Test card


Test card

A test card, also known as a test pattern in the UK, North America and Australia, is a television test signal, typically broadcast at times when the transmitter is active but no program is being broadcast (often at startup and closedown). Used since the earliest TV broadcasts, test cards were originally physical cards at which a television camera was pointed, and such cards are still often used for calibration, alignment, and matching of cameras and camcorders. Test patterns used for calibrating or troubleshooting the downstream signal path are generated by test signal generators, which do not depend on the correct configuration of (and presence of) a camera. Digitally generated cards allow vendors, viewers and television stations to adjust their equipment for optimal functionality.

The test card usually has a set of line-up patterns to enable television cameras and receivers to be adjusted to show the picture correctly. (Compare with SMPTE color bars.) Most modern test cards include a set of calibrated color bars which will produce a characteristic pattern of "dot landings" on a vectorscope, allowing chroma and tint to be precisely adjusted between generations of videotape or network feeds. SMPTE bars—and several other test cards—include analog black (a flat waveform at 7.5 IRE, or the NTSC setup level), full white (100IRE), and a "sub-black", or "blacker-than-black" (at 0 IRE), which represents the lowest low-frequency transmission voltage permissible in NTSC broadcasts (though the negative excursions of the colourburst signal may go below 0 IRE). Between the colour bars and proper adjustment of brightness and contrast controls to the limits of perception of the first sub-black bar, an analogue receiver (or other equipment such as VTRs) can be adjusted to provide impressive fidelity.

Test cards are also typically broadcast with library music (see below), a sine wave reference tone, or the relayed broadcasting of a radio station owned by the same broadcaster. There is now a cult following for test card music.

BBC test cards

BBC test cards are identified by a letter.The most famous British test card is Test Card F which incorporates a colour photograph of Carole Hersee (daughter of BBC engineer George Hersee) playing noughts and crosses with a doll, used on the BBC and ITV from the beginning of colour broadcasts in the late 1960s. It was later updated as Test Card J, and for widescreen broadcasts as Test Card W. Test Card F has often been spoofed by comedians. [ [http://news.bbc.co.uk/1/hi/uk/1282160.stm Test card special] , by Ryan Dilley, BBC News, 19 April, 2001]

Decline

Formerly a common sight, test cards are now only rarely seen outside of television studios, post-production, and distribution facilities. In particular, they are no longer intended to assist viewers in calibration of television sets. Several things have led to their demise for this purpose:

* Modern microcontroller-controlled analogue televisions rarely if ever need adjustment, so test cards are much less important than previously. Likewise, modern cameras and camcorders seldom need adjustment for technical accuracy, though they are often adjusted to compensate for scene light levels, and for various artistic effects.
* Use of digital interconnect standards, such as CCIR 601 and SMPTE 292M, which operate without the non-linearities and other issues inherent to analogue broadcasting, do not introduce colour shifts or brightness changes; thus the requirement to detect and compensate for them using this reference signal has been virtually eliminated. (Compare with the obsolescence of stroboscopes as used to adjust the speed of record players). On the other hand, digital test signal generators do include test signals which are intended to stress the digital interface, and many sophisticated generators allow the insertion of jitter, bit errors, and other pathological conditions that can cause a digital interface to fail.
* Likewise, use of digital broadcasting standards such as the DVB and ATSC eliminates the issues introduced by modulation and demodulation of analogue signals.
* Test cards including large circles were used to confirm the linearity of the set's deflection systems. As solid-state components replaced vacuum tubes in receiver deflection circuits, linearity adjustments were less frequently required (few newer sets have user-adjustable "VERT SIZE" and "VERT LIN" controls, for example). In LCD and other deflectionless displays, the linearity is a function of the display panel's manufacturing quality; for the display to work, the tolerances will already be far tighter than human perception.
* In developed countries such as the United States and the United Kingdom, the financial imperatives of commercial television broadcasting mean that air-time is now typically filled with programmes and commercials (such as infomercials) 24 hours a day, and non-commercial broadcasters have to match this.
* In North America, most test cards such as the famous Indian Head test card of the 1950s and 1960s have long been relegated to history. The SMPTE color bars occasionally turn up, but with most North American broadcasters now following a 24-hour schedule, these too have become a rare sight. Many Canadian Broadcasting Corporation stations broadcast a modified form of the SMPTE bars late at night until late 2006.
* When there are in fact no standard programmes being broadcast on the channels that do not have 24-hour programming, other, more informative features such as educational shows, e.g. the BBC Learning Zone, and teletext-type programmes such as Pages from Ceefax, ITV Nightscreen and 4-Tel On View are often broadcast, the latter type acting as the better test-card substitute as they just roll continuously.
* Australian national broadcaster SBS airs a weather map in place of a test card with music from albums sold by SBS and a ticker at the bottom of the screen during the early hours of the morning.
* Australian community broadcaster Channel 31 in Melbourne airs Fishcam, the output of a videocamera aimed at a fish tank.
* Some Philippine cable networks replace test cards with an advertisement showing the product, "a reason to go to sleep" and the time when the station will sign on.
* In Singapore, since 2004, instead of showing test cards, television channels usually air radio channels while showing their station ID at the same time. On television networks and stations in most of the Third World countries, test cards are still seen because most television networks and stations in those countries do not have 24-hour programming.

