1. Multimedia
Contents
Multimedia
Graphics / Pictures
Audio / Sound
Video

2. Multimedia Multimedia is: Multimedia applications Sound Graphics
Videos
Multimedia applications
Office documents
Webpage content
Movies
Music
Pictures

3. Multimedia Multimedia files are quite large
Use compression to reduce file sizes
Lossless Compression – algorithms reduce size of files
No information is lost
Lossy Compression – algorithm reduces size of files
Some information is lost

4. Multimedia Trade offs between lossless and lossy compression
Lossy can reduce file sizes much more
Example: File compression like 7-zip
Uses lossless compression
If some data is lost, then file becomes corrupted
Lossy compression is used in multimedia

5. Multimedia Example: 38.56666666 Lossless compression Lossy compression
38.56(7)
Lossy compression
38.6

6. Pictures / Graphics Graphics
Bitmap (BMP) - windows
Graphics Interchange Format (GIF)
Joint Photographic Experts Group (JPEG)
Tagged Image File Format (TIFF)
Portable Network Graphics (PNG)
Note – the abbreviations are the file extensions

7. Pictures / Graphics Digitizing Images
Bit Map – each image is laid out in a grid pattern
Pixel - each cell in the image
Pixel could be black or white
Grey scale value
Color
The more pixels, the better the image quality
Digital cameras – megapixels
My camera is 14.1 megapixels
Each picture has 14.1 million cells that compose the pictures

8. Pictures / Graphics Bitmap of a snowman Grey Scale Bit Map Image
The snowman face is a 7x7 bitmap
Composed of 15, 15,  0, 0, 0, 15, 15, 15, 15,  0, 0, 0, 15, 15, 15, 0, 0, 0, 0, 0, 15, 7, 15, 3, 15, 3, 15, 7, 7, 15, 15, 7, 15, 15, 7, 7, 15, 3, 3, 3, 15, 7, 15, 7, 7, 7, 7, 7, 15
The file also contains a header containing the size of the bitmap which is 7 x 7
Bitmap of a snowman

9. Pictures / Graphics Color Bit Map Image
The top photograph is a picture with birds flying in the sky
The bottom picture is one bird blown up to show pixels

10. Pictures / Graphics Example: HTML command bgcolor =“#0F69F3”
RGB (Red-Green-Blue)
All digital images are composed of red, green and blue
Usually represented by hexadecimal numbers
24 = 16;
Numbers – 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, and F
Example: HTML command
bgcolor =“#0F69F3”
bgcolor is background color
Red = 0F, Green = 69, and Blue = F3

11. Pictures / Graphics
Each color has two hexademical digits or 00 – FF, which ranges from 0 to 255
Each color is 28 and three colors =224
24-bit true color
We also have 32-bit color
RBG can make the other colors

12. Pictures / Graphics Windows BitMap Bitmaps do not use compression
Bitmaps have very large file sizes
Easy to calculate the file size
Image is 800 x 600 with 8 bit (1 byte) color
256 color values

13. Pictures / Graphics Calculating Image File Size (BitMap)
Number of pixels = 800 x 600 = 480,000 pixels
Image size = number of pixels  x number of bits
Image size = 480,000 pixels x 1 byte = 480,000 bytes
Image size = 480,000 / 1024 = KBytes

14. Pictures / Graphics Graphics Interchange Format (GIF)
Moderately compresses images
Lossless compression (simple pictures)
Good for simple pictures and graphics
Displays 256 colours or 8 bit
Palette – it chooses the best 256 colors out of 24-bit color
Common for websites
Animated GIFs – images can display simple animation, especially for websites

15. Pictures / Graphics
The animated GIF shows a four cycle gasoline engine
Requires special software to create animated GIFs
File size 369 kb

16. Pictures / Graphics Joint Picture Experts Group (JPEG)
JPEG uses complex mathematical compression
Reduces file size up to ten times that of GIF
Causes lossy compression
Supports True Color - 24 bit color
JPEG is great for photographs
Used on websites

17. Pictures / Graphics Note
If the same JPEG image is re-edited, then the image can degrade
If you have photos that are never edited, then leave them in JPEG
If you re-edit the same photographs, then keep photo in another format
PNG is good; file compression
BMP is okay if you have the space; no compression

18. Pictures / Graphics Picture is 858x643 True color, 32 bit or 4 bytes
Bitmap = 2.2 MB
I converted this to BMP and it was 2.1 MB
Tuzla, Bosnia

19. Pictures / Graphics JPEG (20%) – very small file size; 34 k
JPEG (95%) – medium size; 212 k

20. Pictures / Graphics Portable Network Graphics (PNG)
Uses loseless data compression
Uses 24-bit or 32-bit color
Can be used for webpages
Note: 32-bit color is RBGA
A is for alpha
Alpha allows translucent pictures
50% alpha – can see images behind the picture
Windows Aero effects

21. Pictures / Graphics Creating digital pictures
Scanning – digitizing an image using a scanner
Digital cameras
Paint programs
Screen capture – use prtsc to capture a screen

