What does all this HD technical stuff mean?
As a follow up to the last post about the future of HD voice, this post touches on the more technical side of things, and hopefuilly helps clarify some of the questions that you may have if you are considering the switch to HD. A common term used is in this post is codec, which stands for coder/decoder. When a call is made via a VoIP system the speaker’s message is first coded so that it can be transmitted over an IP network. Once the message reaches its destination it is then decoded for the listener. The relevance of this is in the fact that not all HD phones transmit using the same codec, which can create a problem with compatibility, especially when using HD voice.
HD Codecs
There are a number of different wideband codecs that work with HD voice. Problems arise from the differences in bit rate, sampling rate, and equipment requirements. All of these variations in codecs can make your decision on what HD phones to use a nightmare, and in the long run they can cause compatibility issues. The ITU- standard codec and the most widely used is G.722, which operates at 48, 56, 64 Kbit/s and provides wideband audio at 7 KHz. As HD voice continues to become more prevalent, the industry will push for a single wideband codec. However until then, it’s important to do research on the type of codecs that are integrated into your HD phones.
HD Phones
There is more to HD voice than the codec. While HD compatible phones exist it is probably a better idea to go with HD capable phones. Proper design, HD speakers, and HD microphones are all necessary to get the full HD experience. Most IP phone providers have made a strong push towards HD voice quality phones.
Compatible Equipment and Connections
It’s important to ensure that all your equipment is HD ready and compatible. First, your IP PBX should be capable of reading whatever codecs your HD phone uses. While most IP PBXs recognize the standard G.722 some HD phones incorporate different codecs. If this is the case, upgrades may be in order, but a lot of the time equipment needs to be updated anyway.
Second, it’s important that your service provider can properly transmit HD voice. Any call made outside the company that has to jump on a PSTN won’t be HD quality, but by choosing the right provider calls made in office or between company branches can be guaranteed HD. The trick is to make sure that your provider offers end-to-end SIP. SIP, or session initiation protocol, checks each of the end points to see what codecs they have in common and then transmits the call in the highest possible quality. In this case, the use of different HD phones or soft phones doesn’t have too much of an effect on HD call quality.
Quick Wrap Up
So, what you should take from all this? HD voice is transmitted using a wide variety of codecs , but the most widely used is G.722. To experience true HD quality it may be necessary to buy HD phones, not just phones that are HD compatible. Also, make sure that your IP PBX is HD capable, if not it may be necessary to upgrade. Finally, a provider that offers end-to-end SIP will help guarantee HD quality in the office and between branches, but for calls made outside the office there is no guarantee of HD quality.