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Video recorder scheduling code

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For other uses, see G-code (disambiguation).

VCR Plus+, G-Code, VideoPlus+ and ShowView are different names for essentially the same system for programming video recorders. These names are all registered trademarks of Macrovision, whose corporate predecessor, Gemstar, developed these algorithms for use in integrated endecs.

History

A full view of a typical VFD (Vacuum Fluorescent Display) used in a videocassette recorder

Before the advent of on-screen displays, the only interface available for programming a home video recorder was a small VFD, LED or LCD panel and a small number of buttons. Correctly recording a specific program was therefore a somewhat complex operation for many people. 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 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 (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, G-Code in Japan, China, New Zealand and Australia, VideoPlus+ in Ireland and the UK and ShowView in the rest of Europe and also in South Africa. The system is called VideoPlus+/ShowView in Europe because Philips has a trademark registration for "VCR", and as G-Code ('G' for Gemstar) in Japan because VCR is not a common abbreviation there ('VTR' is used instead). 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 six-digit codes or less.[1][2]

References

  1. ^ http://www.righto.com/papers/vcr.html
  2. ^ K. Shirriff, C. Welch, A. Kinsman, Decoding a VCR Controller Code, Cryptologia, 16(3), July 1992, pp 227-234.
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