EP1360648A2 - Estimation vectorielle recursive 3-d pour amelioration de video - Google Patents

Estimation vectorielle recursive 3-d pour amelioration de video

Info

Publication number
EP1360648A2
EP1360648A2 EP02716230A EP02716230A EP1360648A2 EP 1360648 A2 EP1360648 A2 EP 1360648A2 EP 02716230 A EP02716230 A EP 02716230A EP 02716230 A EP02716230 A EP 02716230A EP 1360648 A2 EP1360648 A2 EP 1360648A2
Authority
EP
European Patent Office
Prior art keywords
pixel region
enhancement
candidate
enhanced
spatio
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP02716230A
Other languages
German (de)
English (en)
Inventor
Erwin B. Bellers
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Koninklijke Philips NV
Original Assignee
Koninklijke Philips Electronics NV
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US09/840,817 external-priority patent/US7042945B2/en
Application filed by Koninklijke Philips Electronics NV filed Critical Koninklijke Philips Electronics NV
Publication of EP1360648A2 publication Critical patent/EP1360648A2/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N7/00—Television systems
    • H04N7/01—Conversion of standards, e.g. involving analogue television standards or digital television standards processed at pixel level
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N7/00—Television systems
    • H04N7/01—Conversion of standards, e.g. involving analogue television standards or digital television standards processed at pixel level
    • H04N7/0135—Conversion of standards, e.g. involving analogue television standards or digital television standards processed at pixel level involving interpolation processes
    • H04N7/014—Conversion of standards, e.g. involving analogue television standards or digital television standards processed at pixel level involving interpolation processes involving the use of motion vectors
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T5/00—Image enhancement or restoration
    • G06T5/50—Image enhancement or restoration using two or more images, e.g. averaging or subtraction
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T2207/00—Indexing scheme for image analysis or image enhancement
    • G06T2207/10—Image acquisition modality
    • G06T2207/10016—Video; Image sequence
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T2207/00—Indexing scheme for image analysis or image enhancement
    • G06T2207/20—Special algorithmic details
    • G06T2207/20021—Dividing image into blocks, subimages or windows

