Streaming-audio technology has certainly matured over the past few years. Better sound quality and greater reliability, in spite of growing Internet congestion, make it more effective than ever for showcasing audio over the Web. There are also more formats to choose from, including Microsoft NetShow and Liquid Audio. Because of its popularity, however, RealAudio remains the unofficial standard among Web developers and listeners alike. RealNetworks now boasts more than 77 million downloads of its RealPlayer software, and the latest version provides more advanced compression for smaller and better-sounding files.
For all its improvements, though, RealAudio is still a far cry from CD quality at low bandwidths. Over a 28.8 kbps modem, the best you can achieve is a 10 kHz frequency response with a 22.05 kHz sampling rate for a mono file. But you can have decent-sounding RealAudio files; there are a number of steps you can take to get the best audio possible. To begin, you'll need a few tools, including an audio-editing application (such as Sonic Foundry's Sound Forge) and copies of the latest RealPlayer utility and RealProducer encoding software. You can download free copies of RealAudio applications from the RealNetworks Web site (for details, see the sidebar "RealAudio Resources").
CAPTUREBefore you record your audio to WAV or AIFF files, you need to decide whether you want mono or stereo audio files and what the sampling rate should be. Don't assume that 44.1 kHz stereo audio is always the best choice; with RealAudio, it may not be. The latest version of the encoding software provides a large selection of codecs (compression/ decompression algorithms), so you can tailor the sound quality of your file to specific Internet connection speeds.
A total of 33 codecs is available through the program, each targeted toward a different bandwidth, from 5 to 96 kbps. Every codec has an optimum sampling rate and provides a frequency response accordingly. If you record your audio files using the optimum sampling rate for your target codec, you'll get better sound quality. You can find a table listing all the codecs and their qualities in the RealSystem Production Guide on the RealAudio Web site.
Whether you use mono or stereo files will also affect the frequency response. Because stereo files have twice as much data to push over the Net, they take up twice as much bandwidth. If bandwidth is limited, something has to give; as a result, stereo files have half the frequency response of mono files. You'll have to decide which is more important: stereo content or the best possible sound quality.
One other consideration: with the free version of RealProducer, you can access only four of the available codecs. For more, you'll need to buy RealProducer Plus ($149.95) or RealProducer Pro ($499).
For consistency's sake, I'll target all examples in the following recommendations to the 20 kbps Music G2 Mono codec. It provides the best quality on a 28.8 kbps connection (with a frequency response of 10 kHz), and it's available with the free RealProducer software. Using this codec, you'll need to record your files in mono, at a sampling rate of 22.05 kHz. For resolution, always go with 16-bit.
OPTIMIZERealAudio uses a lossy compression scheme, which means the codec discards parts of the audio file during the encoding process to shrink the file size. That reduces the frequency response and dynamic range of the audio, but you can compensate for those "losses" by applying a bit of dynamics compression and equalization before you encode. First, be sure to remove the DC Offset (low-frequency, inaudible noise that can result from bad equipment grounding) from your file, because it can introduce unwanted artifacts when you're applying EQ or other types of processing.
Because RealAudio encoding reduces the dynamic range of your audio, adding a bit of compression beforehand will give you some control over the final signal levels rather than leaving them to chance. A good compression ratio is usually somewhere between 2:1 and 4:1; to start, try using about 2:1. That way you'll be able to increase the overall volume while keeping some of the original dynamic range. Too much compression can sometimes add unwanted artifacts to music, making it sound dull and lifeless. The optimal ratio will vary depending on the material; you'll need to use your judgment.
Next, equalize your file, keeping in mind that most of the high-end and extreme low-end content will be lost during encoding. It may take some experimenting; you might begin by cutting the low frequencies below 60 Hz and the highs above 10 kHz, which helps reduce some of the encoding artifacts. To make up for the frequency losses, you can boost some of the bass frequencies (around 200 Hz) that are still intact. You can also boost the midrange around 2.5 kHz, which emphasizes important midrange content, such as vocals. Try increasing the frequencies by about 6 dB and play around with it from there (see Fig. 1).
Now you'll need to normalize your file. Normalization, which raises an audio signal's volume as high as it can go without causing clipping (distortion), guarantees that your file will use the maximum amount of digital resolution available. It also ensures that you'll be feeding the encoder the loudest possible signal, which helps mask low-level artifacts. Don't normalize to 100 percent, though; instead, use 95 percent (or -0.50 dB). The RealAudio encoding process doesn't always handle 0 dB signals very well, so it's best to leave a small amount of room for it to work its magic.
ENCODEConverting files to the RealAudio format used to be a bit tedious, but with RealNetworks' latest encoding software it's simple. RealProducer provides a Recording Wizard, which takes you step-by-step through the process of setting the encoding parameters. The steps include specifying your source file; entering the title, author, and copyright information, which later appears in the Clip Info field of RealPlayer; and selecting file type, target audience, and audio format.
