You might have heard some things about HD, that is cleaner, clearer, easier to understand, etc., but just what’s all the fuss about this HD phone stuff? And just what is HD, anyhow?
There are a lot of questions surrounding HD, and the short answer is, HD is defining high quality audio and deliver that high quality audio to a user. We put together this article to cover the basics about HD, to help you better understand the distinction in quality.
Let’s start with defining High Definition Audio.
What is High Definition Audio?
High Definition Audio, also known as HD Audio, by its proper name Intel® High Definition Audio or its code name, Azalia, is an audio standard for high quality on-board audio first released by Intel in 2004, superseding the AC’97 Specification. The HD Audio standard details a list of specifications necessary to qualify a device as an HD Audio product.
Want to see what the High Definition Audio Specification (HD Audio) standard looks like? Take a look at the “High Definition Audio Specification” document on the Intel website.
So these specification documents get written, defining the standards for HD. But then what? Well, someone has to create a device that meets the specifications. This device could be a piece of hardware or software. A good example of this is the Audio Codec.
What is a Codec?
The word codec is a portmanteau of “compressor-decompressor” or, more commonly, “coder-decoder.” An Audio Codec is a device or computer program capable of encoding and/or decoding an audio digital data stream or signal.
While we can easily get deeper into discussions about codecs – they are a bit of a complicated topic to cover – all we really need to understand is that a codec is a kind of translator that compresses that audio data down into something that stores or transfers well.
If you want to learn more details about codecs and how they work, take a look a this video by LabRatsTV.
So what are some of the codec’s out there that are used, and are there differences between them if they are using similar or identical sets of standards to build them? Well, there’s a long list of codecs and it would take a small book to identify, define and compare the differences between the advantages of one versus another, so let’s stick to two codecs that will clearly illustrate a difference in audio quality.
What is the difference?
Let’s start with the G.711 codec. The G.711′s been around a while, and has become a standard addition to a lot of devices. From Wikipedia,
The G.711 is an ITU-T standard for audio companding. It is primarily used in telephony. The standard was released for usage in 1972. Its formal name is Pulse code modulation (PCM) of voice frequencies.
The G.722 codec is a ITU-T standard 7 kHz wideband speech codec operating at 48, 56 and 64 kbit/s. It was approved by ITU-T in November 1988. Technology of the codec is based on sub-band ADPCM (SB-ADPCM).
For those of you unfamiliar with G.722 it is becoming quite the popular codec to use over G.711 when bandwidth is not an issue. The G.722 codec offers significant improvement in speech quality as the bit rate is higher and there is less compression involved.
It’s one thing to read about the difference between the audio quality, but it’s another to hear the difference yourself, while you might not be able to hear the crisp and clear audio quality of the G.722 codec (HD Audio) though your computer speakers, the difference is readily apparent. Take a listen to the comparison in the video below.
And that about sums up our primer on HD, a technology already deployed and is available with our customers. Have questions? Contact us.
