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Encoding Computer and Audio Hardware RequirementsA few pieces of hardware are necessary to stream audio. Within your computer, certain specifications must be met, such as disk space, processor speed, and RAM. You also need a handful of necessary external objects, such as cabling and speakers. Having a home stereo system of some kind or another—placed close to the computer—is useful, too. Disk SpaceDigital audio, especially raw (uncompressed) stereo audio, takes up a lot of space on a computer's hard drive. A sound file of raw audio requires about 5MB of disk space per channel per minute. Therefore, a three-minute stereo song file is about 30MB. An entire album of three-minute songs requires somewhere in the neighborhood of 500–650MB of disk space, depending on how many songs are on the album. You get the picture. Since you're dealing with using a lot of disk space, it's important to know how much free disk space is available on your authoring computer. With the price of disk space dropping faster then a Chicago Cubs' fly ball, it's feasible to acquire a hard drive large enough to have at least 1GB of disk space free at all times. In a perfect world, a minimum of 2GB of available disk space is recommended for your computer's hard drive. Calculate that figure after all of the applications and the operating system are installed. Disk space on a hard drive can be thought of using the "if you build it, they will come" theory of physical space. More lanes on a freeway do not a quicker commute make. They mean more cars on the freeway at that exact moment. A larger hard drive won't help you get your work done any faster, but you'll be able to have more things going on at once. And it's not like you won't use the additional space. Something always comes along to fill it up (see "Backup Storage" later in this chapter). Processor SpeedComputers get faster clock speeds practically every day. Faster is good in the realm of streaming audio. A faster computer can handle more tasks simultaneously. It also means a smaller chance of getting bogged down or crashing as the machine manipulates big audio files. Nonetheless, older, "slower" machines can do the job, but encoding will take longer. For Windows/PC users, a clock speed of 500MHz minimum is recommended. It's possible to get by on 300MHz, but you'll be catching up on your reading while waiting for audio to process. As of this writing, almost every new, off-the-shelf computer has a processor running at 1GHz clock-speed or higher. For Mac users, a PowerPC era (or newer) machine is required. Machines using the G4 processor running at 450MHz or above are recommended. RAMAs with processor speed and disk space, higher numbers are better. For either Mac or Windows platforms, a minimum of 128MB of RAM is preferred, although it's possible to squeak by on 64MB. New computers typically ship with 256MB of RAM installed. Extra RAM is available for as little as $35 for additional chunks of 256MB. If you're going to do a lot of audio processing, you'll definitely benefit from installing as much RAM as the computer can accommodate. Committed users frequently have 512MB to a full gigabyte of RAM. To measure how much RAM is currently installed on your computer, perform the following simple steps: On a Macintosh:
If you are using Windows:
Audio CardMost Macs process audio right out of the box through RCA or 1/8'' mini plug inputs. Some iMac and iBook hardware does not include audio inputs, so a Universal Serial Bus (USB) audio frob is required. This external device converts regular audio—for example, from your stereo—into the USB interface so that computers can process it. Windows/PC systems generally come bundled with audio capability, but it's wise to peek around at the backside of your machine to make sure. Examining the box is easier than getting the manufacturer on the phone. Look for a single 1/8'' mini plug or dual RCA audio input/output plugs. If your computer doesn't have audio input/output capability, you need to install an after-market audio card. Pick up a SoundBlaster (or a clone) card from your local store or Web site.
