What Is SDV Or Switched Digital Video For Digital Headend Or CATV

sdv switched digital video


Cable Tv companies are having large bandwidth available to deliver the different services. These services are Cable Tv Service, Internet service , Video On Demand , Radio Services and Digital Phone Service. Cable Tv companies stream all the digital video channels into the different digital streams and sends these streams into the field.  While SDV have its different mechanism of broadcasting videos to the customer end.

What Is SDV

SDV stands for Switched Digital Video. As discussed above a Digital Headend stream all the tv services into the different streams and then transmit the signal in the field. It means that it is transmitting all the tv services simultaneously in the field using Optical Fiber Cable and Coaxial cable. Again it means that it is consuming the bandwidth of all channels weather subscribers are viewing all channels or not.

In other words we need to transmit all the tv services to each and every Subscriber even he watch it not. So it consume more bandwidth. There is wastage of bandwidth for the channels that are not watched by subscribers.

Thus SDV is a service which delivers the requested channels by the subscribers. In this manner SDV also save the bandwidth of cable tv.


To understand the working of Switched Digital Video we have figure mentioned below,

sdv system Switched Digital Video

As shown above in the figure a request for a particular channel is made by the subscriber by using the STB or Set Top Box. This request goes into the SDV Server. The SDV Server then send the request to view a particular channel to the EDGE Resource Manager. Then ERM stablish a communication with the EDGE QAM. Then ERM asks for the frequency of the request channel to EDGE QAM. Then ERM gets the tuning parameter for the requested channel from the EDGE QAM.

ERM then sends this tuning parameter to the SDV Server. Now this Switched Digital Video Server sends the parameter to the STB. These parameter are tuned by the STB. This enables the STB to show the request channel to the subscriber.

Note that in this case we need EDGE QAM not QAM. Because QAM supports VOD not to the Switched Digital Video streams. While EDGE QAM supports both VOD and SDV. VOD stands for Video On Demand.

Know more about Difference Between QAM And EDGE QAM.

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In other words there is a tuning software installed in the STB. Whenever a subscriber makes a request for SDV channel then STB upstream the request by using this tuning software. This request goes to the SDV session manager. A pool is allocated for tuning the channels on different frequencies. After tuning the request channel on a particular frequency these tuning parameters are sent to the STB. There may be other subscribers are already viewing the same SDV channel. Then already tuned parameters are sent to the new subscriber to view this channel.

SDV software is used to manage and monitor the Switched Digital Video system. The reports are generated by this SDV software. It shows the health of SDV system. In case if the QAM signal is failed then SDV software also shows the alarm for EDGE QAM too.

There are various number of companies which provides the SDV software like Motorola and Cisco.

Benefits Of Switched Digital Video

It consume less bandwidth near about 50 to 75 % rather than tradition broadcast system. So we can provide more HD channels to subscribers

It deliver the content requested by subscriber in the real time.

We can also monitor the channel programming.

We can deliver good format to our subscribers.

It boosts the relevant ad insertion program.

The channels are increased in numbers by using this.

We can provide most interesting content.


Switched Digital Video is a channel service which works on request of the subscribers. If no one is viewing the particular SDV channel then it goes down to save the bandwidth of the system. It enable us to provide the interesting content to the subscriber on best quality. Instead of QAM a EDGE QAM is essential for the implementation of SDV system. SDV software provide us facility to manage and monitor the SDV system.

Know More About  ECM EMM for Digital Headend

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  1. krishnakant says:

    Dear sir,

    Thank you for posting this valuable article , i have few questions to ask regarding the end bandwidth.

    1. if we can save around 50% bandwidth , we can save the half bandwidth while sending it to an LCO right?
    2. how it can save our bandwidth cost when we will send the signal over carrier to the LCo.
    3. will this be a good option?

    1. Dear Krishankant thanks for your valuable comment.
      We are having a Headend INFO Whatsapp group of experts where we share these technical discussion be part of that group.
      To join it send your whatsapp request at +91 8239222444


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