Copying, downloading and storing music in digital form enables you to listen to it direct from a PC, transfer it to a portable player or burn it to a CD. But which file format should you choose?
This topic is strewn with jargon about compression, codecs and bit rates. Here, we explain why the choice of file format is important, and the benefits and limitations of specific formats.
File formats
A file format is simply a method of organising data for storage and retrieval.
Each type of information has its own range of formats, which dictate the types
of application that can open and read or edit the information.
Some formats are universal, meaning almost any PC program can read them. Others are designed to restrict how the information in the file – music, for our purposes – can be played and shared.
Formats are indicated by a suffix – a full stop followed by three letters (usually an abbreviation of the format name). Each format also usually has its own icon, giving a graphic clue.
The quality of audio depends on the amount of information recorded in digital format for each second of music. This is known as the bit rate: the more bits, the greater the quality. Programs offer a range of bit rates when converting music to a digital format.
The key differences in the common file formats concern how much storage space they require, which music software and portable music players can play them and whether or not the music can be copied.
The most common format is mp3. An mp3 file is compressed, so it only takes a fraction of the space that an uncompressed song would require. It is very easy to copy an mp3, which has made it popular among people who share music online.
The aim of compression technology in most audio file formats is to reduce the information in the file (to about 1MB per minute in mp3’s case) to save space. A few songs uncompressed won’t trouble your hard disk, but a full library could be huge. Reducing file sizes also makes sense if you want to transfer music to a portable player or download it from an online music store.
Compress to impress
Most compression methods remove elements of sound that won’t be missed, such as
tones beyond human hearing. The manner by which each format does this differs,
and isn’t important for our purposes. However, many popular compressed formats
are called ‘lossy’ because some quality is lost when the file is converted. Some
types of sound file use lossless compression, resulting in better-quality,
larger files.
You can play mp3 files in just about any music software or portable player, including many mobile phones. The format also carries something called an ID3 tag, which carries the song title, artist details and other information that users can edit very simply. This makes it easy to organise music. Some hi-fis’ CD players can play mp3 files direct from a disc.
Many other audio formats share some of mp3’s characteristics – they are compressed, can be recorded at varying quality levels and attach song information that can be edited. They differ in the players (software and portable) they can be played on and how they can be copied.
