Subtitles are textual versions of the dialog in films and television programs, usually displayed at the bottom of the screen. They can either be a form of written translation of a dialog in a foreign language, or a written rendering of the dialog in the same language, with or without added information to help viewers who are deaf and hard-of-hearing to follow the dialog, or people who cannot understand the spoken dialogue or who have accent recognition problems. Television teletext subtitles, which are hidden unless requested by the viewer from a menu or by selecting the relevant teletext page (e.g., p. 888), always carry additional sound representations for deaf and hard of hearing viewers. Teletext subtitle language follows the original audio, except in multi-lingual countries where the broadcaster may provide subtitles in additional languages on other teletext pages.
Sometimes, mainly at film festivals, subtitles may be shown on a separate display below the screen, thus saving the film-maker from creating a subtitled copy for perhaps just one showing. Television subtitling for the deaf and hard-of-hearing is also referred to as closed captioning in some countries. More exceptional uses also include operas, such as Verdi's Aida, where sung lyrics in Italian are subtitled in English or in another local language outside the stage area on luminous screens for the audience to follow the storyline.
Today professional subtitlers usually work with specialized computer software and hardware where the video is digitally stored on a hard disk, making each individual frame instantly accessible. Besides creating the subtitles, the subtitler usually also tells the computer software the exact positions where each subtitle should appear and disappear. For cinema film, this task is traditionally done by separate technicians. The end result is a subtitle file containing the actual subtitles as well as position markers indicating where each subtitle should appear and disappear. These markers are usually based on timecode if it is a work for electronic media (e.g., TV, video, DVD), or on film length (measured in feet and frames) if the subtitles are to be used for traditional cinema film.
The finished subtitle file is used to add the subtitles to the picture, either :
directly into the picture (open subtitles);
embedded in the vertical interval and later superimposed on the picture by the end user with the help of an external decoder or a decoder built into the TV (closed subtitles on TV or video);
or converted (rendered) to tiff or bmp graphics that are later superimposed on the picture by the end user's equipment (closed subtitles on DVD or as part of a DVB broadcast).
Subtitles can also be created by individuals using freely-available subtitle-creation software like Subtitle Workshop for Windows, MovieCaptioner for the Mac and Subtitle Composer for Linux, and then hardcode them onto a video file with programs such as VirtualDub in combination with VSFilter which could also be used to show subtitles as softsubs in many software video players.
Same language captions, i.e., without translation, were primarily intended as an aid for people who are deaf or hard-of-hearing. Internationally, there are several major studies which demonstrate that same-language-captioning can have a major impact on literacy and reading growth across a broad range of reading abilities. This method of subtitling is used by national television broadcasters in China and in India such as Doordarshan. This idea was struck upon by Brij Kothari, who believed that SLS makes reading practice an incidental, automatic, and subconscious part of popular TV entertainment, at a low per-person cost to shore up literacy rates in India.
Same Language Subtitling (SLS) is the use of Synchronized Captioning of Musical Lyrics (or any text with an Audio/Video/ source) as a Repeated Reading activity. The basic reading activity involves students viewing a short subtitled presentation projected onscreen, while completing a response worksheet. To be really effective, the subtitling should have high quality synchronization of audio and text, and better yet, subtitling should change color in syllabic synchronization to audio model, and the text should be at a level to challenge students' language abilities.
The "CC in a TV" symbol Jack Foley created, while senior graphic designer at Bostonpublic broadcaster WGBH that invented captioning for television, is public domain so that anyone who captions TV programs can use it.
Closed captioning is the American term for closed subtitles specifically intended for people who are deaf and hard-of-hearing. These are a transcription rather than a translation, and usually contain descriptions of important non-dialog audio as well such as "(sighs)" or "(door creaks)". From the expression "closed captions" the word "caption" has in recent years come to mean a subtitle intended for the hard of hearing, be it "open" or "closed". In British English "subtitles" usually refers to subtitles for the hard-of-hearing (HoH); however, the term "HoH subtitles" is sometimes used when there is a need to make a distinction between the two.
Programs such as news bulletins, current affairs programs, sport, some talk shows and political and special events utilize realtime or online captioning. Live captioning is increasingly common, especially in the United Kingdom and the United States, as a result of regulations that stipulate that virtually all TV eventually must be accessible for people who are deaf and hard–of–hearing.
Some programs may be prepared in their entirety several hours before broadcast, but with insufficient time to prepare a timecoded caption file for automatic play-out. Pre-prepared captions look very similar to offline captions, although the accuracy of cueing may be compromised slightly as the captions are not locked to program timecode.
