__ Compression algorithms shrink hefty media files to net-friendly sizes. __
If you think your 56-Kbps modem is fast, guess again. Even if it really could move data at 56,000 bits per second - actually, it's more like 52 Kbps - it would have to be roughly 25 times faster just to play a CD in real time. (CD audio transmits at 1.4 Mbps.)
If you consider video, then 56 Kbps looks even sorrier. Production-quality digital video plays at roughly 216 Mbps, nearly 3,900 times faster than 56 Kbps. Even a cable modem at top speed (1.5 Mbps) would need to be 144 times faster to play uncompressed video. Let's look at it another way:
To download a minute of CD-quality audio at 56 Kbps takes 25 minutes; to do the same for top-notch video takes 144 minutes. For the average Net user, these download times are unacceptable, which is why we have codecs.
A codec is a formula that removes data - redundant data, data you aren't likely to notice, data that can be derived from other data, and so on - so files can be transmitted more quickly. At the receiving end, a decoder reassembles the data into something coherent. Some codecs are designed to winnow video and audio files so much that they can actually play as they arrive over 28.8-Kbps or even 14.4-Kbps connections, a capability known as streaming. But when you remove that much data, there isn't much left to work with. This is why streaming video often looks like a moving postage stamp.
A codec's effectiveness is measured by three criteria: the processing power needed to decode it, the data rate required to play back encoded data, and how close to the original the final result looks or sounds. For instance, MP3 audio, one of the best-known codecs, can be decoded by an average desktop machine. An MP3 file plays back at roughly 128 Kbps (that is, you can't play it back in real time over a modem; you must download it first, which takes about 4 1/2 minutes per minute of music). And it sounds very close to the original.
Each codec listed here is supported by encoding.com. And each is tailored to address a specific technical challenge (like real-time audio or video) or business challenge (like how to control redistribution once a file has been downloaded).
a2b (AT&T) Based on the state-of-the-art Advanced Audio Coding (AAC) algorithms engineered by AT&T, Dolby Labs, Lucent, Sony, and the Fraunhofer Institute, a2b boasts higher fidelity than MP3 at faster data rates. But the format's real selling point is encryption that limits playback to one player and restricts the number of plays.
Emblaze (Geo Interactive) The hook here is streaming Web video without a browser plug-in; the player is a Java applet. The hitch is that Java is inefficient at number crunching, which is the name of the game in codecs. This, coupled with inefficiencies in the codec itself, makes Emblaze more interesting in theory than in practice.
GTS (Graham Technology Solutions) Like Emblaze, GTS uses a Java-based player to deliver streaming video at dialup data rates.
JPEG (public domain) JPEG(Joint Photographic Experts Group) is the dominant format for graphics on the Web, with higher color resolution and more sophis- ticated compression algorithms. A variation, M-JPEG, is popular in video production.
Liquid Audio (Liquid Audio) The Liquid Audio system is much more than a codec. It addresses a broad range of music-industry needs, from obtaining approvals during production to supplying radio stations to auditioning to selling high-quality audio online. Like a2b, its native codec is AAC, but the architecture can accommodate other codes as well. Liquid Audio also delivers encryption, licensing, and watermarking features.
MP3 (Fraunhofer Institute, Thomson Multimedia) At the center of the current brouhaha over music on the Net lies MPEG-1 Audio Layer 3, a footnote to the MPEG-1 video spec. Tuned to deliver highest efficiency at 128 Kbps, MP3 is too dense to stream over dialup connections but just light enough to encourage downloading entire songs.
MPEG-1 (Philips and others) Developed way ahead of its time, MPEG-1 was the next big thing in CD-ROM video. Multiplying CD-ROM speeds boosted MPEG-1's quarter-screen image up to roughly VHS quality, and the advent of Pentium processors enabled playback without expensive add-in hardware. Look for a comeback as producers find that DVD can't hold enough MPEG-2 data. Incidentally, the intellectual-property rights surrounding MPEG-1 are so entangled that nobody can say who owns it.
MPEG-2 (MPEG-LA Consortium) This is the format for DVD video and for delivering robust and full-screen broadcast programs to cable head-end stations. It takes a 450-MHz PIII to decode the stuff reliably without extra hardware, but the new wave of set-top boxes and Sony's upcoming PlayStation II are bound to increase MPEG-2's base.
QDesign Music (QDesign) Distributed with QuickTime 3.0, this is the codec to beat for stereo audio delivered at dialup data rates. But don't expect to be impressed if you're playing it back with a processor running at less than 100 MHz.
QuickTime 2.5 and 3.0 (Apple) QuickTime isn't a codec. It's a media architecture that encompasses a variety of codecs as well as scrolling titles, real-time video effects, and interactivity. QuickTime 2.5, a CD-ROM-era technology, suffered from a lack of Net savvy and a disparity between Mac and Windows versions. Version 3.0 equalized Mac and Windows and added three quantum-leap codecs: Sorenson Video, QDesign Music, and Qualcomm PureVoice. QuickTime 3.0 also added HTTP streaming (properly called progressive download), which means a file can begin playing smoothly before the whole thing has arrived. True streaming for QuickTime, which begins playback immediately but may lack a smooth listening and visual experience, was released in beta in April 1999, only a few days behind Microsoft's Windows Media Technologies.
RealMedia 5.0 and G2 (RealNetworks) A leader in true streaming video and audio to dialup connections, RealMedia is an architecture that embraces the RealVideo and RealAudio codecs, among others. Version 5.0 was the first implementation that really worked. G2 improved the codecs substantially and added interactive features via SMIL (Synchronized Multimedia Integration Language).
Sorenson Video (SorensonVision) Sorenson Video delivers a vast improvement over its predecessors, including RealMedia G2, at dialup data rates. But its sweet spot is in the cable-modem range, where it can manage dazzling video that doesn't overtax the CPU. As part of QuickTime 4.0, Sorenson will support lower bit rates.
Windows Media Technologies (Microsoft) Combining Video for Windows, ActiveMovie, and NetShow into a unified architecture, Redmond's newly unveiled Windows Media Technologies deals simultaneous body blows to a2b, Liquid Audio, MP3, QuickTime 3.0, and RealMedia G2. The new codecs are impressive - Microsoft Audio Codec 4.0 for audio (the first three versions of which never left the laboratory) and Microsoft MPEG-4 for video (a premature stab at implementing the Moving Picture Experts Group's next-generation standard, which remains to be approved). Microsoft has built in features for intellectual-property protection and ecommerce. Expectations are running high, but it's all still in beta and currently promises more than it delivers.