CD-ROM DriveAny modern computer sold within the past five years typically comes with a CD-ROM drive installed. A CD-ROM drive is essential for bringing audio in from a compact disc. If you don't have a CD-ROM drive in your computer, it's a straightforward task to hook up your home stereo CD player—which is also, technically, a CD-ROM drive, except that it reads audio only, not data—to your computer's audio inputs. If you're going to purchase a new computer, consider getting a CD-RW. CD-RW stands for Compact Disc-Read and Write. These are also known as CD burners. The price is slightly higher, but having and using a CD burner just might change your musical life. Like the CD-ROM, a CD-RW can read audio or data CDs but, unlike the CD-ROM, it can also create, or burn, CDs, with audio or other file formats. Using blank CDs—easily purchased just about anywhere—you can use CD burners for backing up applications and crucial data, moving files off of your hard drive to make space for other work, or even creating the ultimate party mix CD for your next hoe-down. CD-RW burning speeds are constantly increasing and, yet again, it's good to get the fastest burner available. Backup StorageMake sure important files are backed up in case of disaster. Unfortunately, crashes and data loss happen more often than the computer industry would like to admit. Think of backups as insurance. Most professionals back up their work on a daily basis. The backup operation eventually becomes second nature and is always a good idea. Here, system speed can make a big difference. Transferring copies of your work to an external hard drive or removable storage media (Jaz or Zip disks, for example), burning work-in-progress files onto a CD using a CD-RW drive or the older, tried-and-true computer-tape systems (such as DAT or cassette) are all serviceable. Given all options, either using an external hard drive or burning to a CD is recommended. Sound SourceThe sounds that you will be streaming over a network have to come from somewhere, and typically it's the CD-ROM drive or your home stereo. Extra Credit users might have mixers and more complex systems (see Chapter 11, "Advanced Audio Optimization"). In the most basic example, though, making the pieces of the entire system talk to each other is simply a matter of connecting the source of the sound to your computer's audio inputs. The source might be a CD, cassette, phonograph, radio, television, or even a live microphone. Of course, you could use existing digital files gleaned from the Internet and saved on your desktop. Answering machines have been used as well, too much general amusement. The possibilities are endless. Cabling and Audio RoutingAlmost every home stereo consumer electronic device comes with a set of RCA cables. Most sound cards come with 1/8'' stereo mini plugs for input and output. You'll recognize 1/8'' plugs from the headphone and line outputs of portable CD or MP3 players. Refer to Figure 2.1 to see the difference between the two types of cable plugs. Figure
2.1 Cabling is necessary when connecting to and from each type and size of external audio source. Advanced users will investigate higher-quality cabling options such as XLR breakout boxes and pricey, but nice professional grade cable. The difference in audio quality between a 1/8'' mini jack and stereo RCA cable is negligible.
All of the tools must be hooked together in the physical world so that they can do their thing in the digital world. After everything is set up, the cabling might look like plastic spaghetti that's fallen behind the desk, but the principle is basic. Simply route your audio source to your computer (see Figure 2.2). Figure
2.2 Monitor SystemMonitor is a fancy word describing what you use to listen to your audio—it's your speakers, really. Your monitor could be little portable headphones for $5 or big, heavy, wooden speaker boxes costing thousands of dollars apiece. Your home stereo speakers will do fine. By the way, speakers are the most important element in your audio food chain, and this is an appropriate place to spend a little money. Depending on how careful a listener you are and how important audio quality is to you, a decent pair of speakers (that's right, a pair—stereo is where it's at!) is key for being able to hear what's going on. In addition, having quality speakers makes it easy to hear important frequency differences when performing advanced audio optimizations. Many brands and models of self-powered speakers are specifically designed to be directly connected to a computer's audio output. These can be remarkably inexpensive and of good quality. A small system that includes a subwoofer is recommended. It shouldn't be necessary to spend more than $40 for a good computer speaker system. Encoding Computer Software RequirementsThere are a number of pieces of software to fit into the streaming audio puzzle. Below is a list of the basic tools you'll need. Operating Systems: Windows and MacintoshThe operating system (OS) is the platform upon which all of your applications rest. Streaming audio software tools and applications are upgraded so rapidly that it's helpful to have the most recent and stable version of your OS as possible. For Windows users, it's advisable to have Windows 98 or newer. For Macintosh users, OS 9.1 or newer is recommended. Streaming Audio PlayersA player is a computer software application for playing back your streaming (or downloaded) audio