Newsroom captioning involves the automatic transfer of text from the newsroom computer system to a device which outputs it as captions. It does work, but its suitability as an exclusive system would only apply to programs which had been scripted in their entirety on the newsroom computer system, such as short interstitial updates.
In the United States and Canada, some broadcasters have used it exclusively and simply left uncaptioned sections of the bulletin for which a script was unavailable. Newsroom captioning limits captions to pre-scripted materials and, therefore, does not cover 100% of the news, weather and sports segments of a typical local news broadcast which are typically not pre-scripted, last second breaking news or changes to the scripts, ad lib conversations of the broadcasters, emergency or other live remote broadcasts by reporters in-the-field. By failing to cover items such as these, newsroom style captioning (or use of the Teleprompter for captioning) typically results in coverage of less than 30% of a local news broadcast.
Communication Access Real-Time Translation (CART) stenographers, who use a computer with using either stenotype or Velotype keyboards to transcribe stenographic input for presentation as captions within 2–3 seconds of the representing audio, must caption anything which is purely live and unscripted, however, the most recent developments include operators using speech recognition software and revoicing the dialog. Speech recognition technology has advanced so quickly in the United Kingdom that about 50% of all live captioning is through speech recognition as of 2005. Realtime captions look different from offline captions, as they are presented as a continuous flow of text as people speak.
Realtime stenographers are the most highly skilled in their profession. Stenography is a system of rendering words phonetically, and English, with its multitude of homophones (e.g., there, their, they’re), is particularly unsuited to easy transcriptions. Stenographers working in courts and inquiries usually have 24 hours in which to deliver their transcripts. Consequently they may enter the same phonetic stenographic codes for a variety of homophones, and fix up the spelling later. Realtime stenographers must deliver their transcriptions accurately and immediately. They must therefore develop techniques for keying homophones differently, and be unswayed by the pressures of delivering accurate product on immediate demand.
Submissions to recent captioning-related inquiries have revealed concerns from broadcasters about captioning sports. Captioning sports may also affect many different people because of the weather outside of it. In much sport captioning's absence, the Australian Caption Centre submitted to the National Working Party on Captioning (NWPC), in November 1998, three examples of sport captioning, each performed on tennis, rugby league and swimming programs:
Heavily reduced: Captioners ignore commentary and provide only scores and essential information such as “try” or “out”.
Significantly reduced: Captioners use QWERTY input to type summary captions yielding the essence of what the commentators are saying, delayed due to the limitations of QWERTY input.
Comprehensive realtime: Captioners use stenography to caption the commentary in its entirety.
The NWPC concluded that the standard they accept is the comprehensive realtime method, which gives them access to the commentary in its entirety. Also, not all sports are live. Many events are pre-recorded hours before they are broadcast, allowing them a captioner to caption them using offline methods.
Because different programs are produced under different conditions, a case-by-case basis must consequently determine captioning methodology. Some bulletins may have a high incidence of truly live material, or insufficient access to video feeds and scripts may be provided to the captioning facility, making stenography unavoidable. Other bulletins may be pre-recorded just before going to air, making pre-prepared text preferable.
In Australia and the United Kingdom, hybrid methodologies have proven to be the best way to provide comprehensive, accurate and cost-effective captions on news and current affairs programs. News captioning applications currently available are designed to accept text from a variety of inputs: stenography, Velotype, QWERTY, ASCII import, and the newsroom computer. This allows one facility to handle a variety of online captioning requirements and to ensure that captioners properly caption all programs.
Current affairs programs usually require stenographic assistance. Even though the segments which comprise a current affairs program may be produced in advance, they are usually done so just before on-air time and their duration makes QWERTY input of text unfeasible.
News bulletins, on the other hand can often be captioned without stenographic input (unless there are live crosses or ad-libbing by the presenters). This is because:
Most items are scripted on the newsroom computer system and this text can be electronically imported into the captioning system.
Individual news stories are of short duration, so even if they are made available only just prior to broadcast, there is still time to QWERTY in text.
For non-live, or pre-recorded programs, television program providers can choose offline captioning. Captioners gear offline captioning toward the high-end television industry, providing highly customized captioning features, such as pop-on style captions, specialized screen placement, speaker identifications, italics, special characters, and sound effects.
Offline captioning involves a five-step design and editing process, and does much more than simply display the text of a program. Offline captioning helps the viewer follow a story line, become aware of mood and feeling, and allows them to fully enjoy the entire viewing experience. Offline captioning is the preferred presentation style for entertainment-type programming.
