DV editing - the actual process

After you have the digital video in compressed format and have captured onto your computer’s hard drive, editing can start which spans two basic functions – database management and rendering. The database management aspect means keeping track of where your various scenes are, how long you want them to be, and then in what order you want them to play back in. The kind of thing which we call time line.

When you edit a scene , actually you are editting the time line – deciding where the scene begins and ends, you are not really changing the scene at all. You are simply telling the editing software’s database to keep track of these new video locations and use them when playing back the video. This is why it is easy to change your clipstart and end frame or in and out frame, as well as to create alternate versions of the same clip. When you edit your video together, the database then keeps track of which scene should be played first, which should be played second, and so on. If your entire movie consisted only of cuts, the video would not have to change at all. The database would simply have to keep track of all the in and out points, as well as the playback order of the trimmed scenes.

Because it is just a database of play commands – not an actual video file, it is easy to re-arrange the scenes over and over again until you get them just right as per your plan of edit.

Creating a Digital Video for Edit

The captured video from your analog type of camcorder like a VHS or 8m camcorder, your video and audio footage has to be converted into a digital format such as MPEG. The video has to be converted from an analog representation (sort of like the groves in a vinyl record) to a series of digital 1s and zeros. There are a bunch of hardware solutions that can do this. These digital capture cards can be inserted in your computer. Prices start belwo 100$ each and can go up to the thousands, depending on quality, bandwidth, features and bundled softwares.

If you really want to avoid opening you computer to install capture card, you can use a MPEG peripheral device such as the Dazzle Digital Video Creator. You plug your analog video (S-video or standard) into the box and then the MPEG digitized video flows over a USB or parallel cable into the computer.

Also you do not need to playback from tape. You can plug your camcorder or video camera into your computer or MPEG device and capture it directly to the hard drive, eliminating tape. Unfortunately, unless you are using a small portable notebook computer, this limits your videotaping mobility.

As part of the hard drive capture process, the digitized video needs to be compressed and made smaller. Raw video streams out at 30 megabytes a second or more. That is a lot of data and most of computers and hard drives cannot handle that flow. By using a variety of compression technologies, the video throughput can be shrunken by a factor of 3 to 1 to 100 to 1. In general, the more you compress your video, the more you reduce your quality. However, compression rations of 3 to 1 and 4 to 1, usually do not create noticeable loss.

Current compression technologies work by analyzing the video stream and assessing which video information can be left out and eliminated. For example, if you have a person standing in front of a blue wall, the technology recognizes that the blue wall is uniform in color and is not changing, Therefore it can be compressed a lot more than the person who is talking.

The choice of compression technologies is wide including QuickTime, Motion jpeg (M-JPEG), MPEG1, MPEG2 and the new MPEG 4. Confusing the issue is that a technology such as M-JPEG may have various different codecs (short for COmpression-DECompression) that actually do the compression and decompression of the video and audio. You also need to remember that various codecs may not talk to each other.