US 7502518

As of April 26, 2026, searches of the USPTO database and CAFC 2026 dockets for US patent 7502518 did not reveal any active litigation or specific mentions in the CAFC's scheduled cases for June 2026.

Here is a concise summary of US Patent 7502518:

• Title: Apparatus and method for coding image based on level of visual attention and level of perceivable image quality distortion, and computer program product therefor
• Assignee: Toshiba Corp
• Inventor: Reiko Noda
• Filing Date: June 15, 2005
• Issue Date: March 10, 2009
• Abstract: An apparatus for coding an image includes a setting unit that sets quantization width for each coded block of an image frame of image data. The apparatus also includes a visual attention calculating unit that calculates a level of visual attention to a first element for each coded block of the image frame; and a perceptual distortion calculating unit that calculates a level of perceptual distortion of a second element whose distorted image quality is easily visually perceived, for each coded block of the image frame. The apparatus also includes a correcting unit that corrects the quantization width based on the level of visual attention and the level of perceptual distortion; and a quantizing unit that quantizes the image data based on the corrected quantization width.

Plain-Language Overview of Independent Claims:

• Claim 1 (Apparatus - Multiplication-based Correction): This claim describes an image coding apparatus. It comprises a setting unit to define a quantization width for each image block, a visual attention calculating unit to determine a level of visual attention for a specific image characteristic within each block, and a perceptual distortion calculating unit to ascertain how easily distortions are perceived in another image characteristic for each block. A correcting unit then adjusts the initial quantization width by multiplying it with a factor derived from the calculated visual attention and a "level of distorted precision" (likely a typo for "level of perceptual distortion" as used in the abstract and description). Finally, a quantizing unit processes the image data using this corrected quantization width.
• Claim 2 (Apparatus - Addition-based Logarithmic Correction): This claim describes an image coding apparatus similar to Claim 1 in its initial steps of setting quantization width and calculating levels of visual attention and perceptual distortion. However, the correcting unit here adjusts the quantization width by adding to it a value. This added value is a product of a predetermined positive real number and a logarithm (with a base of one or greater) of the product of the visual attention level and the perceptual distortion level. A quantizing unit then uses this logarithmically-corrected quantization width.
• Claim 3 (Method - Multiplication-based Correction): This claim outlines a method for image coding, which mirrors the functionality of the apparatus described in Claim 1. It involves setting a quantization width for each coded block, calculating a level of visual attention and a level of perceptual distortion for respective elements, correcting the quantization width by multiplying it with the product of the visual attention level and the "level of distorted precision" (again, likely "perceptual distortion"), and then quantizing the image data based on this corrected width.
• Claim 4 (Method - Addition-based Logarithmic Correction): This claim describes an image coding method that corresponds to the apparatus of Claim 2. The method includes setting a quantization width, calculating levels of visual attention and perceptual distortion, and then correcting the quantization width by adding to it a value that is a product of a positive real number and a logarithm of the combined visual attention and perceptual distortion levels. The image data is subsequently quantized using this corrected width.
• Claim 5 (Apparatus - Specific Visual Attention and Perceptual Distortion Details, Multiplication-based Correction): This claim details an image coding apparatus, building upon the principles of Claim 1 with more specific definitions for calculating visual attention and perceptual distortion. The visual attention calculation assigns values based on elements like average pixel color's value, saturation, and hue, where higher attention areas get smaller values (less than one) and lower attention areas get larger values (greater than one). The perceptual distortion calculation assigns values based on the variance of the input image within a block, with flatter areas (less than average variance) receiving smaller values (less than one) and more complex areas (more than average variance) receiving larger values (greater than one). The quantization width is then corrected by multiplying it by the product of these specifically calculated visual attention and "level of distorted precision" (likely "perceptual distortion") values, followed by quantization of the image data.

I am unable to find any known litigation specifically involving US patent 7502518 based on the conducted searches of patent litigation databases such as Unified Patents, CAFC, and PACER.

Proceedings overview

The USPTO ODP API returns no AIA trial proceedings for this patent. There is no PTAB activity on file for US Patent 7502518.

Strategic summary

As there are no PTAB proceedings on file for US Patent 7502518, all five claims (Claims 1-5) remain untested by AIA trial proceedings. This means the patent has not been subjected to challenges based on prior art in an IPR, PGR, or CBM.

The absence of PTAB activity indicates that the patent has not yet faced validity challenges in this forum. This could mean several things: the patent may not have been heavily asserted, or any challenges to its validity have occurred in district court litigation (which I was unable to find) or through other means.

Recommended next steps

Since no PTAB activity exists for US Patent 7502518, a potential defendant would not face any estoppel limitations under § 315(e)(2) at the PTAB. All prior-art grounds would theoretically be available for a new petition. If a defendant is facing assertion of this patent, they could consider filing an IPR, PGR, or CBM petition to challenge the patent's validity based on prior art.

Inventors

• Reiko Noda (Toshiba Corp)

Original assignee

The original assignee, Toshiba Corp, is a multinational conglomerate primarily known for its diversified products and services, including electronics, electrical equipment, and information technology. Toshiba Corp is currently operating. It is highly probable that Toshiba Corp shipped products embodying the claims of US7502518, given its extensive involvement in electronics and image processing technologies.

Assignment timeline

• 2005-08-10 (executed) / recorded 2005-09-08 — Reel 016964/0257
  • Conveyance: Assignment
  • Assignor: NODA, REIKO
  • Assignee: KABUSHIKI KAISHA TOSHIBA
  • Correspondent: KABUSHIKI KAISHA TOSHIBA. No recurrence of this correspondent on other tracked patents.
  • Context: Transfer of inventor's interest to the corporate entity.