"SDH" is an American term the DVD industry introduced. It is an acronym for "Subtitles for the deaf and hard-of-hearing", and refers to regular subtitles in the original language where important non-dialog audio has been added, as well as speaker identification, useful when the viewer cannot otherwise visually tell who is saying what.
The only significant difference for the user between "SDH" subtitles and "closed captions" is their appearance: SDH subtitles usually are displayed with the same proportional font used for the translation subtitles on the DVD; however, closed captions are displayed as white text on a black band, which blocks a large portion of the view. Closed captioning is falling out of favor as many users have no difficulty reading SDH subtitles, which are text with contrast outline. In addition, DVD subtitles can specify many colors, on the same character: primary, outline, shadow, and background. This allows subtitlers to display subtitles on a usually translucent band for easier reading; however, this is rare, since most subtitles use an outline and shadow instead, in order to block a smaller portion of the picture. Closed captions may still supersede DVD subtitles, since many SDH subtitles present all of the text centered, while closed captions usually specify position on the screen: centered, left align, right align, top, etc. This is very helpful for speaker identification and overlapping conversation. Some SDH subtitles (such as the subtitles of newer Universal Studios DVDs/Blu-ray Discs) do have positioning, but it is not as common.
DVDs for the U.S. market now sometimes have three forms of English subtitles: SDH subtitles, English subtitles, helpful for viewers who are Hearing and whose first language may not be English (although they are usually an exact transcript and not edited into Simple English), and closed caption data that is decoded by the end-user's closed caption decoder. Most anime releases in the U.S. only include as subtitles translations of the original material; therefore, SDH subtitles of English dubs ("dubtitles") are uncommon. 
High-definition disc media (HD DVD, Blu-ray Disc) uses SDH subtitles as the sole method because technical specifications do not require HD to support line 21 closed captions. Some Blu-ray Discs, however, are said to carry a closed caption stream that only displays through standard-definition connections. Many HDTVs allow the end–user to customize the captions, including the ability to remove the black band.
Use by those not deaf or hard-of-hearing
Although same-language subtitles and captions are produced primarily with the deaf and hard-of-hearing in mind, many hearing film and television viewers choose to use them. This is often done because the presence of closed captioning and subtitles ensures that not one word of dialogue will be missed. Bars and other noisy public places often make closed captions visible for patrons where dialogue would otherwise be drowned out. Films and television shows often have subtitles displayed in the same language, if the speaker has a speech impairment. In addition, captions may further reveal information that would be difficult to pick up on otherwise. Some examples of this would be the song lyrics; dialog spoken quietly or by those with accents unfamiliar to the intended audience; or supportive, minor dialog from background characters. It is argued that such additional information and detail will enhance the overall experience and allow the viewer a better grasp on the material. Furthermore, people learning a foreign language may sometimes use same-language subtitles to better understand the dialog while not having to resort to a translation.
In some Asian television programming, captioning is considered a part of the genre, and has evolved beyond simply capturing what is being said. The captions are used artistically; it is common to see the words appear one by one as they are spoken, in a multitude of fonts, colors, and sizes that capture the spirit of what is being said. Languages like Japanese also have a rich vocabulary of onomatopoeia which are used in captioning.
In some East Asian countries, such as China, Korea and Japan, subtitling is common in some genres of television. In these languages, written text is less ambiguous than spoken text, so subtitling may offer a distinct advantage to aid comprehension. Although people in China generally speak Putonghua, the standard spoken language, different speakers have different accents due to their native dialects and subtitles bridge this gap (even though most programmes are in Putonghua) as most Chinese speakers understand the one standard form of written Chinese. Subtitling is also common in taped interviews during news broadcasts, as accents in East Asian languages can be difficult to understand by those unfamiliar with them.
In India, Same Language Subtitling (SLS) are common for films and music videos. SLS refers to the idea of subtitling in the same language as the audio. SLS is highlighted karaoke style, that is, to speech. The idea of SLS was initiated to shore up literacy rates as SLS makes reading practice an incidental, automatic, and subconscious part of popular TV entertainment. This idea was well received by the Government of India which now uses SLS on several national channels, including Doordarshan.
Subtitles can be used to translate dialog from a foreign language to the native language of the audience. It is the quickest and the cheapest method of translating content, and is usually praised for the possibility to hear the original dialog and voices of the actors.
Translation of subtitling is sometimes very different from the translation of written text. Usually, when a film or a TV program is subtitled, the subtitler watches the picture and listens to the audio sentence by sentence. The subtitler may or may not have access to a written transcript of the dialog. Especially in commercial subtitles, the subtitler often interprets what is meant, rather than translating how it is said, i.e. meaning being more important than form. The audience does not always appreciate this, and it can be frustrating to those who know some of the spoken language, because spoken language may contain verbal padding or culturally implied meanings, in confusing words, if not adapted in the written subtitles. The subtitler does this when the dialog must be condensed in order to achieve an acceptable reading speed. i.e. purpose being more important than form.
