Digital Media

1
Digital Media Data Representation
2
Why Digital Media Requirements Matter

• Storage Management and Planning
• How much must be stored
• How to store it efficiently
• Compression Approaches
• Lossy vs. Lossless Formats
• Transmission Management and Planning
• Sound Music (Phone, Radio, CD vs. MP3 quality)
  
• Graphics (BMP, JPEG, GIF, etc).
• Note Size matters especially for web
  transmission
• Quality versus Size Tradeoffs

3
Character Representation Codes
4
Information Theory

• Permutations (Unique Combinations) translate to
  how many different states can be stored and
  transmitted
• Series of bits represents permutations through
  unique sequences of on off
• Powers of 2 (2n)

5
Understanding Binary

• Most modern media, data representations,
  transmissions and computer based addressing
  schemes use binary, Eg.
• Images including pictures video (jpg, mpeg)
• Sound and Music (CDs, MP3)
• Digital Photography (RAW, jpg, tiff)
• Color schemes on Web Pages (RGB005533)
• Internet Protocol (IP) addresses (192.23.55.231)

6
Powers of 2 Binary Numbers
23 23 26 23 23 26 23 8 26 64
Same as 8 8 64
7
Binary Position Table
8
Representing Decimal Numbers in Binary

• Decimal to Binary Conversion
• Convert decimal 105 to Binary Bit (Binary
  Digit)
• 8th position Subtract 128? NO gt 0
• 7th position Subtract 64? YES gt 1 ? 105
  64 41
• 6th position Subtract 32? YES gt 1 ? 41 32
  9
• 5th position Subtract 16? NO gt 0
• 4th position Subtract 8? YES gt 1 ? 9 8
  1
• 3rd position Subtract 4? NO gt 0
• 2nd position Subtract 2? NO gt 0
• 1st position Subtract 1? YES gt 1 ? 1 1
  0
• So decimal 105 has a Binary Equivalent
  of 01101001

9
Converting Binary Numbers to Decimal

• Binary to Decimal Conversion
• Convert 10010110 (binary) to Decimal
• 1st position 1 x 128 128
• 2nd position 0 x 64 0
• 3rd position 0 x 32 0
• 4th position 1 x 16 16
• 5th position 0 x 8 0
• 6th position 1 x 4 4
• 7th position 1 x 2 2
• 8th position 0 x 1 0
• ? Sum 150

10
Media File Compression

• Definition
• Image and sound files can be quite large, and
  larger files mean more storage space and slower
  downloads. Compression means file size
  reduction. Compression schemes can be lossy or
  lossless.

11
Lossy vs. Lossless Compression

• Lossy
• Lossy algorithms accept some degradation in the
  image or sound in order to achieve smaller file
  size.
• Lossless
• A lossless compression algorithm discards no
  information. It looks for more efficient ways to
  represent an image or sound, while making no
  compromises in accuracy.

12
Number of Colors

• of color options in a pixel is given by the
  following formula
• color options 2 of bits of image
• Example if a file format is said to have 8 bits
  (or one Byte), it supports 28 256 colors

13
Size comparisons for Familiar Formats
14
Quality Comparison
JPG, High quality (319 K)
JPG, absurdly high compression (18 K)
15
Representing Graphics and Video

• Storage per representation scheme
• Resolution Number of pixels per image
• Color Quality Number of bits/pixel
• Motion Quality Number of frames/second
• Duration Number of seconds
• Codec Compression ratio
• Image File sizes and quality
• Bitmap (original) vs. JPEG (lossy compressed)
• See next slide

16
.BMP (442 KB) vs. .JPG (21KB)
17
Vector Graphics GIF example

• Combines geometrical shapes to create artificial
  images.
• Generally uses much less storage space than real
  images.
• Adobe Illustrator Software

18
Digital Graphics Applications

• Desktop Publishing
• CAD (Computer Assisted Design)
• 3D modeling
• Computer Animation (Toy Story)
• Photo Editing (Photoshop/Elements)
• Digital Video (Movies, editing, Forensic
  Graphics, etc.)
• Education and Training. (e.g. Virtual Chemistry
  Lab developed at BYU)
• Video Games (Halo, Madden NFL Football)
• Advertising Promotion (Prius)
• Interactive TV (Video on Demand, tCommerce, PVR)

19
Digital Photo Editing

• Another advantage of digitizing images and sound
  is that computers and software may be used to
  enhance or modify the original artifact. This is
  much easier and less expensive than using analog
  methods.
• The following modification was a simple edit
  using Photoshop elements.

20
(Photo Editing Adjust Contrast Brightness)
Original vs. Filtered
21
High Definition TV

• HD Lines per screen horizontal scan
• 480
• 720
• 1080 highest resolution
• Scanning Formats
• i Interlaced 2 half-frames (every other line)
  make a complete picture
• p Progressive full frame displayed generally
  best
• Capability Terminology
• HD Ready Display only requires HD source
  (e.g. HD tuner)
• Integrated HDTV Has HD TV tuner built-in only
  needs antenna
• (this is also called HD Built-in)
• HD Built-in DCR digital cable ready requires
  a cable card to receive digital cable, or antenna
  to receive over-the-air broadcasts.

22
Representing Sound

• Sampling rates (frequency) (Hertz)
• Sampling resolution (bits per sample)
• Number of channels (mono vs. stereo)
• Duration of sound (Time)

23
Common Sound File Formats

• .aac Advanced Audio Coding (Apple)
• .au Audio used with Apple Linux OS
• .cda - Compact Disc Audio traditional CD
• .mid MIDI commands
• .mp3 common music compression format
• .ra Real Audio (company)
• .wav Waveform Audio (Windows raw audio)
• .wma Windows Media Audio - compressed

24
Quality MP3 At Different Encoding Bit Rates
Source http//www.pcmag.com/print_article/0,3048,
a35271,00.asp
25
QUIZ