For file type, you choose between Single Rate or SureStream. A single-rate file is optimized for only one type of Internet connection, and it can be streamed from any Web server. With SureStream, you can encode a file for up to six different bandwidths; when a visitor listens to your file, RealPlayer determines which encoding to use according to the speed of the Internet connection. For example, if a fast connection gets bogged down due to Net congestion, RealPlayer automatically switches to lower-bandwidth encoding to prevent playback from stalling. SureStream files, on the other hand, require RealServer for playback; they can't be streamed from just any Web server.
Once the Recording Wizard has guided you through the parameter settings, you simply click the Start button, located in the Recording Controls section of the RealProducer main screen (see Fig. 2). Your file is now encoded and saved as a RealAudio file with an RM extension. If you have RealPlayer installed on your system, you can click the Play button to hear how it sounds.
DELIVERRealProducer makes adding RealAudio files to your Web site as simple a matter as encoding them. You no longer need to code HTML files by hand. The Web Page Wizard steps you through the creation of a Web page containing a link to your RealAudio file or an embedded player. You specify the name of your file and whether you want RealPlayer embedded on the page or in a separate window that pops up when a visitor clicks a link. If you elect to embed the player, you can choose a Player Control Layout specifying what controls are displayed-from basic Play and Stop buttons to the full standard player with transport controls, information panel, and status panel. You can even opt to have the RealAudio file play back automatically as soon as the Web page is viewed.
Your newly created Web page is then saved with the same name as your RealAudio file, but with an HTML extension. If you want to include your RealAudio file on an existing Web page, you can easily open the new Web page (created by the wizard) in any text editor and copy the code into your existing Web page. Copy all the code between the HTML comments and .
The Publishing Wizard walks you through the process of posting your file to a Web server. Just enter the file name of the Web page you want to publish and select a Publishing Profile. The profile allows you to choose an Internet service provider from a list that includes special considerations, such as uploading to AOL. Most likely, however, you'll just use the Generic-No Defaults profile. Next, select the streaming method you want: from a standard Web server or RealServer. RealAudio files stream more reliably from RealServer, so that's the best way to go if your ISP offers it. Now enter your server specifics (such as address) along with your user name and password, so the wizard can access your account. Your files are then automatically uploaded, ready to be browsed by your adoring fans (see Fig. 3).
FINAL CONSIDERATIONSThe new version of RealAudio comes with two other interesting features. RealPix lets you assemble GIF and JPEG images into a streaming slide show with special effects such as zooms and dissolves-a cool way to display photographs along with your sound. RealText lets you stream text along with your audio so you can display song lyrics or other information as the music plays. Both RealPix and RealText require RealServer for playback because of synchronization issues; for tips on how to use these features, you can download the RealProducer Authoring Kit for free from the RealNetworks site.
RealAudio is a great way to showcase your music on the Web, provide a taste of what's on your new CD, or even enhance your site with informative sound clips, such as radio interviews. Whatever your goal, if you follow the tips I've outlined, you'll have some of the best-sounding RealAudio files on the Internet.
Scott R. Garrigus is an author, musician, and multimedia expert. You can hear excerpts from his cassette release Pieces of Imagination in RealAudio format on his Web site at www.garrigus.com.
You can find all the tools and information you need to work with the RealAudio format on the RealNetworks Web site at the following download locations:
RealPlayer G2www.real.com/products/player/index.htmlDownload the latest version of RealPlayer for free, or purchase RealPlayer Plus for additional functionality.
RealProducer G2www.real.com/products/tools/producer/index.htmlDownload the free RealProducer software to encode your files, or purchase RealProducer Plus or RealProducer Pro, which provide additional encoding features.
RealProducer G2 Authoring Kitwww.real.com/products/tools/authkit/index.htmlThe RealProducer Authoring Kit, a free download, provides information about developing your own RealAudio, RealVideo, RealPix, RealText, and RealFlash files. It includes production guides for all five formats.
RealSystem G2 Production Guideservice.real.com/help/library/guides/production/realpgd.htmYou can read the RealSystem Production Guide online if you don't want to download the RealProducer Authoring Kit.
RealAudio Bandwidth Codec Chartsservice.real.com/help/library/guides/production/htmfiles/audio.htm#racodecsYou can also read the RealAudio Codec Charts online without having to download the RealProducer Authoring Kit.
The Real Forumproforma.real.com/mario/devzone/realforum.htmlThe Real Forum listserv is an e-mail discussion group focused on the use of RealNetworks products. You can post messages about the best methods for creating content using RealNetworks technologies and about the planning and implementation of streaming-media Web sites.