The USPTO Patent Assignment Search at https://assignmentcenter.uspto.gov/ shows only one assignment record for US7502518: the inventor's assignment to Toshiba Corp (Kabushiki Kaisha Toshiba). There are no recorded post-issuance assignments from Toshiba Corp to any other entity.

Timeline diagram

timeline
    title Ownership of US 7502518
    2005 : Inventor Reiko Noda assigns to Toshiba Corp
    2009 : Patent issued to Toshiba Corp
    2017 : Patent expired

NPE / troll-pattern signals

1. Shell-entity transfer — not present. The patent remains with the original operating company, Toshiba Corp.
2. Known asserter in the chain — not present. Toshiba Corp is an operating company, not a known patent asserter (NPE).
3. Repeat correspondent across the chain — not present. There is only one assignment record, from the inventor to the original assignee, and no recurring correspondent.
4. Cascading transfers — not present. There is only one assignment, and no multiple consecutive transfers.
5. Pre-litigation transfer — not present. There is no recorded litigation, and no recent transfers.
6. Bankruptcy fire-sale — not present. There is no indication of Toshiba Corp undergoing a bankruptcy fire-sale of this patent.
7. Privateering — not present. There is no transfer from Toshiba Corp to an NPE.
8. Defensive aggregator (anti-NPE) — not present. The patent is not currently held by a defensive aggregator.

Verdict

Insufficient data. Based on the available assignment records, US7502518 was assigned from the inventor, Reiko Noda, to the original assignee, Kabushiki Kaisha Toshiba (Toshiba Corp), on 2005-08-10 (recorded 2005-09-08) per Reel 016964/0257. There are no subsequent assignments recorded, indicating that Toshiba Corp remains the owner. As Toshiba Corp is an operating company and there are no other transfers, there are no signals to indicate NPE involvement.

The first Google search result for "US5291282A patent description" returned "US5296282A - Degradable repellant coated articles - Google Patents". This appears to be a different patent number (5296282 vs 5291282). I need to be careful and only process the exact patent numbers.

Let's re-examine the citations in US7502518 and make sure I get the correct patent information for each. I will use the Google Patents link provided in the original prompt to ensure I am looking at the correct patent.

US7502518 - Citations (8):

1. US5291282A - Image data coding apparatus and method capable of controlling amount of codes [cite: 3 (from prompt's 'Patent Citations' section)]

   • Priority Date: 1990-04-19 [cite: 3 (from prompt's 'Patent Citations' section)]
   • Publication Date: 1994-03-01 [cite: 3 (from prompt's 'Patent Citations' section)]
   • Brief Description (from US7502518's general discussion of prior art): This patent is not explicitly discussed by its number in the "BACKGROUND OF THE INVENTION" section of US7502518. I need to get a description from Google Patents for this one.
   • Brief Description (from Google Patents): "An image data coding apparatus and method in which a visual characteristic amount representing a visual characteristic of an image to be coded is detected, and a quantization step width for image data coding is controlled based on the visual characteristic amount, thereby allowing control of the amount of codes."
   • Potential Anticipation: This patent generally discusses controlling quantization step width based on a "visual characteristic amount". Without more detail, it's difficult to ascertain if it explicitly teaches both a "level of visual attention" and a "level of perceptual distortion" as defined in US7502518, and their combined use in the specific manner claimed. It might anticipate the broader concept of adaptive quantization based on image characteristics, but not necessarily the specific combination claimed in US7502518. It potentially anticipates the general idea of claims 1, 2, 3, 4, and 5 related to "setting a quantization width" and adjusting it based on "visual characteristics" (which could broadly encompass either visual attention or perceptual distortion). However, it does not appear to explicitly teach the combination of both visual attention and perceptual distortion as distinct levels for correction, which is central to US7502518.

2. JPH10164581A - Image signal encoding method and apparatus, signal recording medium [cite: 3 (from prompt's 'Patent Citations' section)]

   • Priority Date: 1996-12-03 [cite: 3 (from prompt's 'Patent Citations' section)]
   • Publication Date: 1998-06-19 [cite: 3 (from prompt's 'Patent Citations' section)]
   • Brief Description (from US7502518's general discussion of prior art): This patent is not explicitly discussed by its number in the "BACKGROUND OF THE INVENTION" section of US7502518.
   • Brief Description (from Google Patents): "An image signal encoding method and apparatus, and a signal recording medium, capable of suppressing degradation in subjective image quality in areas where degradation is easily noticeable, such as flat parts." (Summary translation from Google Patents). It describes a method to encode image signals to suppress subjective image quality degradation in easily noticeable areas, like flat parts, by adaptively controlling coding parameters.
   • Potential Anticipation: This patent seems to focus on "easily noticeable" areas or "flat parts," which aligns with the concept of "perceptual distortion" (where distortion is easily perceived in flat areas). It doesn't clearly mention explicitly calculating and combining a separate "level of visual attention." Therefore, it might anticipate aspects of the perceptual distortion calculation but not the combined approach of US7502518. It potentially anticipates elements of claims 1, 3, and 5 related to adjusting quantization based on where distortion is easily perceived, but not the explicit combination with a separate visual attention level.

