0:24-cv-62093
T52 Ltd v. Citrix Systems Inc
I. Executive Summary and Procedural Information
- Parties & Counsel:
- Plaintiff: T52 Ltd. (England and Wales)
- Defendant: Citrix Systems, Inc. (Delaware)
- Plaintiff’s Counsel: The Concept Law Group, P.A.; DiNovo Price LLP
- Case Identification: 0:24-cv-62093, S.D. Fla., 02/05/2025
- Venue Allegations: Venue is alleged to be proper based on Defendant maintaining a regular and established place of business, transacting business, and committing the alleged acts of infringement within the Southern District of Florida.
- Core Dispute: Plaintiff alleges that Defendant’s virtual desktop and application delivery products infringe eight patents related to technologies for efficiently processing and compressing remote graphics, including methods for generating compression assistance data and for sharing a single graphics processing unit (GPU) among multiple programs.
- Technical Context: The patents address core technical challenges in server-based computing, where graphically intensive applications are run on a central server and the visual output is streamed to a remote user, a foundational technology for the Virtual Desktop Infrastructure (VDI) and cloud gaming markets.
- Key Procedural History: The complaint alleges that Defendant had pre-suit knowledge of the patents through multiple notice letters sent between 2013 and 2022. It further alleges knowledge through Defendant’s own patent prosecution activities, where the parent application to the patents-in-suit was cited as prior art against Defendant’s patent applications as early as 2011.
Case Timeline
| Date | Event |
|---|---|
| 2002-03-01 | Earliest Priority Date for all Patents-in-Suit |
| 2011-03-29 | U.S. Patent No. 7,916,147 Issues |
| 2011-04-04 | Plaintiff's patent family allegedly cited during Defendant's patent prosecution |
| 2011-12-20 | U.S. Patent No. 8,081,192 Issues |
| 2012-06-19 | U.S. Patent No. 8,203,568 Issues |
| 2013-06-18 | U.S. Patent No. 8,466,922 Issues |
| 2013-08-14 | First alleged notice of infringement sent to Defendant |
| 2013-09-17 | Plaintiff's patent family allegedly cited during Defendant's patent prosecution |
| 2013-09-26 | Plaintiff's patent family allegedly cited during Defendant's patent prosecution |
| 2015-08-18 | U.S. Patent No. 9,113,146 Issues |
| 2015-08-25 | U.S. Patent No. 9,117,285 Issues |
| 2016-07-29 | Second alleged notice of infringement sent to Defendant |
| 2016-08-23 | U.S. Patent No. 9,424,621 Issues |
| 2017-12-26 | U.S. Patent No. 9,852,490 Issues |
| 2022-10-31 | Third alleged notice of infringement sent to Defendant |
| 2025-02-05 | Complaint Filed |
II. Technology and Patent(s)-in-Suit Analysis
U.S. Patent No. 7,916,147 - “Centralised Interactive Graphical Application Server,”
The Invention Explained
- Problem Addressed: The patent’s background section describes the technical challenges of delivering high-end graphical applications from a central server to a remote user. Specifically, it identifies the high computational cost of video compression and the network latency introduced by the compression process, which can degrade the user experience (’147 Patent, col. 2:39-49). Conventional compression techniques rely on "brute force" pixel-by-pixel comparison of video frames, which is computationally intensive (Compl. ¶60).
- The Patented Solution: The invention proposes a method to make compression more efficient by exploiting pre-rendering information available in synthetically generated graphics (’147 Patent, col. 21:10-17). Instead of only analyzing the final pixel data, the system intercepts the graphics instructions sent from an application to the GPU. It analyzes these instructions to generate "compression assistance data" (e.g., motion vectors), which is then used by an encoder to compress the final rendered image much more efficiently (Compl. ¶67; ’147 Patent, col. 4:38-44, Fig. 6).
- Technical Importance: This approach seeks to reduce the processing power and time required for video encoding in server-based graphics applications, which could enable higher quality and more responsive remote experiences over standard broadband networks (Compl. ¶65).