Especially in fansubs, the subtitler may translate both form and meaning. The subtitler may also choose to display a note in the subtitles, usually in parentheses (“(” and “)”) or as a separate block of on-screen text. This allows the subtitler to preserve form and achieve an acceptable reading speed, by leaving the note on the screen, even after the character has finished speaking, to both preserve form and allow for understanding. For example, the Japanese language has multiple first-person pronouns (see Japanese pronouns), and using one instead of another implies a different degree of politeness. In order to compensate, when translating to English, the subtitler may reformulate the sentence, add appropriate words and/or use notes.
Realtime translation subtitling, usually involving simultaneous interpreter listening to the dialog quickly translating, while a stenographer types, is rare. The unavoidable delay, typing errors, lack of editing, and high costs regard very little need for translation subtitling. Allowing the interpreter to directly speak to the viewers is usually both cheaper and quicker, however, the translation is not accessible to people who are deaf and hard–of–hearing.
Some subtitlers purposely provide edited subtitles or captions, to match the needs of their audience, for learners of the spoken dialog as a second or foreign language, visual learners, beginning readers who are deaf or hard-of-hearing and for people with learning and/or mental disabilities. For example, for many of its films and television programs, PBS displays standard captions representing speech the program audio, word-for-word, if the viewer selects "CC1", by using the television remote control or on-screen menu, however, they also provide edited captions to present simplified sentences at a slower rate, if the viewer selects "CC2". Programs with a very diverse audience also often have captions in another language. This is common with popular Latin American soap operas in Spanish. Since CC1 and CC2 share bandwidth, the Federal Communications Commission (FCC) recommends translation subtitles be placed in CC3. CC4, which shares bandwidth with CC3, is also available, but programs very seldom use it.
Subtitles vs. dubbing and lectoring
The two alternative methods of 'translating' films in a foreign language are dubbing, in which other actors record over the voices of the original actors in a different language, and lectoring, a form of voice-over for fictional material where a narrator tells the audience what the actors are saying while their voices can be heard in the background. Lectoring is common for television in Russia, Poland, and a few other East European countries, while cinemas in these countries commonly show films dubbed or subtitled.
The preference for dubbing or subtitling in various countries is largely based on decisions taken in the late 1920s and early 1930s. With the arrival of sound film, the film importers in Germany, Italy, France and Spain decided to dub the foreign voices, while the rest of Europe elected to display the dialog as translated subtitles. The choice was largely due to financial reasons (subtitling is inexpensive and quick, while dubbing is very expensive and thus requires a very large audience to justify the cost), but during the 1930s it also became a political preference in Germany, Italy and Spain; an expedient form of censorship that ensured that foreign views and ideas could be stopped from reaching the local audience, as dubbing makes it possible to create a dialogue which is totally different from the original.
Dubbing is still the norm and favored form in these four countries, but the proportion of subtitling is slowly growing, mainly to save cost and turnaround-time, but also due to a growing acceptance among younger generations, who are better readers and increasingly have a basic knowledge of English (the dominant language in film and TV) and thus prefer to hear the original dialogue.
Nevertheless, in Spain, for example, only public TV channels show subtitled foreign films, usually at late night. It is extremely rare that any Spanish TV channel shows subtitled versions of TV programs, series or documentaries. In addition, only a small proportion of cinemas show subtitled films. Films with dialogue in Galician, Catalan or Basque are always dubbed, not subtitled, when they are shown in the rest of the country. Some non-Spanish-speaking TV stations subtitle interviews in Spanish; others do not.
In many Latin American countries, local network television will show dubbed versions of English-language programs and movies, while cable stations (often international) more commonly broadcast subtitled material. Preference for subtitles or dubbing varies according to individual taste and reading ability, and theaters may order two prints of the most popular films, allowing moviegoers to chose between dubbing or subtitles. Animation and children's programming, however, is nearly universally dubbed, as in other regions.
Since the introduction of the DVD, some high budget films include the simultaneous option of both subtitles and/or dubbing. Often in such cases, the translations are made separately, rather than the subtitles being a verbatim transcript of the dubbed scenes of the film. While this allows for the smoothest possible flow of the subtitles, it can be frustrating for someone attempting to learn a foreign language.