files. Because you're learning several streaming formats, several players are necessary. Windows Media, RealMedia, and QuickTime all require their own players to stream files encoded using these formats. MP3 files, because manufacturers recognize MP3's popularity and because MP3 is not a proprietary format, can be streamed through any of the previously mentioned players, as well as a host of free or shareware players available online. Even though these freeware and shareware players are small, free, and simple to install, you can still purchase any number of other third-party players. These third-party players often take up a lot of memory, feature all manner of groovy visual effects to go along with your music, and cost as much as a tank of gas. This book uses Winamp, a popular and free download from http://www.winamp.com, as a basic MP3 streaming player for Windows. For the Macintosh MP3 streaming player, the book will use iTunes, which can be found at http://www.apple.com/itunes. A list of players can be found in the Appendix, "Tools and Resources." Rippers and EncodersA ripper is a software application that pulls, or rips, a song from the CD in your computer's CD-ROM drive onto your computer as an uncompressed, raw audio file (WAV for Windows and AIFF for Macintosh). An encoder is a format-specific software application that squeezes, or encodes, the raw audio file on your computer to a tiny size, making it ready for uploading to your streaming server. Software tools are available that perform both tasks of ripping and encoding. Appropriately enough, they're called ripper/encoders. The examples in this book separate these two steps, so ripper/encoders won't be covered in depth. A list of other rippers, encoders, and ripper/encoders can be found in the Appendix. Waveform EditorsAlmost like having a recording studio in a computer, waveform editing allows users to manipulate audio files in complex and necessary ways, at the click of a mouse. Volume level adjustments, fades, normalizing, and equalization, among other things, become easy to do. For Windows users, this book uses SoundForge 5.0 (http://www.sonicfoundry.com). For Macintosh users, Peak 2.6 LE (http://www.bias-inc.com) is the tool of choice. A list of other waveform editors can be found in the Appendix. Finding the Format That FitsEach format has advantages and drawbacks. (See Chapter 1, "Introduction to Streaming Audio," for more information.) These factors include cost, ease-of-use, reliability, scalability (how many different ways you can encode), and the way they can work with other technologies. If you want to reach as many people as possible, consider providing multiple formats. In this way, listeners can choose what works best for them. Operating System PerformanceAnyone who has struggled with making Internet applications work properly knows that some formats perform better on certain operating systems than others. This is particularly noticeable for platforms created by the big players who also create operating systems. Microsoft's Windows Media provides the best experience for Windows users, whereas Apple's QuickTime is measurably more stable on MacOS. OS-independent formats RealMedia and MP3 used to favor Windows because of Microsoft market share dominance. With Apple's Phoenix-like rise from the ashes, RealMedia and MP3 performance on both operating systems has pretty much evened out. With increased consumer demand for Macintosh versions of the tools, companies have dedicated more resources to programming them efficiently on the Macintosh. Users who plan to run their own streaming server using existing computers need to know on which operating system each streaming server can run. Many high-end users use a version of Unix (typically Linux, FreeBSD, or Solaris). See Table 2.1. Table 2.1 Streaming Server Operating System Availability by Format
Cost: Licenses, Hardware, and BandwidthThe costs associated with running a streaming server are broken down into a few key areas: hardware, bandwidth, and licensing. Bandwidth and hardware remain the same regardless of the format. Hardware costs include the price of server computers, routers, and cable (see the section called "Server Computer and Audio Hardware Requirements," later in this chapter). Bandwidth costs are directly related to how many listeners tune in. Refer to "Server Stream Distribution" in Chapter 1 for a further discussion of bandwidth costs. As noted in Chapter 1, server stream licensing is different for each format. Table 2.2 illustrates which formats require payment for software, which require additional fees based on how many concurrent users you want to support, and which provide basic-level free versions. Table 2.2 Streaming Server Fees by Format
