What Is VOD Or Video On Demand For Cable Tv Services

vod video on demand


Base of cable tv was to deliver TV services to their subscribers. But as we all know technology is growing day by day then there is need for cable tv headends to update their services time to time. Earlier cable tv were using Analog Headend but now it have upgraded to Digital Headend.

As Cable Tv industry is growing subscribers are feeling more comfortable. Earlier subscriber need to watch the TV serials and movies on the broadcaster scheduled time. But as this cable tv industry is growing now subscriber do not need to sit in front of tv in the scheduled time. Subscribers now can watch their serials when they want to watch.

Thus except delivering TV services cable tv also provides services like,

Radio Sevice

Internet Service





Let us have a look on what is VOD or VOD meaning.

What Is VOD

VOD is abbreviated for Video On Demand. It is one of the most interesting services provided by the cable tv. As its name indicate that it provides the video to the subscriber on his demand. There is list of programs available in the Set Top Box which subscriber can read in the VOD section.

The subscriber needs to select the particular movie or show from this list. Then request for this goes to the VOD server and then server deliver it to the subscriber end. This is expensive service. Because in the VOD content manager we need to store more and more data to fulfill the subscriber request. Also it requires high data transfer rate.

What Is SDV Switched Digital Video

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Working Of VOD And Architecture

To understand the VOD architecture and VOD Working we need to see the cache miss and cache hit figure below. So there are two types of situations to understand it.

(1) Cache Miss Situation

As shown below in the figure there are 5 peers. When a request is made from peer 1 then this request goes into the Index Server. The Index server then analyse the request. So after analyzing this request Index Server found that this requested program is not available in already available peers or in his cache memory. Then Index Server send this request to the Central Video Server as show in 2 number path. So this is two way communication between Central Video Server and Index Server.

cache miss for VOD

This communication is done by the medium of Optical Fiber. Then this Central Video Server sends the request program to the Index Server. Now Index Server forward this program to request peer or subscriber mentioned in 3 number path.

Now if Index server found that this program is requesting many times with the different peers. Then according to the algorithm Index Server store this program into the cache memory.  So that it can fetch again to provide better processing.

We called this cache miss situation because Index Server did not found requested program into cache memory.

(2) Cache Hit Situation

In this situation when a subscriber request for a particular program. Then this request goes into the Index Server as mentioned in 1. Now this Index server analyse this request. After analyzing Index Server found that this program is already running in different peer.

cache hit for vod

Then it sends the request to the peer which already running this program as mentioned number 2 path. In this request the index server request the peer to broadcast the program to the requested peer as mentioned in number 3 path. Now this peer is broadcasting the program for the first peer as shown in the figure.

We called it cache hit situation because requested content was found in the Index server cache.

Requirements For Video On Demand

There are basically two types of requirements for VOD system implementation

(1) Bi directional Amplifiers

After implementation of VOD server there is requirement for both side communication means sending and receiving data. Co axial is the medium threw which these signal will go from one place to another place. We use amplifier to boot the signal to send long distance. These amplifiers should be bi directional because amplifiers need to send and receive the multimedia data.

(2) STB capability

For peer to peer communication there is requirement of STB which supports this. Means stb can send and receive the data. It costs high.


Video On Demand meaning is that subscriber can select what and when he needs to watch. He needs not to depend on broadcaster’s scheduled programs. VOD is expensive and interesting service. VOD content manager needs to store large variety of content to fulfill the requirement of subscribers. To provide large collection of movies we needs to have licencing from companies.

VOD supports peer to peer communication method. For Video On Demand we need to have high data transmission rate so that subscriber can easily do forward , rewind , pause and play.

Know More About   SDV Or Switched Digital Video

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