1. Utilizing digital media files
Some type of digital files
Text files (all ASCII encoded)
Audio files (bits encode height of sound samples)
Image files (picture elements are encoded)
Video files
Compressed files (any data type can be compressed)
Tools that manipulate digital data
Ex: snipper; paint; photoshop; etc.
Chapter8 Digital Media

2. What types of files are on your computer?
Click on libraries in the task bar
View documents; video; music; pictures
Check on the file type and the size of the file
Perhaps play a sample tune or show a video
Chapter8 Digital Media

3. Application Layer Chapt 7
Audio Basics
Acoustic (pressure) wave to input device (ear)
Humans can hear within the 20Hz –20kHz range
Can distinguish about 1M distinct levels
Sensitive to changes in a few msec
Analog phone lines limit bandwidth to 4 kHz band
8000 samples/sec sufficient to capture all information in that band
levels chosen; these introduce quantizing noise
The above would require about 64kbps data rate
Less used because data is compressed (lossy compression)
Application Layer Chapt 7

4. Application Layer Chapt 7
Audio CDs
44100 samples/sec for a 22kHz band
16 bit samples to encode 65k levels
Requires a kbps data rate (1.4Mbps for stereo) for continual transmission (without compression)
Uncompressed files require about 10 MB for one minute and 450 MB for 45 minutes, which is how long a typical album runs
Application Layer Chapt 7

5. Sound Synthesizing MIDI standard for musical synthesizers
Standard includes connector, cable, etc.
Encoding for different types of instruments
Event (foot pedal, key)
Parameters (note’s pitch, amplitude, length)
Digital audio files contain digitized actual sound patterns
MIDI (.mid, .cmf, .rol) is synthesized – plays “sound” from instructions
Chapter8 Digital Media

6. MIDI (continued) Advantages Disadvantages
files are much smaller (10KB instead of 30MB)
Simple background for budding musicians
Prints sheet music
Disadvantages
Not as good
Lacks tonal qualities
Vocals are particularly poor
Chapter8 Digital Media

7. Identifying sound files
Sound files can be identified by extension
.aac, m4p, mp4, (iTunes- good quality)
.mp3 (compressed) – common for Web streaming because of its comparatively smaller size
.wav, .aif – uncompressed; large files
.wav is also popular for streaming audio since file is played as it is downloaded (with a small buffer to prevent jitter)
You can use a .wav file on an HTML tag
<bgsound src=“mymusic.wav”>
Chapter8 Digital Media

8. Hardware for audio data
Sound card, speakers, microphone, headphone
Sound card may be plugged into expansion slot
Sound card circuitry may be built into the system board
Saves space
Sound card sends output to speakers or headphones, input from microphone
Uses digital signal processing
Chapter8 Digital Media

9. Digital Signal Processing
Digital signal processing transforms between digital pulses representing bits into analog sound waves for output to humans
Transforms sound waves to digital pulses for storage on digital devices
May also handle compression and decompression
Chapter8 Digital Media

10. Software for audio data
Specific software “understands” specific audio formats
Windows Media Player can interpret
Wav, WMA, MP3 and other formats
SmartPhones –Apps, etc.
Chapter8 Digital Media

11. Bitmap graphics Grid of dots (grid implemented as an array)
Each cell is called a pixel (picture element)
The color of each pixel (or black/white) is stored as a binary number
rgb encoding (typically 8 bits each)
fun thing to try with web pages
Browser may not support all colors (saves bits – colors that are supported are called a palette)
Chapter8 Digital Media

12. Scanners Scanners convert printed image into a bitmap graphic
You could also take a picture of the page with a digital camera
Camera stores data on memory card
Not volatile
Can be erased and reused
Some of these pictures requires MBs storage
Chapter8 Digital Media

13. Image resolution
Image resolution is expressed in terms of pixels per row and column
150 x 100 pixels means that there are 150 columns of pixels (horizontal) and 100 rows of pixels (vertical)
150 x 100 is considered low resolution
3888 x 2592 (high end camera) is high res
About 10.1 megapixels
Chapter8 Digital Media