Most organizations outsource their streaming server needs to other companies that specialize in this area. These companies wrap hardware, bandwidth, system administration, and licensing fees together for you. If you're streaming to a small number of listeners (up to 25 concurrent listeners), you can avoid fees in all formats. If you are serving a middle-sized streaming audience (up to 200 concurrent listeners) and intend to run your own server, you will do well to avoid formats that charge a per-user license. It might be better to outsource streaming server needs at this level. Complexity and FlexibilityThe common basic audio stream consists simply of a link on a Web page that opens the correct player, allowing the user to listen to the author's content. Authors might want to provide a more compelling experience by including video content, playlists, digital rights management (DRM), synchronization with other media, or other forms of interactivity. Your specific needs play a critical role in which format you choose. Windows Media and RealMedia have done extensive work to provide digital rights management, for example. If you plan to provide any of these somewhat more complex interactive add-ons to your streaming audio, spend time researching each format. Some formats have strengths and reliability in different areas. It's also not uncommon that the engineer who is making it all happen might be more comfortable with one particular format than another. Server Computer and Audio Hardware RequirementsThe following sections offer basic hardware requirements for setting up your own streaming server, as opposed to leasing from a third party. Note: A streaming server must support every one of your listeners. Its requirements shift radically based on a constantly fluctuating amount of concurrent users. The examples in this book use a machine that needs to unicast a 56k stream to 100 concurrent users. Disk SpaceYour streaming server will need enough disk space to not only store all of your streaming media, but also to store logfiles documenting users (so that you can run reports on that data) and the operating system. Logfiles on a heavy-use streaming server can quickly take up gigabytes of disk space. Streaming servers should start with at least a 40GB hard drive. More high-end users will want to consider hundreds of gigabytes of disk space and even optimized disk systems such as the fast SCSI RAID configurations. Processor SpeedSince server computers need to be very flexible to deal with widely varying processing demands it's best to have as fast a clock-speed as you can get. Macintosh and Windows recommendations are below. For Windows/PC (or Linux/FreeBSD UNIX) users, a clock speed of 1GHz minimum is recommended. For Mac users, a PowerMac G4 running at 850MHz or above is recommended. RAMFor streaming media server computers, at least 1GB of RAM is recommended. It's possible to get by on less, but with pricing where it is these days, why bother risking running out of memory? Network CardYou'll want to make sure you have a 100Mbps-network card to give yourself enough networking headroom. Due to TCP/IP networking protocols, 10Mbps cards can start to have problems with collisions and retransmission far below the theoretical 10Mbps maximum. Backup StorageAs always, back up your vital data. Backing up gigabytes of data can be time-consuming work, so choose a method that's quick, local, and portable (so you can remove the data backup to another location in case of fire, earthquake, or other disaster). Digital linear tape (DLT) is a good solution for server backups, but having extra disk drives dedicated for backups is often a cheaper (and quicker to recover from) solution. Serving from Your Encoding ComputerIf you plan to use the same computer to serve and encode, remember to account for the hardware requirements that both duties involve. It's unwise to choose this configuration if you are serving any more than 25 users because it doubles the chance of problems. What might only be a temporary resource glitch on an encoding computer could turn into a fatal error when shared with a streaming server. However, serving from your encoding computer to low numbers of concurrent users still doesn't guarantee seamless operation. If you do choose to encode and stream from the same computer, one way to increase the reliability of your stream is to use a dedicated box just for that purpose. Network Bandwidth RequirementsA big part of streaming audio is about transferring encoded streams across networks. Transferring a single stream from your authoring computer to a server computer on the other side of the room requires a small amount of bandwidth. Transferring many files or live streams to servers at a remote location and providing for heavy streaming traffic can require enormous government-level amounts of bandwidth. Here's a general assessment of bandwidth needs for streaming audio. AuthoringAuthoring streaming audio requires a certain amount of network connectivity (bandwidth) between you (the author), a streaming server, and your listeners. The bandwidth that is necessary between the encoding computer and your streaming server is based on whether you're using a live or on-demand encoding scenario. For on-demand encoding, any connection will suffice. Author scheduling requirements are the only important factor in uploading content. Authors can leave a transfer running all night over a dial-up modem connection or do it all in 10 minutes over a broadband DSL line. Although the former scenario might make you drink yak-butter tea and wear burlap, either speed still gets the job done. When authoring within the live scenario, sufficient bandwidth must exist between the author's encoding computer and the streaming server to enable the stream to be delivered in real-time. Advanced users set up dedicated connections, such as ISDN lines, as insurance to lessen the chance of a stream's delivery being affected by Internet connectivity bottlenecks. A live stream's smooth delivery is also assisted by keeping some headroom within your connectivity. Always factor in a little space for network overhead, emergency troubleshooting, or