In the traditional subtitling countries, dubbing is generally regarded as something very strange and unnatural and is only used for animated films and TV programs intended for pre-school children. As animated films are "dubbed" even in their original language and ambient noise and effects are usually recorded on a separate sound track, dubbing a low quality production into a second language produces little or no noticeable effect on the viewing experience. In dubbed live-action television or film, however, viewers are often distracted by the fact that the audio does not match the actors' lip movements. Furthermore, the dubbed voices may seem detached, inappropriate for the character, or overly expressive, and some ambient sounds may not be transferred to the dubbed track, creating a less enjoyable viewing experience.
Subtitling as a practice
In several countries or regions nearly all foreign language TV programs are subtitled, instead of dubbed, notably in:
Arab Middle East and North Africa -- Modern Standard Arabic-language subtitling, used for foreign programming/cinema and often used when Arabic dialects are the primary medium of a film/TV program. Countries such as Lebanon, Algeria, and Morocco also often include French subtitling simultaneously.
Belgium (Subtitles in Dutch in Flanders, dubbed into French in Wallonia, bilingual [Dutch-French] subtitles in Flemish movie theaters, dubbed versions in Wallonia. Children's shows and teleshopping are dubbed)
Indonesia (Subtitles in Indonesian, some foreign movies have subtitles of more than one language)
Israel (Non-Hebrew television programmes and films are always translated into Hebrew with subtitles. Bilingual Hebrew/Arabic or Hebrew/Russian subtitling, showing translation into both languages simultaneously, is very common on public TV channels. Dubbing is restricted to programmes and films aimed at children below school age. As of 2008 the closed captioning industry in Israel is on the rise since a law has been approved, stating that all the Hebrew programmes of The Israeli Television must be subtitled for the hearing impaired. Moreover, in recent years it became a norm in other channels and broadcasting bodies in Israel.)
Malaysia (Subtitles in Malay for programming of various languages except anime or other certain programmes dubbed into Malay, as well as certain Malay-language live action programs to English. Also appearing for programming in Indonesian since 2006 except for local news reports with Indonesian people speaking. All movies on 35mm film subtitled in Malay and Simplified Chinese. Usually, animation and 3D movies are exempted from subtitling (though studios may choose to add subtitles at their discretion). Indian and Chinese movies usually have subtitles of more than one languages)
Singapore (Even though the official language of Singapore is English, and the indigenous language is Malay, many TV programmes have Chinese subtitles for the benefit of immigrants from China, now settled for many generations)
It is also common that television services in minority languages subtitle their programmes in the dominating language as well. Examples include the WelshS4C and IrishTG4 who subtitle in English and the Swedish FST5 in Finland who subtitle in the majority language Finnish.
In Wallonia (Belgium) films are usually dubbed, but sometimes they are played on two channels at the same time: one dubbed (on La Une) and the other subtitled (on La Deux), but this is no longer done as frequently due to low ratings.
In Australia, one FTA network, SBS airs its foreign-language shows subtitled in English.
Subtitles in the same language on the same production can be in different categories:
Narrative This is the most common type of subtitle. Narrative subtitles are those in which spoken dialogue is displayed. These are most commonly used to translate a film with one spoken language and the text of a second language.
Forced These are common on movies. Forced subtitles only provide subtitles when the characters speak a foreign or alien language, or a sign, flag, or other text in a scene is not translated in the localization and dubbing process. In some cases, foreign dialogue may be left untranslated if the movie is meant to be seen from the point of view of a particular character who does not speak the language in question.
Content Content subtitles are a North American Secondary Industry (non-Hollywood, often low-budget) staple. They add content dictation that is missing from filmed action or dialogue. Due to the general low budget allowances in such films, it is often more feasible to add the overlay subtitles to fill in information. They appear most commonly seen on America's Maverick films as Forced Subtitles, and on Canada's MapleLeaf films as optional subtitles.
Content subtitles also appear in the beginning of some higher-budget films (e.g. Star Wars) or at the end of a film (e.g. Gods and Generals)
Titles only Dubbed programs use this sort of subtitle. Titles only provide only the text for any untranslated on-screen text. They are most commonly forced (see above).
Bonus Bonus subtitles are an additional set of text blurbs that are added to DVDs. They are similar to Blu-ray Discs' in-movie content or to the "info nuggets" in VH1 Pop-up Video. Often shown in popup or balloon form, they point out humorous blunders in the filming or background/behind-the-scenes information to what is appearing on screen.
Localized Localized subtitles are a separate subtitle track that uses expanded references (i.e. "The sake [a Japanese Wine] was excellent as was the Wasabi") or can replace the standardized subtitle track with a localized form replacing references to local custom (i.e. from above, "The wine was excellent as was the spicy dip").
