Introduction to Interactive Media 03: The Nature of Digital Media

Introduction to Interactive Media

03: The Nature of Digital Media


WHY DO WE NEED TO UNDERSTAND THE NATURE OF DIGITAL MEDIA?


Digital is our Medium

• All of the materials we work with as interactive media creators must be digital.


SO WHAT DOES IT MEAN TO BE DIGITAL?


Digital is not Analog

• Analog data is continuous

• Digital data consists of separate, discreet pieces.


An analog /digital analogy

Hour glass to tell time. Wind mill motion.


Anything Digital is Made of Bits

• A bit is a 0 or a 1.– 1 = on, 0 = off

• All digital files are ultimately comprised of 0s and 1s.


HOW DO WE CONVEY COMPLEX INFORMATION USING ZEROS AND ONES?


Bits and Bytes

• Putting bits together allows you to encode more complex data.

• E.g. if we use 2 bits, we can represent 4 different possible things.– 00, 01, 10, 11


Building Digital Codes

• Number of distinct bit combinations that can be produced is given by the formula 2n. – n = number of bits used in the code.

• Adding a bit to the string of bits, doubles the number of possibilities you can represent.

2 1 2 2 2 3 2 4 2 5 2 6 2 7 2 8

2 items 4 items 8 items 16 items

Complete the table to identify the number of distinct items represented by 2 5, 2 6, 2 7, and 2 8.


Common Codes

• ASCII-8, an 8 bit code. – 256 characters in English language.

• Letter A = 0100 0001• Number 5 = 0011 0101

• 24-bit color. – Displays the full range a human eye can perceive.

• 16-bit sound. – Plays the full decibel range the human ear can perceive.


8 Bits = 1 Byte

• File sizes are often referred to in Bytes, Kilobytes (1000 bytes) and Megabytes ( 1 million bytes).

• File size indicates number of bits in the file.

• How many bits are in a 40KB file?


SO… IF EVERY FILE IS JUST ZEROS AND ONES, HOW DOES YOUR COMPUTER KNOW WHAT TO DO WITH IT?


Digital Files

• A container for binary codes.• File formats define how instructions and data are

encoded in the file.• Without a specific file format, a binary code has no

meaning.


All About Files

• File size– Measured in units of bytes.

• 1 byte = 8 bits• Kilo (1,000) Bytes, Mega (1 million) Bytes, (1 billion) Giga Bytes.

• File extensions – Series of letters to designate the file format.

• .fla, .exe, .rtf, .jpg• Help the OS find the right program to launch the file.

• File compatibility – Ability to use the file in a different platform of hardware and software.


Different File Types

• Program files– Contain executable instructions.

• Data files– Can hold text, images, sounds, video, animation.


Data File Compatibility

• Cross-platform compatible files.– Open and use on any computer hardware and software

configuration, e.g. .JPG, .TXT

• Files that are native or specialized to the application that created the data file.– Require source application to open the file.

• E.g. PhotoShop files .PSD


File Maintenance

• Preserve original and derivative files

• Effective file maintenance involves:– Identification - create descriptive file names– Categorization - group related files– Preservation - back-up

• Why is file maintenance so important in this field?


HOW DO WE CONVERT ANALOG INFORMATION INTO DIGITAL FILES.


Digitization

• To be able to manipulate images, sound, video it must be in a digital format.

• Analog -> Video Conversion = Sampling• Always involves making a compromise.


Examples of Analog -> Digital

• Digital camera

• Scanner

• Recording audio on computer or with digital audio recorder

• Digitizing video or shooting video on a digital video camera


Sampling = How much to capture?

Sampling analyzes a small portion of the analog source and converts it to digital code.


Sample Quality

• Factors that influence sample quality– Sample Resolution.

• Number of bits used to represent digital sample.– More bits = more precision.

– Sample Rate.• Number of samples taken in a given unit of time (sounds)

or space (images).– More samples taken - more info within a given space


How Sample Resolution Affects Quality

Image Sound8 bits / sample 8 bits / sample

24 bits / sample 16 bits / sample

Which image uses fewer bits to describe the color sample?

Which image and sound sample will have better quality?


How Sample Rate Affects Quality

Image Sound72 pixels / inch 11 kHz

300 pixels / inch 44 kHz

Which image has higher spatial resolution?

50ppi 300ppi


IF CONVERSION TO A DIGITAL FORM REQUIRES A COMPROMISE – WHAT ARE THE PROS?


Pros of Being Digital

• Reproduction without generation decay.• Editing and re-editing is much easier

than with analog media.• Integration of media using cut, copy,

paste is more efficient.• Distribution over Internet - nearly

everyone can be reached by anyone else.


HOW DO WE DELIVER ALL THESE BITS AND BYTES OVER THE INTERNET?


File Compression

• Process of re-encoding digital data to reduce file size.

• Codec: a program to compress a file into a smaller size and decompress it into a usable form.

• Improvements in compression techniques have facilitated the advancement of sharing, displaying images, video and audio over the Internet


Lossy vs. Lossless Compression

• Lossy– Number of bits is reduced and some data

is lost. – Lossy strategies include MP3 and JPEG

compression.

• Lossless– Efficient encoding reduces file size without

loss of original data.– Lossless strategies include TIF


Lossy or Lossless Compression?

1. Photograph of sailboat on ocean.2. Journal article explaining

nanotechnology.3. 1812 Overture by New York

Philharmonic Orchestra.4. Database of student names and

addresses.5. Video of hot air balloon flying over a

cornfield.


NOT ALL DIGITAL FILES ARE STORED IN THE SAME WAY.



Digital Encoding of Media

• Description-based encoding– A detailed representation of the discrete

elements that comprise the media.

• Command-based encoding– A set of instructions the computer follows to

produce the digital media.



Digital Coding ComparedDescription

(All Audio except MIDI, PhotoShop files)

Command(Flash, Illustrator, MIDI)

Advantages

Represent natural scenes and sounds.

File sizes are small.

Supports detailed editing. Scaled without distortion.

Limitations

Large file sizes. Not appropriate for detailed photographs and natural sounds.

Lose quality if enlarged. Requires knowledge of music and vector image creation.


Command vs. Description

• Let students do green circle exercise.Introduction to Interactive Media

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Introduction to Interactive Media 03: The Nature of Digital Media