Key Claims at a Glance
- The complaint asserts independent Claim 1 (Compl. ¶104).
- The essential elements of Claim 1 are:
- intercepting a first set of instructions for a graphics processor module relating to how to render image frames;
- generating a second set of instructions for the graphics processor module;
- processing the first or second set of instructions to generate first graphics data (image frames);
- processing the second set of instructions to generate second graphics data;
- processing the second graphics data to generate compression assistance data;
- processing the first graphics data using the compression assistance data to generate a compressed video data signal;
- wherein generating the second set of instructions comprises analyzing the first set of instructions to determine which instructions are useful for generating the compression assistance data.
- The complaint reserves the right to assert infringement of other claims (Compl. ¶105).
U.S. Patent No. 8,081,192 - “Centralised Interactive Graphical Application Server,”
The Invention Explained
- Problem Addressed: As a continuation of the application leading to the ’147 Patent, this patent addresses the same technical problem: the inefficiency and high latency of compressing synthetically generated graphics for remote display using conventional, pixel-based methods (’192 Patent, col. 2:50-58).
- The Patented Solution: The invention describes a method of intercepting graphics instructions from software before rendering. These instructions are analyzed to identify information useful for compression. Based on this analysis, a second set of instructions can be generated, and processing these instructions yields "compression assistance data" that is then used to efficiently generate the final compressed video signal (’192 Patent, Abstract; col. 4:48-62).
- Technical Importance: The technology aims to improve the performance of remote graphics systems by integrating the compression process more closely with the graphics generation pipeline, avoiding the computational expense of traditional video encoding techniques (Compl. ¶69).
Key Claims at a Glance
- The complaint asserts independent Claim 1 (Compl. ¶120).
- The essential elements of Claim 1 are:
- intercepting graphics instructions outputted by graphics generating software;
- analyzing the graphics instructions to determine which are useful for generation of compression assistance data;
- generating a second set of instructions responsive to the analysis;
- processing the graphic instructions (or the second set) to generate graphics data (image elements);
- processing a portion of the second set of instructions to generate compression assistance data;
- processing the graphics data using the compression assistance data to generate the compressed video data signal.
- The complaint reserves the right to assert infringement of other claims (Compl. ¶121).
U.S. Patent No. 8,203,568 - “Sharing a graphical processing unit between a plurality of programs,”
Technology Synopsis
The patent addresses the problem of conventional systems requiring a dedicated GPU for each concurrent graphics application, which increases hardware cost, space, and power requirements (Compl. ¶73). The claimed solution is a method for sharing a single GPU among multiple programs by providing control instructions to manage how the GPU processes instructions from each program, storing the resulting frames in separate, non-overlapping memory locations, and then separately compressing and transmitting each frame to its respective remote device (Compl. ¶74-75, 133).
Asserted Claims
Independent Claim 1 (Compl. ¶133).
Accused Features
The accused functionality is Citrix’s “Shared GPU” feature in its Hypervisor product, which allegedly allows a single physical GPU to be used by multiple virtual machines concurrently (Compl. ¶79, 86).
U.S. Patent No. 8,466,922 - “Centralised Interactive Graphical Application Server,”
Technology Synopsis
The patent describes a method for generating multiple compressed image signals. The method involves determining a difference between graphics instructions from different programs, generating compression assistance data responsive to that difference, processing the instructions to generate distinct sets of pixels for each program, and then using the assistance data to compress and transmit the pixel data as separate signals (Compl. ¶146).
Asserted Claims
Independent Claim 1 (Compl. ¶146).
Accused Features
The accused functionalities are Citrix’s HDX and Thinwire technologies, which are alleged to use differential analysis to improve compression efficiency (Compl. ¶79, 82-83).
U.S. Patent No. 9,113,146 - “Centralised Interactive Graphical Application Server,”
Technology Synopsis
This patent claims a method for generating compressed image data by identifying a graphics instruction that has an "influence on a co-ordinate associated with the image data." Compression assistance data is then generated that relates to the coordinate of a specific pixel, and this data is used to process the final pixel data into a compressed format (Compl. ¶159). This suggests a more granular, coordinate-based approach to generating compression assistance.
