Video recorder scheduling code - AbsoluteAstronomy.com

VCR Plus+, G-Code, VideoPlus+ and ShowView are different names for essentially the same system for programming video recorder

Video recorder

A video recorder may be any of several related devices:*Digital video recorder ; Personal video recorder *DVD recorder*Videocassette recorder *Video tape recorder...

s. These names are all registered trademarks of Macrovision

Macrovision

Rovi Corporation is a globally operating, US-based company that provides guidance technology, entertainment data, copy protection, industry standard networking and media management technology for digital entertainment devices and services...

, whose corporate predecessor, Gemstar, developed these algorithms for use in integrated endec

Endec

An endec is a device which acts as both an encoder and a decoder on a signal or data stream, either with the same or separate circuitry or algorithm...

History

Before the advent of on-screen displays, the only interface available for programming a home video recorder was a small LED or LCD panel and a small number of buttons. Correctly recording a specific program was therefore a somewhat complex operation for many people; scores of jokes have referred over the years to the need to "have a 12-year-old" or someone technically adept to successfully program a home video recorder or to avoid having a perpetual blinking "12:00" on the recorder's display. G-Code, VideoPlus+ and ShowView were introduced to remove this difficulty.

Concept

The central concept of the system is a unique number, a PlusCode, assigned to each program, and published in TV listings in newspapers and magazines. To record a program, the number is taken from the newspaper and typed into the video recorder, which will then record on the correct channel at the correct time. The number is generated by an algorithm

Algorithm

In mathematics and computer science, an algorithm is an effective method expressed as a finite list of well-defined instructions for calculating a function. Algorithms are used for calculation, data processing, and automated reasoning...

from the date, time and channel of the programme, and so does not rely on anything being broadcast over the air. This means it will not compensate for a disrupted schedule due to live sporting events or news bulletins, but many video recorders with these systems also incorporate Programme Delivery Control

Programme Delivery Control

Programme delivery control is specified by the standard ETS 300 231, published by the European Telecommunications Standards Institute...

(PDC) and will use that to alter times if possible.

Branding

This system has been licensed to TV and VCR manufacturers in about 40 countries, but is known under different names. It is known as VCR Plus+ in the USA and Canada

Canada

Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

, G-Code in Japan

Japan

Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

, China

China

Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...

, New Zealand

New Zealand

New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...

and Australia

Australia

Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

, VideoPlus+ in Ireland

Ireland

Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...

and the UK

United Kingdom

The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

and ShowView in the rest of Europe

Europe

Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

and also in South Africa

South Africa

The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...

. The system is not called VCR Plus in Europe or Japan firstly because Philips

Philips

Koninklijke Philips Electronics N.V. , more commonly known as Philips, is a multinational Dutch electronics company....

has a trademark registration for "VCR", secondly because the acronym "VCR" is not commonly used outside North America. However, because TV programs' schedules are different, the coding has to be adjusted in each of the regions and recording equipment is not interchangeable.

Algorithms

The actual algorithms used to encode and decode the TV guide values from and to their time representations were published in 1992, but only for 6 digit codes or less.

Several open source code 6 digit examples are available. An implementation using Excel macros is also available.

One problem found during reverse engineering efforts is that the algorithm seemed to change for seven and eight digit codes.

Although not well known, code that also works with 7 and 8 digit codes was posted anonymously in 2003. The source code

Source code

In computer science, source code is text written using the format and syntax of the programming language that it is being written in. Such a language is specially designed to facilitate the work of computer programmers, who specify the actions to be performed by a computer mostly by writing source...

for the full 8 digits was written in C and later converted to Perl

Perl

Perl is a high-level, general-purpose, interpreted, dynamic programming language. Perl was originally developed by Larry Wall in 1987 as a general-purpose Unix scripting language to make report processing easier. Since then, it has undergone many changes and revisions and become widely popular...

External links

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