A quick guide to audio codecs

What is it?
Standing for, COder / DECoder, although it's the second part of the word that most people are more familiar with, it's the part an MP3 player, iPod, mobile phone or computer handles whilst playing file-based music.

Without going really technical and just giving the basics, the COder part of codec is used to initially transform the large audio files from a normal music CD into much smaller files by compressing it. Whereas the DECoder part of codec, uncompresses the compressed file for playback and to be heard.

There's a lot more involved within this of course, but for the purposes of this piece we won't go into too much scary detail with the heavy maths and science behind it. However, we will be addressing the different codecs used, which are all best to think of as file types, like a .doc file or a .pdf file. As the most frequent ones used are just that, a file type, with the likes of MP3, as an example, one of the most popular ones used today.

What are the variations of the technology?
There are two main camps the file formats fall under, lossy and lossless. Both are chiefly used to compress these rather big audio files making up a CD, into ones that fit nicely on to portable media players.

Lossless is a tad more advanced and not really in common place usage as yet, but lossy is around everywhere and more likely than not you've used it in the past. Lossy, as the word hints uses a compression method where some of the quality can be lost in the process. This is the trade off which comes from reducing in size the initial large audio track. Within these means of encoding there are also a few levels or bitrates used to improve the quality and marginally increase the size along the way.

Lossy is probably misleading as a term, as it indicates a lot of information has been lost. This isn't so you'd notice, as the hardware or the software used for playback of the audio compensates in certain ways. To the normal ear, the difference isn't noticeable from playing a CD on a Hi-Fi, to the same codec based file version on a portable device.

iTunes uses a Lossy format, seen in their.AAC files or its more formal title, Advanced Audio Coding. The MP3 file format uses the same compression methodology. Depending on the way you obtain music, you'll have possibly come across one or the other by now.

There are other file formats around that you may have heard of. The likes of a WAVE file or .WAV format is also a well known one. This is more or less an uncompressed file taking up vast amounts of space. In fact, it's the closest size to the actual one taken up by a single track on the CD. It's not really used or preferred anymore, so we'll talk about the more common placed ones you'll easily recognise.

Recently in the news there has been the subject of Apples iTunes store going DRM-free, where some have wrongly associated DRM as an actual codec or file format. Instead, DRM or Digital Rights Management is a way of licensing the music solely for certain computers and devices. This locks down the music and prevents any illicit sharing of those files to others, without any additional payment being received. With the iTunes dropping DRM as a way of regulating their music distribution it allows many computers to use those files, with various different devices taken into consideration.

Why should I care?
Size does matter, it boils down to just that. We can tell you this, most of those codecs used bring down the initial size of those massive CD tracks by up to 58% and there's a reason for that.

If you've ever bought or used a blank CD to burn data, you'll realise it can hold up to 700MB of data. This doesn't bode well for portable MP3 players or even iPods and their storage space.

With the average flash-based portable music player being around the 2GB mark, you really aren't getting a great choice of music with not even three albums being able to fully fit on a device. Hence the reason codecs exist and are used for reducing in size the audio from those CDs, down to a marginal amount for the likes of an iPod.

700MB CDs are the worst case scenarios and are normally used for those compilation albums with lots of tracks, with the average size of the other version being at the 650MB capacity mark. Even then, not all the space is used on a CD, just for your information.

What's a good example in practice?
It's best to highlight the popular usage behind codecs by an example, with the most obvious one being that of reducing the audio files from a CD into MP3 files.

A music CD that comes out as 454MB in size, with a running time of 45 minutes can be brought down to just 41MB in total size. This is with a level of audio quality that's almost the same as CD, with a 128Kbps bitrate count.

This goes some way to showing the true benefits of the MP3 codec and the reason for its wide usage today. With a standard 2GB flash MP3 player being able to hold 48 albums, it's a far cry from just 3, you'll undoubtedly agree.

Is there a competing technology that I should be aware of?
There isn't another technology competing in the same realm as such, other than the more advanced codec formats we'll mention later.

Although you could consider the "streaming audio" codecs and their formats as an alternative, whereas the ones we've spoken about here are primarily used as static sources for music. That's a subject for another time, but it's worth taking note it could be seen as an alternative.

What is in store for the future?
Lossless is the next step up from the lossy codecs, as these do not lose any of the quality whilst encoding. The file size here is much higher, with an average 2:1 ratio being used, where the average lossy is a reduction by a 10th.

These could be considered to be for the real music connoisseurs at this stage, in saying that the quality can be heard over lossy formats. It's almost the step up from FM to digital radio in the way it comes across, on good playback equipment.

There are several reasons for the technology being held back, the main one being the adoption of these codecs with names like FLAC and APE, by device manufactures. There are more and more companies addressing and including these formats, but hardly enough.

Also, as compared to MP3 files the size is quite vast and therefore the amount stored will be less on portable music players. With the size of storage ever increasing on these devices, the link with that and the adoption of this codec could be heavily tied in together.