22. Pictures / Graphics Software Create pictures by hand
Microsoft Paint – comes with Windows
Paint,net - free
Enhance photographs
Microsoft Picture Editor
Google Picasso
Paint.net
Professional Software
Adobe Photoshop
Adobe Illustrator
Adobe Pagemaker

23. Pictures / Graphics Conclusion For websites JPEG GIF PNG
Cannot use BMP or TIFF; too large

24. Pictures / Graphics Conclusion No compression Lossless compression
BMP
TIFF
Lossless compression
GIF
PNG
Lossy compression
JPEG

25. Audio / Sound Data is processed in two ways: analog or digital
People generally process analog data that is continuous wave patterns.
Everything we see and hear is transmitted to our eyes and ears as light and sound waves.
We are equipped with analog receptors
A computer is digital
Two discrete states: on (or 1) and off (or 0).

26. Audio / Sound Computers: Analog to digital converters
Convert analog to digital
Microphone
Digital to analog converters
Convert digital to analog
CD, MP3, etc.
Analog and digital signals

27. Audio / Sound
Sound cards and Modems are digital- to-analog and analog-to-digital signal converters
The Wave file (.wav) – used in PCs.
Windows systems sounds
Start up sound
Many game sounds
Wave files do not use compression
Files are quite large

28. Audio / Sound Wave file is created by
Sampling sound – convertor samples the sound so many times per second
CD quality is 44,100 samples per second
Less sampling is lower quality
Sound information is stored as bits
Commonly 8, 16, or 32 bit sound file
Sampling – how often a sound file is read
Bitrate – how much information is stored per second
Includes magnitude
Includes how often sound is sampled

29. Audio / Sound

30. Audio / Sound
MP3 (MPEG-1 Audio Layer 3)
MP3 compresses sound information
Uses lossy compression
Some information is lost
Example: 128 kbits per second
Reduces the file size of CD sound quality by 11 times
Good for webpages, because file sizes are small
Note – many audio sound formats exist; usually for movie files

31. Audio / Sound Audio Software
Audio Editing Software lets users modify audio clips and produce studio quality sound tracks.
Contains equalizers, controls, etc to modify clips
Rippers – converts audio to different formats
Windows 7 contains a music CD to MP3 ripper

32. Videos More complex Has RGB color and sound RGB is Red-Green-Blue
Video has three colors and a sound
Stream – picture and sound change over time
Requires much more information

33. Videos Frame – the dimensions of a video in pixels
Width x height
Example: 320x120
Each picture has color
24-bit color
Picture changes each second
Called bit rate
Bit rate 25 frames per second

34. Videos Our video is one hour (or 3600 seconds)
File size = (frame)(color)(bit rate)(time)
= 320*120*24*25*3600 = 82 Giga bits
= 10.4 GB
Video files are always compressed
Most use lossy compression
Use compression to reduce size of the image of a frame
Use compression to reduce the bit rate

35. Videos Frame – dimensions of the video Bit rate
Small videos can be blown up
Bit rate
Important for video quality
The higher the bit rate, the higher the quality
Videos – fast motion requires a higher bit rate
Example – vastly simplified

36. Videos An example of a video compression Uses three frames
I-frame: The true picture
P-frame: predict which pixels change
B-frame: uses difference between the next frame and previous frame

37. Videos
Compressor-decompressor (CODEC) – a program that encodes or decodes a streaming file
Streaming file is video and/or audio
Companies hold patents or copyrights for their codecs
Restrictions apply

38. Videos Video files Files are containers (not codec) mp4 Matroska (mkv)
Windows (avi)
Windows (wmv)
Flash video (flv)
Files are containers (not codec)
A variety of codecs are used which are in the file
MPEG2 is a codec
Used for DVDs

39. Videos Some codecs are open source Windows pays for the rights
Some codecs play in MediaPlayer
Users either use
K-lite – a windows program that contains most codecs
VLC Player – media player that contains most codecs
Software may be illegal in the United States

40. Videos
Linux is free
They do not pay for rights to use codecs
Installers have to manually install codecs
Most distributions want to be legal, especially for businesses
Distribution is a particular Linux operating system
Most do not come with codecs
Forums teach people how to install codecs

41. Videos Ubuntu – install codes as software update
Manually install DVD codec via terminal
Businesses and companies can get into trouble installing codecs without paying for them
England
Linux Mint – comes with all codecs including DVD
France

42. Videos
Video editing software - users can modify a segment of a video, called a clip.
Users can
Reorder sequence of clips
Reduce length of clip
Add special effects to clips
Add extra tracks to clip (eg. Sound, text captions)
Video Editing Software usually includes audio editing capabilities.

43. Videos Video editing – requires a very fast computer Expensive program
VirtualDub.org – free video editing
Powerful filters to clean video
Had trouble encoding videos
Files were much bigger

44. Videos
DVD ripping – the process of converting a DVD into a regular video file
Converting may or may not be illegal in the U.S.
Software may or not be illegal in the U.S.
Windows – most programs were terrible
Linux – AcidRip
Free simple program
Majority of the time produced good quality videos with good file sizes
Linux tends to be faster than Windows