Asserted Claims
Independent Claim 1 (Compl. ¶159).
Accused Features
The accused functionality is Citrix’s "Selective H.264" or "Actively Changing Regions" feature, which identifies specific regions of the screen for different compression treatment (Compl. ¶83).
U.S. Patent No. 9,117,285 - “Centralised Interactive Graphical Application Server,”
Technology Synopsis
The patent claims a system for producing compressed image data. The system comprises an instruction interception module, a GPU, and memory. It operates by intercepting instructions, identifying one that influences a coordinate in the image data, generating compression assistance data related to that coordinate, processing the instruction to generate pixels, and then using the assistance data to compress the pixels (Compl. ¶172). This appears to be a system claim counterpart to the method claimed in the ’146 Patent.
Asserted Claims
Independent Claim 1 (Compl. ¶172).
Accused Features
The accused functionality is Citrix’s selective or region-based compression as implemented in its HDX and Thinwire technologies (Compl. ¶79, 83).
U.S. Patent No. 9,424,621 - “Centralised Interactive Graphical Application Server,”
Technology Synopsis
This patent claims a method for generating compressed image transmissions from multiple programs. The method involves outputting graphics instructions from first and second programs, modifying instructions from each to create modified sets, processing both sets on a GPU to generate separate sets of pixels, and then processing and transmitting the compressed data for each (Compl. ¶186). The "modifying" step is identified as a key element performed to facilitate compression.
Asserted Claims
Independent Claim 1 (Compl. ¶186).
Accused Features
The accused functionalities are Citrix’s GPU-sharing and compression technologies in products like Hypervisor and those using HDX/Thinwire (Compl. ¶79, 86).
U.S. Patent No. 9,852,490 - “Centralised Interactive Graphical Application Server,”
Technology Synopsis
This patent claims a system with a "graphics instruction modification module (GIMM)" that modifies instructions from a program, processes them on a GPU to generate pixels, and then determines differences or similarities between pixels at different points in time to facilitate compression and transmission (Compl. ¶199). The claims focus on the system architecture for instruction modification and temporal analysis for compression.
Asserted Claims
Independent Claim 11 (Compl. ¶199).
Accused Features
The accused functionalities are Citrix’s GPU-sharing and compression technologies (Compl. ¶79, 86).
III. The Accused Instrumentality
Product Identification
The complaint identifies the Accused Instrumentalities as product suites including Citrix Hypervisor (formerly XenServer), Citrix DaaS (formerly Citrix Virtual Apps and Desktops), and products incorporating Citrix’s HDX and Thinwire technologies (Compl. ¶79).
Functionality and Market Context
The accused products provide virtual desktop and application delivery, allowing users to access graphically intensive software remotely. The complaint alleges that two specific functionalities infringe the patents-in-suit. First, the HDX/Thinwire technology allegedly provides compression assistance by using a "Selective H.264" codec that "sense[s] regions of transient content (fluid images or video) and encodes it" using a video codec, while non-transient regions are compressed differently (Compl. ¶83). The complaint includes a screenshot from Citrix's product documentation showing a user interface for configuring this feature, described as "Use video codec when preferred" (Compl. p. 25). Second, the "Shared GPU" feature of Citrix Hypervisor allegedly "allows one physical GPU to be used by multiple VMs concurrently" by passing the "graphics commands of each virtual machine... directly to the GPU" (Compl. ¶86). The complaint provides a screenshot of a configuration menu for creating "vGPU enabled VMs" to support this allegation (Compl. p. 27). Citrix allegedly markets these products as providing a "high-definition experience on any device" for intensive workloads (Compl. ¶92-93).
