Huffman Coding

1
Huffman Coding

• Brandon Dalton and Scott Fields
• ECE 551
• 12 02 - 2003

2
Huffman 101

• Optimal coding based on P(x)
• Can decode by reading bits L-gtR
• ISO 8-bit characters a-z
• P(x) based on standard English

3
Structure
4
(No Transcript)
5
Design Process

• Overall Project Assessment
• Joint Entity Design (spec I/Os)
• Derivation of Truncated Huffman Code
• Individual Block Implementation
• Combine Blocks within Modelsim
• Testbench with Modelsim
• Synthesis
• On-board Testing and Debug

6
Issues

• Correct Simulation / Correct Hardware
• Different VHDL constructs
• Libraries, non-bounded loops, storage
• Timing
• Propagation Delay
• Synchronization
• Debugging Time e(design time)
• Useless Complier Warnings/Errors
• Ground trace driven by a primitive gate
• Iteration Limit Exceeded (Modelsim)
• Place and Route Lockups

7
Troubleshooting Tips

• Good VHDL Reference(s)
• Modular Code Allows Partial Function
• Google for Warnings/Discussion
• Close Partner Interaction

8
References

• http//groups.google.com/groups?groupcomp.lang.vh
  dl (VHDL newsgroup)
• The Designer's Guide to VHDL. 2nd Edition by
  Peter J. Ashenden.
• http//www.fm.vslib.cz/kes/data/vhdl_ref.pdf
  (online vhdl reference synthesis based)
• http//www.wam.umd.edu/taowei/414web/pages/images
  /9-1.gif (letter frequencies)
• http//www.utoronto.ca/webdocs/HTMLdocs/NewHTML/is
  o_table.html (ISO 8859 codes)
• http//www.gzip.org/deflate.html (Huffman trees)
• http//www.howtodothings.com/userdata/113/tree.gif
  (tree graphic)