Using Video

The science of video Why do we perceive it?

The psychology of video Where do we use it?

The technology of video How can you capture and edit it? QuickTime VR process

The science of video

Exploited human visual limitation:We cannot perceive easily visual differencewhen they change faster than 10 Hz

The psychology of video

A powerful medium, conveying: Motion Changing facial expressions Associated audio

Significant emotional impactTend to relate video with realityDisadvantage:

Slow for users with dialup connections (but improves quickly)

Best for users with broadband connections Which is approaching half of U.S. households that have Internet

connection Includes most company intranets

The technology of video

If it is recorded as raw video, i.e., a full image per frame, it can be huge.

Rate = frames/sec (aka: fps) Raw size = frame size * length of video For 10 sec raw 30 fps video of size 640 x 480 true color video

(640 * 480 pixels) * (24 bits/pixel) * (30 frames/sec) * 10 sec / 8 bits/byte = ________

Compression algorithms record only differences between frames

Quicktime .mov Mpeg Avi

5

Tips for recording video

Choose camera carefully.

Steady the camera, use a tripod.

Avoid shooting into light and backlit scenes.

Limit pans and zooms.

Frame the subject.

Make inventory of required shots.

Use highest resolution available.

Add external microphones.

Use headphones to monitor sound quality.

Record background sound for use in editing.

Don’t break the time code.

Medium shot

Close up shot

Extreme close-up – the best

Video formats for the Web

Name File extension

Originator Additional

codec?

Streaming? Additional

player?

Audio-Video Interlaced

.avi Microsoft Yes No No

QuickTime .mov .qt Apple Yes Configurable

No

MPEG Video (MPEG-4)

.mpg Motion Picture Expert Group

No No No

Real Video .ram .rm RealNetworks

No Yes – requires server software

Yes

Chapter 11: Multimedia

Copyright © 2004 by Prentice Hall