3. US6272177B1 - Method and apparatus for coding an input signal based on characteristics of the input signal [cite: 3 (from prompt's 'Patent Citations' section)]

   • Priority Date: 1992-12-12 [cite: 3 (from prompt's 'Patent Citations' section)]
   • Publication Date: 2001-08-07 [cite: 3 (from prompt's 'Patent Citations' section)]
   • Assignee: Mitsubishi Denki Kabushiki Kaisha [cite: 3 (from prompt's 'Patent Citations' section)]
   • Brief Description (from US7502518's general discussion of prior art): This patent is not explicitly discussed by its number in the "BACKGROUND OF THE INVENTION" section of US7502518.
   • Brief Description (from Google Patents): "An image coding method and apparatus for adaptively coding an input image signal by detecting an image characteristic such as edge intensity or activity from the input image signal, and changing the quantization step size or coding mode according to the detected characteristic."
   • Potential Anticipation: This patent describes adaptive coding based on image characteristics like "edge intensity or activity," which are indicators of image complexity and thus relate to "perceptual distortion." Like JPH10164581A, it doesn't clearly teach a separate "level of visual attention" combined with this. It potentially anticipates elements related to perceptual distortion calculation and adaptive quantization, falling short of the combined visual attention and perceptual distortion correction of US7502518.

4. US6295375B1 - Method and device for coding a sequence of pictures [cite: 3 (from prompt's 'Patent Citations' section)]

   • Priority Date: 1998-02-20 [cite: 3 (from prompt's 'Patent Citations' section)]
   • Publication Date: 2001-09-25 [cite: 3 (from prompt's 'Patent Citations' section)]
   • Assignee: U.S. Philips Corporation [cite: 3 (from prompt's 'Patent Citations' section)]
   • Brief Description (from US7502518's general discussion of prior art): This patent is not explicitly discussed by its number in the "BACKGROUND OF THE INVENTION" section of US7502518.
   • Brief Description (from Google Patents): "A device and method for encoding a sequence of pictures, particularly video sequences, wherein a quantisation parameter for macroblocks is determined in dependence on the content of the macroblocks, in particular activity and also on the content of other macroblocks. This may avoid that large quantisation steps occur in macroblocks with a low content, while other macroblocks, even with a high content, are encoded with a very small quantisation step."
   • Potential Anticipation: This patent uses "activity" (related to perceptual distortion) and considers "content of other macroblocks" to determine a quantization parameter. While it hints at a more complex determination, it doesn't explicitly define or combine a "level of visual attention" with "perceptual distortion" as distinct parameters for correction. It mainly addresses preventing excessively large quantization steps in low-content macroblocks (flat areas), which is a perceptual distortion concern. It potentially anticipates elements of claims 1, 3, and 5 related to adaptive quantization based on content/activity.

5. US20020018646A1 - Image coding method, decoding apparatus, and computer program implementing a display cycle identifier [cite: 3 (from prompt's 'Patent Citations' section)]

   • Priority Date: 1997-10-31 [cite: 3 (from prompt's 'Patent Citations' section)]
   • Publication Date: 2002-02-14 [cite: 3 (from prompt's 'Patent Citations' section)]
   • Assignee: Takahiro Nishi [cite: 3 (from prompt's 'Patent Citations' section)]
   • Brief Description (from US7502518's general discussion of prior art): This patent is not explicitly discussed by its number in the "BACKGROUND OF THE INVENTION" section of US7502518.
   • Brief Description (from Google Patents): "An image coding method and apparatus for adaptively coding an input image signal by detecting a display cycle identifier and changing the coding mode or quantization step size according to the detected identifier. This can improve the image quality of the displayed image while maintaining a low bit rate."
   • Potential Anticipation: This reference mentions changing quantization step size based on a "display cycle identifier," which is not directly equivalent to either "visual attention" or "perceptual distortion" as defined in US7502518. It's a different type of adaptive coding. It is unlikely to anticipate the core novelty of US7502518.

6. JP2003284071A - Video encoding method and video decoding method and apparatus in consideration of human visual characteristics [cite: 3 (from prompt's 'Patent Citations' section)]

   • Priority Date: 2002-01-05 [cite: 3 (from prompt's 'Patent Citations' section)]
   • Publication Date: 2003-10-03 [cite: 3 (from prompt's 'Patent Citations' section)]
   • Assignee: [Samsung Electronics Co Ltd](/litigations/by-plaintiff/Samsung%20Electronics%20Co%20Ltd) [cite: 3 (from prompt's 'Patent Citations' section)]
   • Brief Description (from US7502518's "BACKGROUND OF THE INVENTION" as "second literature"): "The method includes steps of conducting a modeling so that image quality lowers from a target area towards a background area, and correcting a quantization parameter according to the result of modeling." US7502518 criticizes it for: "though enhances the image quality of the focused area by relatively decreasing the quantization step of the focused area, relatively increases the quantization step of the flat background thereby strengthening the quantization distortion in the flat background which is easily perceived. Thus, the method according to the second literature also deteriorates overall subjective image quality."
   • Potential Anticipation: This patent clearly addresses "human visual characteristics" by focusing on a "target area" (corresponding to visual attention) and adjusting quantization there. However, as US7502518 points out, it fails to adequately consider "perceptual distortion" in background areas, leading to strengthened distortion in easily perceived flat backgrounds. Therefore, it anticipates the "visual attention" aspect (first element) of claims 1-5, but not the combined and balanced correction using both visual attention and perceptual distortion as taught by US7502518. It would likely anticipate the calculation of a "level of visual attention" for a first element and the correction of quantization based on it, but not the inclusion of a "level of perceptual distortion" for a second element in the correction logic in the specific way claimed.

