First consider

Type of video - Entertainment, instructional, commercial, presentation

How it's used - Immediate access, reference, archive, kiosk, interactive, hyperlinks

Delivery methods - Web (modem or LAN), CD, DVD, tape

Quality vs filesize - Bigger windows and higher quality takes more storage and faster equipment for playback. Web streaming won't allow this high data rate.

Formats to consider

Video can be most difficult to compress when it's highly detailed, has lots of motion (especially camera motion), or lots of fast cuts. These all increase the required data rate to hold quality consistent. Looked at another way, motion and detail decrease quality for a set data rate. The following samples represent this difficult to compress video in order to show what this type of clip looks like when digitized.

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Real Video

Reasonable quality at low data rates. Best mostly for web streaming. Window size is usually small, frame rate is low. Can be set to disallow saving. Players available for Windows or Mac. www.real.com

Quicktime

Reasonable quality at low data rates, great for web or video CD. Allows streaming, multiple layers, captions, and hyperlinks. Can be set to disallow saving. With video CD the window can be large and frame rate high, if played on a very fast computer. Players available for Windows or Mac. www.apple.com/quicktime

AVI

Best use is video on CD. With video CD the window can be large and frame rate high, if played on a very fast computer. Players available for Windows or Mac. www.microsoft.com

MPEG-1

High quality quarter screen video using larger data rate. Gives full frame rate for best motion, also scales well to full screen. Does not stream, must be downloaded for web use. Also works well for video CD or DVD. Players available for all systems. Audio files can also be compressed well, and will stream. www.mpeg.org

MPEG-2

Very best quality with very large data rate. Full motion and full frame. Best quality for DVD and satellite delivery. Requires special hardware for playback. Not advisable for web or CD.

All formats have adjustable audio rate/quality, but generally audio quality must be limited for any web use, especially streaming.

Maximum video file sizes in MB

Other useful notes

A 100 MB Zip disk can hold:
71 min of Real, QT, or AVI @ T1
9 min of MPEG-1
1.5-3 min of MPEG-2

A CD can hold:
7.5 hrs of Real, QT, or AVI @ T1
59 min of MPEG-1
10-21 min of MPEG-2

A DVD can hold (per layer):
7 hrs of MPEG-1
1-2.5 hrs MPEG-2

Digital Video Mini Glossary

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