Selecting the right format (Designing Web Audio)

5.3. Selecting the right format

Each format discussed in this chapter has advantages and disadvantages depending on the requirements of your project. There is no single format appropriate for every situation. To determine which format is best for you, first identify your needs, then select the format that best suits those needs. There are huge differences in server requirements for broadcasting CD-quality music to a limited audience versus wide-scale broadcasting to a large audience with diverse bandwidth capacity. Similarly, the differences between authoring and delivering interactive content such as a game or product demo versus encoding and broadcasting a video file are completely different.

RealAudio, MP3, and Flash are familiar names, but a host of alternative formats, including Windows Media, RMF, and Liquid Audio might better suit your needs. Let's take a look at the factors that will determine the most appropriate format for you.

5.3.1. Interactive sound design capabilities

Before you look at browser compatibility, cost, audio fidelity, and server performance, you will need to determine whether you need a format that supports interactive presentations or one that supports continuous playback of audio and video files. Several formats such as Flash, Shockwave, and Beatnik are designed for rich interactive media content such as games, educational material, product demos, and promotional pieces where instantaneous feedback via sound effects are essential.

In contrast, formats such as RealMedia, MP3, Windows Media, and QuickTime are primarily designed for continuous playback of audio and video files where server-side bandwidth negotiation and management are key. When they do support interactivity, it is usually in a more limited form such as slide shows and synchronized sound with video or text.

First, determine whether you want a format for delivering interactive content or simply a format for encoding and broadcasting audio and video files, then let the following criteria guide your final decision.

5.3.2. Browser compatibility

Let's face it, if people do not have the plug-in or technology to view or listen to your content, it is much harder to get your message across. This does not mean that you have to select a format that has 100% acceptance, but you will need to assess how tech-savvy your audience is and what format is going to be the most widespread among your target audience. If you are targeting a tech-savvy audience, they will be more likely to download the newest version of the plug-in if they do not have it installed. Do not count on a less technical audience to successfully download and install new technologies.

5.3.3. Cost for streaming audio

To add streaming to your web site, you may need to purchase one or more of the following:

Encoding software to convert your raw media files into the appropriate format for web delivery
Dedicated server software to stream your encoded media files
Hardware to install your server on (this may include several systems for redundancy and scalability)
Bandwidth to transmit data from your server over the Internet

The cost of streaming can range from free to hundreds of thousands of dollars depending on how many of the above items you will need to purchase. For example, if you are already running an NT server and have a dedicated T1 line, you can use Windows Media for no extra cost. Some vendors provide free introductory-level streaming solutions such as Real Networks. If you have administrative access privilege to your web server, you can install the free Basic RealServer G2. Alternatively, if you are a multimedia producer and own a copy of Macromedia Director or Flash, you can export Shockwave files and stream them from your regular web server for free.

On the other end of the spectrum, if you are a major Internet portal running a hot Sun machine with thousands of simultaneous listeners, you are going to need a healthy budget for equipment and bandwidth and, if you are using RealMedia, the appropriate number of streaming licenses. Keep in mind that you may not need to spend as much on streaming licenses as you may have thought. A 60-stream license can go a long way. If your average user listens to your audio for five minutes or less, you can deliver 17,280 streams per day with a 60-stream license.

5.3.4. Learning curve and documentation support

As is the case with limited budgets, everyone has a tolerance level for learning new technologies. Keep in mind that some formats provide much more documentation and software tools for getting started. RealMedia, for example, has outstanding documentation and software support, including sophisticated tools for automatic server configuration. In contrast, other formats such as MP3 and MIDI are not all-in-one proprietary streaming solutions but are merely standards for audio compression or musical notation and thus do not offer a single source for documentation and support.

Besides documentation and support, the real hurdle depends on the scale of your streaming needs. If you merely want to broadcast the annual company report to a few hundred nationwide sales representatives, streaming audio is a much simpler affair versus competing with Spinner.com to become the king of Internet radio. The difference in the infrastructure required for streaming to a few hundred listeners per day versus tens of thousands is night and day. If you are broadcasting to a huge audience with a scalable robust system, the learning curve is going to be much steeper than setting up a free Basic RealServer or throwing some audio files up on your HTTP web server. Large-scale professional broadcasting requires advanced configurations and logistics, such as multicasting with multiple servers and backup systems in place for redundancy.

5.3.5. Audio fidelity and compression

Audio fidelity for the end listener is determined by the quality and specific setting of the codec used for audio compression and decompression. Better compression algorithms, such as MP3, result in higher fidelity audio playback over the same bandwidth connection. A udio fidelity is also determined by the target file size and bandwidth settings you are using when encoding the sound file. A larger target file size requires less compression and audio degradation but more end-listener bandwidth capacity.

Server performance -- the ability of the server to detect and send the appropriate stream to the end listener -- is often just as important a factor in producing an overall quality listening experience as the codec.

5.3.6. Low bandwidth performance overall

Nobody likes to scrimp on quality or excitement, but if you have to tailor your media to fit the lowest common denominator of your audience, you will have to make some tough choices. Some formats, such as RealMedia, excel in bandwidth and browser compatibility. Other formats, such as Shockwave or Flash, work better in high-bandwidth 56 Kbps and DSL environments and provide little to no support for server-side bandwidth negotiation.

There are two factors to consider when selecting a format for low-bandwidth environments: the inherent ability of the format to provide compelling media with small file sizes, and the server-side technology to manage the delivery of media when constrained by low or fluctuating bandwidths.

Beatnik, for example, packs a huge punch of interactive excitement in an extremely compact file size because it utilizes MIDI. The use of bandwidth-friendly MIDI technology gives Beatnik an inherent advantage over Shockwave or RealMedia. On the other hand, RealMedia provides better server-side support for ensuring that files get delivered and do not drop out, regardless of the bandwidth of the end user.

5.3.7. Server performance and software quality

Thinking big? For those of you who need to stream audio and video content to thousands of simultaneous listeners on the scale of a CNN, NPR, or C|net, you will need a format that provides powerful server-side features and tools. And if you plan on broadcasting live events, you will need a real-time encoding and streaming system that runs on a dedicated web server.

RealMedia and Windows Media are the leading technologies for large-scale broadcasting, with SHOUTcast (MP3) and QuickTime close runners-up. The RealServer and Windows Media Server provide bandwidth negotiation that ensures smooth audio playback for the end listener and prevents annoying drop-outs when bandwidth fluctuates.

Beyond the actual server software you choose to install, whether it's RealMedia, Windows Media, SHOUTcast (MP3), or QuickTime, streaming to a large audience is just as much or more about the hardware and bandwidth as the format you choose. Large-scale broadcasting requires multiple systems, servers, and huge bandwidth connections. That's why many companies outsource their media broadcasting to companies like Broadcast.com or Network24.com. For a further analysis of the characteristics of each format, refer to Appendix B, "Audio Format Comparison". It contains a chart that will help you select the appropriate format.