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Academic Technology

New Media Station Documentation - Digital Video Basics

Digital video can mean many things. At the most general, it means any computer file or network transmission that contains video—moving images plus sound. To create digital video, an encoding process converts an analog video signal from a tape or camera into binary computer data. It is also possible to directly capture live action and sound to a digital file using a digital video camera. Either way, the encoding process produces a file that stores a representation of the images and sound in a particular format. Using a computer, these files can be played back and edited.

In most cases and for much of this documentation, digital video refers to one particular encoding process and its resulting format that is very widely used today. This format is DV, which appropriately stands for Digital Video. DV allows for both high quality recording as well as non-destructive editing. Unlike editing analog video where the quality is reduced with each copy, the digital information is not degraded when working with DV files, no matter how many copies or edits are made.

Here are some technical details on DV:

In layman's terms that means DV handles standard US (NTSC) and European (PAL) television resolutions and allows for stereo sound at CD-quality. It also means that DV is BIG! For every second of DV, there are 25,000,000 bits of data. A 5-minute long video will be stored as a nearly 1-gigabyte file in DV format. This is important to keep in mind in terms of both time (see below) and space to save your work.

In order to work with DV, you must either record the material in DV format in the first place using a DV camcorder (aka Mini-DV camera), or a converter device is necessary to encode the analog video signal, like that from a VHS tape, in DV format. You also need a computer and editing software to do the work. In order to interface the camera or converter with the computer, a connection is made using the Firewire standard. Firewire is a high-speed interface also known as iLink and IEEE 1394 that can easily handle the high bits-per-second data rate require needed to transfer digital video in real time.

The Student Computing Cluster "New Media" workstations have all of this available. Our hardware and software currently includes:

These workstations allow users to import video content from DV cameras, VHS tape, or other video source into the computer. From there, the DV file can be edited using iMovie to cut and paste together video clips, add and edit audio tracks, incorporate still images, create titles, and perform various transitions and special effects. The final product can be saved as a QuickTime movie file, written back to MiniDV or VHS tape, or burned to a DVD.

Much of the work on our New Media workstations is done using Apple's iMovie software. iMovie is a fairly easy program to learn. The rest of this documentation covers specific tasks about working with iMovie in our particular environment. If you are interested in general information about iMovie, there are many good sources already available:

One last note about working with digital video—it takes time—lots and lots of time. For starters, the time it takes to get the video from the tape into the computer takes as long as it does to play the tape. To capture a half-hour long video, it will take 30 minutes. The time it takes to do the editing will vary depending on the complexity of your project. Finally, outputting the final product also takes a lot of time. If you are making a QuickTime file or a DVD, the video must be encoded into a different format. This encoding process can take one to two times the length of the video. To record back to tape, you have to play the file and record in real time, just like capturing it in the first place. The time issue is important to be aware of upfront, but the power, capabilities, and just plain fun of working with DV do make up for it. Just plan accordingly!