# US 5,710,602 A · Gain correction for encoding video images > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,710,602 A - Document ID: US5710602A - Status: Granted - Kind: A - Application number: 08/536,619 - Filed: 1995-09-29 - Granted: 1998-01-20 - Earliest claimed: 1995-09-29 - Assignees: Intel Corporation - Inventors: Thomas R. Gardos; Joe Monaco - Web page: https://patentgrep.com/patent/US5710602A ## CPC - H04N 5/20: Circuitry for controlling amplitude response - H04N 5/52: Automatic gain control - H04N 9/76: for mixing of colour signals (H04N9/75 takes precedence) - H04N 9/8042: {involving data reduction} - H04N 19/80: Details of filtering operations specially adapted for video compression, e.g. for pixel interpolation (H04N19/635, H04N19/86 take precedence) - H04N 19/85: using pre-processing or post-processing specially adapted for video compression - H04N 21/4143: {embedded in a} Personal Computer [PC] - H04N 21/426: Internal components of the client {; Characteristics thereof} (H04N5/44 takes precedence) - H04N 21/44: Processing of video elementary streams, e.g. splicing a video clip retrieved from local storage with an incoming video stream or rendering scenes according to encoded video stream scene graphs - G09G 2340/125: wherein one of the images is motion video - H04N 19/20: using video object coding - H04N 21/4223: Cameras (H04N23/00 takes precedence) - H04N 21/4788: communicating with other users, e.g. chatting {(arrangements for providing for computer conferences, e.g. chat rooms, to substation in data switching networks H04L12/1813; distributed application using peer-to-peer [P2P] networks H04L67/104)} - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION - G09G: ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION (arrangements for transferring data between digital computers and displays G06F3/14; static indicating arrangements comprising an association of a number of separate sources or light control cells G09F9/00; static indicating arrangements comprising integral associations of a number of light sources H01J, H01K, H10H, H05B33/12; scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission, details thereof H04N1/00) ## Abstract A background region of the current image is compared to a reference region to characterize the gain associated with the current image. The values of the unsaturated background pixels of the current image are then adjusted to correct for the characterized gain before encoding the current image. In a preferred embodiment, the reference region is generated based on the previous n frames in the video sequence. ## Claims ### Claim 1 A computer-implemented process for processing video signals, comprising the steps of: (a) selecting a background region of a current image of a video stream; (b) generating a reference region using regions corresponding to background regions of one or more images of the video stream; (c) characterizing gain of the current image based on the reference region and the background region; and (d) generating a gain-corrected image by correcting the current image based on the gain. ### Claim 2 (depends on 1) The process of claim 1, further comprising the step of encoding the gain-corrected image to generate compressed data for the current image. ### Claim 3 (depends on 1) The process of claim 1, wherein step (c) comprises the step of characterizing the gain .alpha., wherein: ##EQU9## wherein: g›x! are the pixels of the reference region; and f›x! are the pixels of the background region. ### Claim 4 (depends on 1) The process of claim 1, wherein step (c) comprises the step of characterizing the gain .alpha., wherein: ##EQU10## wherein: g›x! are the pixels of the reference region; and f›x! are the pixels of the background region. ### Claim 5 (depends on 1) The process of claim 1, wherein step (d) comprises the step of skipping foreground pixels in the current image. ### Claim 6 (depends on 5) The process of claim 5, wherein step (d) comprises the step of skipping saturated background pixels in the current image. ### Claim 7 An apparatus for processing video signals, comprising: (a) means for selecting a background region of a current image of a video stream; (b) means for generating a reference region using regions corresponding to background regions of one or more images of the video stream; (c) means for characterizing gain of the current image based on the reference region and the background region; and (d) means for generating a gain-corrected image by correcting the current image based on the gain. ### Claim 8 (depends on 7) The apparatus of claim 7, wherein further comprising means for encoding the gain-corrected image to generate compressed data for the current image. ### Claim 9 (depends on 7) The apparatus of claim 7, wherein means (c) characterizes the gain .alpha., wherein: ##EQU11## wherein: g›X! are the pixels of the reference region; and f›x! are the pixels of the background region. ### Claim 10 (depends on 7) The apparatus of claim 7, wherein means (c) characterizes the gain .alpha., wherein: ##EQU12## wherein: g›x! are the pixels of the reference region; and f›x! are the pixels of the background region. ### Claim 11 (depends on 7) The apparatus of claim 7, wherein means (d) skips foreground pixels in the current image. ### Claim 12 (depends on 11) The apparatus of claim 11, wherein means (d) skips saturated background pixels in the current image. ### Claim 13 A storage medium encoded with machine-readable computer program code for processing video signals, wherein, when executed by a computer, the computer program code causes the computer to: (a) select a background region of a current image of a video stream; (b) generate a reference region using regions corresponding to background regions of one or more images of the video stream; (c) characterize gain of the current image based on the reference region and the background region; and (d) generate a gain-corrected image by correcting the current image based on the gain. ### Claim 14 (depends on 13) The apparatus of claim 13, wherein the computer program code causes the computer to encode the gain-corrected image to generate compressed data for the current image. ### Claim 15 (depends on 13) The apparatus of claim 13, wherein the computer program code causes the computer to characterize the gain .alpha., wherein: ##EQU13## wherein: g›x! are the pixels of the reference region; and f›x! are the pixels of the background region. ### Claim 16 (depends on 13) The apparatus of claim 13, wherein the computer program code causes the computer to characterize the gain .alpha., wherein: ##EQU14## wherein: g›x! are the pixels of the reference region; and f›x! are the pixels of the background region. ### Claim 17 (depends on 13) The apparatus of claim 13, wherein the computer program code causes the computer to skip foreground pixels in the current image. ### Claim 18 (depends on 17) The apparatus of claim 17, wherein the computer program code causes the computer to skip saturated background pixels in the current image.