What is a CODEC & How Does It Apply To VoIP?

What is a CODEC & How Does It Apply To VoIP?
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The next thing we need to talk about are the Codecs, C-O-D-E-C, if you canít read that. The codecs, this is how the voice traffic is actually encoded and encapsulated. So when you are talking on the phone, your communication has to get put into little packets and sent down the network. Your codec is what determines how this happens. So if you want really high quality communication Voice over IP traffic and you have a lot of bandwidth then you will use a codec that uses a lot of bandwidth and you have high definition audio communication back and forth. But letís say youíre on a kind of crappy network, you donít have a lot of bandwidth on the network, your codec is what will determine and you can say, ìI want to use a lesser grade codec where our communication is not going to sound as good but it will use less bandwidth.î
So the main thing with codecs that you have to remember is codecs determine the quality or sound actually I should say, sound quality of the conversation. So how much static is on the line, is this high definition audio communication or is this something that sounds like youíre on a CD? That is determined by the codec you use and then also, the bandwidth that is used for the communication. So the codec determines the quality of the sound and then how much bandwidth is being used when you talk to somebody over this small business phone systems and Voice over IP (VoIP) network. So when you pick up the phone and you call Bob in the office, five offices down, how much bandwidth is that communication going to take? Is it going to take 10 kilobytes per second? Is it going to take 4 kilobytes per second? Itís all determined by the codec that you are using. So this codec is basically like I say, itís what encapsulates and it determines the sound quality and the bandwidth used.
Now most of you if you are dealing with small offices with pretty good networking gear, you donít really have to worry too much about the codec. So whatever Voice over IP server you use will have codecs built in. Some codecs are proprietary which means you have to pay money in order to use codec. But when you buy your server, you will either get a license to use that proprietary codec that is there or they will give you open source codecs to use.
So like I say, if you download Asterisk or Switchvox or sipX, they have open source codecs already built into it so you can just use those codecs for your Voice over IP communications. No problem. The only issue is of course, being open source, they are not necessarily the best codecs that you can be using. So the sound quality is probably going to be pretty good and it will be probably more than what you need but the bandwidth used is going to be more than some of the better proprietary codecs out there.
So basically whenever you pick up the phone, the sound quality will be fine but each telephone call is going to take more bandwidth than necessarily is needed. Now, if you are dealing, like I say, if you are dealing with a hundred people or a thousand people on a network, you have to worry about network congestion because if you have a thousand people on a network and 50 people are on the phone, all those little 10 kilobyte per second Voice over IP communications can start taking up a lot of bandwidth. So what you should think about is if you are dealing with large networks, is you may have to buy a proprietary codec for your Voice over IP system. Normally, they run ñ I think they are about $5 per device that will be connecting to the network.
So if you are noticing, if you switch over to a Voice over IP system and you notice your bandwidth starting to get constricted, you may think about having to change your codec. Hopefully, you can change your free open source version but if that is still using too much bandwidth, you can change to proprietary codec. Again, you will probably pay about $5 per phone or per device that will be connecting but you can normally get really high quality communications down to about 4.5 kilobytes per second I think is what the good ones used. So basically, these proprietary codecs will give you high quality sound with lower bandwidth. So thatís the codecs. Again, codecs, this is what encapsulates and decides the sound quality and the bandwidth usage of your Voice over IP traffic.
So weíve talked about the protocols now and weíve talked about the codecs. The final thing that we need to talk about is a network latency and QoS or quality of service. Now, both of these things Iíve talked a lot about in other classes so Iím going to run through them here just because if you are showing up in the beginning of this will give you the information but we talk about this much more in many of our other networking classes.
Why Quality of Service (QoS) Matters
So the first thing Iíll just run through really quick is quality of service. Again, weíve talked about this a lot. But what this is used for is since you are now using your network not only for computer communications but also for telephone, for Voice over IP communications. You have to be careful that your computers donít use all your network bandwidth because if your computers start using all your network bandwidth, you have no bandwidth left for your telephone system.
So if one of the dingbats in accounting decides that they are going to download BitTorrent files, they are going to download pirated movies and they start using all the bandwidth on the network, well then when you go to make a phone call, you are not going to be able to make a phone or the quality will be very, very, very poor because all the bandwidth is being used by that idiot in accounting to download BitTorrent files. Again, once you start ñ you have a larger and larger company, your percentage or whatever numbers, you get more and more idiots. So when you have a 50-person company, you probably have one or two idiots. When you have a 100-person company, you have 5 idiots. When you have 1000-person company, you hope you only have 50 idiots. I mean thatís kind of how it goes.

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