Since the GEN IPTV Subscription in the late 1920’s the consumer has selected the channel to view by selecting a number on the TV such as channels 2 to 13 for VHF and 14 to 69 for UHF. With the advent of cable TV this has changed somewhat with channel options from 2 to about 99. The average consumer has become very comfortable with this system.
When the industry began development of digital TV and compression they had to develop a new system. The standard that was developed was established by the Advanced Television Standards Committee (ATSC).
Because digital compressed TV is now capable of transmitting more than one program on a TV channel it was decided to give the program a Major channel number and a Minor channel number separated by a period (.).
For instance a digital program that is carried on VHF channel 6 would be called 6.1. If there was a second or third program being transmitted they would be called 6.2 or 6.3. If they were transmitted on a UHF channel they would be 45.1, 45.3 and 45.7. To make things even more confusing the FCC mandated that TV stations being transmitted on Channels 2-6 move to another frequency. This often resulted in a channel that was known for 50 years as Channel 3 to be transmitted on UHF channel 26 but called 3.1… Very confusing indeed.
When these programs were picked up by the local cable company it tended to get even more confusing until the Virtual channel numbering system was introduced. This is because on a cable system, there can have as many as 10 or 12 programs carried on one channel and the channel may be irrelevant to the program number or traditional channel number.
With the introduction of a virtual channel number system a number is assigned to a Program regardless of where the channel is actually carried on the system. This means the number displayed on the TV or Cable box will be between 2 and 999 and will not have any duplicates and no minor numbers such as a.1 or.2. The system operator can assign any virtual number.
For instance, when we look at channel 3 mentioned above it is transmitted by the broadcaster on UHF channel 26. The cable company may place it on the cable on channel 57.3 but they have set it on virtual channel number 3. This way when you select channel 3 on your cable box, the old channel 3 you watched for years is what you get.