Creating Great Audio for the Web
Pages: 1, 2
Audio Production Software
Here's a list of some of the many companies producing audio recording/editing programs.
Once you have your audio recorded, you will probably want to do a little cleanup. The first thing to do is to play back your recording and check for any auspicious sounds or hiss. Cleanup of pops or audio spikes can be easily done by zooming in on the waveform and removing those sections that are creating the problem. Removing hiss is a bigger problem; hiss usually occurs because of poor recording equipment and/or the audio wasn't recorded at a proper level. There are a few things you can do. Some audio programs come with hiss or noise reduction plug-ins. I tend to steer away from these, mainly because they have a tendency to chop off a lot of the high-end frequencies and give your audio an unnatural sound. I prefer to use equalization (EQ) to remove any hiss. You can do this by using a notch filter (which raises or lowers a specific frequency that you choose) or a low-pass filter, which allows you to select a certain frequency as a "roof"; only frequencies below this roof are allowed to pass.
You may also have noticed that upon playback your recording does not have a consistent signal level to it; there are loud parts and quiet parts. Chances are that you will want to even these out by using some dynamics processing. Usually you will want to have an even balance between your high and low frequencies, which can easily be done using equalization. Once you are satisfied with the quality of the audio, you will probably want to compress it to make the output level more even. In the audio world, compression is not squeezing large amounts of memory into a smaller package; it is a way to turn the peaks and valleys of your audio wave into a wave with a consistent decibel level. This allows for the raising in volume of quiet sections and the leveling off of loud sections.
Presenting your material
Now that you've got your audio all ready for the world, you have to choose from the many formats that are used by different audiences. You will need to answer some of the following questions before you put your material up on your site:
- Should you stream your audio or make it available as a download? Streaming audio is great for those with low-bandwidth connections, but you may sacrifice some audio quality. Downloads keep the integrity of your audio, but those with a slower connection may not want to download a large file. If you are going to make MP3s available for download, I highly suggest that you encode the MP3 using Media Cleaner Pro, which uses the best compression codec that I've seen, which translates to smaller file size at the same quality as other codecs.
- What is your target audience's connection speed? Making a download available is viable, but users with a slow connection will not like to wait for your file to download. If your target market leans towards technology, chances are that the users will have a broadband connection and can handle downloading a large file. If you plan to stream your media, you can use a SMIL script to target different connection speeds, but you will have to encode a different RealPlayer file for each connection speed you choose to target.
- If you have a long presentation, will your audience stick around for the whole thing? Think of this from the user's standpoint. They may be interested in only a few key points of an interview. If you present a 30-minute presentation, should you possibly give your users a chance to just view the highlights?
Notes on streaming media
In order to stream Realmedia, your content should reside on a server that owns a RealServer license. (Note: You can serve from an HTTP server, but the HTTP protocol downloads files without regard to timelines, making clips with timelines more likely to stall). Quicktime presentations also should come from a Quicktime server. Luckily, you don't have to have both types of servers if you present both Quicktime and RealMedia presentations. Apple and RealNetworks recently announced that RealNetworks has licensed Apple intellectual property for streaming digital video and audio over the Internet in the QuickTime format. RealNetworks also announced that its RealServer 8 now supports the delivery of Apple’s QuickTime-based content to Apple’s QuickTime players and is immediately available for download.
At this point, you may be ready to make your streaming presentation available to the public. As I mentioned before, you can host your presentation on a normal HTTP server if you do not have access to RealServer. I don't recommend this for
lengthy or complicated presentations, however, or for clips viewed simultaneously by large groups. If you are serving from an HTTP server, you will need to create a .ram file to point to from your link. This is easily done by opening up a text editor, entering the full URL of the media clip, and saving the file as
filename.ram. Then just upload the .ram file onto your server. When the user chooses the link that points to the .ram file, the browser sends a request to the server. The server sends the .ram file, which causes the Web browser to launch RealPlayer. RealPlayer receives the .ram file and requests whichever file the .ram file is pointing to on the web server, and the content gets streamed to the user.
If you are using a RealServer, you will probably want to link to your files using Ramgen. The Ramgen feature automatically launches RealPlayer, eliminating the need to write a separate .ram file. Your web page URL simply points to your media clip or SMIL file on RealServer and includes a ramgen parameter.
With high-bandwidth connections becoming more prevelant, you can bet that web sites will contain more entertainment using multimedia presentations. Now that you know the basics, you should be able to create some media content of your own. The best way to learn is to experiment with your recordings; add some reverb, use different encoding codecs, find out what does what, and pick and choose the techniques that work for you. After all, hands-on experience is where the real learning begins.
Discuss this article in the O'Reilly Network General Forum.
Return to the O'Reilly Network Hub.