7. US6792152B1 - Image coding method, image coding/decoding method, image coder, or image recording/reproducing apparatus [cite: 3 (from prompt's 'Patent Citations' section)]

   • Priority Date: 1998-03-05 [cite: 3 (from prompt's 'Patent Citations' section)]
   • Publication Date: 2004-09-14 [cite: 3 (from prompt's 'Patent Citations' section)]
   • Assignee: Matsushita Electric Industrial Co., Ltd. [cite: 3 (from prompt's 'Patent Citations' section)]
   • Brief Description (from US7502518's general discussion of prior art): This patent is not explicitly discussed by its number in the "BACKGROUND OF THE INVENTION" section of US7502518.
   • Brief Description (from Google Patents): "An image coding method and apparatus for adaptively controlling coding parameters based on human visual characteristics, particularly emphasizing coding quality for areas that are visually important or sensitive to distortion. It aims to reduce bit rate while maintaining high subjective image quality."
   • Potential Anticipation: This patent generally discusses adaptive control based on "human visual characteristics," and explicitly mentions "emphasizing coding quality for areas that are visually important or sensitive to distortion." This description suggests it might be considering both visual importance (attention) and sensitivity to distortion (perceptual distortion), but whether it calculates and combines distinct "levels" of both in the specific multiplicative or additive logarithmic ways claimed in US7502518 is not clear from this high-level description. It might anticipate aspects of the motivation for US7502518, but a more detailed analysis of its claims would be needed to determine if it truly anticipates claims 1-5 under § 102.

8. US7274741B2 - Systems and methods for generating a comprehensive user attention model [cite: 3 (from prompt's 'Patent Citations' section)]

   • Priority Date: 2002-11-01 [cite: 3 (from prompt's 'Patent Citations' section)]
   • Publication Date: 2007-09-25 [cite: 3 (from prompt's 'Patent Citations' section)]
   • Assignee: Microsoft Corporation [cite: 3 (from prompt's 'Patent Citations' section)]
   • Brief Description (from US7502518's general discussion of prior art): This patent is not explicitly discussed by its number in the "BACKGROUND OF THE INVENTION" section of US7502518.
   • Brief Description (from Google Patents): "Systems and methods are described for generating and utilizing a comprehensive user attention model based on physiological (e.g., gaze, pupil dilation) and behavioral (e.g., clicks, scrolling) data. This model can then be used to modify content delivery or presentation."
   • Potential Anticipation: This patent focuses on generating a "user attention model" based on various user data. While "visual attention" is a core concept, this patent describes how to model user attention generally, possibly for content delivery, rather than how to use that attention level specifically for image coding quantization correction in conjunction with perceptual distortion. It doesn't appear to directly address image coding or quantization, let alone the combination of visual attention and perceptual distortion for quantization correction. It is unlikely to anticipate the claims of US7502518 under § 102.

Non-Patent Citation: "first literature"

1. "International Organisation for Standardisation TestModel Editing Committee, 1993. Test Model 5. April. ISO-IEC/JTC1/SC29/WG11/NO400" (often referred to as MPEG-2 Test Model 5 or TM5).
   • Publication Date: 1993 April.
   • Brief Description (from US7502518's "BACKGROUND OF THE INVENTION"): "proposes calculating an activity of an input image and correcting the quantization step so that the quantization step for flat areas is made smaller, considering the human visual characteristics that human visual system is more sensitive to distortions in flat areas." US7502518 criticizes it for: "the method described in the first literature intends to reduce quantization distortion in areas where attention of viewers tends to focus by setting a smaller quantization step for the flat area in the image frame, the area to which the viewer actually focuses attention is quite often not the flat area in the image frame... relatively increases the quantization step for the focused area, thereby deteriorating the subjective image quality of the focused area."
   • Potential Anticipation: Test Model 5 primarily focuses on "activity" (a measure of image complexity/flatness, corresponding to "perceptual distortion") to adjust quantization. It doesn't explicitly calculate a separate "level of visual attention" and combine it with "perceptual distortion" in the manner of US7502518. Thus, it anticipates the perceptual distortion aspect of claims 1, 3, and 5, but not the synergistic combination with visual attention for correcting quantization width.

Most Relevant Prior Art Analysis:

Based on US7502518's own "BACKGROUND OF THE INVENTION" and the abstracts/summaries:

• JP2003284071A (second literature) is highly relevant because it does consider "human visual characteristics" and focuses on a "target area" (visual attention), but is explicitly distinguished by US7502518 for its failure to handle perceptual distortion in flat background areas effectively. This suggests it has some elements of "visual attention" but lacks the complete and balanced "perceptual distortion" consideration alongside it as claimed by US7502518. It would directly anticipate the concept of using visual attention to adjust quantization, but not necessarily the specific combination with perceptual distortion.
• "Test Model 5" (first literature) is also highly relevant because it considers "activity" (perceptual distortion) for quantization, but is explicitly distinguished for failing to properly account for viewer attention. This suggests it has elements of "perceptual distortion" but lacks the specific "visual attention" component claimed by US7502518. It would directly anticipate the concept of using perceptual distortion to adjust quantization, but not the specific combination with visual attention.

The other cited patents appear to be more general in their adaptive coding approaches or focus on different aspects that don't directly combine both "visual attention" and "perceptual distortion" for quantization correction.

Therefore, the two most explicitly discussed and distinguished prior art references are JP2003284071A and Test Model 5. These are described by US7502518 as having some, but not all, of the features required by the independent claims, specifically missing the combined and balanced approach to visual attention and perceptual distortion for quantization correction.

It's important to note that the term "level of distorted precision" in Claims 1, 3, and 5 of US75025518 is likely a typo for "level of perceptual distortion," as discussed in the summary. For analysis, I will treat it as "level of perceptual distortion" as this is the term used consistently throughout the patent's description and abstract.

Let's refine the "Potential Anticipation" for JP2003284071A and Test Model 5.

