To understand how VoIP works, you will be taken through the process of voice transmission from one end to the other. The process starts with a person talking into the mouthpiece on one end of a VoIP call.
This analog voice signal must first be sampled and digitized. Voice sampling is usually done 8,000 times per second (8KHz). In order to reduce bandwidth, a voice CODEC is used.
A voice CODEC is a compression/decompression algorithm that is optimized for the voice frequency range. The bit stream uncompressed is 64Kbps. By using an available CODEC, the bit stream can be reduced to 8Kbps or less.
In order for the compressed voice data to be sent over the Internet, it must go through a process called packetization. This is a packet consisting of a small sample of the voice data (usually 10-30 milliseconds).
While being routed through the Internet, these packets can get delayed or even lost. This can cause degradation in voice quality. Simply put, there are various mechanisms in place to compensate for these problems and help smooth out the audio.
Once all the packets arrive on the listening end of the call, they must be reassembled to their original state. The packets are decompressed and converted from a digital to analog voice signal.
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