1. 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

2. Audio (Sound)

Compression and Rarefaction of Air


Digitized Audio vs Sequences

MP3 = digitized audio
MIDI = sequenced audio

3. Digital Audio Issues


Sampling rate (how many samples a second)

Resolution of each sample – amount of information

Quantization
CD Quality = 44.1 kHz with 16 bit resolution (stereo)
10.5 Megabytes to store 1 minute

4. 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

5. 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


6. 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


7. Digital Video

Sampling and Quantizing


DV = sequence of digitized images


8. 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