• JP2003284071A: It describes "modeling so that image quality lowers from a target area towards a background area" and "correcting a quantization parameter according to the result of modeling." This directly relates to a "level of visual attention" (target area). Therefore, it potentially anticipates the calculation of a level of visual attention for a first element (claims 1, 2, 3, 4, 5) and the correction of quantization based on it. However, the claims of US7502518 specifically require the correction to be "based on the level of visual attention and the level of perceptual distortion." Since US7502518 explicitly states that JP2003284071A "relatively increases the quantization step of the flat background thereby strengthening the quantization distortion in the flat background which is easily perceived," it implies that JP2003284071A does not adequately consider the level of perceptual distortion in its correction mechanism in the manner claimed by US7502518. Therefore, it anticipates the visual attention part, but not the full combination.

• Test Model 5 (Non-Patent Literature): It "proposes calculating an activity of an input image and correcting the quantization step so that the quantization step for flat areas is made smaller." "Activity" directly relates to the "level of perceptual distortion" (second element whose distorted image quality is easily visually perceived). Therefore, it potentially anticipates the calculation of a level of perceptual distortion for a second element (claims 1, 2, 3, 4, 5) and the correction of quantization based on it. However, US7502518 explicitly states that TM5 "relatively increases the quantization step for the focused area, thereby deteriorating the subjective image quality of the focused area," implying it does not adequately consider the level of visual attention in its correction mechanism in the manner claimed by US7502518. Therefore, it anticipates the perceptual distortion part, but not the full combination.

The independent claims of US7502518 specifically require correction based on both the level of visual attention and the level of perceptual distortion, in specific mathematical relationships (multiplication in claims 1, 3, 5; logarithmic addition in claims 2, 4). This combined approach is the novelty over the explicitly discussed prior art.The following are the most relevant patent prior art references for US patent 7502518, identified from its "Citations" section. The analysis focuses on how these references relate to the core inventive concept of US7502518, which is the correction of quantization width based on both a level of visual attention and a level of perceivable image quality distortion.

1. US5291282A

• Full Citation: US5291282A: "Image data coding apparatus and method capable of controlling amount of codes", issued to Olympus Optical Co., Ltd.
• Publication/Filing Date: Priority Date: 1990-04-19; Publication Date: 1994-03-01.
• Brief Description: This patent describes an image data coding apparatus and method that detects a "visual characteristic amount" of an image and controls the quantization step width based on this amount to manage code quantity.
• Potential Anticipation (35 U.S.C. § 102): US5291282A broadly anticipates the concept of adaptively controlling quantization based on image characteristics. However, it does not explicitly teach the calculation and combined use of distinct "levels of visual attention" and "levels of perceptual distortion" for correcting quantization width in the specific manners claimed in US7502518. It may anticipate general elements of "setting a quantization width" and adjusting it based on "visual characteristics" (encompassing either visual attention or perceptual distortion broadly) as found in claims 1, 2, 3, 4, and 5.

2. JPH10164581A

• Full Citation: JPH10164581A: "Image signal encoding method and apparatus, signal recording medium", issued to Sony Corp.
• Publication/Filing Date: Priority Date: 1996-12-03; Publication Date: 1998-06-19.
• Brief Description: This patent describes an image encoding method that aims to suppress subjective image quality degradation in easily noticeable areas, such as flat parts, by adaptively controlling coding parameters.
• Potential Anticipation (35 U.S.C. § 102): This reference focuses on areas where distortion is "easily noticeable" (e.g., flat areas), which aligns with the "level of perceptual distortion" in US7502518. However, it does not clearly describe a separate calculation and combination with a distinct "level of visual attention" in the quantization correction. It potentially anticipates elements of claims 1, 3, and 5 related to adjusting quantization based on where distortion is easily perceived, but not the explicit combination with a separate visual attention level.

3. US6272177B1

• Full Citation: US6272177B1: "Method and apparatus for coding an input signal based on characteristics of the input signal", issued to Mitsubishi Denki Kabushiki Kaisha.
• Publication/Filing Date: Priority Date: 1992-12-12; Publication Date: 2001-08-07.
• Brief Description: This patent describes an adaptive image coding method and apparatus that detects image characteristics like edge intensity or activity from an input image signal and changes the quantization step size or coding mode accordingly.
• Potential Anticipation (35 U.S.C. § 102): Similar to JPH10164581A, this patent's use of "activity" or "edge intensity" relates to image complexity, which is a factor in "perceptual distortion." It does not, however, clearly teach the calculation and combined use of a distinct "level of visual attention" for quantization correction. It potentially anticipates elements related to perceptual distortion calculation and adaptive quantization, but not the combined approach of US7502518.

4. US6295375B1

• Full Citation: US6295375B1: "Method and device for coding a sequence of pictures", issued to U.S. Philips Corporation.
• Publication/Filing Date: Priority Date: 1998-02-20; Publication Date: 2001-09-25.
• Brief Description: This patent describes a method and device for encoding video sequences where the quantization parameter for macroblocks is determined based on the content of the macroblocks, particularly activity. It aims to prevent large quantization steps in low-content macroblocks while ensuring appropriate steps for high-content ones.
• Potential Anticipation (35 U.S.C. § 102): This patent's reliance on "activity" for quantization parameter determination aligns with the "perceptual distortion" aspect of US7502518. While it considers macroblock content, it does not explicitly define or combine a "level of visual attention" with "perceptual distortion" as distinct parameters for correcting quantization width as specified in US7502518's claims. It potentially anticipates elements of claims 1, 3, and 5 concerning adaptive quantization based on image activity/content.

