1. GUI Final Project: MPEG Maker
Computing for Imaging Science
(SIMG-726)
Andrew Adams
02 Mar 2006

2. Overview Objectives Widget Definitions Input Files
MPEG Formats and Frame Rates
Output File
Status Windows
Widget Event Handler
Get & Display Image
Format and Frame Rates
Research Specific Requirements
MPEG Generating Function
MPEG Object
Error Handling
Conclusion / Future Work

3. Objectives Something useful for my research (video processing)
Simple interface to convert 100s of images into MPEGs
“Non-standard” frame rates (i.e. 1 to 2 frames per second)
Complex enough to demonstrate an understanding of the IDL widget environment
File input/output
Select various settings
Text and Image Status
“Make MPG” function call (IDLgrMPEG object)

4. Widget Definitions - Functionality
Input filename format: prefix + NNN + suffix
Example: Frame011-RGB.pnm (digits = 3)
Frame indexing (start and stop frames)
Reduced frame rate (option)
Output filename and location
Text status window
Image status window
Clear and Quit

5. Widget Definitions – Blank GUI
Input Specs – widget_label
Select image – widget_button
cw_field (widget data entry field)
Prefix & Suffix
Number of Digits
Start & Stop Index
Output Specs - widget_label
MPEG Format & Frame Rate
cw_pdmenu (pull down menu)
cw_bgroup (button group)
Repeated Frames – cw_field
Reduced FR – widget_text
Clear/Make/Select – widget_button
Output file – cw_field
Display – widget_draw
Status – widget_text
Quit – widget_button

6. Widget Definitions – Pull Down Menus

7. Widget Definitions – Global Data
global_data = { draw_id: window1, $ ;Image status window
window_id: window_id, $ ;Image status window
prefix_id: prefix, $ ;Input filename
suffix_id: suffix, $ ;Input filename
istart_id: istart, $ ;Frame index (start)
istop_id: istop, $ ;Frame index (stop)
idigits_id: idigits, $ ;Index format (# of digits)
format_id: format, $ ;MPEG format
frame_rate_id: frame_rate, $ ;MPEG frame rate
rep_frames_id: rep_frames, $ ; No. of repeated frame
rfr_text_id: rfr_text, $ ; Reduced frame rate
outfile_id: outfile, $ ; Output filename
text_id: textbox } ; Text status window

8. Widget Definitions – Default Values
No. of digits = 3
(001 to 999)
Format = 0 (MPEG1)
Frame rate = 5
(30 fps)
Repeated frames = 1 (no effect)
Output file = ‘MPGOUT.mpg’
(Note: Output file directory defaults to “my documents” in windows)

9. Widget Event Handler Get Image Format and Frame Rate
Query_image to check format
Open & Display (.png OK as is, .pnm had to be reversed)
Put filename in Prefix and Suffix fields
Update text status window
Format and Frame Rate
Button groups (global_data  get value)
Update text status window (string array index)
formats = ['MPEG1', 'MPEG2']
rates = ['23.976', '24', '25', '29.97', '30', '50', '59.94', '60']

10. Widget Event Handler – Get Image
Representative filename is put in both Prefix and Suffix fields…

11. Widget Event Handler – Get Image
…which can be edited by the user as necessary.
Start and Stop indices are also filled in.

12. Widget Event Handler – Research Requirement
Need MPEGs with frame rates of 1-10 fps
Example:
Frame rate = 24fps
Repeated frames = 6
RFR = 24 / 6 = 4 fps
Repeated frames value (1 – 30) is input manually…
…reduced frame rate (RFR) is calculated and text status window updated.

13. Widget Event Handler – Status Window
Text Status Window (Log)
Update text window whenever settings change
Keeps the user aware of current settings before MPEG
Serves as a log of activity
Clear button
Restores default values
Does NOT clear the log window
Quit button

14. MPEG Generating Function - IDLgrMPEG
Query_image to check image format
Open and Display images
Grayscale (.png) OK, Color (.pnm) needed to be reversed*
GUI display is updated for each image in sequence
Does not affect the runtime significantly (& keeps user entertained!)
Build IDLgrMPEG object
IDLgrMPEG::Put adds image to object
IDLgrMPEG::Save writes object to .mpg file
Obj_destroy before returning
* Note: Color images had to be reversed about the rows using REVERSE(image,3) for display and about the columns using REVERSE(image,2) before adding to the MPEG object! (Trial & Error…)

15. MPEG Generating Function – Error Handling
Final task in GUI development
In most cases, return -1 with error message
Defaults set for:
Digits, format, frame rate, and repeated frames
Then proceed with make MPEG and return 0)

16. DEMONSTRATION…

17. …in case of technical difficulties (it really does make MPEG files!)

18. Conclusion Objectives were met Future work Useful research tool
Better understanding of widgets in IDL
Future work
IDL crashes when query_image function gets a bad filename
Scroll window
String array rewritten…display bottom
Save to text file?)