Image Sequences

1
Image Sequences

• John H. Krantz
• Hanover College

2
Outline

• Slideshows
• Why
• Presenting Using Redirects
• Video (if interested)
• Background
• Delivering in a Webpage

3
Why Slideshows

• Example 1
• Indicate sequence of events
• Carries sense of change
• From Billy sense of momentum in photo
• Original Loftus Eye Witness testimony was done
  this way
• How?
• One easy way use redirects

4
Here is an example

• Avi is 5 meg uncompressed, a t 161 kb compressed
  but louse image quality images are 35 kb each

5
Previous Student Slideshows

• Here are the work of previous students

6
Code for redirect

• lthtmlgt
• ltheadgt
• lttitlegtImage Sequencelt/titlegt
• ltMETA HTTP-EQUIV"refresh" CONTENT"3
  URLpage01.html"gt
• Number is number of seconds before redirect
• lt/headgt
• ltbodygt
• ltpgt
• This will change in 3 seconds, aboutlt/pgt
• ltp align "center"gt
• ltimg border"0" src"Bobby0000.jpg" width"512"
  height"384"gtlt/pgt
• lt/bodygt
• lt/htmlgt

7
Make A slide show

• Edit in Text editor
• Just edit new page for link
• Change image shown
• Use Save as
• Remove meta tag for last image

8
Motion Reproduction

• Frame rates of monitors far exceed what is needed
  for movement update
• NTSC video 30 updates per second
• Movies 24 updates per second
• Most web video 10 to 15 frames/sec

9
Computer Video

• Most Update rates are 10-15 frames/sec
• 5 fps 10 fps 15 fps

Probably not enough for speech and subtle
facialexpressions.
10
Flicker

• Critical threshold of flicker rates is about 60
  Hz in the fovea
• But gets higher for larger stimuli
• Recommended flicker rates between 66 Hz and 120
  Hz (Bridgeman, 1998)
• Most monitors are adequate in this value
• Notice difference between flicker and frame
  update rate.
• Wagon wheel effect.

11
Stimulus Duration

• Pixels are not on continuously during a frame
• In part this is necessary for clean motion
• Typical CRT phosphors last about 4 msec.
  (Bridgeman, 1998)
• On LCD and other technologies, persistence is
  longer
• Makes motion less clean but flicker less
  noticeable

12
Differences in Persistence
Fast motion will be less clean on an LCD screen
13
General Video Issues

• Image size
• Keep it small
• 320 x 240 is not uncommon
• Image color depth
• Normally full color
• Video Length
• The shorter the better
• This file is 5.5 meg in QuickTime and it is 17
  seconds

14
General Video Issues

• Frame rate recall difference between apparent
  motion and flicker
• 10 to 15 is really fine for most cases
• And best you can expect on web

15
Acquiring with a Digital Camera

• Find format of your video camera
• mine is QuickTime
• Can use digital zoom
• original camera images are much larger than movie
  images so will be shrunk down
• And digital zoom is before movie image

16
Acquiring with a Digital Camera

• Hold camera still or not?
• Movies are limited in duration
• mine is 30 sec or size of disk for 320x240
• It is 120 sec if 160x120
• Image quality is reasonably good if presented in
  original size
• But image quality may be reduced to get on web

17
Editing with QuickTime Pro

• Open more than one
• Basics
• Opens MOV, mpg, avi, mp3, etc.
• Get Movie Information on Movie Menu (ctrl-j in
  Windows)
• Tracks separate slices of information played at
  same time as other tracks
• Look under the Edit menu

18
QuickTime Pro Interface
Playback head
In marker Out marker
Selected region
19
Basic Editing

• Selecting a region to edit
• Use guides at bottom
• Called In and Out Markers
• Selected region is darkened
• Arrow keys to fine tune
• Cut and Paste operation
• Paste is at playback head

20
Adding Tracks

• Copy as before
• Use Edit Add adds the video track
• Use Edit Extract Tracks
• Then Edit Add
• Can extract sound this way to a movie
• Can add scaled so new track is not length of old
  movie

21
Deleting Tracks

• Use Edit Delete Tracks
• Remove any unwanted sound from video

22
More Advanced Editing with QuickTime Pro

• Adding text to beginning
• Make any graphic
• Resize to movie size so know how it will look
• Select al (ctrl-A)
• Then cut and paste to beginning
• Another paste for each additional frame

23
More Advanced Editing with QuickTime Pro

• Overlaying Text
• Use a gif file with a transparent background
• Use a text file
• File Import
• Any .txt
• Press Option button
• Select keyed text
• Change background to white and foreground to text
  color
• I like changing it to bold
• Add tracks as before

24
More Advanced Editing with QuickTime Pro

• Filtering portions of movie
• Delete regions do not want to filter
• Use the export function
• Click on Options
• Click on Filter
• Pick pattern
• Use cut and paste to reassemble

25
Saving for Web

• Format
• You must compress
• Uncompressed files will be very large
• Lead very slow download
• Duration
• For same reason, keep videos short

26
To Stream or Not to Stream

• Steaming
• Starts sooner
• Can be large files
• Can stop
• Relatively lower quality and quality depends on
  connection
• General Protocol RTP/RTSP

• Regular Delivery
• Wait for entire file
• Keep to small files
• Keeps Speed
• Relatively better quality, but quality depends
  upon monitor and format

27
Streaming vs. HTTP Fast Start

• HTTP Fast Start is a feature of QuickTime
• Allows playing after part of file downloaded
• Fewer stops
• No special software
• Still keep files relatively small
• Some loss of image quality

28
Embedding a QuickTime Movie in a Web Page

• ltp align"center"gt
• ltOBJECT CLASSID"clsid02BF25D5-8C17-4B23-BC80-D34
  88ABDDC6B"
• WIDTH"480" HEIGHT"376
• CODEBASE"http//www.apple.com/qtactivex/qtplugin.
  cab"gt
• ltPARAM NAME"src" VALUE"start.mov"gt
• ltPARAM NAME"controller" VALUE"false"gt
• ltPARAM NAME"target" VALUE"myself"gt
• ltPARAM NAME"href" VALUEclip.mov"gt
• ltEMBED WIDTH"480" HEIGHT"376"
  CONTROLLER"false" TARGET"myself"
  HREFclip.mov"
• SRC"start.mov" BGCOLOR"FFFFFF" BORDER"0"
  PLUGINSPAGE"http//www.apple.com/quicktime/downlo
  ad/indext.html"gt
• lt/EMBEDgt
• lt/OBJECTgt
• lt/pgt
• Example http//ati.fullerton.edu/jkrantz/session3
  /video/

29
Assignment

• Have Fun!