Definitions

  • the present invention is directed, in general, to video enhancement systems and, more specifically, to maintaining spatio-temporal consistency during video enhancement.
  • a spatial-temporal resolution which is higher than the normal resolution and refresh rate. For example, a 100 Hertz (Hz) screen refresh rate may be employed for the television display rather than the standard 50 or 60 Hertz.
  • Hz 100 Hertz
  • the field rate the number of interlaced screen images or "fields" for the television— within the program signal received will typically be only 50 fields per second, the number of fields for display must be doubled.
  • a field memory a memory with the capacity to store a digitized version of a complete television field
  • one technique for doubling the field rate involves simply writing to the field memory at a first rate and reading from the field memory at a second rate which is double the first rate.
  • field rate up- conversion by simple field repetition results in each movement phase (i.e., frame) being displayed multiple times, with moving objects appearing slightly displaced from their expected spatio-temporal (space-time) position in the repeated movement phases as illustrated in Fig. 5.
  • the space-time positioning 501a, 501b and 501c of an object moving linearly across the screen within a sequence of three fields n-2, n-1 and n is shown in Fig. 5.
  • Field rate up-conversion by field repetition produces intermediate fields (not labeled) in which the space-time positioning of the object is 503a, 503b and 503c rather than the expected space- time positioning of 502a, 502b, and 502c.
  • motion picture cameras While the displacement is almost unnoticeable to the human eye at video information captured at normal field rates (50-60 Hz) employed by video cameras and the like, motion picture cameras have, for historical electro-mechanical reasons, operated at a capture rate of 24 frames per second. While modern motion picture cameras have been improved, much film exists which was recorded at that previously-standard capture rate. Such film is normally converted for television display by running the film at approximately 25 frames per second and then scanning each frame twice such that adjacent pairs of identical fields are created within the video information.
  • High definition television often imposes a requirement differing from— and either in addition to or in lieu of— field rate up-conversion: image resolution enhancement.
  • image resolution enhancement requires up- conversion from one resolution and the corresponding pixel size 601a and/or pixel density 602a to a higher resolution having a smaller pixel size 601b and/or greater pixel density 602b.
  • Known interpolation techniques are employed to generate the additional pixels required from the original video information.
  • the shape or magnitude of edges within an image significantly contribute to the overall impression of "sharpness" for the image. Accordingly, various edge enhancement techniques such as frequency peaking and luminance transient improvement (LTI) have been developed for use during image resolution enhancement.
  • LTI luminance transient improvement
  • Frequency peaking involves linear boosting or "peaking" of selected spatial frequencies within the image, often with a bandpass or highpass filter to enhances the associated spatial frequencies and with adaptive control to avoid “unnaturalness” relating to, for example, peaking large and steep edges.
  • luminance transient improvement preserves the magnitude of the edge but increases the steepness of the edge, "pulling" samples near the edge on both sides towards the edge.
  • Existing edge enhancement algorithms enhance the sharpness of an image based on the spatial information of the original image, often utilizing control parameters determined by a small spatial neighborhood of a given pixel position.
  • a primary object of the present invention to provide, for use in a video signal processor, a technique for enhancing video information which evaluates candidate vectors of enhancement algorithms utilizing an error function biased towards spatio-temporal consistency with a penalty function.
  • the penalty function increases with the distance— both spatial and temporal— of the subject block from the block for which the candidate vector was optimal. Enhancements are therefore gradual across both space and time and the enhanced video information is intrinsically free of perceptible artifacts.
  • Fig. 1 depicts a system in which video enhancement with spatio-temporal consistency is implemented according to one embodiment of the present invention
  • Fig. 2 illustrates in greater detail a system for video enhancement with spatio- temporal consistency according to one embodiment of the present invention
  • Fig. 3 illustrates a logical organization of video information for video enhancement with spatio-temporal consistency according to one embodiment of the present invention
  • Fig. 4 is a high level flow chart for a process of video enhancement with spatio-temporal consistency according to one embodiment of the present invention
  • Fig. 5 is an illustration of displacement of a moving object from an expected position as a result of field rate conversion through field repetition;
  • Figs. 6 A and 6B are comparative illustrations for spatial resolution enhancement.
  • Fig. 1 depicts a system in which video enhancement with spatio-temporal consistency is implemented according to one embodiment of the present invention.
  • System 100 includes a receiver 101, which in the exemplary embodiment is a high definition digital television (HDTV) large-screen or wide-screen television receiver.
  • receiver 101 may be an intermediate transceiver or any other device employed to receive or transceive video signals, as for example a transceiver retransmitting video information for reception by a high definition television.
  • receiver 101 includes a video enhancement mechanism as described in further detail below.
  • Receiver 101 includes an input 102 for receiving video signals and may optionally include an output 103 for transmitting enhanced video signals to another device.
  • receiver 101 includes a high definition television display 104 upon which images rendered or otherwise generated according the enhanced video information are displayed.
  • Fig. 1 does not explicitly depict all components within the high definition television receiver of the exemplary embodiment. Only so much of the commonly known construction and operation of a high definition television receiver and the components therein as are unique to the present invention and/or required for an understanding of the present invention are shown and described herein.
  • Fig. 2 illustrates in greater detail a system for video enhancement with spatio- temporal consistency according to one embodiment of the present invention.
  • Receiver 101 includes a video signal processor 201, which may be implemented by a single integrated circuit device or a combination of integrated circuit devices.
  • Nideo signal processor 201 includes an enhancement vector estimator 202 and enhancement processor 203 which perform the video enhancement processing.
  • Nideo signal processor 201 in the exemplary embodiment is the device from which the enhanced video output is transmitted either to display 104 or to a storage medium (not shown).
  • Enhancement processor 203 performs the processing on received video signals required to enhance the video for display.
  • Image or video enhancement is a broad area which may be roughly divided into three categories: restoration of "lost" (image/video) information; elimination of artifacts; and enhancement of selected image/video characteristics.
  • restoration of "lost" (image/video) information is a broad area which may be roughly divided into three categories: restoration of "lost" (image/video) information; elimination of artifacts; and enhancement of selected image/video characteristics.
  • the present invention is not limited to any particular category of video enhancement, for the purposes of simplicity resolution enhancement, which falls within the third category, will be utilized to describe and explain the invention. Nonetheless, those skilled in the art will understand that the invention may be readily adapted or extended to video enhancements other than resolution enhancement and falling within any of the three categories listed.
  • Enhancement processor 203 together with enhancement vector estimator 202 in the exemplary embodiment, performs spatial resolution enhancement on the video information received.
