Frequently Asked Questions (Module 7.2.2)

by Tina Mani — last modified Aug 21, 2012 05:27 AM
In this unit, Tina Mani gives answers to some frequently asked questions relating to Internet Protocol Television (IP TV), Mobile TV, role of Set Top Box (STB) in an IP TV network, features provided with IP TV services, Time Shift Television, Digital Video Recording, the difference between an MPEG-2 and MPEG-4, etc.

What is the difference between IPTV and Mobile TV?
Mobile TV is the availability of regular TV channels to view on your mobile. The network conditions of a wireless network are unpredictable, and hence the technology is built to adapt to varying conditions. Mobile TV and internet TV (TV viewing on the PC using an internet connection) are also sometimes referred to as Over The Top TV.  IPTV makes assumptions about the reliability of the transport mechanism and works well only if the transport network provides sufficient bandwidth and like fixed line broadband, or cable as a medium of transmission.

What is the bandwidth required for acceptable quality of TV viewing?
With MPEG-2 compression, an SDTV signal requires about 3 Mbps, and a HDTV signal requires about 16Mbps.  However, with MPEG-4 compression, an SDTV signal requires 1.5 Mbps and an HDTV signal requires about 8 Mbps.

What is the role of a set top box (STB) in an IPTV network?
An IP set-top box sits in the house and acts as an interface between the television set and a broadband network. It tunes to the right channel by listening to the multicast address for the channel, and decodes the signals so they can be played by a TV. It keeps a copy of the program guide or electronic program guide (EPG). It handles content protection using digital rights management (DRM). Set-top boxes also come with a browser interface for Web browsing and connectivity to external services provided by the service provider or partners. It provides home networking to connect to other devices like PCs or tablets in the house, and allows the playback and rendering of content stored on the PC (photos, music, and personal videos).

What features are usually provided with IPTV services?
Services like Video on Demand, Digital Video Recording (DVR), Time Shift television, games, interactive television like voting, and purchases from the TV can be provided with IPTV. The key difference between this and regular TV is the interactivity, which is possible because there is an uplink path from the user to the TV headend, which is different from satellite services with a one way path only from the headend to the user.

What is Time Shift Television?
Live TV programs are made available for viewing later by recording a day’s or weeks’ worth of programs either remotely or on a hard disk available on the set top box. These programs can be watched any time rather than only at the scheduled program time. This also allows ads to be skipped while viewing.

What is Digital Video Recording?
Live TV programs are made available for viewing later by recording a day’s or weeks’ worth of programs either remotely or on a hard disk available on the set top box. These programs can be watched any time rather than only at the scheduled program time. This also allows ads to be skipped while viewing.

How is Video on Demand different from Pay per View Services available with Cable and DTH services?
To offer Pay per View Services, a few fixed movies are made available for a period of time and ordered using an out of band message like an SMS. “Out of band” means, that a different medium from the one being used for television is used for communication with the service provider. Some service providers offer set top boxes with hard disk capacity built in, and transfer a collection of movies to the set top box, which can be viewed on purchase. In this case the choice of movies is limited by the capacity of the hard disk. True Video on Demand involves a big collection of movies that sit on the remote server, and that can be accessed from the customer premises whenever needed.

What is the difference between MPEG-2 and MPEG-4?
MPEG-2 was the original standard compression technique used for digital TV. MPEG-4 (also known as AVC) was introduced for low or variable bit rate mediums like mobile or internet, and various devices like mobile, PC and TV.[1] Demand for High Definition (HD) videos and larger screens made MPEG-4 attractive for the TV medium as well. MPEG-4 provides much higher compression ratios than MPEG-2, and better error protection for unreliable mediums of transport.[2]

Is IPTV service possible over cable?
Yes, IPTV over cable is achieved using the DOCSIS 3.0 specs for Cable, this is described in the module on Cable TV.


[1].http://bit.ly/RcJs47
[2].http://bit.ly/RcJxEN

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