14. Bitmaps
Bitmaps do not change their resolution even if you stretch (or shrink) the image
If you stretch it enough, lines will start looking jagged
You can start to see the boxes of the pixels
Chapter8 Digital Media

15. Outputting Images Printers have a specified dpi (dots per inch)
If your image’s resolution is less than that, the printer will “fill in” the print grid
Make the resolution of your image greater than your printer’s dpi, but not much greater
Similarly on your computer
Right click on your desktop; pick screen resolution: 1440 x 900 recommended
A larger image would require scrolling
Chapter8 Digital Media

16. File size
You should reduce large file sizes of images for web attachments; possibly even for s
You can crop your picture
Snipping tool
Paint and other tools allow cropping
Paint allows you to change resolution or save in compressed form
Chapter8 Digital Media

17. Color Depth Typically each pixel encodes 3 colors (rgb)
8 bits for each color is called True Color bitmap
A 3.1 megapixel file with 32-bit color encoding needs 10MB of storage
You can redefine your color palette
Perhaps limit the existing one or add to the existing (limited) palette
Colors in html <body bgcolor=“ffffff”>
Chapter8 Digital Media

18. Image compression Lossless compression
Let’s look at Run-length encoding
Example: assume that a 256-color bitmap encodes each pixel in 8 bits of 1 ( ).
Suppose an image has 167 consecutive white pixels (ordinarily this would require 167 bytes)
It could be encoded in 2 bytes (167 in binary followed by for the color white
What happens if each pixel is a different color?
Chapter8 Digital Media

19. Image compression Lossy compression Example: JPEG encoding
Preprocesses adjacent pixels of similar values to be represented by the same value
Then uses run length encoding
I tried saving a jpeg file as a gif file (worst quality compression) and could not see a difference in quality nor much in size
Chapter8 Digital Media

20. File compression in general
Shareware compression programs
Ultimatezip, PKZIP and WinZip
WinRAR trial usage available at
supports Zip plus compression
supports UNIX utilities (tar, gz)
Don’t use them if file is already compressed
Chapter8 Digital Media

21. Compression with WinZip
Right click file icon
Choose send to
Choose compressed (zipped) folder
Windows will automatically decompress these folders on the receiving end when they are selected
Note .zip extension
Chapter8 Digital Media

22. Vector Graphics
Files with .wmf, .ai, .dxf, .eps extensions are images stored in vector graphics
Instructions rather than bitmaps
Less storage space
Generally poorer quality than bit maps
Shading is limited
Scalable!!! Easier to change; delete portions
Good for web browsers
Adobe’s Flash software uses vector graphics
Chapter8 Digital Media

23. Digital Video .wmv, .flv, .bdmv, .mov, .mpg extensions
To change an analog movie to digital we use a video capture device through the USB port
Webcams can capture a series of still photos in digital form; store in your computer
Digital video camera transfers digital video to your computer; better quality than webcams
Chapter8 Digital Media

24. Video editing software
Video editing software helps you cut out portions (and rearrange, if required) and also to synchronize audio tracks onto video data
Chapter8 Digital Media

25. Digital Data convenience tools
Time shifting
Allows hearing, viewing data later
Place shifting
Allows hearing, viewing data somewhere else
Format shifting
Allows using data on different devices
Chapter8 Digital Media

26. Digital Rights Management
How to prevent copyright infringement
Protected data can be “captured” by
Capturing wireless signals
Cracking encryption
Filming videos as they are played
Recording music as it is played
Copying disks or computer files
Analog data copyrights are routinely violated by copying – but it is harder
Chapter8 Digital Media

27. Digital Rights Mgmt Techniques
Signal scrambling to protect your rights
Basically this is encryption
Useful for satellite TV
Digital watermarks
Pattern of bits inserted (typically multiple times) in a data stream used to track, identify, limit use
Broadcast flags – can prevent copy, decrypt, even fast forwarding (over ads)
Chapter8 Digital Media

28. Computer generated film content
CGI Animation
Specifically for generating incremental (in-between) images within scenes
Rendering
Converting 2-dimensional images into 3-dimensions
Insertion of dead movie actors into ads
How to distinguish what is real?
Chapter8 Digital Media