CXO

Edit digital media content

If you work with sound and/or video media content, you may need to know how to edit the digital format. Here's how.

By Joseph T. Sinclair

Sound editing

The key to creating quality streaming audio is to make the signal as strong as possible without creating distortion.

Audio editing programs not only record but also enable sound editing and filtering so that you can both improve the quality of and rearrange your audio. Audio editing programs let you cut and paste audio clips just as you would cut and paste text in a word processor; you can also add sound bites (including sound effects) at any point in a recording and run filters such as noise reduction and hiss reduction.

You can use these techniques without being an audio engineer. Sound Forge XP, a sound editing program with specialized features for the Web, includes excellent information in its user manual about editing and filtering. If you are an audio engineer, you might want to try the professional versions of the sound editors Cool Edit and Sound Forge.

The best way to get an acceptable, noise-free sound is to record it properly in the first place. You can try using filters to reduce noise, although their capabilities are limited: they can't make a poor recording into a good one. If you don't have a noise-free recording, you cannot use audio compression effectively because compressing the file will actually make the noise louder. Audio compression is important, however, because it reduces the range of the sound dynamics and thus enables an increase in the volume without an increase in distortion. In every case, check the DC offset before you begin.

You should also equalize the recording during editing. Equalization boosts the volume in several portions of the audible frequency spectrum to change the tone of the recording. What you want to do is boost the middle frequencies to offset the bass effect that will be caused later, during encoding. The last step in your sound editing is normalization. Never skip this step; it increases the volume as much as possible without distorting the signal. If you plan to encode your clips, start with the strongest quality audio, because encoding diminishes a signal significantly.

Video editing

Video editing is a different animal from audio editing. Although inexpensive editing software is available and comes bundled with video capture cards, you will probably find it tedious to use. Real-time video editors provide more convenience but remain quite expensive. Many real-time editors are hardware-software combinations with five-digit prices. Avid Technology is a leader in making such systems. For the Mac, Apple's new Final Cut Pro is a professional-quality digital video editing system available for $999 retail.

Unfortunately, video editing programs are among the most complicated programs you'll ever use, but you can still do some simple things without being a videographer: you can cut and paste, add on and add in, make transitions, and add titles without much expertise. Adobe Premiere, available for a retail price of $549, is one of the most robust video editing programs for nonprofessionals.

Sound quality needs special attention in video production, so all of our recommendations about sound quality apply to video as well as audio.

Joseph T. Sinclair developed the first gourmet food store on the Web in 1994 using Web database technology. He has written seven books about the Web.

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