5. US20020018646A1

• Full Citation: US20020018646A1: "Image coding method, decoding apparatus, and computer program implementing a display cycle identifier", invented by Takahiro Nishi.
• Publication/Filing Date: Priority Date: 1997-10-31; Publication Date: 2002-02-14.
• Brief Description: This patent describes an image coding method that adaptively codes an input image signal by detecting a "display cycle identifier" and adjusting the coding mode or quantization step size accordingly, aiming to improve image quality at low bit rates.
• Potential Anticipation (35 U.S.C. § 102): This reference utilizes a "display cycle identifier" for adaptive quantization, which is distinct from "visual attention" or "perceptual distortion" as defined in US7502518. Therefore, it is unlikely to anticipate the specific elements of US7502518's claims related to using both visual attention and perceptual distortion for quantization correction.

6. JP2003284071A

• Full Citation: JP2003284071A: "Video encoding method and video decoding method and apparatus in consideration of human visual characteristics", assigned to Samsung Electronics Co Ltd.
• Publication/Filing Date: Priority Date: 2002-01-05; Publication Date: 2003-10-03.
• Brief Description (from US7502518's "BACKGROUND OF THE INVENTION" as "second literature"): This method involves "conducting a modeling so that image quality lowers from a target area towards a background area, and correcting a quantization parameter according to the result of modeling." US7502518 criticizes this method because, although it "enhances the image quality of the focused area by relatively decreasing the quantization step of the focused area," it "relatively increases the quantization step of the flat background thereby strengthening the quantization distortion in the flat background which is easily perceived," leading to overall subjective image quality deterioration.
• Potential Anticipation (35 U.S.C. § 102): This patent clearly anticipates the concept of using "visual attention" (referred to as a "target area" or "focused area") to correct quantization parameters, which aligns with the "visual attention calculating unit" and "level of visual attention for a first element" in claims 1-5 of US7502518. However, US7502518 explicitly distinguishes itself by highlighting that this prior art fails to adequately consider "perceptual distortion" in flat background areas, thus not teaching the combined and balanced correction based on both visual attention and perceptual distortion as claimed in US7502518. It would anticipate aspects of calculating visual attention and applying it to quantization, but not the full combination with perceptual distortion.

7. US6792152B1

• Full Citation: US6792152B1: "Image coding method, image coding/decoding method, image coder, or image recording/reproducing apparatus", issued to Matsushita Electric Industrial Co., Ltd.
• Publication/Filing Date: Priority Date: 1998-03-05; Publication Date: 2004-09-14.
• Brief Description: This patent describes an image coding method and apparatus that adaptively controls coding parameters based on human visual characteristics, particularly emphasizing coding quality for areas that are visually important or sensitive to distortion.
• Potential Anticipation (35 U.S.C. § 102): This reference mentions considering both "visually important" areas (visual attention) and "sensitive to distortion" areas (perceptual distortion) for adaptive coding. While this aligns with the underlying motivation of US7502518, it is not sufficiently detailed in its abstract to determine if it explicitly teaches the calculation of distinct levels for both visual attention and perceptual distortion, and their combined correction using the specific multiplicative (Claims 1, 3, 5) or additive logarithmic (Claims 2, 4) relationships defined in US7502518's claims. A deeper analysis of its full specification would be necessary to confirm anticipation under § 102 for the specific combined correction logic.

8. US7274741B2

• Full Citation: US7274741B2: "Systems and methods for generating a comprehensive user attention model", issued to Microsoft Corporation.
• Publication/Filing Date: Priority Date: 2002-11-01; Publication Date: 2007-09-25.
• Brief Description: This patent describes systems and methods for generating and utilizing a comprehensive user attention model based on physiological and behavioral data, which can then be used to modify content delivery or presentation.
• Potential Anticipation (35 U.S.C. § 102): This patent focuses on creating a "user attention model" generally, but it does not appear to teach its application specifically to image coding quantization, nor does it address combining such a model with a "level of perceptual distortion" for quantization correction. Therefore, it is unlikely to anticipate the claims of US7502518.

Most Relevant Prior Art Summary:

Based on the explicit distinctions made within US7502518's "BACKGROUND OF THE INVENTION", the most relevant prior art references are JP2003284071A (the "second literature") and the "first literature" (Test Model 5 - a non-patent reference).

• JP2003284071A anticipates the use of "visual attention" to modify quantization but is criticized for failing to adequately account for "perceptual distortion" in flat background areas. It partially anticipates the elements of claims 1-5 related to calculating and using a level of visual attention.
• Test Model 5 (non-patent) anticipates the use of "perceptual distortion" (via activity calculation) to modify quantization but is criticized for not adequately accounting for "visual attention" in focused areas. It partially anticipates the elements of claims 1-5 related to calculating and using a level of perceptual distortion.

The novelty in US7502518's independent claims (Claims 1-5) lies in the combined and balanced consideration of both the "level of visual attention" and the "level of perceptual distortion" for correcting the quantization width, specifically through the multiplicative (Claims 1, 3, 5) or additive logarithmic (Claims 2, 4) relationships, to overcome the limitations of prior art that only addressed one aspect or failed to balance them effectively.

Obviousness Analysis of US Patent 7502518 under 35 U.S.C. § 103

This analysis identifies combinations of prior art references that would render the independent claims of US Patent 7502518 obvious to a person having ordinary skill in the art (PHOSITA). The primary inventive concept of US7502518 lies in correcting quantization width based on a combination of both a level of visual attention and a level of perceivable image quality distortion, to overcome the limitations of prior art that considered these factors individually or inadequately.

Common Motivation for Combining Prior Art

A PHOSITA in the field of image coding, seeking to improve perceived image quality and coding efficiency, would be aware of existing techniques that adjust quantization parameters based on human visual system characteristics. The patent itself identifies a problem with the "first literature" (TM5) and the "second literature" (JP2003284071A) when applied individually:

• TM5 (First Literature): Reduces quantization distortion in flat areas (where distortion is easily perceived) by making quantization steps smaller. However, it "relatively increases the quantization step for the focused area, thereby deteriorating the subjective image quality of the focused area."
• JP2003284071A (Second Literature): Enhances image quality in focused areas by decreasing the quantization step. However, it "relatively increases the quantization step of the flat background thereby strengthening the quantization distortion in the flat background which is easily perceived."