possible line problems. If you know you have 128k available (as with ISDN lines), don't send more than an 80k or 100k stream over it. When using a residential DSL connection to send a live stream to a server, encode your audio at bit rates as low as possible to minimize the chance of interruption. The average route from the author's computer to the listener's computer involves about 10 other computers scattered throughout the Internet. (It's not uncommon to go through 20 or even 30.) Each computer you go through is another place you have absolutely zero personal control over the connection's stability. Remember, if your live encoding stream is interrupted, it affects every person who is listening. Streaming ServerUnicast streaming means that a separate copy of each audio stream is sent to every concurrent listener. This also explains why the largest bandwidth requirements are between the streaming server and listeners. If 100 people are listening to a single 56Kbps stream at the same time, it's necessary to provide for 100 users at 56Kbps each. This amounts to 5600Kbps, or 5.4Mbps. As you can see, a popular stream being accessed by many people at the same time can quickly require substantial bandwidth at the server. Although you've heard it already, it bears repeating: When choosing a format, it's vital to estimate how many people you need to stream to concurrently. The more users to which a streaming server delivers content, the more resources (Internet connectivity and computer processing power) that are required. These resource requirements quickly become more pronounced when you improve the quality of your content by encoding at higher bit rates. Obviously, streaming a song to two people simultaneously doesn't require as powerful a server and as much bandwidth as streaming an Emmylou Harris concert live to 10,000 people. You might be able to stream the former from a residential DSL connection, but you can't do the latter without a rack of computers and many megabits of bandwidth. When determining how many concurrent users you want to support, remember to allow extra headroom for other related traffic. For example, if you're using the same network connection for serving Web traffic, calculate in those requirements as well. If you plan on running a streaming server from a home connection, also include whatever bandwidth you might need for browsing the Web, sending and receiving e-mail, and so on. Finally, always check with the ISP that is hosting your server to get bandwidth cost estimates. Take a look at Table 2.3 to get a feel for how much bandwidth is required for your projected audience. Table 2.3 Streaming Server Bandwidth Needs by Audience Size
About Your Audio SourceIt's always preferable to use the absolute best-sounding source material when creating audio files for streaming. The nasty hissing and distortion heard on old cassette tapes only becomes worse through the process of encoding. For the purposes of clarity, try to bring your audio into the computer from a digital source (CD, DAT, minidisc, or digital video, for example). Still, perfectly serviceable streaming audio files can be crafted using analog sources (such as Hi-8, VHS, phonograph record, or clean cassette). For live streaming, be mindful of the Gain Chain to assist you in achieving the highest possible audio quality (see "The Gain Chain" in the next section). Audio OptimizationSince the sound quality of streaming audio is so often defined by its limitations it's helpful to do a little modifying to the overall tone and shape of your source audio. Don't worry, the process is pretty straightforward and, once you've tried it the first time, you'll realize it's actually kind of fun. You're changing the way your source audio sounds and you'll find you can do some odd things. Maybe you won't actually end up saving your source audio in those odd and interesting ways, but it's nice to know you can do it, just the same. Below are a couple of tools and techniques to get you started. The Gain ChainFrom the first time a sound source is recorded, and with each succeeding generation, the overall quality of your audio is defined by the gain setting. The gain is simply the volume at which the sound source is recorded onto the recording medium (tape, minidisc, DAT, and so on). Too high a gain setting creates unwanted distortion. Too low a gain setting requires the listener to turn up the volume so high that the inherent distortion of that recording medium (usually below the threshold of hearing at normal volume levels) becomes plainly audible. Both scenarios are bad juju. The key is to set the volume level as high as it will go within any given recording medium without distorting. Trust your ears here. If it sounds good, it usually is. FadingThe human ear and brain are typically not too keen on sounds that begin and end abruptly. If you are creating short audio streams from a longer piece of sound, fade in the beginning of the segment and fade out the end. Experiment with fast and slow fades to see which makes more sense for that particular piece of audio. Your waveform editor is the application to perform these simple functions. It is also helpful to place one or two seconds of silence at the beginning of your streaming audio file. Before your online listener actually hears a sound, they'll often experience a brief awkward pause while the server accessed by their computer gets its act together. This is called buffering.
