Frame synchronization: Difference between revisions

Revision as of 02:14, 14 April 2012

Revision as of 05:35, 5 May 2012

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While receiving a stream of [[data frame|framed]] [[data]], '''frame synchronization''' or '''framing''' is the process by which incoming frame alignment signals (i.e., a distinctive [[bit]] sequences/a or [[syncword]]s), are identified (i.e.that is, distinguished from data bits), permitting the data bits within the frame to be extracted for decoding or retransmission. This is sometimes referred to as ''framing''.

== Framing ==

If the transmission is temporarily interrupted, or a [[bit slip]] event occurs, the receiver must re-synchronize.

[[Image:Frame Synced Stream.jpg|frame|none|Frame synchronized PCM stream — telemetry application]]

The transmitter and the receiver must agree ahead of time on which frame synchronization scheme they will use.

The most commonCommon frame synchronization schemes are:

;Framing bit: A common practice in [[telecommunication]]s, for example in [[T-carrier]], is to insert, in a dedicated [[time slot]] within the frame, a noninformation bit or '''framing bit''' that is used for [[synchronization]] of the incoming data with the receiver. In a [[bit stream]], framing bits indicate the beginning or end of a frame. They occur at specified positions in the frame, do not carry information, and are usually repetitive.

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===Television===

{{further|Time base corrector}}

A '''frame synchronizer''' is a device used in [[live television]] [[television production|production]] to match the timing of an incoming [[video]] source to the timing of an existing video system. They are often used to "time in" consumer video equipment to a professional system but can be used to stabilize any video. The frame synchronizer essentially takes a picture of each [[Film frame|frame]] of incoming video and then immediately outputs it with the correct synchronization signals to match an existing video system. A [[genlock]] signal is required to provide a means for video synchronizing with the house reference.

===Telemetry===

[[Image:PCM Stream.jpg|frame|none|PCM Stream prior to frame synchronization]]

In [[telemetry]] applications, a ''frame synchronizer'' is used to frame align a serial pulse code modulated ([[PCM]]) binary stream.

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==See also==

* [[Asynchronous start-stop]]

* [[Phase synchronization]]

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==References==

{{FS1037C MS188}}

===Scientific articles===

* J. L. Massey. "Optimum frame synchronization ". IEEE trans. comm., com-20(2):115-119, April 1972.

* R Scholtz. "Frame synchronization techniques", IEEE Transactions on Communications, 1980.

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==External links==

* [http://www.ulyssix.com Telemetry Ground Station Processing Electronics telemetry link]

* [http://www.algolith.com/products/broadcast/frame-synchronization/index.html Algolith Frame Synchronizer Solutions]