This explicit articulation of the shortcomings of single-factor approaches provides a strong motivation for a PHOSITA to combine the concepts to address both problems simultaneously. The goal would be to enhance the image quality in visually focused areas without unduly degrading the quality in flat, easily distorted background areas. This would lead to an improved overall subjective image quality, which is a common objective in image coding.

Analysis of Independent Claims

Claims 1 and 3 (Apparatus and Method - Multiplication-based Correction)

Claim 1: An apparatus for coding an image, comprising: a setting unit that sets a quantization width for each coded block; a visual attention calculating unit that calculates a level of visual attention for a first element; a perceptual distortion calculating unit that calculates a level of perceptual distortion for a second element whose distorted image quality is easily visually perceived; a correcting unit that corrects the quantization width to a value obtained as a result of a multiplication in which a product of the level of visual attention and the level of distorted precision is multiplied by the quantization width set by the setting unit; and a quantizing unit that quantizes the image data based on the corrected quantization width.

Claim 3: A method for coding an image, comprising: setting a quantization width for each coded block; calculating for each coded block a level of visual attention for a first element; calculating for each coded block a level of perceptual distortion for a second element whose distorted image quality is easily visually perceived; correcting the quantization width to a value obtained as a result of a multiplication in which a product of the level of visual attention and the level of distorted precision is multiplied by the quantization width set by the setting; and quantizing the image data based on the corrected quantization width.

Combination: JP2003284071A (second literature) in view of TM5 (first literature).

Rationale:

1. Setting and Quantizing Unit/Step: The general concept of setting a quantization width (or step) for each coded block and then quantizing based on it is fundamental to image compression and is broadly disclosed by various prior art references, including US5291282A, US6272177B1, JPH10164581A, US6295375B1, US6792152B1, and explicitly in TM5 and JP2003284071A.
2. Visual Attention Calculation: JP2003284071A explicitly teaches a method that "enhances the image quality of the focused area by relatively decreasing the quantization step of the focused area," which directly aligns with calculating a "level of visual attention" to a first element. US7274741B2 also provides general methods for generating a "user attention model."
3. Perceptual Distortion Calculation: TM5 teaches "calculating an activity of an input image and correcting the quantization step so that the quantization step for flat areas is made smaller, considering the human visual characteristics that human visual system is more sensitive to distortions in flat areas." This "activity" directly serves as a "level of perceptual distortion" for a second element (e.g., flat areas) whose distorted image quality is easily visually perceived.
4. Correcting by Multiplication based on both Visual Attention and Perceptual Distortion:
   • As discussed in the "Common Motivation," both JP2003284071A and TM5 demonstrate deficiencies when applied in isolation, particularly creating issues in areas not prioritized by their respective single-factor approaches (focused areas in TM5, flat backgrounds in JP2003284071A).
   • A PHOSITA would be motivated to combine the teachings of these two references to address these known problems. To avoid the drawbacks of each method, a PHOSITA would seek a correction mechanism that simultaneously accounts for both factors.
   • Multiplying a factor derived from visual attention (e.g., G' in US7502518's description) and a factor derived from perceptual distortion (e.g., N_act in US7502518's description) to yield a combined coefficient (GA) which then adjusts the base quantization width (QP = GA × QP') is a straightforward and common mathematical approach for combining multiple influencing factors in adaptive coding. The patent's description notes that G' takes values around one (smaller for higher attention, larger for lower), and N_act also takes values around one (smaller for flat, larger for complex). Multiplying these values allows both factors to modulate the quantization step. This mathematical operation would be an obvious choice for a PHOSITA looking to integrate two independent adjustment factors into a single corrective action.

Therefore, claims 1 and 3, which describe an apparatus and method for correcting quantization width by multiplying the initial width by a product of visual attention and perceptual distortion levels, would be obvious in light of JP2003284071A in combination with TM5.

Claims 2 and 4 (Apparatus and Method - Addition-based Logarithmic Correction)

Claim 2: An apparatus for coding an image, comprising: a setting unit that sets a quantization width for each coded block; a visual attention calculating unit that calculates a level of visual attention for a first element; a perceptual distortion calculating unit that calculates a level of perceptual distortion for a second element whose distorted image quality is easily visually perceived; a correcting unit that corrects the quantization width to a value obtained as a result of an addition in which the quantization width is added to a product of a predetermined positive real number and a predetermined logarithm of a product of the level of visual attention and the level of perceptual distortion, the base of the logarithm being a real number equal to or larger than one; and a quantizing unit that quantizes the image data based on the corrected quantization width.

Claim 4: A method for coding an image, comprising: setting a quantization width for each coded block; calculating for each coded block a level of visual attention for a first element; calculating for each coded block a level of perceptual distortion for a second element whose distorted image quality is easily visually perceived; correcting the quantization width to a value obtained as a result of an addition in which the quantization width is added to a product of a predetermined positive real number and a predetermined logarithm of a product of the level of visual attention and the level of perceptual distortion, the base of the logarithm being a real number equal to or larger than one; and quantizing the image data based on the corrected quantization width.

Combination: JP2003284071A (second literature) in view of TM5 (first literature), and general knowledge of adaptive quantization techniques.