Extended/Expanded Extended subtitles combine the standard subtitle track with the localization subtitle track. Originally found only on Celestial DVDs in the early 2000s, the format has expanded to many export-intended releases from China, Japan, India and Taiwan. The term "Expanded Subtitle" is owned by Celestial, with Extended being used by other companies.
Subtitles exist in two forms; open subtitles are 'open to all' and cannot be turned off by the viewer; closed subtitles are designed for a certain group of viewers, and can usually be turned on/off or selected by the viewer - examples being teletext pages, US Closed captions (608/708), DVB Bitmap subtitles, DVD/Blu-ray subtitles.
While distributing content, subtitles can appear in one of 3 types:
Hard (also known as hardsubs or open subtitles). The subtitle text is irreversibly merged in original video frames, and so no special equipment or software is required for playback. Hence, very complex transition effects and animation can be implemented, such as karaoke song lyrics using various colors, fonts, sizes, animation (like a bouncing ball) etc. to follow the lyrics. However, these subtitles cannot be turned off unless the original video is also included in the distribution as they are now part of the original frame, and thus it is impossible to have several variants of subtitling, such as in multiple languages.
Prerendered (also known as closed) subtitles are separate video frames that are overlaid on the original video stream while playing. Prerendered subtitles are used on DVD and Blu-ray (though they are contained in the same file as the video stream). It is possible to turn them off or have multiple language subtitles and switch among them, but the player has to support such subtitles to display them. Also, subtitles are usually encoded as images with minimal bitrate and number of colors; they usually lack anti-aliasedfont rasterization. Also, changing such subtitles is hard, but special OCR software, such as SubRip exists to convert such subtitles to "soft" ones.
Soft (also known as softsubs or closed subtitles) are separate instructions, usually a specially marked up text with time stamps to be displayed during playback. It requires player support and, moreover, there are multiple incompatible (but usually reciprocally convertible) subtitle file formats. Softsubs are relatively easy to create and change, and thus are frequently used for fansubs. Text rendering quality can vary depending on the player, but is generally higher than prerendered subtitles. Also, some formats introduce text encoding troubles for the end-user, especially if very different languages are used simultaneously (for example, Latin and Asian scripts).
In other categorization, digital video subtitles are sometimes called internal, if they are embedded in a single video file container along with video and audio streams, and external if they are distributed as separate file (that is less convenient, but it is easier to edit/change such file).
Can be turned off/on
Multiple subtitle variants (for example, languages)
Yes, though all displayed at the same time
Difficult, but possible
Majority of players support DVD subtitles
Usually requires installation of special software, unless national regulators mandate its distribution
Visual appearance, colors, font quality
Low to High, depends on video resolution/compression
Low to High, depends on player and subtitle file format
Transitions, karaoke and other special effects
Depends on player and subtitle file format, but generally poor
Inside original video
Separate low-bitrate video stream, commonly multiplexed
Relatively small subtitle file or instructions stream, multiplexed or separate
None, though subtitles added by re-encoding of the original video may degrade overall image quality, and the sharp edges of text may introduce artifacts in surrounding video
The EBU format defined by Technical Reference 3264-E  is an 'open' format intended for subtitle exchange between broadcasters. Files in this format have the extension .stl (not to be mixed up with text "Spruce subtitle format" mentioned above, which also has extension .stl)
The Timed Text format currently a "Candidate Recommendation" of the W3C (called DFXP) is also proposed as an 'open' format for subtitle exchange and distribution to media players, such as Microsoft Silverlight.
Reasons for not subtitling a foreign language
Most times, a foreign language is spoken in film, subtitles are used to translate the dialogue for the viewer. However, there are occasions when foreign dialogue is left unsubtitled (and thus incomprehensible to most of the target audience). This is often done if the movie is seen predominantly from the viewpoint of a particular character who does not speak the language. Such absence of subtitles allows the audience to feel a similar sense of incomprehension and alienation that the character feels. An example of this is seen in Not Without My Daughter. The Persian language dialogue spoken by the Iranian characters is not subtitled because the main character Betty Mahmoody does not speak Persian and the audience is seeing the film from her viewpoint.
Subtitles as a source of humor
Occasionally, movies will use subtitles as a source of humor, parody and satire.
In Austin Powers in Goldmember, Japanese dialog is subtitled using white type that blends in with white objects in the background. An example is when white binders turn the subtitle "I have a huge rodent problem" into "I have a huge rod." After many cases of this, Mr. Roboto says "Why don't I just speak English?", in English. In the same film, Austin and Nigel Powers directly speak in Cockney English to make the content of their conversation unintelligible; subtitles appear for the first part of the conversation, but then cease and are replaced with a series of question marks.