CompressionCompression (standard lossless audio compression) is a gentle massaging or sculpting of sound to smooth out the difference between loud and soft sections. Compression is useful for preparing audio files for encoding. Streaming formats, after being piped through online networks, tend to sound better if the pre-encoded source audio is all about the same volume. A waveform editor is the tool to use here. Audio gurus spend lifetimes understanding the nuances of perfect compression. But this is only streaming audio, so don't stress it. Most waveform editors provide a few basic settings. Try a little bit of compression on your audio file, prior to the encoding process. Let your ears be your guide.
EQSpeaking of streaming audio's ability to deliver decent sound, did we mention carving up the sound frequency spectrum? Format codecs are able to squish large raw audio files down to a tiny size by removing parts of the audio that are seen as redundant. Using your waveform editor, perform the following basic EQ changes to your source audio to help them be better sounding streaming audio files, especially when encoding at low (below 56Kbps) and medium (up to 96Kbps) bit rates. If you do plan to encode at low to medium bit rates, especially when using the live encoding scenario, remove the lowdown lows (39Hz and below). Your audio file won't need them where it's going. While you're at it, toss out the high-end highs (18kHz and above), too. When encoding for streams below 56Kbps, experiment with boosting mid frequencies (around 2.5kHz) to compensate for the frequencies you threw away. The overall sound quality of low bit rate encoded spoken word files especially benefit from this treatment. All this sonic manipulation won't sound very good when compared to the original source recording, but it'll translate a lot better through the encoding process as a sonically legible file. The encoder (when encoding at low bit rates) removes these frequencies anyway. Performing these EQ changes prior to the encoding process frees the computer to spend more time doing a good job encoding the frequencies that matter. You won't have to adjust much unless you're actually removing certain frequency ranges. A little boost or cut of certain frequencies goes a long way. On-Demand Audio: Getting Your Source into Digital FormatIn the following two examples, you'll rip a song from a CD to a digital (uncompressed) audio file on your computer desktop.
In the following two examples, you'll convert a song from an audio source to a digital (raw, uncompressed) audio file on the computer desktop.
Converting to the Necessary Digital File Format (Macintosh/AIFF and Windows/WAV)You can use your waveform editor to convert digital sound files to different file formats (AIFF to WAV and vice versa). Both SoundForge and Peak will read and play both AIFF and WAV files, among others. Use your waveform editor to Save As in your chosen digital file format. Brief General Overview of Online Music Legal IssuesUp until the early 1990s, the U.S Government took a hands-off approach to the Internet and its uses. The Digital Millennium Copyright Act (DMCA), passed in 1998, has attempted to address copyright issues relating to use of music on the Web. As of this writing, recent changes show some hint of relaxing the stranglehold that the music business is attempting to enforce over online use of copyrighted music. This is important because it means people who want to create online radio stations using others' music now have a simple way to get permission to do so. If you aren't interested in educating yourself about this hot big money topic, that's fine. But do remember that when it comes to creating streaming audio files online, the simple and safe approach works best. If you own the rights, you can do whatever you want with your audio. If you use audio from another source—a source to which you don't own the rights—you are bound by local copyright law. Like all laws, you are responsible for toeing the line. Ignorance is no excuse! Turn to the Appendix for resources that provide more in-depth information about how those laws work. SummaryNow you've got a handle on some of the key issues around authoring your own streaming audio and, heck, you've now got a digitized, uncompressed raw audio file on your desktop just begging to be encoded and streamed. Let's get to it!
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