Use of test patterns and test cards is still common "within" television production facilities. Many of these still have analogue infrastructure, and currently as of March 2006 analogue transmissions are still found worldwide (though the United States is currently scheduled to require broadcasters to switch off the NTSC service in 2009--NTSC may still be a viable transmission means for cable television for several more years). Many artistic settings are still made by using test cards or test patterns in conjunction with devices like waveform monitors and vectorscopes (most modern waveform monitors include vectorscope capability), and while digital transmission eliminates many of the "analogue" effects associated with analogue television, digital broadcasting has its own set of issues.

A brief history of BBC test card music

Music was chosen to be broadcast along with the test card from the early 1950s. Prior to that test tones were used which were not a great deal of fun if you were a TV engineer tuning in to test transmissions. Once a reliable method of providing music was approved, originally via 78 rpm discs played live before the introduction of tape in 1955, test tones took more of a back seat.

In the UK broadcasts of recorded music were governed by the needletime agreement the BBC had with the Musicians' Union. The reason for the restriction was the MU felt the BBC would not need to employ musicians if it were allowed to broadcast as many recordings as it liked. (Certainly, since needletime restrictions were removed in the 1990s the BBC has concentrated more on commercial recorded music in its tv and radio output.)

However, trade tests were not likely to impinge on an artist's career to a great extent so for these purposes a method of using library music was connived at. Specifically, if recordings came from abroad and were not available to buy in the shops, they could qualify for an 'all broadcasting rights' agreement. Contrary to some rumours, these were not copyright or royalty-free: they attracted a lower rate on PRS scale values based on expected audience but that was the only financial concession. Publishers would donate recordings free of initial charge to the BBC and would rely on the PRS (performing) royalties their transmission would generate for their return. This was unique to the UK: most other countries either relayed radio output or test tone behind their test cards.

In the early 1950s then, 78rpm records were played live. The selection of music was made by persons unknown at TV centre and this persisted until 1959. By this time tape had been introduced and the relatively small library of suitable recordings held at TVC had been repeated and recycled up to their limit and beyond.

It was known that a gentleman by the name of David Allan was working for Sound Archives and was gathering quite a library of ABR non-needletime music. So the production of BBCtv trade test tapes switched to Sound Archives at Broadcasting House. David created his first batch of 6 tapes in 1959 and this success was to lead to him being given charge of a new department called Foreign Recordings in about 1970. By this time the world's music publishers had cottoned onto the fact that by now there were two networks, BBC1 and BBC2, each pumping out trade tests for much of the day. They needed music and there were royalties to be had. Thus the material flowed in and David was able to pick and choose what he wanted. Of course, the trade test tapes were not the primary purpose of his department; music was needed to fill the schedules of the Light programme/radio two as well as the need for music for tv.

In 1972 the familiar half-hour music sequences punctuated by the station identification signal (the musical notes B-B-C played on a celeste) gave way to 60 - 70 minute sequences made possible by a reduction in tape speed from 15ips to 7.5 ips. The ident disappeared too.

Some would argue this was the most creative era of BBC test card music. Without doubt there was always great care given to the compilation of these tapes. David told me he always tried to create a musical programme in which there would always be some items which, whilst he did not dislike them, would not be his favourite styles. This was to ensure that there would be something for those who did not share his musical taste.