IV. Analysis of Infringement Allegations
U.S. Patent No. 7,916,147
| Claim Element (from Independent Claim 1) | Alleged Infringing Functionality | Complaint Citation | Patent Citation |
|---|---|---|---|
| a) intercepting a first set of instructions for said graphics processor module... | Citrix products allegedly intercept graphics commands from virtual machines to direct them to a shared GPU or analyze them for compression. | ¶79, 86 | col. 5:6-10 |
| b) generating a second set of instructions for said graphics processor module... | Citrix's analysis of display data to identify "actively changing regions" for selective video encoding is alleged to constitute the generation of new instructions for the GPU and compression system. | ¶83, 85 | col. 4:45-51 |
| c) processing said first set of instructions... to generate first graphics data, said first graphics data comprising image frames; | The Accused Instrumentalities render the image frames for display on the remote user's device. | ¶79, 82 | col. 4:52-54 |
| d) processing said second set of instructions... to generate second graphics data; | The complaint’s theory suggests that the process of identifying "actively changing regions" results in a form of secondary data used for compression. | ¶83, 85 | col. 4:55-56 |
| e) processing said second graphics data to generate compression assistance data; | The identification of which specific screen regions are "transient" is alleged to be the claimed "compression assistance data." | ¶83 | col. 4:57-59 |
| f) processing said first graphics data using said compression assistance data to generate a compressed video data signal; | The Accused Instrumentalities allegedly use the identified "actively changing regions" to apply H.264/H.265 video compression only to those selected parts of the screen. | ¶83 | col. 4:60-62 |
| wherein the generation of said second set of instructions comprises analyzing said first set of instructions... | Citrix's technology allegedly "senses" or analyzes the display data to determine which areas require video encoding, which the complaint maps to this limitation. | ¶83 | col. 21:38-44 |
U.S. Patent No. 8,081,192
| Claim Element (from Independent Claim 1) | Alleged Infringing Functionality | Complaint Citation | Patent Citation |
|---|---|---|---|
| a) intercepting graphics instructions outputted by graphics generating software; | The Accused Instrumentalities allegedly intercept graphics commands to facilitate GPU sharing and compression. | ¶79, 86 | col. 4:48-50 |
| b) analyzing the graphics instructions to determine which of the graphics instructions are useful for generation of compression assistance data; | The "Selective H.264" feature allegedly analyzes display content to determine which regions ("transient content") are suitable for video codec compression. | ¶83 | col. 4:51-53 |
| c) generating a second set of instructions responsive to the results of the analysis; | The complaint alleges this analysis results in instructions for the system to apply specific compression techniques to identified regions. | ¶83, 85 | col. 4:54-55 |
| d) processing the graphic instructions... to generate graphics data comprising one or more image elements; | The system renders the final image for the user. | ¶79, 82 | col. 4:56-60 |
| e) processing at least a portion of the second set of instructions to generate compression assistance data; | The identification of "actively changing regions" is the alleged compression assistance data generated from the analysis. | ¶83 | col. 4:61-62 |
| f) processing at least a portion of the graphics data using... compression assistance data to generate the compressed video data signal. | The system allegedly applies H.264/H.265 compression only to the identified transient regions of the rendered frame. | ¶83 | col. 4:63-67 |
Identified Points of Contention
- Scope Questions: A central question may be whether Citrix's high-level process of "sens[ing] regions of transient content" (Compl. ¶83) meets the claim requirement of "analyzing... instructions" (’147 Patent, Claim 1g). The defense may argue that its technology performs a form of image-space or frame-buffer analysis rather than the instruction-level analysis described in the patents' specifications, which detail modifying instructions related to 3D objects before they are rendered (’147 Patent, col. 10:1-15).
- Technical Questions: The complaint does not specify the precise technical mechanism by which the Accused Instrumentalities identify "actively changing regions." A key factual dispute may be what evidence exists that this process involves intercepting and analyzing the underlying graphics API calls or driver instructions, as opposed to analyzing the pixel data after rendering has begun but before compression is complete. The distinction between analyzing pre-rendering instructions versus post-rendering pixel data could be critical.
