VoIP (Voice Over IP) Codecs

Voice over Internet Protocol or VoIP is a revolutionary technology which takes analog audio signals and turns them into digital data which can be transmitted over the internet. It has the potential to wholly revolutionize the world's phone system. Its providers are already very successful and major carriers, such as Vonage, AT&T are in the process of setting up VoIP plans across United States. Above all, VoIP is basically very clever invention which has the future capability to replace the so called traditional phones or even cell phones because of quality and cost.

Now we talk about VoIP codecs: Codec which basically stands for Corder-Decorder functions by converting audio signals into compressed digital signals for the purpose of transmission and again into uncompressed signals to replay. This is the essence of Voice over Internet Protocol. Codecs sample the audio signals thousands times per seconds and thereby accomplish the very purpose of conversion. Example- G.711codec which samples the audio at a speed of 64000 times a second. Each tiny sample is converted into digital data and then compressed for transmission. Now after reassembling 64000 samples, pieces of missing audio become very small to the human ear, that when you listen seems like one continuous second. It depends on the codec which is being used that's what are the sampling rates like 64,000 times per second, 32,000 times per second or 8000 times per second. Out of this most commonly used codec is G.729A codec which has sampling rate of 8000 times per second.

A Codec uses advanced algorithm for the purpose of sorting, sampling, and compressing and finally packetize the data. The most prevalent algorithm is CS-ACELP algorithm in VoIP. It stands for conjugate-structure algebraic-code-excited linear prediction. It functions by organizing and streamlining the bandwidth availability. Another aspect of this is Annex-B which functions by creating the rule of transmission as it states that if no one is talking then don't send the data. This rule created so much efficiency in its greatest ways that packet switching became superior to circuit switching. The codec works by using the algorithm for converting and sorting everything out. But it fails when you don't know where to send the data. This problem is handled through the use of soft switches. These switches use a numbering system so as to route the phone call towards the area codes. Based on this numbering system anyone can be located conveniently, no matter in which corner of the world.

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