1973 saw the arrival of David's successor, John Ross-Barnard. John began his broadcasting career as a pirate radio DJ and had been one of the first continutiy announcers on BBC2.His style of trade test tape was rather more commercial than David's but then his brief was somewhat different. It was during his tenure that the BBC got rid of many of the house orchestras and so more radio two style material was required to make up for this. John also introduced the concept of the publisher tape; that is where a tape would be compiled by one of the contributing publishers rather than by John or one of his staff. It allowed Foreign Recordings - by this time known as International Recordings - to concentrate more on keeping radios one and two on air but the diversity and character of many trade test tapes suffered accordingly, the publishers' main concern being to get their copyrights played on air.

Publisher tapes became the mainstay of John's successor, John Billingham, whose era was not noted for great things on BBC trade. Next in line for the baton in the relay race was Mike Harding. He was the final incumbent who oversaw the dissolution of International Recordings as the needletime restrictions were abolished. So too was the test card: rolling Ceefax pages replaced it in 1983 and the music was toned down and sanitised. It became the worst type of lift music with only a few exceptions although it began to liven up a little in the 1990s. However, many would say that musical integrity was sacrificed in favour of attempts at being 'hip' with material that tried to be jazz/funk but failed.

Test card music became popular in its own right when many people realised a genuine enjoyment of a source of mainly instrumental music which had given way to 24 hr broadcasting.

For many years those who enjoyed it were frustrated that as non-needletime, it was not possible to buy any of it on record. Now however, a lot of the music has been cleared for commercial release. See the following links: Apollo Sound [http://www.apollosound.co.uk link title] and Acclaim Records [http://www.tradetesttapes.co.uk link title]

Gallery



Other test cards include Convergence.

UK Test Card Timeline

Test patterns for photocopiers

A lesser-known kind of test pattern is used for the calibration of photocopiers [http://www.pcstats.com/articleview.cfm?articleid=1339&page=4] [http://www.thing.net/~grist/cyano/jangva/roomecho.htm] . Photocopier test patterns are physical sheets that are photocopied, with the difference in the resulting photocopy revealing any telltale deviations or defects in the machine's ability to copy.

In numismatics

Television has had such an impact in today's life, that it has been the main motif for numerous collectors' coins and medals. One of the most recent ones is The 50 Years of Television commemorative coin minted in March 9 2005 in Austria. The obverse of the coin shows a "test pattern", while the reverse shows several milestones in the history of television.

References

External links

* [http://testcard.wikia.com/ Test Card wikia]
* [http://www.mire-project.com/index.php/index.php?lang=EN-en mire.project] - Street art work about television test patterns
* [http://www.tv-testbild.com/ TV Testbild] - very informative, but in German language only
* [http://www.burosch.de/ Burosch AudioVideo-Technology] - advanced HDTV test patterns
* [http://www.meldrum.easynet.co.uk/mhp/testcard/index.html The Test Card Gallery]
* [http://www.pembers.freeserve.co.uk/Test-Cards/ Television Test Cards, Tuning Signals, Idents and Clocks]
* [http://www.barney-wol.net/video/video.html Barney Wol's website] has details of the development of UK testcards F, J and W
* [http://www.testcardcircle.org.uk Test Card Circle] Details of Test Cards and music.
* [http://www.625.uk.com/tv_logos/flash2.htm 625 UK dot com Flash Files] - high quality Macromedia Flash examples of almost all British test cards and station idents (the test cards are at the bottom of the page and include C, D, F, J, W and ETP-1)
* [http://www.irish-tv.com/rtetests.asp Irish TV Testcards] - Pictures of Test Cards used by the Irish TV broadcasters RTÉ, TV3 and UTV.
* [http://www.culturehole.com/testpattern SMPTE Bars] in CSS and XHTML
* [http://svt.se/svt/jsp/Crosslink.jsp?d=60572&a=704530&lid=puff_704517&lpos=extra_0 SVT test cards] - Picture gallery of test cards from Swedish Television (SVT), in Swedish
* [http://www.stereo.ru/whatiswhat.php?article_id=59 Russian Test Cards]


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