V. Key Claim Terms for Construction
The Term: "analyzing said first set of instructions" (’147 Patent, Claim 1)
Context and Importance: This term is central to the core inventive concept of using pre-rendering information to aid compression. The infringement case for the compression-related patents will likely depend on whether the alleged actions of the Accused Instrumentalities fall within the construed scope of this term. Practitioners may focus on this term because the complaint maps it to Citrix's high-level description of "sens[ing] regions of transient content," which may or may not involve the specific type of instruction-level analysis detailed in the patent.
Intrinsic Evidence for Interpretation:
- Evidence for a Broader Interpretation: The patent states that an "advantage of the present invention is that it exploits the fact that with synthetic images there is... access to information relating to the images prior to its rendering and that this information can facilitate the compression process" (’147 Patent, col. 21:10-17). This broader statement of purpose could support an interpretation covering any method that leverages pre-rendering information, not just a specific implementation.
- Evidence for a Narrower Interpretation: The detailed description provides specific examples of analysis, such as feeding instructions to a subsidiary processor with "lighting and shading aspects turned off or altered" or rendering objects with a "unique, flat colour" to identify them (’147 Patent, col. 10:1-15). These specific embodiments could support a narrower construction limited to direct manipulation and analysis of the graphics instructions themselves.
The Term: "compression assistance data"
Context and Importance: This is the direct product of the "analyzing" step and the input to the final compression step. The parties will likely dispute whether the output of Citrix's "sensing" process—the identification of which regions are "transient"—constitutes "compression assistance data" as claimed.
Intrinsic Evidence for Interpretation:
- Evidence for a Broader Interpretation: The specification provides a non-exhaustive list of what this data can be, stating it "includes motion vector data" but also giving "examples of other types," such as "which parts of a scene—if any—to encode as separate objects" (’147 Patent, col. 4:38-44). This suggests the term is not limited to just motion vectors.
- Evidence for a Narrower Interpretation: The patent's "Reasons for Allowance," as quoted in the complaint, specifically references "analyzing said first set of instructions to determine which instructions of said first set of instructions are useful for the generation of compression assistance data," tightly linking the data to the instruction analysis (Compl. ¶72). The primary embodiments focus heavily on generating motion vectors, which could suggest a narrower scope centered on that type of data (’147 Patent, col. 10:60-11:20).
VI. Other Allegations
- Indirect Infringement: The complaint alleges inducement of infringement based on Defendant's affirmative acts of encouraging its customers to use the accused functionalities. It cites Defendant's product documentation, user guides, and configuration interfaces that allegedly instruct users on how to enable and use the infringing compression and GPU-sharing features (Compl. ¶84-87, 112). Contributory infringement is alleged on the grounds that the accused software components have no substantial non-infringing use when configured for their intended purpose (Compl. ¶98, 114).
- Willful Infringement: The complaint alleges willful infringement based on Defendant's alleged knowledge of the patents since at least August 14, 2013, via direct notice letters (Compl. ¶40, 115). It further supports this allegation by claiming Defendant had knowledge via its own patent prosecution activities, where the parent application of the patents-in-suit was cited as prior art against Defendant's own applications (Compl. ¶44-47).
VII. Analyst’s Conclusion: Key Questions for the Case
- A core issue will be one of technical mechanism: what is the actual method by which Citrix's HDX/Thinwire technology identifies "actively changing regions"? The case may turn on whether this is accomplished by analyzing pre-rendering graphics instructions as described in the patents, or through a different method, such as a post-rendering, image-space analysis, that may not be covered by the claims.
- A key legal question will be one of definitional scope: can the claim term "analyzing... instructions," which the patent specification illustrates with specific examples of generating modified instruction sets for a secondary processor, be construed broadly enough to encompass the alleged "sensing" function performed within Citrix's integrated software architecture?
- For the patents related to GPU sharing, a central question will be one of functional mapping: does the Citrix Hypervisor's management of multiple virtual machines on a single GPU perform the specific steps of the asserted claims, particularly with respect to providing "control instructions" to store frames in separate memory locations and coordinating with an encoder for distinct remote transmissions?