1. Digital Media Dr. Jim Rowan ITEC 2110 Wednesday, August 29

2. Roll call Jones, Crystal L. Marsh, Kerreen A. Thompson, Daniel G. Tran, Christopher V.

5. single sample

7. two samples

9. three samples

11. four samples

13. five samples

15. How frequently should I sample? too few –small file size (good) –not a faithful representation when replayed too many –large file size (bad) –excellent representation when replayed The Nyquist rate –twice as many samples as the frequency –ok file size –faithful representation when replayed

16. Sampling Artifacts Under-sampling (too few samples) of continuous data can produce undesired artifacts –audio distortion –jagged edges on images –Moire’ patterns on images –retrograde motion on video

17. Sampling Artifacts (cont.) Not enough quantization levels when sampling continuous data can produce undesired artifacts Images –too few color: colors look artificial –loss of fine distinction –too few grey levels: gradients become steps –too few brightness levels: posterization

18. Sampling Artifacts (cont.) Not enough quantization levels when sampling continuous data can produce undesired artifacts Audio –too few amplitude levels, quantization noise - hiss 8 bits (256 amplitude levels) produces discernable noise 16 bits (65536 amplitude levels) CD quality, no discernable hiss –general sound “fuzziness”

19. Multimedia Hardware Requirements Multimedia consumption? –requires only a lower powered machine Multimedia production? –requires a more powerful computer –consider “fields of gold.mp3” 26+megabytes of data uncompressed 1.2 megabytes of data compressed –images are produced in layers then flattened for consumption

20. Hardware requirements Video capture requires large areas of contiguous disk space Frequent disk defragmentation is required http://en.wikipedia.org/wiki/Defragmentatio n

21. defragmentation black is occupied space white is available space memory before memory after largest contiguous space is 5 largest contiguous space is 11 and there are 6 of these

22. Hardware requirements: Form factor... screen real estate makes a difference –size is smaller? –can/should affect the format of the display cannot simply display the same page on –a desktop computer –a cell phone –a pda

23. Hardware requirements Form factor... Displayed unmodified laptop display of my GGCwiki site Treo LG VX3400

24. Hardware... RAID Redundant Array of Inexpensive Disks Designed as a hardware failsafe –multiple copies of the same data Can be used to speed data transfer –(you may need this in multimedia production) http://en.wikipedia.org/wiki/RAID

25. RAID redundant 94731990 disk #1 disk #2 disk #3 disk #4 disk #5 disk #6 disk #7 disk #8

26. RAID overlapped (fast) 7 3 1 9 9 4 0 9 94731990 disk #1 disk #2 disk #3 disk #4 disk #5 disk #6 disk #7 disk #8

27. Networks Local Area Network (LAN) –local routers, bridges, switches... Internet –Uses TCP/IP protocol (the rules your communication must follow) –http://en.wikipedia.org/wiki/TCP/IP –you get access through an ISP

28. Network access... dial up connection –phone modem –limited to 56,000 bps (bits, not bytes) max downstream (internet to modem) –33.6 kbps upstream (modem to internet) –rarely get these speeds

29. Network access... ADSL –asymmetric digital subscriber line –over copper phone wires –limited to short distance from phone switch –6.1 mbps (million bps) downstream –640 kbps upstream

30. Network access... Other options –Cable modem (also asynchronous) –satellite with phone (also asynchronous) –satellite alone (expensive but available in the boonies) –local wireless networks –high altitude tethered balloons –transmission over power lines

31. Commercial internet users Provide web servers for others to put websites on Large commercial enterprises will have their own web server T1 connection 1.544 mbps T3 connection 44.7 mbps

32. Servers & Clients... Clients consume internet content Your browser is a client Clients request content from servers –by sending a server an HTTP://URL message which is a request for a web page Servers respond to requests for internet content –send requested web pages to Clients The content is sent in HTML code –HTML is interpreted by the client (browser) and displayed on your machine

33. Servers & Clients... URL is a human-readable name uniform resource locator takes the form www.amazon.com/newStuff/index.html The domain name: www.amazon.com The file you want to see is: newStuff.index.html the name maps to a number called an IP address http://en.wikipedia.org/wiki/IP_address

34. Servers & Clients... servers have fixed IPs so they are easy to find your computer probably uses DHCP which is a dynamic (changing) IP An example: my IP right now (assigned through dhcp) is: 10.0.106.91 my IPv6 address (new addressing scheme) is fe80:0000:0000:0000:0211:24ff:fe8f:abb6

35. yahoo.com (server) 235.01.30.564 The Internet you at home running a browser (client) DHCP: walmart.com (server) 100.43.153.07 ggc.usg.edu (server) 145.67.33.73

36. yahoo.com (server) 235.01.30.564 The Internet you at home running a browser (client) DHCP: 10.0.91.35 walmart.com (server) 100.43.153.07 ggc.usg.edu (server) 145.67.33.73 ISP

37. yahoo.com (server) 235.01.30.564 The Internet www.yahoo.com = 235.01.30.564 you at home running a browser (client) http://www.yahoo.com walmart.com (server) 100.43.153.07 ggc.usg.edu (server) 145.67.33.73

38. yahoo.com (server) 235.01.30.564 The Internet you at GGC running a browser (client) DHCP: walmart.com (server) 100.43.153.07 ggc.usg.edu (server) 145.67.33.73

39. yahoo.com (server) 235.01.30.564 The Internet you at GGC running a browser (client) DHCP: 322.21.5.36 walmart.com (server) 100.43.153.07 ggc.usg.edu (server) 145.67.33.73 ISP

40. yahoo.com (server) 235.01.30.564 The Internet www.walmart.com = 100.43.153.07 you at starbucks running a browser (client) HTTP://www.walmart.com walmart.com (server) 100.43.153.07 ggc.usg.edu (server) 145.67.33.73

41. MIME types Multipurpose Internet Mail Extension Allows the transmission of more than just ASCII text (like you’d expect in an email) MIME types are specified in the header Huge variety of MIME types are allowed –audio, images, video –compressed files

42. A word about standards Standards allow cooperation But standards require agreement Works well during slow growth But in a rapidly changing environment... –frequently obsolete before adopted One company may dominate the market becoming the de-facto standard

43. Questions?