Editing Closed captioning (section)

== Digital television interoperability issues ==
The US [[ATSC Standards|ATSC]] [[digital television]] system originally specified two different kinds of ''closed captioning'' datastream standards: the original analog-compatible (available by [[EIA-608|Line 21]]) and the more modern digital-only [[CEA-708]] formats are delivered within the video stream.<ref name="atsc.org" /> The [[Federal Communications Commission|US FCC]] mandates that broadcasters deliver (and generate, if necessary) both datastream formats with the [[CTA-708|CEA-708]] format merely a conversion of the Line 21 format.<ref name="atsc.org" /> The [[Canada|Canadian]] [[CRTC]] has not mandated that broadcasters either broadcast both datastream formats or exclusively in one format. Most broadcasters and networks to avoid large conversion cost outlays just provide [[EIA-608]] captions along with a transcoded [[CTA-708|CEA-708]] version encapsulated within [[CTA-708|CEA-708]] packets.

=== Incompatibility issues with digital TV ===
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 [[Television|TV]] is able to display it.

Originally, CC information was included in the picture ("line 21") via a [[Composite video|composite video input]], but there is no equivalent capability in digital video interconnects (such as [[Digital Visual Interface|DVI]] and [[HDMI]]) between the display and a "source". A "source", in this case, can be a [[DVD player]] or a [[Terrestrial television|terrestrial]] or cable digital television receiver. When CC information is encoded in the [[MPEG-2]] data stream, only the device that decodes the [[MPEG-2|MPEG-2 data]] (a source) has access to the ''closed caption'' information; there is no standard for transmitting the CC information to a display monitor separately. Thus, if there is CC information, the source device needs to overlay the CC information on the picture prior to transmitting to the display over the interconnect's video output.

The responsibility of decoding the CC information and overlaying onto the visible video image has been taken away from the TV display and put into the "source" of DVI and HDMI digital video interconnects. Because the TV handles "mute" and, when using [[Digital Visual Interface|DVI]] and [[HDMI]], a different device handles turning on and off CC, this means the "captions come on automatically when the [[Television|TV]] is muted" feature no longer works. That source device—such as a [[DVD player]] or [[set-top box]]—must "burn" the image of the CC text into the picture data carried by the [[HDMI]] or [[Digital Visual Interface|DVI]] cable; there's no other way for the CC text to be carried over the [[HDMI]] or [[Digital Visual Interface|DVI]] cable.<ref>
{{cite web |url=https://denon.custhelp.com/app/answers/detail/a_id/299/~/hdmi-support-for-closed-captioning |title=HDMI Support for 'Closed Captioning' |archive-url=https://web.archive.org/web/20210213061121/https://denon.custhelp.com/app/answers/detail/a_id/299/~/hdmi-support-for-closed-captioning |archive-date=2021-02-13 |url-status=dead}}
</ref><ref>
{{cite web |url=https://video.stackexchange.com/questions/14977/what-types-of-cables-support-closed-captioning |title=What types of cables support closed captioning?}}
</ref><ref>
{{cite web |author=Steve Barber
|url=https://www.nchearingloss.org/article_digcap.htm |title=Understanding Digital Captions |archive-url=https://web.archive.org/web/20240226160247/https://www.nchearingloss.org/article_digcap.htm |archive-date=2024-02-26 |url-status=dead}}
</ref><ref>
{{cite web |author=Neil Bauman
|url=https://hearinglosshelp.com/blog/getting-captions-on-your-new-tv-the-good-the-bad-and-the-downright-frustrating/ |title=Getting Captions On Your New TV—The Good, the Bad and the Downright Frustrating}}
</ref><ref>
{{cite web |author=Stuart Sweet
|url=https://blog.solidsignal.com/tutorials/can-get-closed-captioning-hdmi-directv/ |title=Can you get closed captioning over HDMI with DIRECTV?|date=31 May 2022 }}
</ref><ref>
{{cite web |url=https://creativecow.net/forums/thread/closed-captions-support-in-hdlink/ |title=closed captions support in HDLink}}
</ref>

Many source devices do not have the ability to overlay CC information, for controlling the CC overlay can be complicated. For example, the [[Motorola]] DCT-5xxx and -6xxx cable set-top receivers have the ability to decode CC information located on the [[MPEG-2]] stream and overlay it on the picture, but turning CC on and off requires turning off the unit and going into a special setup menu (it is not on the standard configuration menu and it cannot be controlled using the remote). Historically, [[DVD player]]s, [[Videocassette recorder|VCRs]] and set-top tuners did not need to do this overlaying, since they simply passed this information on to the TV, and they are not mandated to perform this overlaying.

