This course introduces techniques and concepts of digital video editing. Students will produce movies and discuss practical ways to distribute to various audiences.

Analog vs. Digital

An analog video signal is what we see represented when we watch a VCR tape. It 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.

Copying analog videotape results in a drop in quality. This is because every time an analog signal is amplified, electronic noise is introduced into the signal. Every time this is repeated more noise is added resulting in poorer and poorer quality compared to the original signal. For audio, the noise is a hiss or hum. Video noise is a subtle snow pattern in 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 are set in stone. 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.

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 video digitized and into your computer. This process is called capturing. 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 pointss 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 VCR tape or burn on to a DVD/CDR. Then invite all your family and friends over to watch your beautiful work of art. They will be cheering and begging for more.

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. The NTSC (National Television Standards Committee) system consists of 525 lines per frame. (Only about 480 reach the average viewer) the remaining lines are used for information such as closed captioning for the hearing impaired. 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. One frame is about 1/30th of a second, or 30 frames per second. In reality NTSC is 29.97 frames per second. Progressive scanning occurs on computer monitors and some high end televisions.

Interlaced Scan

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 is used to reduce flicker and brightness variation during the scanning process.

Our good ole American Standard:
NTSC (National Television Standards Committee)
525 lines per frame @29.97 fps @ 60 Hertz

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

Video Formats

• DV (digital video)
  • MiniDV
  • DVDPro-25
  • DVCAM
  • Image quality is the same across all three, the way the information gets writen is different. All are digital formats.
• SD (standard definition)
  • DVCPro-50 (digital)
  • Betacam SX (digital)
  • Betacam SP (common analog format)
  • DigiBetacam (digital)
  • Used for high end broadcasting and cable casting
• HD (high definition)
  • HDV 1440x1080 (JVC 1280x720p, Sony 1920x1080i)
  • DVCPro-HD(100)
  • HD - 1080i = 1920x1080

Video Sizes

Video is fixed in size - 72 DPI

DV-NTSC 720x480
DV-PAL 720x576

SD-NTSC 720x486
SD-PAL 720x576t

Why did DV switch to 720x480 instead of 720x486? Because both numbers are divisible by 4 and compression is done in blocks of 4x4.

HD-18 different scan rates in US
HD comes in progressive or interlace

HD 480i and p
Broadcast

HD 720i &p - 1280x720
HD 1080i &p - 1920 x1080

All HD formats are 16:9

HD 720p and HD 1080i are the most common.

HDV 1440x1080

JVC downgrades to 1280x720p
Sony stretchs to 1920x1080i