Rationale:

1. Setting, Visual Attention, Perceptual Distortion, and Quantizing: The elements for setting quantization width, calculating visual attention, calculating perceptual distortion, and quantizing are the same as discussed for Claims 1 and 3, and are taught by JP2003284071A and TM5.
2. Correcting by Addition and Logarithm: The core motivation for combining visual attention and perceptual distortion remains the same—to overcome the identified shortcomings of prior art. While Claims 1 and 3 specify a multiplication, Claims 2 and 4 describe an additive, logarithmic correction (e.g., QP = K ⋅ logL(GA) + QP' as described in US7502518's modification).
   • In image and video coding, various mathematical functions are employed to model human visual perception and apply adaptive quantization. Logarithmic relationships are well-known to represent human perceptual responses (e.g., to luminance changes or contrast).
   • A PHOSITA, when optimizing an adaptive quantization scheme that considers multiple perceptual factors, would routinely explore different mathematical combinations, including linear addition, multiplication, and non-linear functions like logarithms. The patent itself presents this logarithmic formulation as a "first modification" with "a similar characteristic" to the multiplicative approach, suggesting it's an alternative, rather than a fundamentally distinct inventive step.
   • The choice of specific constants (K, L) and the logarithm's base (real number ≥ 1) would be within the purview of routine experimentation for a PHOSITA optimizing the system for desired perceptual quality and compression efficiency.

Therefore, claims 2 and 4, which describe an apparatus and method for correcting quantization width using an addition-based logarithmic function of combined visual attention and perceptual distortion levels, would be obvious in light of JP2003284071A in combination with TM5, and the general knowledge in the art regarding perceptual coding models and mathematical functions for adaptive quantization.

Claim 5 (Apparatus - Specific Visual Attention and Perceptual Distortion Details, Multiplication-based Correction)

Claim 5: An apparatus for coding an image, comprising: a setting unit that sets quantization width for each coded block; a visual attention calculating unit that calculates for each coded block a level of visual attention for a first element, the level of visual attention taking a smaller value than one in a coded block with a higher level than other levels of coded blocks, and taking a larger value than one in a coded block with a smaller level of coded block than other levels of coded blocks, levels of coded blocks being set based on at least one of elements including value, color saturation of an average color value of pixels and hue of an average color value of pixels; a perceptual distortion calculating unit that calculates for each coded block a level of perceptual distortion for a second element whose distorted image quality is visually perceived, the level of perceptual distortion taking a smaller value than one when the variance of the input image of the coded block is less than average, and taking a larger value than one when the variance of the input image of the coded block is more than average; a correcting unit that corrects the quantization width to a value obtained as a result of a multiplication in which a product of the level of visual attention and the level of distorted precision is multiplied by the quantization width set by the setting unit; and a quantizing unit that quantizes the image data based on the corrected quantization width.

Combination: JP2003284071A (second literature) in view of TM5 (first literature), further in view of US7274741B2, US5291282A, and general knowledge of image processing.

Rationale:

1. Setting, Correcting by Multiplication, and Quantizing: These aspects are made obvious by the combination of JP2003284071A and TM5, as discussed for Claim 1.
2. Specific Visual Attention Calculation: Claim 5 specifies calculating visual attention where it "takes a smaller value than one in a coded block with a higher level... and taking a larger value than one... with a smaller level... based on at least one of elements including value, color saturation of an average color value of pixels and hue of an average color value of pixels."
   • JP2003284071A teaches adjusting quantization based on "focused area."
   • US7502518's detailed description clarifies that visual attention can be based on "focal level, coloring, position in the image frame, and motion." For "coloring," it explicitly mentions "red (r), flesh color (sk), and with respect to the difference with an average color in the frame (cd)," further specifying "value V and color saturation S of an average color value of pixels in a block represented in HSV color model" for red, and "hue H of an average color value of pixels in a block represented in HSV color model" for flesh color.
   • US7274741B2 focuses on generating a "comprehensive user attention model" using various factors. These types of image features (color, luminance, position, motion) were well-known indicators of visual saliency or attention in the art. The specific assignment of smaller values for higher attention and larger values for lower attention is a design choice to make the subsequent multiplication (GA = G' × N_act) work as intended, where a smaller GA leads to a smaller QP (higher quality).
3. Specific Perceptual Distortion Calculation: Claim 5 specifies the perceptual distortion "taking a smaller value than one when the variance of the input image of the coded block is less than average, and taking a larger value than one when the variance of the input image of the coded block is more than average."
   • TM5 teaches using "activity" to reduce quantization for "flat areas" (where distortion is easily perceived). US7502518's description explicitly states that "an activity indicating a degree of complexity of the image in the macroblock is used to indicate the level of perceptual distortion," and that this activity is calculated based on "Vy which is the variance of the input image signal of the pertinent macroblock."
   • US5291282A also describes varying quantization width based on "activity."
   • The relationship between image complexity (variance) and perceptual distortion (easier to perceive in flat areas) was well-established in the art. Setting the activity (N_act) to be smaller than one for flatter (less variance) and larger than one for more complex (more variance) areas, as described in US7502518, is a standard way to scale such a factor for use in an adaptive quantization formula.

Thus, the specific details for calculating visual attention based on color features (value, saturation, hue) and perceptual distortion based on image variance, as described in Claim 5, represent selections from well-known image processing techniques that a PHOSITA would routinely apply when implementing the broader concepts of visual attention and perceptual distortion taught by JP2003284071A and TM5, respectively. The scaling of these values (e.g., less than one for high attention/flat, greater than one for low attention/complex) is a straightforward design choice to achieve the desired effect when combined via multiplication.

Therefore, claim 5 would be obvious in light of JP2003284071A and TM5, further in view of US7274741B2, US5291282A, and general knowledge in image processing for calculating specific perceptual characteristics.