Two types of media

Time-dependent or Time-independent

Digital Video and Audio are time-dependent

Time-dependent media stress the system

Sampling or Sequencing

Raster (Bit-map) or Vector

Digitized Sound or MIDI

Digital Video or Animation


Audio (Sound)

Compression and Rarefaction of Air

Digitized Audio vs Sequences

MP3 = digitized audio

MIDI = sequenced audio


Digital Audio Issues

Sampling rate (how many samples a second)

Resolution of each sample – amount of information


CD Quality = 44.1 kHz with 16 bit resolution (stereo)

10.5 Megabytes to store 1 minute


Digital Audio Formats

.snd – Macintosh sound format (sound file)

.wav – Microsoft sound format (wave file)

Real Audio format for WWW

.mp3 - MP 3 files (Motion Picture Experts Group)

Uses compression to get audio files down in size

MPEG 1 Audio Layer-3


MIDI Musical Instrument Digital Interface

Records performance information

Sequence of notes or actions

Can be used to control other things

Much more efficient than waveform audio recordings

Use MIDI Sequencers, Synthesizers


Digital Video

The eye sees motion when shown over 24 images a second

A digital video clip is a sequence of images

Animated or Digitized

Quality is a matter of

Frames (samples) per second

Resolution of images

Size of files makes it hard to use digital video

Bandwidth problems within computer


Digital Video

Sampling and Quantizing

DV = sequence of digitized images


Digital Video Formats

NTSC – National Television Standards Committee

1953 Standard for television signal (PAL, SECAM)

QuickTime – Apple format (for both PC and Mac)

Allows different types of compression

.qt or .mov

MPEG – different formats

Do not confuse with MP3 files – audio files

DVD – (Digital Video Disk or Digital Versatile Disk – uses MPEG-2 for video)

4.3 Gigabytes (other standards coming)

AVI – Microsoft (Audio Video Interleave)

Flash (SWF) - Animation format for Web


Created by Geoffrey Rockwell, October, 2003