| An uncompressed digital music file (such as that on a | | | | terms of efficiency and file size reductions. WMA |
| music CD) uses 10MB or more per minute (at least | | | | supports DRM, so can have both protected and |
| 30MB for a 3 minute song). | | | | unprotected audio files. Most devices and players |
| These files have to be compressed to the more usual | | | | support the unprotected WMA files - Apple iTunes |
| levels of 3-5MB per song. Compression rearranges the | | | | software can convert them to AAC files. |
| sequence of numbers, sometimes throwing away less | | | | Ogg Vorbis |
| significant information, in order to reduce the file size. | | | | Unlike the other formats, Ogg Vorbis is a completely |
| The way the compression is achieved leads to the | | | | open-source, patent-free, professional audio encoding |
| many different audio file formats available. Below is a | | | | and streaming format. There are no licensing fees for |
| list of the popular formats used by MP3 players. | | | | using this codec. If you are an artist that's goods news. |
| MP3 (MPEG Layer 3) | | | | You won't have to pay any fees if you distribute your |
| MP3 is a perceptual audio coding algorithm, developed | | | | songs, which you would if you use, say, MP3. It is yet |
| by the MPEG group. Although its a lossy compression, | | | | another lossy compression, but much better than MP3. |
| the digital audio sounds exactly as, or very close to, | | | | An Ogg Vorbis audio file encoded at 110Kbps gives a |
| the original sound. The algorithm attempts to adapt the | | | | smaller size and sounds better than an MP3 file |
| compression to the characteristics of the human | | | | encoded at 128Kbps. 160Kbps gives |
| perception of sound. This compression algorithm can | | | | very-near-CD-quality audio encoding. Although it's |
| handle both constant and variable bit rate | | | | open-source, this codec compares very favourably to |
| compressions. For good quality music, a bit rate of at | | | | WMA, AAC, WMA Pro etc (see Wikipedia for more |
| least 192Kbps is recommended - this is near CD | | | | on this). This format is rising in popularity due to its |
| quality. 256Kbps per second is better. There is very | | | | open-source nature and freedom from licensing issues. |
| little quality difference between 256Kbps and 320Kbps, | | | | MIDI(Musical Instrument Digital Interface) |
| but the later will have a larger file size. MP3 files have | | | | MIDI is one of the old formats, but still very much in use |
| no Digital Rights Management (DRM) technology built in | | | | today. Its not really a compression algorithm, but a |
| - meaning they are freely portable. That's not to say its | | | | synthesized music format. MIDI files consist of lists of |
| legal to move music files from one device to another. | | | | commands which tell a synthesizer when to start/stop |
| AAC (Advanced Audio Coding) | | | | playing a specific note of a specific instrument, and |
| A newer, lossy audio compression format developed | | | | may include the volume and modulation of the note. |
| by the same MPEG group. AAC is more efficient than | | | | With MIDI you can play a number of instruments at |
| the popular MP3 format, and requires less processing | | | | once, or just play one instrument at a time. These files |
| power to decode. Its also not backward compatible | | | | are generally tiny compared to normal audio files such |
| with MP3. AAC-compressed audio at 96 Kbps | | | | as MP3, WMA, AAC. Because this is synthesized |
| generally exceeds the quality of MP3-compressed | | | | music, its quality greatly depends on the quality of the |
| audio at 128 Kbps. AAC supports DRM, but you can | | | | synthesizer on your PC's sound card or the quality of |
| have both protected or unprotected formats. The | | | | the synthesized instruments in your software. One |
| unprotected format is freely portable, while the | | | | application for MIDI files is as mobile phone ring tones. |
| protected format is locked by the DRM used. Apple | | | | RealAudio (RM/RAM) |
| uses the AAC format for its iTunes and in QuickTime. | | | | This format from RealNetworks was at the fore-front |
| Audio compressed at 128Kbps using AAC sounds | | | | of internet audio formats for many years. This format |
| very close to the original sound, which means a smaller | | | | is usually streamed, rather than downloaded. It can be |
| file size for the same audio quality compared to the | | | | played using the RealPlayer or RealOne software. A |
| MP3 format. The file will be about 75% of the size an | | | | good number of internet radio stations still use this |
| MP3 compression would produce. | | | | format for their broadcasts. The audio can be |
| WMA (Windows Media Audio) | | | | streamed at different bit rates to satisfy bandwidth |
| WMA is another lossy compression format, developed | | | | constraints. If you are on a dial-up internet connection, |
| and owned by Microsoft, and used in Windows Media | | | | the music quality you get is lower than if you are on |
| Player for DRM management. This compression is | | | | broadband. |
| more efficient than MP3, and comparable to AAC in | | | | |