofor example, provides English subtitles for many of its Spanish programs in CC3.
Ceefax and Teletext can have a larger number of captions for other languages due to the use of multiple VBI lines. However, only European countries used a second subtitle page for second language audio tracks where either the NICAM dual mono or Zweikanalton were used.
Digital television interoperability issues[ edit ] Americas[ edit ] The US ATSC digital television system originally specified two different kinds of closed captioning datastream standards: Most broadcasters and networks to avoid large conversion cost outlays just provide EIA captions along with a transcoded CEA version encapsulated within CEA packets.홀로 데이트･DATING ALONE
Incompatibility issues with digital TV[ edit ] Many viewers find that when they acquire a digital television or set-top box they are unable to view closed caption CC information, even though the broadcaster is sending it and the TV is able to display it. Originally, CC information was included in the picture "line 21" via a composite video input, but there is no equivalent capability in digital video interconnects such as DVI and HDMI between the display and a "source".
A "source", in this case, can be a DVD player or a terrestrial or cable digital television receiver. Other apps or web-based media players might show a CC button or other custom controls.
On your iPhone, iPad, or iPod touch While watching a movie, tap the screen to open the playback controls. Choose the language or subtitles that you want to use.
- Change the subtitles or audio language for iTunes Store movies and TV shows
If you want to customize captions or subtitles, tap Style, then choose from the options. On your Mac or PC Move your pointer over the video.
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Click Accessibility, then click Captions in the sidebar. Select "Prefer closed captions and SDH" to turn it on. If you want to customize captions and subtitles, choose from the options on this screen. If you want to customize captions and subtitles, choose different options from the menu to the right of Caption Style or click the Configure button. Swipe right to see the Subtitles or Audio menus. Swipe down and choose the language or subtitles that you want to use. If you want to customize captions and subtitles, choose Style, then choose from the options.
On Apple TV 2nd generation or Apple TV 3rd generationhold down Select on your remote for three seconds while a video is playing to see the Subtitles tab. Learn more Some apps and websites provide custom caption controls for videos.