Forgent Inc. vs. High-Tech Giants

Gautam Altekar

Technology

A compression method for digital imagesJoint Photographic Experts Group

Used all over the web Used by most digicams

JPEG

Litigants

• Plaintiff: Forgent, Inc.– 200 employees, video-conferencing products– (1997) Acquired JPEG-related patent in merger– (2004) Business down, so started asserting patent

• Defendants: Those making money from JPEG images– Adobe, Dell, Kodak, Xerox, Microsoft, etc. (31

total)Does JPEG infringe Forgent’s patent?

JPEG overview

• A lossy-compression method for digital images

• Some image degradation, but very good compression

JPEG – 100% quality, 83K

Original image, 200K JPEG – 1% quality, 1K

Why is the compression so good?

• Key idea: discard information in the higher frequencies– For example, edges (horizontal and vertical)– For example, highly-textured surfaces

Original image, 200K JPEG – 1% quality, 1K

(1) Isolate high frequency info

Image in the spatial domain Image in the frequency domain

8x8 pixel blockOriginal imageHorizontal frequency

Vertical frequency

(2) Discard high frequency info

• Round the upper frequencies to a high multiple

• Result: many redundant elements (e.g., zeros)

Image in the frequency domain Image in the frequency domain after quantization

Horizontal frequency

Vertical frequency

Horizontal frequency

Vertical frequency

Forgent’s patent

• U.S. Patent No. 4,698,672 (issued 1987) – a method for eliminating redundancy in data

Size: 8x8x8 = 512 bits Size: 22 bitsImage after Forgent’s encoding

Horizontal frequency

Vertical frequencyImage in the frequency

domain after quantization

Does JPEG infringe this patent?

11 100110 0 101 10 1010 0 110

Forgent: (1) Run-length encoding

• Write the number of preceding 0’s rather than each 0

Image after run-length encoding

Horizontal frequency

Vertical frequencyImage in the frequency

domain after quantization

(0,3)(-3) (1,4)(-6) (0,3)(-2)(0,6)(-26)

# of

pr

eced

. ze

ros

# bits in coefficient

coefficient

Process in diagonal order

Forgent: (2) Run-length + Huffman coding

Run-length encoded image has redundancy(0,3) (3)(1,4)(-6) (0,3) (2)(0,6)(-26)

Huffman table Run-length + Huffman encoded image

11(-26)0(-3)10(-6)0(-2)

11 100110 0 101 10 1010 0 110

JPEG infringes Forgent’s patent

• Standard suggests Run-length + Huffman encoding– Most implementations do this

• Standard suggests Arithmetic coding as alternative to Huffman coding – But Arithmetic coding is patented

• Is JPEG doomed?– Sony and others might’ve thought so– Forgent collected $90 million in royalties

Public Patent Foundation (PUBPAT) saves JPEG

• PUBPAT found prior art for Forgent’s patent, filed 1986– Tescher et al: U.S patent 4,541,012, issued 1985

• PUBPAT asks USPTO to re-examine Forgent’s patent– Tescher et al. issued before Forgent filed– Forgent did not disclose this work

USPTO invalidates the patent

Forgent’s patent• “…first run length code

values representing the number of consecutive first values followed by said second value in a digital number…”

Tescher et al.’s patent• “…a run length code

corresponding to the number of successive quantized coefficients having value zero is generated…”

Key reason 1: Both use Run-length encoding

USPTO invalidates the patent

Forgent’s patent• “[a method] in which a

table containing a plurality of run-length code values…and said code values statistically organized…such that statistically more frequent code values are represented by shorter code lengths…”

Tescher et al.’s patent• “[a method] in which..run

length code values…are encoded using dedicated Huffman code table shown in Appendix A.”

Key reason 2: Both do Huffman on Run-length encoded data

Huffman codes

Lessons

• Disclose all prior-art– PUBPAT: “If you don’t disclose, we will.”

• Even an invalid patent is worth something– Forgent made $90 million in licensing royalties

(e.g., from Sony)

• Standards (such as JPEG) may need special protection– Hard to collect all prior work

Thanks!