Introduction

This applet can decode MPEG I video stream. You may think that Java is not fast enough to decode MPEG streams in realtime. But the results which this applet shows enable us to predict that it will be possible in very near future. By huge amount of optimizations, 240x170 MPEG stream can be played at the speed of 28 frames on my Pentium II 300 notebook computer. The first version of this applet could only show 7.6 frames per a second on the same computer.

I will first show you the performance of my applet on various environments. And during testing performance of my applet, I realize that JVMs which many company developed show different performances and this applet can be used for evaluating them.

And then I introduce optimization techniques which I have used for this applet. It will include some general rules and good materials for Java performance.

Lastly you can see my Java MPEG Player applets - An enhanced UI VOD, a simple UI VOD and a simple MPEG player versions. An enhanced UI(User Interface) VOD is superset of all ths players. It supports auto-adjusted screen, display a title and subtitle of a movie and a rate control of MPEG streams.

Performance

• Test MPEG file
  	File Length : 198 frames File Size : 483K File Duration : 6 sec Frame Rate : 30 fps Video Data Rate : 74KB/s Video size : 240 x 176

• Performance results on various machines using IE4

  Pentium Pro 200 running Windows 95 : 21.37 fps Pentium II 300 running Windows 98 : 28.14 fps Pentium II 333 running Windows 95 : 32.07 fps Pentium II 350 running Windows 95 : 35.16 fps Pentium III 550 running Windows 98 (using IE5) : 50.98 fps

• Performance results on Pentium II 300 at a local network

  Internet Explorer 4.01 : 28.14 fps Netscape Commnicator 4.51 : 28.63 fps IBM JDK 1.1.7 : 27.87 fps

• Performance results on Pentium II 300 at a local machine

  Internet Explorer 4.01 : 29.47 fps Netscape Commnicator 4.51 : 28.43 fps IBM JDK 1.1.8 : 30.65 fps

Optimization Techniques

• IDCT calculation
  • 1D IDCT
    - integer IDCT using integer multiplication and shift
    - skipping IDCT calculations if it holds all zero terms.
    - collapsing calculations
    - avoid using array
    - avoid useless assignments
  • 2D IDCT
    - divide row/col IDCT for avoiding useless assignment and calculation
    
• YCrCb to RGB conversion
  - table-driven multiplication
  - collapsing calculations
  - avoid useless assignments
  
• Reconstruction
  - loop unrolling technique
  
• Parsing
  - VLC decoding with hierarchical table - using berkeley MPEG code
  
• Java optimization
  - collapsing calculations
  - avoid using array
  - avoid useless assignments
  - loop unrolling
  - avoid multiplication
  - avoid type casting
  - using final and static functions
  
• Memory Usage
  - bounded memory usage by reusing objects and arrays
  
• a good site for Java Optimizations

Java MPEG Players

• Enhanced UI VOD Player
  	Display a movie title and subtitle Play, pause and resume the movie Auto-adjust screen to match the movie size Display average frames per seconds Select various movies Rate control (selectable in setting) Auto replay or not (selectable in setting) Play time or frame display (selectable in setting)

• Simple UI VOD Player
  	Display a movie title Play, pause and resume the movie Display average frames per seconds Select various movies Auto replay Rate control (selectable as parameter)

• Simple MPEG player
  	Play, pause and resume the movie Display average frames per seconds Display controls or not (selectable as a parameter) Rate control (selectable as parameter)

Other Experimental Players

• MPEG Audio Layer Player supports layer I, II, III.
  
• MPEG Audio/Video Player combines video and audio decoders.

Publication

• Disclaimer: The following publications are covered by copyright. Permission to make digital/hard copy of all or part of the following papers, technical reports, and presentations for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage. To copy otherwise, to republish, to post on servers, or to redistribute to lists requires prior specific permission.

• Dohyung Kim and Jihong Kim, "Design and implementation of a Java-based MPEG-1 video decoder", Consumer Electronics, IEEE Transactions on, Vol. 45, Issue 4, pp. 1176 - 1182, Nov. 1999

updated by Kim Dohyung ( dhkim@iris.snu.ac.kr ) Last modifed at 1999/5/3