In The Impostors one character speaks in a foreign language, while another character hides under the bed. Although the hidden character cannot understand what is being spoken, he can read the subtitles. Since the subtitles are overlaid on the film, they appear to be reversed from his point of view. His attempt to puzzle out these subtitles enhances the humor of the scene.
The movie Airplane! and its sequel feature two inner-city African Americans speaking in heavily accented slang, which another character refers to as if it were a foreign language: "Jive". Subtitles translate their speech, which is full of colorful expressions and mild profanity, into bland standard English, but the typical viewer can understand enough of what they are saying to recognize the incongruity. Transcript of the dialog
Scene 1: Susie Chef and Mater Speaks Chinese with English Subtitles and Luigi, Mama Lopolino and Uncle Topolino speaks the Languages with English Subtitles.
In the Carl Reiner comedy The Man with Two Brains, after stopping Dr. Michael Hfuhruhurr (Steve Martin) for speeding, a German police officer realizes that Hfuhruhurr can speak English. He asks his colleague in their squad car to turn off the subtitles, and indicates toward the bottom of the screen, commenting that "This is better — we have more room down there now".
In the opening credits of Monty Python and the Holy Grail the Swedish subtitler switches to English and promotes his country, until the introduction is cut off and the subtitler "sacked". In the DVD version of the same film, the viewer could choose, instead of hearing aid and local languages, lines from Shakespeare's Henry IV, part 2 that vaguely resemble the lines that are actually being spoken in film, if they are "people who hate the film".
In Scary Movie 4, there is a scene where the actors speak in faux Japanese (nonsensical words which mostly consist of Japanese company names), but the content of the subtitles is the "real" conversation.
In Not Another Teen Movie the nude foreign exchange student character Areola speaks lightly accented English, but her dialog is subtitled anyway. Also, the text is spaced in such a way that a view of her bare breasts is unhindered.
In Trainspotting the leading characters have a conversation in a crowded club. To understand what is being said, the entire dialog is subtitled.
Simon Ellis' 2000 short film Telling Lies juxtaposes a soundtrack of a man telling lies on the telephone against subtitles which expose the truth. 
Animutations commonly use subtitles to present the comical "fake lyrics" (English words that sound close to what is actually being sung in the song in the non-English language). These fake lyrics are a major staple of the Animutation genre.
In an episode of Angry Beavers, at one point Norbert begins to speak with such a heavy European accent that his words are subtitled on the bottom of the screen. Daggett actually touches the subtitles, shoving them out of the way.
In the American theatrical versions of Night Watch and Day Watch, Russian dialogues are translated by subtitles which are designed accordingly to the depicted events. For instance, subtitles dissolve in water like blood, tremble along with a shaking floor or get cut by sword.
The film Crank contains a scene where Jason Statham's character understands an Asian character's line of dialogue from reading the on-screen subtitle. The subtitle is even in reverse when his character reads the line. Later, an exclamation made by another Asian character is subtitled, but both the spoken words and the subtitles are in Chinese.
In Fatal Instinct, also directed by Carl Reiner, one scene involving two characters talking about their murder plan in Yiddish to prevent anyone from knowing about it, only to be foiled by a man on the bench reading the on-screen subtitles.
Ken Loach released the film Riff-Raff into American theatres with subtitles not only so people could understand the thick Scottish accents, but also to make fun of many Americans' need for them (mentioned in the theatrical trailer). Loach has continued this process with some of his other films.
In Bobby Lee's "Tae Do," a parody of Korean dramas in a Mad TV episode, the subtitles make more sense of the story than the Korean language being spoken. The subtitles are made to appear as though written by someone with a poor understanding of grammar and are often intentionally made longer than what they actually say in the drama. For example an actor says "Sarang" ("I love you"), but the subtitle is so long that it covers the whole screen.
In Dead Ringers (comedy), journalists interview a group of Afghan terrorists in English, but one of them gets subtitled and sees it. He gets mad because he takes as an insult the fact that he is the only one to gets subtitled.
In Mel Brooks film Men in Tights, the thoughts of Broomhilde's (Megan Cavanaugh) horse Farfelkugel are shown as subtitles when Broomhilde attempts to jump on saddle off balcony. As Farfelkugel shudders, the showtitles show "She must be kidding!"
In the television series Drawn Together, the character Ling-Ling can only be understood through English subtitles, as his dialogue is delivered in a nonexistent language referred to as "Japorean" by Abbey DiGregorio, the voice actress for the character.
