|Online Digital Audio|
|Home Theater Feature Articles Audio Related Articles|
|Written by Kim Wilson|
|Monday, 01 March 1999|
Streaming audio over the Internet is a reality primarily due to developers like RealNetworks and Liquid Audio. To hear such audio content (or downloaded files), digital players (plug-ins) are stored in your hard drive. In most cases, you need a dedicated player for each type of encoded file. However, in the pursuit for a less chaotic Internet, Liquid Audio provides a plug-in for their G2 player that handles Real Audio files. To make matters worse these are not the only music files that can be found. For each type of proprietary sound file, there is an exclusive player and, so, the compatibility dance continues.
Aside from this hodgepodge of incompatible formats, there is the bigger concern over the quality of available material. Not just the content itself but the actual sound reproduction. Audio files are heavily compressed, often limiting bandwidth and resolution so drastically it sounds like a transistor radio.
Unfortunately, when streaming or downloading audio through that small 56kbps (thousands of bits per second) portal we call a modem extreme data reduction becomes essential.
The Download Dilemma
Of course, data reduction is hardly a new concept. The Moving Pictures Experts Group (MPEG) has been in place for years with the express responsibility to study and approve video and audio compression algorithms. (Currently, MPEG-2 Video is used for DVD and DSS, whereas MPEG-2 Audio is the multi-channel scheme on DVDs distributed in Europe.)
Comprised of three different compression schemes, it would seem that it is MPEG-1 Audio that has found a home on the Internet. Layer I provides a 4:1 compression equating to 384kbps and was initially developed for, the now defunct, DCC (Digital Compact Cassette). Layer II achieves decent sound quality at bit rates from 256-192kbps. Layer III adds a number of advanced features to improve audio quality at low bit rates of 112 to 128kbps (12:1 compression). The frequency resolution is 18 times higher than Layer II, further reducing redundancy. However, to attain CD quality the bandwidth must exceed 15kHz.
Whether sound quality is actually lost when audio signals are so heavily compressed is still debatable. Generally speaking though, this sort of compression is far more preferable to merely reducing resolution or sampling rate as a solution for smaller, faster downloads.
The MP3 Revolution
Gaining tremendous popularity on the Internet are files encoded with the MPEG-1, Layer III compression scheme. These web-based audio files are identified with the .mp3 suffix. It's important to note these are not MPEG-3 files. In fact, there is no MPEG-3 standard.
These MP3 files provide a venue for new and undiscovered artists. The days of an Internet superstar, who isn't signed to a major label, is a definite possibility. However, beware. There is a lot of really, really bad music in the MP3 format.
To play these files, yet another dedicated player is required, though Liquid Audio's next generation player will accommodate MP3 files. Some players provide EQ settings and display the bit rate of the file. Encoders are also available for making your own MP3 files.
Hand-held portable devices such as the RIO, manufactured by Diamond Multimedia, can store and play MP3 files. The Rio has no moving parts and records on a built-in 32-MB flash memory for 1 hour of continuous music. Additional cards can be purchased for archiving files.
The real concern about MP3 files and, online music in general, are the usual issues over intellectual property. MP3 samples can be obtained from several online sources, the easiest to remember being MP3.com. They claim to offer tens of thousands of free and legal MP3 files. This would mean that all uploaded samples are there with the express permission of the original copyright holder. Of course, that seems rather implausible.
As sound quality and download times improve through radical compression techniques, music archive sites are bound to continue gaining popularity. Many sites are interlinked for simple access to thousands of recordings. However, this consistent exchange of files increases the potential of pirated material.
Legitimizing Online Music
Before mainstream artists will ever support music distribution over the Internet, security precautions must be established. Liquid Audio was the first to offer a secure end-to-end online distribution solution. Focusing on both the needs of the music industry and the demands of consumers, Liquid Audio's codec incorporates Dolby Digital (AC-3), MPEG-2 AAC (Advanced Audio Coding) and MP3.
While MP3 web sites offer underground and unsigned artists a forum to distribute their work, Liquid Audio provides software tools for sites to offer previews and purchases of CD-quality music from today's most popular artists. Their solution ensures copyright protection and tracking royalties for the artist and their label.
These tracks are said to be identical to the CD Audio files and once purchased (averaging 99¢ per song) and downloaded to your hard drive, you can organize a folder to burn your own individualized CD. Liquid Audio supports most CD-R drives through a relationship with Adaptec. Take a test drive today, there are thousands of songs for sale at Musicblvd.com, Amplified.com, Musicmaker.com, and Platinumcd.com.
In December 1998, the Recording Industry Association of America (RIAA) introduced the Secure Digital Music Initiative (SDMI). It would seem the RIAA and its members recognize that the Internet is, by now, a force of (synthetic) nature and want to ensure their artists copyright protection in addition to guaranteeing consumers a convenient and legal access to quality music.
Many in the industry have voiced dissatisfaction with the SDMI because it lacks specifics, however, everyone agrees that an open standard is essential for the future of online music.
If the SDMI stays on target, there should be a standard for portable players by the end of 1999. However, a standard for online distribution will probably not be available until mid 2000. Many hope there will be a single player solution, preventing the current practice of different players for each type of file.
To facilitate the goals of the SDMI, the Genuine Music Coalition has been created. It's supported by a number of leading record labels, software/hardware/MP3 online vendors, music retailers, Web developers, broadband providers, artists and producers. A "Genuine Music" logo will accompany legitimately encoded content sold or freely distributed on the Internet, providing digital authentication of the music's origin and ownership.
Standardization seems to be leaning toward MP3 technology, even though other techniques such as MPEG-2 AAC and the upcoming MPEG-4 are, technically, superior compression schemes. The old Beta vs. VHS battle is about to be waged again. Though inferior, MP3's popularity may well turn the tide.
The standard for the actual MPEG-4 was finalized at the end of 1998, and it provides additional functionality to MPEG-2 AAC including bit rate scalability, error resilience and Spatilization (3D audio). A MPEG-4 Version 2 standard should be available by the end of this year.
Even if MP3's popularity is enough for it to become the basis of the Internet's open standard for online music, eventually codecs that facilitate 5.1 audio such as MPEG-4 will have to be included. However, no one thinks that 5.1 audio will become much of a factor on the Internet for at least a year, maybe more.
It's really a wait and see situation, though it would seem that the powers-that-be see huge dollar signs in the expanse of cyberspace and this ultimately guarantees improved content and accessibility. The key to the success of online music for purchase or preview is security first, then a simple, convenient means of distribution that amounts to point and click for consumers.
A Final Note
From a high-end audio perspective, transparency is always the goal and lossy compression techniques such as the ones employed on the Internet make high-end aficionados nervous. From day one the high-end audio community disagreed with the decision to make Dolby Digital a defacto standard because of its high compression rate (10:1-12:1). It was this same group that embraced DTS due to its modest 4:1 compression and demonstrably superior resolution.
While the standards set for DVD-Audio are less than perfect, it represents the first breakthrough in lossless compression with Meridian's Lossless Packing (MLP). Now there are no indications that lossless compression is making its way to the Internet (or even your living room) anytime soon but it does represent the potential for compressed audio that is truly transparent. You can bet there will be many heated discussions on this topic if the future of mainstream music distribution over the Internet is dependent on lossy compression technologies.