Silence compression

  "it provides an excellent way to remove Redundancy(or more aptly Recurrence).For efficient communication across network silence compression is preferred."

It allows transmission bandwidth to be reduced to a significantly silence period.

Silence compression provides a way to squeeze redundancy out of sound files. The silence compression scheme is essential for efficient voice communication systems. It allows significant reduction of transmission bandwidth during a period of silence.

A silence compression scheme include a voice activity detection (VAD), a silence insertion descriptor (SID) and a comfort noise generator (CNG) module.

              Silence compressor=VAD = SID + CNG 

Parameters used for silence compression

• Threshold value
• The way to encode silence
• Threshold for recognizing start of silence
• An indication of when silence is over
• A parameter to get a threshold, which means that there is no silence until or unless there is three silence in the rows.

Voice activity detection(VAD):

       * It is also known as speech activity detection or speech detection.
       * It is technique that is used in Speech Recognition and detection of human voice.
       * The main Use of VAD is in speech coding and speech matching.
       * It can be used for speech processing and deactivating some processes during non-speech section of an audio hearing.
       * It can avoid unnecessary coding/transmission of silence on VOIP services.
       * It saves on computation and network bandwidth.

Comfort noise (or comfort tone):

       * It is synthetically submissive background noise.
       * it is used in radio and wireless communications to fill the artificial silence.
       * The result of receiving total silence, especially for a prolonged period,has a number of unwanted effects on the listener, including the 
         following:
       * it may be believed that transmission has been lost, and therefore hang up prematurely.
       * The speech may not be endurable and difficult to understand.       

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