In the television series Green Acres episode “Lisa's Mudder Comes for a Visit” (season 5 episode 1), Lisa and her mother converse in Hungarian, with English Subtitles. First, Lisa looks down and corrects the subtitles, “No no no, I said you hadn't changed a bit! We have a lot of trouble here with subtitles.”, and they change. Mother's Japanese chauffeur asks “I begga pardon - I bringa bags inna house?” that elicits a gong sound and Japanese subtitles. This is followed by Mother’s great dane barking with the subtitles “I've seen better doghouses than this” with Lisa responding “We're not interested in what the dog says”, and the subtitles disappear. Later, the subtitles ask farmhand Eb if they will be needing any more subtitles for the episode.
In the UK television series "Top Gear", in episode 6 of Series 13, they purposely mistranslate the song sung by Carla Bruni, having her supposedly denouncing hatred towards the trio of presenters ("but mainly James May") for destroying what is claimed to be her own Morris Marina.
One unintentional source of humor in subtitles comes from illegal DVDs produced in non-English-speaking countries (esp. China). These DVDs often contain poorly-worded subtitle tracks, possibly produced by machine translation, with humorous results. One of the better-known examples is a copy of Star Wars Episode III: Revenge of the Sith whose opening title was subtitled, "Star war: The backstroke of the west". 
Many words such as "Mum/Mom", "pyjamas/pajamas", and so on, are commonly spelled according to the accent or national origin of the person speaking, rather than the language, country, or market the subtitles were created for. For example, a British film released in the United States might use "Mum" when a British character is speaking, while using "Mom" when an American character is speaking.
Phone captioning is a free service provided by the US government in which specially-trained operators provide transcriptions for hearing-impaired telephone users.
^ McCall, W. (2008). Same-Language-Subtitling and Karaoke: The Use of Subtitled Music as a Reading Activity in a High School Special Education Classroom. In K. McFerrin et al. (Eds.), Proceedings of Society for Information Technology and Teacher Education International Conference 2008 (pp. 1190-1195). Chesapeake, VA: AACE.http://go.editlib.org/p/27350
^ Gannon, Jack. 1981. Deaf Heritage–A Narrative History of Deaf America, Silver Spring, MD: National Association of the Deaf, p. 266-270 (PDF)(PDF)
^Caption Colorado (2002). "Caption Colorado". Archived from the original on 2007-08-23. http://web.archive.org/web/20070823115204/http://www.captioncolorado.com/about/index.html. Retrieved 2007-10-24. ""Real-time" vs. Newsroom Captioning
Caption Colorado offers "real-time" closed captioning that utilizes unique technologies coupled with the talents of highly skilled captioners who use stenographic court reporting machines to transcribe the audio on-the-fly, as the words are spoken by the broadcasters. real-time captioning is not limited to pre-scripted materials and, therefore, covers 100% of the news, weather and sports segments of a typical local news broadcast. It will cover such things as the weather and sports segments which are typically not pre-scripted, last second breaking news or changes to the scripts, ad lib conversations of the broadcasters, emergency or other live remote broadcasts by reporters in-the-field. By failing to cover items such as these, newsroom style captioning (or use of the TelePrompTer for captioning) typically results in coverage of less than 30% of a local news broadcast. … 2002"
Premiere Offline Captioning
Premiere Offline Captioning is geared toward the high-end television industry, providing highly customized captioning features, such as pop-on style captions, specialized screen placement, speaker identifications, italics, special characters, and sound effects.
Premiere Offline involves a five-step design and editing process, and does much more than simply display the text of a program. Premiere Offline helps the viewer follow a story line, become aware of mood and feeling, and allows them to fully enjoy the entire viewing experience. Premiere Offline is the preferred presentation style for entertainment-type programming. … 2002"
^Federal Communications Commission (FCC) (2008-05-01) (swf). Closed Captioning and the DTV Transition. Washington, D.C.. Event occurs at 1m58s. http://www.dtv.gov/video/DTV_ASL-Part3.html. "In addition to passing through closed caption signals, many converter boxes also include the ability to take over the captioning role that the tuner plays in your analog TV set. To determine whether your converter box is equipped to generate captions in this way, you should refer to the user manual that came with the converter box. If your converter box. If your converter box is equipped to generate captions in this way, then follow the instructions that came with the converter box to turn the captioning feature on/off via your converter box or converter box remote control. When you access the closed captions in the way, you also will be able to change the way your digital captions look. The converter box will come with instructions on how to change the caption size, font, caption color, background color, and opacity. This ability to adjust your captions is something you cannot do now with an analog television and analog captions."
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