Some years ago, the compression of sound files was revolutionised by mp3. Since then, the world of the web has changed a lot, because now it is possible to download music with good quality and yet small file sizes.

The key to the success of mp3 is its ability to reduce the size of uncompressed CD-Quality sound files to about a tenth of their original size - almost without an audible loss of quality.

Almost.

Hearing tests have shown that, in some cases even at high bitrates¹, many people hear a difference between the encoded mp3 and the original file. This is where Ogg Vorbis comes in.

Ogg Vorbis is another lossy² audio compression format. And, yes, it sounds better than mp3. In most cases, that is. There are a few known samples where Vorbis has quality problems while mp3 at the same bitrate sounds fine. These are exceptions, though, and mp3 has similar problems with other samples.

Ogg Vorbis at a bitrate of 80 kbps usually has about the same quality as mp3 at 128 kbps, and listening tests comparing Vorbis and mp3 at similar bitrates are almost always won by Vorbis³.

While mp3 is usually encoded with constant bitrates⁴, Ogg Vorbis uses variable bitrates by default, where the quality stays constant.

Free as a Bird

Ogg Vorbis is free as in 'free beer', because it costs nothing, but also free as in 'freedom' or 'free speech'. This means that the format specifications and the encoder/decoder source code are open to everyone, and everybody may create improved versions or similar derivates if they like. This kind of freedom ensures that the format will always be usable as long as someone is interested, because everyone with enough knowledge can port it to new platforms⁵. Mozilla is another example of free open source software.

Contrary to popular belief, however, mp3 is not free. Thomson Consumer Electronics and the German Fraunhofer Institute (which developed mp3) still hold patents to core technologies used in mp3. Thomson claims that distributing mp3 encoders/players without a license from them is illegal, at least in countries which recognise software patents (like the USA and Japan).

The free nature of Vorbis has already made it very popular with game developers who don't want to pay licenses for using mp3 in their products. Many popular games like 'Halo' and 'Doom 3' use it for their ingame sounds and music.

Really No Patent Problems?

It has been claimed by some that Vorbis uses technology patented by others, and that companies using Vorbis might run into trouble because of patent violations. In fact, an article in 'ISO Bulletin', May 2002, points out that 'it is a fact that it is virtually impossible today to develop an audio or video coding standard with reasonable performance that does not infringe on one, or more likely several, patents'. However, it seems that nobody sued the inventors of Vorbis yet, or companies using it, and some believe that all the talk about patent violations in Vorbis has been brought up by big companies in order to promote their own proprietary formats.

About the Name

Ogg is actually the name of a container format used by several codecs⁶. An Ogg file can contain several data streams at once, like video and the corresponding audio. Vorbis is the name of the actual audio compression format.

Some believe that Ogg was named after Nanny Ogg from Terry Pratchett's Discworld books. However, the true origin of the name is a tactical manoeuvre from the game 'Netrek' that used up many of the player's resources. Vorbis, on the other hand, really is named after deacon Vorbis from Pratchett's book Small Gods.

The Basic Idea Behind It

As some people may recall from school, sound is made up of waves. It is normally recorded on a computer by checking the current level of the wave many thousand times per second, and then storing the results. This is also how sound is stored on a CD. The human ear, however, measures the frequency components of the sound, and most of the information it receives is instantly rejected without even reaching the brain.

Ogg Vorbis, as most other modern audio formats, takes advantage of this and drops information about the sound that the ear would not care about anyway⁷. Then, the remaining information can be stored in a much smaller way.

For a more detailed (and complicated) description of the encoding/decoding algorithm used by Vorbis, you should read the official documentation.

Vorbis on Mobile Devices

As there are many portable mp3-players around, one could ask why hardware producers don't simply add support for Vorbis to all their new devices (there being no license fees or patent problems - it's free!). There are in fact several reasons for this: one problem is that Vorbis needs more memory than mp3 when decoding, because the frames can be bigger than frames in mp3, but also because Vorbis uses various setup values which have to be stored somewhere. This makes it more expensive to build a chip to implement the decoder in hardware, and many of the programmable DSPs used in the more expensive players either don't have enough memory or aren't fast enough.

Ogg Vorbis is also, compared to mp3, a relatively new format and is not as widespread, therefore integrating the ability to play Vorbis wouldn't catch that many customers yet.

Some of the more expensive devices support Vorbis, though, and there are already a few cheap USB-stick players that can play it.

Alternatives

Of course Ogg Vorbis is not the only better-than-mp3 format. Here are some other examples, with short descriptions:

• AAC - The official successor of mp3. It is better than Vorbis at low bitrates.
• MPC - Developed based on mp2, good at medium bitrates (~140kbps).
• MP3 Pro - A modified version of mp3, good at low bitrates (below 96kbps). It can also be used with standard mp3-players, but with slightly worse quality that a 'normal' mp3 would be.

In terms of quality, these formats play in the same league as Vorbis. Deciding on one is mainly a thing of personal preference or special requirements⁸.