Show view
The ShowView System, developed by the company GEMSTAR (a subsidiary of Macrovision [1]), is a recording technology incorporated into recording devices, such as home videos (VHS) or DVD recorders. To use this system, all you need is a VCR or DVD recorder that incorporates the technology and a printed medium that publishes the ShowView numbers. By entering the code into the remote control of the recording device, you can record instantly or schedule the recording of the desired programs.
History
Initially, the system was released by the company GEMSTAR in the United States and Canada, under the name VCR Plus+. Later, in the early 1990s, the system was introduced by the same company in the UK and Ireland under the name VideoPlus+, in the rest of Europe and South Africa under the name ShowView, and in Japan, China, New Zealand and Australia under the name G-Code. In Europe it was consolidated in most countries, except Spain.
In 1992, Ken Shirriff, Curt Welch and Andrew Kinsman made public the encoding and decoding algorithms that until then had been the exclusive property of GEMSTAR based on their own studies. They only published the algorithms for codes of up to 6 digits. Subsequently the algorithms for 7 and 8 digit codes were published anonymously.
Showview Channel Codes
The codes used are series of 1 to 9 digits that correspond to the television programs. They are generated by a unique algorithmic formula that encodes the basic parameters used in a video recording such as the day, the TV channel, its start time or the end time. By entering it, the ShowView system automatically activates the recorder's counter: tuning to the right channel at the right time, recording the program and finally turning off the recorder.
ShowView codes are a standard editorial service in television listings. They are published in more than 2,000 publications in more than 24 countries. In Europe, ShowView codes are found in practically all national and regional newspapers as well as in the main TV and teletext magazines.
These codes are expressly prepared so that the programs with the most audience or that are broadcast in the most popular time slots correspond to the combinations with fewer digits.
It should also be noted that the coding varies according to the geographical area, since in certain countries the television channels tend to program their schedule in a certain way. For example, in the United States there are many programs of long duration, above 5 hours (for example, baseball games), and they are usually scheduled to start at fixed times. In other countries, such as the UK, there is much more variability in terms of the length and time of television programmes.
PDC (Program Delivery Control)
Program Delivery Control is a system created by TV channels to identify each program during its broadcast. In this way, the PDC system becomes a complement to the Showview system and offers the user the possibility of recording any program even if there are alterations in its broadcast, such as delays, extensions or cancellations.
This PDC signal is made up of variables such as the TV channel, the date and time the program starts. An instant before the start of this, the TV channel sends the corresponding PDC signal that makes the video start up and start recording. During the emission the PDC signal is sent at regular intervals of 30 seconds. When the TV channel interrupts the emission of the PDC signal, the video stops recording and turns off automatically.
This PDC signal is sent multiplexed with the teletext signal. Teletext information is divided into 40-byte packets. The DPC is found in package number 30.
All technical information can be found and downloaded in pdf format from ETSI [2] under the reference ETS 300 231.
VPS (Video Programming System)
In some countries such as Austria, Germany, Switzerland or the Czech Republic, the VPS system (Video Programmer System) is used, which is a system similar to the PDC. The only difference with the PDC is the way the signal is sent.
While the PDC signal is sent together with the teletext signal, the VPS signal is sent during the VBLANK vertical line blanking process; Specifically, on line 16.
Features
Showview allows the recording of a specific program. No need to look up what your start time is. It is enough to enter the code of said program.
Another advantage is not recording the advertising that is incorporated during the broadcast. During the commercial, the TV channel stops sending the code of the program and the recorder stops recording. Once finished, the TV station sends the program code again and the recorder starts recording again after the point where it stopped. The result is the recording of a program without commercial breaks.
It also prevents counterprogramming. Since the start time is ignored, if a program is canceled at the last minute or is moved from the schedule to another time, the recorder will detect it and will not record another program than the one entered.
In addition, another advantage is the recording of long programs. There are programs that are recorded live and it is difficult to establish the end time. With ShowView it is possible to record, for example, the overtime of a football match.
Finally, it also offers the advantage of avoiding emission delays. It is common for a program to start slightly later than the advertised time. Since with ShowView only the broadcast of that program is recorded, if it starts late it doesn't matter since it does not take into account the start time.
PTY (Program Type Indicator)
This flag bears a resemblance to the PDC. While the PDC identifies programs, the PTY identifies subject areas. For example, if you want to record all the scientific programs, you just have to enter the PTY code of the scientific area.
There is an option to record emergency broadcasts. This is useful if you want to record any breaking information on any channel.