Many modern digital television receivers can be directly connected to cables, but often cannot receive scrambled channels that the user is paying for. Thus, the lack of a standard way of sending CC information between components, along with the lack of a mandate to add this information to a picture, results in CC being unavailable to many hard-of-hearing and deaf users.

The [[EBU]] [[Ceefax]]-based teletext systems are the source for closed captioning signals, thus when teletext is embedded into [[DVB-T]] or [[DVB-S]] the closed captioning signal is included.<ref>{{Cite web|url=https://www.etsi.org/deliver/etsi_en/300700_300799/300743/01.03.01_60/en_300743v010301p.pdf|title=ETSI EN 300 743: Digital Video Broadcasting (DVB); Subtitling systems}}</ref> However, for DVB-T and DVB-S, it is not necessary for a teletext page signal to also be present ([[ITV1]], for example, does not carry analogue teletext signals on [[Sky UK|Sky Digital]], but does carry the embedded version, accessible from the "Services" menu of the receiver, or more recently by turning them off/on from a mini menu accessible from the "help" button).

The [[BBC|BBC's]] Subtitle (Captioning) Editorial Guidelines were born out of the capabilities of [[Teletext]] but are now used by multiple European broadcasters as the editorial and design best practice guide <ref>{{Cite web|url=https://bbc.github.io/subtitle-guidelines/|title=BBC Subtitle Guidelines|website=bbc.github.io|access-date=2019-07-19|archive-date=2019-10-20|archive-url=https://web.archive.org/web/20191020222240/http://bbc.github.io/subtitle-guidelines/|url-status=dead}}</ref>

=== New Zealand ===
In New Zealand, captions use an [[EBU]] [[Ceefax]]-based teletext system on [[Digital Video Broadcasting|DVB]] broadcasts via [[Satellite television|satellite]] and [[cable television]] with the exception of [[MediaWorks New Zealand]] channels who completely switched to [[DVB-T|DVB]] [[Run-length encoding|RLE]] subtitles in 2012 on both [[Freeview (UK)|Freeview]] satellite and [[UHF]] broadcasts, this decision was made based on the [[TVNZ]] practice of using this format on only [[Digital Video Broadcasting|DVB]] [[UHF]] broadcasts (aka [[Freeview (UK)|Freeview HD]]). This made [[composite video]] connected TVs incapable of decoding the captions on their own. Also, these [[Pre-rendering|pre-rendered]] subtitles use classic caption style opaque backgrounds with an overly large [[Point (typography)|font size]] and obscure the picture more than the more modern, partially transparent backgrounds.

=== Digital television standard captioning improvements ===
The [[CTA-708|CEA-708]] specification provides for dramatically improved ''captioning''
* An enhanced character set with more [[Diacritic|accented letters]] and non-Latin letters, and more special symbols
* Viewer-adjustable text size (called the "caption volume control" in the specification), allowing individuals to adjust their TVs to display small, normal, or large captions
* More text and background colors, including both transparent and translucent backgrounds to optionally replace the big [[black]] block
* More text styles, including edged or [[drop shadow]]ed text rather than the letters on a solid background
* More text fonts, including [[monospaced]] and proportional spaced, [[serif]] and [[sans-serif]], and some playful cursive fonts
* Higher [[Bandwidth (computing)|bandwidth]], to allow more [[data]] per minute of [[video]]
* More language channels, to allow the encoding of more independent caption streams
As of 2009, most closed captioning for digital television environments is done using tools designed for analog captioning (working to the [[EIA-608|CEA-608]] [[NTSC]] specification rather than the [[CTA-708|CEA-708]] [[ATSC standards|ATSC]] specification). The captions are then run through transcoders made by companies like EEG Enterprises or [[Evertz Microsystems|Evertz]], which convert the analog [[EIA-608|Line 21 caption format]] to the digital format. This means that none of the [[CTA-708|CEA-708]] features are used unless they were also contained in [[EIA-608|CEA-608]].