Pure Java-Based Streaming MPEG Player

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Pure Java-Based StreamingMPEG Player
Osama Tolba, Hector Briceño, and Leonard
McMillan Laboratory for Computer Science M.I.T.
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Presentation Overview

• 1. Motivation
• 2. System Architecture
• 3. Novel IDCT Algorithm
• 4. Results

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1. Motivation

• Explosion in multimedia Web content
• Cross-platform functionality
• Applet no need to pre-install native plug-ins
• Streaming no need for large auxiliary storage
• TV set-top decoders
• Customized sessions (multiple streams, etc.)

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Java Pros Java Cons

• Platform independent
• Small footprint
• Compact programs (40KB Jar file)
• Networking routines

• Interpreted (slow)
• Security restrictions
• Display performance
• Evolving API 1.0, 1.1
• Varied results (JIT)

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2. Modular System Architecture

• Source-player architecture
• Customizable session
• Memory requirements

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Proxy Server

• Overcomes security restrictions
• Forwards bits to decoder
• Limited buffer
• Implemented in C

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3. Forward-Mapping IDCT

• Decoder bottlenecks
• FMIDCT McMillan Westover, DCC 92
• Combined table lookup

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Forward-Mapping IDCT
Dequantized DCT Coefficients
Luminance or Chroma
K u, v 8x8 Basis
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IDCT Basis Functions

• Unique coefficients in each basis function
• Shared coefficients
• Only 28 out of 4096

Unique Coefficients
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Improved FMIDCT

• Basis function symmetry
• 4x4 accumulator arrays instead of 8x8
• Reduced computation, fit in registers

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H
Q
-H
Q
4
V
D
V
-D
B
A
H
Q
-H
Q
-V
-D
-V
D
K1,1 Type D Symmetry
C
D
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FMIDCT Flow Chart
For each symmetry type
Retrieve scaled basis vector
Symmetry Types
Accumulate in Qa, Qb, Qc, Qd
Qf Qa Qb Qc Qd Hf (Qa - Qb Qc - Qd)
R Vf R (Qa Qb - Qc - Qd) Df R (Qa - Qb -
Qc Qd) R
Mirroring matrix
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Dequantizer Cache
p level, qval, qscale, type

• Level macroblock quantizer scale
• qval quantized symbol
• qscale element quantizer scale
• type intra/inter-frame encoding

Hashing H(p)
In cache?
I u,v dequantize(p)
N
Translate to index of scaled vector
Y
Index cacheEntryH(p)
Store index in cache
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4. Results

• 176 x 144 _at_ 28 fps, 352 x 240 _at_ 11 fps
• Decode 1.8 M pix/sec, Display 670K pix/sec

display
decode
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User Interface

• http//compvid.lcs.mit.edu/cv/mpeg/

• PIP / visual controls

• Std menus / controls

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Summary

• Portable, streaming player
• Efficient FMIDCT algorithm
• Modular design, customizable sessions
• Promising performance, bottlenecks exist
• Further Work
• Time vs. quality trade-off
• Rate control, skip frame display

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Acknowledgements

• Sponsored by DARPA (agreement F30602-97-1-0283)
• http//www.mpeg.org