VideoPlus+ / ShowView
Programming your VCR
VideoPlus+ codes are a set of numbers printed in TV listing guides that inform a video recorder which channel and at what time a programme is on. Most new videos now have VideoPlus+ buttons on their handsets.
VideoPlus+ is the UK version of a system which started in the United States in the 1990s under the name VCR+. There is also a Continental European version called ShowView. All these names are registered trade names of GemStar Inc. ShowView, VCR+ and VideoPlus+ differ technically.
The objective of both systems is to encode the day number, channel number and the published start time and duration of a TV programme as a number of no more than 8 digits (or 9 with some ShowView codes) such that the encoding can be called proprietary, and that GemStar can raise revenue by selling the codes to newspapers. They also licence use of the system to be built into VCRs and stand-alone decoder handsets.
Codes are cunningly arranged to be small numbers in the case of prime-time material and progressively longer numbers for the more obscure time slots. It is done by arranging popular timeslots to be earliest in a giant lookup table.
Because the US, UK and Continental European ideas of television scheduling differ, different variants of the basic encoding system exist.
The US broadcasters arrange 99% of their programming to start and end on 30-minute boundaries, frequently have programmes with lengths up to and including five hours (American football or baseball) and have a lot of channel numbers to choose from. There are thus 480 timeslots on 48 channels which get 6 digit-or- fewer codes in VCR+. There are 8 timeslots on the first 4 channels which get 3 digit-or-fewer codes in VCR+.
There are 2000 timeslots on 16 channels which get the 6-digit treatment in VideoPlus+ because in the UK there are fewer channels used on the whole but have a lot more variety in programme lengths and start times. The longest VideoPlus+ programme with a 6-digit code is 3 hours long. As with VCR+ , there are 8 timeslots on the first 4 channels which can get 3 digit-or-fewer codes. In VideoPlus+ these first four channels are allocated to the 4 original terrestrial broadcasters, BBC1, BBC2, ITV and C4.
As a matter of interest, the satellite company UK Gold uses a strategy similar to the US versions, but is allocated a channel number greater than 16. This makes every UK Gold programme receive a 7 or 8 digit code, yet if it had been allocated a channel number of 16 or less, almost every programme would get a short code, and the prime time slots would often be only 4 digits long. The same goes for Discovery Channel.
Programmes whose starts and durations give them indexes 0-127 on the lookup table, and which are on channels 1-16, will have the same codes in VCR+ and VideoPlus+. This means all the 1,2,3 and 4-digit codes, plus some of the 5-digit codes are the same in the two systems.
Because the 1 and 2 digit codes are the same on VCR+ and VideoPlus+, the following trivia hold for both systems:
Encoded along with the channel number and timeslot index is a programme date (just a number from 1-31). A decoder will usually assume that if the decoded day number is less than yesterday's day number, then it really refers to next month. So, codes can be published up to 27-29 days in advance of the programme's broadcast. There are "illegal" codes in the system, referring to the non-existent dates at the end of certain months. Commercial decoders seem to produce an error report if these codes are tried, though the internet codec (below) will still encode and decode them. There also are a few "illegal" codes which could in theory be validly decoded as occurring on the 32nd of the month. These are not handled even on the Internet codecs though.
VideoPlus+ and its variants don't cope with unexpected changes to programme transmission times (which is dealt with by PDC) nor can it cope with daylight-saving time switchovers.
(Notes copyright 1994-2000 Steve Hosgood where permission is granted for non-commercial re-distribution. VCR+, VideoPlus+ and ShowView are registered trademarks of GemStar Inc.)
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