Video Editing I - Overview

This course introduces techniques and concepts of digital video editing. Students will produce short video programs, critique peers work and discuss distribution to various audiences.

Introduction to Digital Non-Linear Editing

Analog vs. Digital


analog waveAn analog video signal is a signal that is continuous with varying voltage levels and frequency. The high part of the wave is the bright part of the picture, while the low parts of the wave consist of dark parts of the picture.

A digital video signal assigns numbers to the amplitude and frequency of an analog signal and breaks it down into 1's and 0's. These numbers correspond to the original analog signal and don't change. A number of “0100” might represent a value of 3 on the analog wave. Therefore if you make a copy of a copy of a copy there will be no loss in quality because the anolog wave file isn't copied, the number assigned to the wave form is.

Linear vs. Nonlinear Before we had Non Linear Editing (NLE), we had the dreaded Linear Editing. Thank goodness for all the advances in digital technology. Did you ever hook up one VCR to another so that you could edit a tape? Well you may not have known it, but you were performing linear editing. Basically, you could add parts to your new tape in a linear fashion. There was no easy way to go back and add something or fix a mistake in the middle of your work.

Professional editors were able to purchase very expensive assemble editing systems. These systems often included tilters, special effects, and the ability to edit and add transitions from two or more video sources (A/B roll editing). Only very expensive, high-end editing decks were able to insert editing in the middle of your work.

Non Linear Editing (NLE) is editing done from your hard drive. All you need is some editing software and a way to get your digitized video and into your computer. Once your files are on your hard drive they can be assembled in any order by simply clicking and dragging. Since it's all digital, you can select In and Out points of each video clip, add effects and transition, add multiple video or audio tracks (compositing), create titles, and bring in graphics. You are only limited by your imagination and the hours in a day.

When you're done editing and fine tuning your movie (which is really never), you're ready to export your video to a format that makes sense for your audience. Internet video sites such as YouTube are very common and easy to access and often a good choice.Then invite all your family and friends over to watch your beautiful work of art or post the video on Facebook.

Video Basics
Our beloved TV (at least one in every household) has a screen, which we like to stare at. One might think that the picture on the TV screen consists of frames, like a really fast slide show. It does contain frames, but each frame is made up of 2 fields. TV monitors consist of hundreds of horizontal lines. Along each of these lines there are thousands of points of brightness and color information. The means by which video images are recorded and displayed is a scanning process.

Interlaced Scan
The lines do not just appear in a linear fashion say from top to bottom (progressive scanning), they are interlaced. This means that the lines are scanned, first odd, then even. A scan from the top to the bottom is called a field. Upon the second scan one frame is completed. Therefore there are 2 fields to a frame. The topmost scan line is called the upper field and the other is called the lower field.

  1. A picture is scanned from top to bottom.
  2. The odd lines are scanned to create field 1.
  3. The even lines are scanned to create field 2.
  4. Field 1 and 2 are combined to form 1 frame (interlacing).

*Interlacing had been used to reduce flicker and brightness variation during the scanning process.

Progressive Scan
Progressive scanning does happen in a linear fasion. So it starts with the top scan line and move in order to the bottom. You see this on our HD TVs, computer screens, etc.

Our good ole American Standard (No longer used):
NTSC (National Television Standards Committee)
525 lines per frame @29.97 fps @ 60 Hertz

Current HDTV standards
High-definition television (HDTV) resolution much better (about five times as many pixels) than standard-definition television (NTSC).

HDTV formats:
1080p: 1920×1080p:
1080i: 1920×1080i:
720p: 1280×720p:
"p" = progressive scan
"i" = interlaced scan

Other standards include:
PAL (Phase Alternative Line)
625 lines per frame @ 25 fps @ 50 Hertz
Used in Europe, Asia, southern Africa
SECAM (Sequential Couleur avec Memoir)
625 lines per frame @ 25 fps @ 50 Hertz
Used in France, Middle East, N. Africa