What is DVB ASI Asynchronous Serial Interface

dvb asi asynchronous serial interfaxce


If you are a headend engineer then probability you have gone threw ASI signal. Initially some MSOs were using ASI digital headends but later on they have converted their headends in IP Headend.

We have seen some digital headend devices like encoders provide the ASI Signal output. So in this article we will get to know in detail what is ASI Signal and DVB ASI Signal Data Rates.

What Is ASI

ASI stands for Asynchronous Serial Interface. ASI is Transport Stream mechanism or protocol which used in headends and satellite broadcast etc. It is encapsulation method used to encapsulate the  Transport Stream which developed by MPEG encoders into a 270 Mbps signal. This 270 Mbps data rate is very high so it can support many different transport stream applications. It is compatible with SD and HD-SDI signal routing and distribution.

In Other Words,

ASI is data format of streaming which carries MPEG Transport Stream. So ASI signal can carry multiple SD ,  HD programs. Thus ASI signal is final output after the video compression. This compression can be MPEG 2 or MPEG4.

There are two types of transmission format used by the ASI signal,

188 byte

204 byte

188 byte transmission is common ASI TS. while if we implement the Reed Solomon Error Correction data then packet size extend to 204 bytes.

ASI signal is carried in 75 Ohm coaxial cable. BNC connectors are used both ends of the cable. Transmission of ASI data can be wireless or fiber link.

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As shown above in the figure ATSC broadcast have the payload of 19.3 Mbps. While ADV ASI have payload of maximum 213 Mbps which is more than ATSC broadcast. Also stream bitrate of ASI is 270 Mbps.

ASI can carry more data than ATSC. Because as shown above in the figure each packet is transmitted in short gap. be gaining of each packet is same at the time as it would have been in original content. The gaps between packets are filled by the comma characters.

North america uses ATSC broadcast.

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DVB (Digital Video Broadcasting) ASI signal can pass through routing. It can also transmitted threw the microwave transmitters.


ASI signal is a protocol how Transport Stream are transmitting. There is a gap between two packets known as coma characters.

If a encoder is giving ASI signal output then this encoder can be MPEG 2 or MPEG  4 encoder because ASI signal is final product output after video compression.

This is all about DVB ASI.

Know More About  What Is SDI Signal

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  1. kamal says:

    thank you sir


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