In 1995 the only compressed audio format for public use on the web was MP3, and sharing full bandwidth music files over dial-up connections was completely out of the question. Today there is a bewildering array of formats, but with broadband at only 50% of the online population (summer 2005) and MP3 still the most common download format things aren’t a lot different.
Broadband will make bigger files and lossless encoding increasingly feasible, and new high-compression formats like Ogg Vorbis and MP4 (Advanced Audio Coding, AAC) have a number of advantages, but they’re not for universal use just yet.
MP3 is still the best way to put music on your web site. Proprietary formats like Flash, Real Audio, Quicktime (QT) and even Windows Media Audio (WMA) have a smaller audience. Most PCs, Macs and other systems (e.g. Linux) can play MP3s and they’re as small you can get with today’s compression—about 10% of the equivalent CD file size. The downside of MP3 is sound quality but if you want to be heard by the largest audience it’s the only choice for broadcasting from your site. I wouldn’t sell MP3 because AAC, WMA and Ogg are just as easy to make and sound much better.
MP3 isn’t an open standard and the owners could charge for it in some way. But I group it with “more open” formats for now.
Ogg FLAC and Vorbis are proper open standards. FLAC is a lossless codec and compresses a CD to about half the original size. Vorbis is a lossy codec and compresses to around 10% like MP3 but sounds better. There is no danger of Ogg being limited by its owners and it is increasingly popular but still less common than MP3.
Open Media Commons initiative is sponsored by Sun and aimed at creating an open-source, royalty-free digital-rights management standard.
Full bandwidth music files from unprotected CDs play on most jukebox software and are feasible but lengthy downloads on fast broadband. They are easily stored in open WAV or AIFF format.
Proprietary formats include Real, Apple AAC, Sony ATRAC, and Windows Media with various DRM options. Some of these are licensed (Windows, Sony) others aren’t (Apple). All have a limited audience and most are only available through particular players. Download aggregators help to reduce this complexity for content providers, and it is possible to offer these formats without encoding them all yourself.
Multimedia formats including Apple Quicktime, MS Windows Media, Macromedia Flash or Shockwave. These formats use more expensive authoring software and have a smaller audience.
MiniDisc (discontinued in mid-2007) was a consumer format controlled by Sony which used compression called ATRAC. It had built-in copy-protection (SDMI) and interface limitations to prevent sharing ATRAC files. The OpenMG jukebox and EMB Internet connection used by NetMD were also designed to lock-down content, even on domestic recordings.
Real Audio is a RealNetworks proprietary file format compressed using a system called CELP. Basic Real encoders and players are available free. Media files are compressed by matching slices of data against a library of waveforms and replacing them with codes. These codes are turned back into media data by looking up the same library in the player. CELP is also used in mobile phones. Real player advertising and registration are quite intrusive for users and a significant section of the online community simply won’t install it.
RealNetworks products and web sites use and play a number of other codecs beside Real Audio, including WMA and AAC (not the Apple flavour).
WeedShare, PassAlong and others of this type wrap audio files in cascading DRM that pays content owners and users for onward sharing and sales. These are proprietary when they use WMA and require Windows (they are not cross-platform).
With CD and cassette, people became used to universal, play-anywhere media they could copy. Mainstream Internet music is still very primitive and there are many barriers to useability.
Your multi-track recorder probably has a number of file options and you might use a standard compact format such as MP3 for demos. Any format that compresses more than 50% is probably lossy. This means audio detail is lost when recordings are made and it can’t be recovered. Even when a full-size 16-bit CD is re-made from the compressed file it won’t sound the same as the original.
A problem arises when a lossy copy is compressed again. When a further copy is made using another compressed format (e.g. MP3 to MP3, or WMA to Ogg) the sound will be noticeably degraded. This is called concatenation loss and it gets worse as further compression of any kind is reapplied.
In theory a series of coding and decoding operations would be transparent but this is rarely true in practice.
So remember the history of any copies and don’t double up any type of lossy compression unless you’re prepared to lose quality. Copies made over digital connections are usually OK because the data is normally mirrored, not re-compressed.
There are numerous audio file convertors available online and they work in various different ways. All are subject to concatenation loss and can’t make true digital copies of the original.
Whatever format you choose for downloads there are three main file size issues.
The chances of anyone downloading anything much over a megabyte, unless they know what it is, are slim. In practice a fast analogue modem takes 3 – 5 minutes to download a megabyte. This will change when broadband (DSL) is more widespread in the UK. Basic broadband is about ten times faster but even then small file sizes increase your chance of getting heard.
The common MP3 bit rate is 160kbps, although some people use higher rates. You can make smaller MP3s using mono (half the size obviously) and lower bit rates. For demos, I think 64kbps mono is fine, and the file size for a three minute number (about a megabyte) is as big as you want for an ad hoc download.
If you halve the size of your download files you also halve the bandwidth your visitors might use (although they probably won’t all log on at once new releases might cause peaks, and word of mouth can cause surges from time to time).
Bandwidth exhaustion can mean:
All web hosts have some limit on bandwidth even if they say otherwise. I prefer a proper bandwidth agreement because your site is more likely to stay accessible and you’ll know if you can afford it when you get a peak.
On a site like mine MP3 files occupy well over 95% of the server space. It’s worth knowing how many downloads you can keep before you need to buy more space—the formula is quite simple. It takes about a megabyte for every minute of good quality MP3 stereo (if you use mono you can double the number of files or length of time).
| Type | Size | 1 minute | Example | |
|---|---|---|---|---|
| Uncompressed | stereo | 100% | 10 Megabytes | CD, WAV, AIFF |
| Compressed (lossless) | stereo | 50% | 5 Megabytes | FLAC, Apple Lossless |
| Compressed (lossy) | stereo | 10% | 1 Megabyte | Ogg (Vorbis), WMA, MP3, AAC |
| mono | 5% | 0.5 Megabytes | ||
| Lossy encoding at higher bit rates makes bigger files | ||||
You might find files on your host server take up more room than they do on your PC. This is because different size discs store files differently, so don’t make your calculations too tight.
I don’t think this is a real issue. It’s fairly easy to do either as long as your server supports streaming. Streaming isn’t really an option on a dial-up connection, but most players can be set-up to start playing downloads before they’re complete. The only application where streaming is necessary is radio-style programming; for individual tracks it doesn’t make much difference.
Remember to fill out the artist, title and comments (e.g. copyright, web site, email) information for your MP3 tracks, and check that your jukebox or play-list software uses the (more or less) standard ID3v2 tags.
There is a place for ISRC codes in the MPEG file specifications, and in the ID3v2.3/4 specification (TSRC) but people normally use the ID3 comment (COMM) field instead. Retailers or aggregators will tell you how they want you to tag your tracks (often in the filename itself).
Other important aspects of releasing tracks and albums are covered on the CD release page. Most of this applies to download releases too.
There’s more about using ftp and getting online in Web sites, Your web site and Search engines.
If you want to make downloads available through sites other than your own there are options in Digital distribution and Download sites.
Aggregators and download sites provide information packs telling you how to format and submit your tracks.