  • the technique for estimation of enhancement vectors according to the present invention is similar to the recursive search block matching motion estimation process described in the references identified above.
  • enhancement vector estimator 202 includes one or more caches 205a-205n for temporary storage of pixel information relating to processing of a block of pixels, one or more block enhancement units 206a-206n, an enhancement vector memory 207, and a best enhancement selection unit 208 which identifies and selects the best enhancement on a per block basis as described in further detail below.
  • Fig. 3 illustrates a logical organization of video information for video enhancement with spatio-temporal consistency according to one embodiment of the present invention.
  • the organization depicted is employed for block enhancement by video signal processor 201 depicted in Fig. 2.
  • the video information to be enhanced includes a plurality of successive pictures (which may be either fields or frames) to be displayed in sequence at a predefined rate.
  • "Successive,” as used herein, refers to a subject picture being in consecutive series with another picture within the sequence, without regard to whether the subject picture is before or after the other picture within the video information.
  • a portion of the sequence of pictures, n-2, n-1, n, n+1 and n+2 is shown in Fig. 3.
  • Each picture comprises a two- dimensional array of pixels having coordinates (x,y) from the lower left corner of the
  • each picture is logically divided into an array of blocks of pixels B(X) of a predetermined number of pixels in width and height and having a center X .
  • the blocks or pixel regions may be rectangular as depicted or may be any other shape.
  • Block enhancement units 206a-206n within video signal processor 201 enhance the received video information on a per block basis.
  • spatial resolution enhancement will be employed to explain the present invention. Specifically, an increase in the spatial resolution of the incoming video by a factor of two in both spatial dimensions of the fields will be employed to describe the present invention.
  • An initial estimate of higher spatial resolution video information G(x, ⁇ ) based on the lower resolution video information F(x, ) may be initially created by a simple spatial up-conversion—that is, a sample-rate conversion interpolation filter within block enhancement units 206a-206n is employed to obtain a higher resolution image.
  • G(x,n) (v,W,(F(x,n))) .
  • W, () within the above equation indicates enhancement of the image data quality (where spatial resolution has already been enhanced by sample-rate conversion) by an algorithm i within a set of algorithms.
  • W 0 (F(x,n)) could be the image data after frequency peaking while W, (F(x, n)) may be the result after luminance transient improvement.
  • the penalty P ⁇ within the error function given above is a monotonic decreasing function of the norm of the enhancement vector V , introducing a large penalty for small coefficients and a small penalty for large coefficients.
  • the penalty P 2 is employed to bias the enhancement vector V towards a spatial-temporally consistent solution since this penalty depends on the selected enhancement vector candidate C . Accordingly, the value of penalty P 2 is selected from a predefined list of penalty values which are optimized for the application.
  • Each enhancement vector candidate C is preferably selected from enhancement vectors previously determined to produce the smallest error function values for blocks within a spatio-temporal neighborhood around the block B(X) being processed.
  • a "Y-prediction" estimator for recursive search block matching motion estimation in which spatial prediction vector candidates C sp and C SP2 are the vectors selected for blocks one block dimension above and to either side of and within the same field as the subject block B(X) while a temporal prediction candidate
  • C TP is the vector selected for a block two blocks directly below and within the previous field n -1 from the field n containing the subject block B(X) .
  • Selection of candidate enhancement vectors from the enhancement vectors which produced optimal results within the spatio-temporal neighborhood of the subject block B( ⁇ ) speeds the process of determining the best enhancement (the enhancement vector which produces the smallest error, or other suitable criteria for enhancement results, for the subject block B(X) ) since it is very likely that enhancement(s) similar to those producing the best results for other blocks within the neighborhood of the subject block B(X) will produce the best results for the subject block B(X) .
  • all possible candidate vectors of enhancement algorithms may be tested for each block.
  • the set of candidate vectors employed may change during processing of the video information, with, for example, all possible candidate vectors being tested for the first few fields of the video information and then a smaller subset of candidate vectors being employed for remaining fields, or with the selection of candidate vectors being otherwise refined as the video information is processed.
  • one candidate is always updated with a random update vector.
  • Several candidates may compete with each other, with the candidate yielding the smallest error ⁇ (C,X,n) being selected as the enhancement vector for the data within the subject block B(X) .
  • Fig. 4 is a high level flow chart for a process of video enhancement with spatio-temporal consistency according to one embodiment of the present invention.
  • the process 400 performed by the video signal processor 202 depicted in Fig. 2 utilizing the logical organization of video information illustrated in Fig. 3, begins with receipt (step 401) of video information for enhancement.
  • a block within a current field of the received video information is first selected (step 402) and a simple enhancement, in this case sample rate conversion, is performed.
  • the block is also enhanced utilizing each of a plurality of selected candidate enhancement vectors consisting one or more enhancement algorithms employed jointly or individually, such as frequency peaking and luminance transient improvement.
  • An error function value where the error function includes a bias towards spatio-temporal consistency, is then computed for each candidate enhancement vector (step 404) and the enhancement corresponding to the candidate vector having the lowest error function value is selected (step 405) for display as part of the enhanced field.
  • a determination as to whether all blocks within the current field have been processed is then made, followed by selection and processing of a next block within the current field (step 407) if additional blocks remain and initiation of processing on the next field (step 408) if the current field has been completely processed. Once initiated, the process proceeds until interrupted by an external influence, such as the receiver being turned off or the reception of video information being interrupted.
  • the present invention allows enhancements to video information (other than position within a repeated field) to be processed in a manner inherently producing spatio- temporally consistent results.
  • the error function employed to select the best enhancement vector of enhancement algorithms is biased towards spatio-temporal consistency by addition of a penalty increasing as candidate vectors differ from a block being enhanced by either space, time, or both.
  • the selected enhancement produces changes which are gradual over space and time and inherently free of spatio-temporal varying artifacts.
  • machine usable mediums include: nonvolatile, hard-coded type mediums such as read only memories (ROMs) or erasable, electrically programmable read only memories (EEPROMs), recordable type mediums such as floppy disks, hard disk drives and compact disc read only memories (CD- ROMs) or digital versatile discs (DNDs), and transmission type mediums such as digital and analog communication links.
  • ROMs read only memories
  • EEPROMs electrically programmable read only memories
  • CD- ROMs compact disc read only memories
  • DNDs digital versatile discs

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Television Systems (AREA)
  • Picture Signal Circuits (AREA)
  • Image Processing (AREA)

Abstract

L'invention concerne un processeur de signal vidéo, destiné à améliorer une information vidéo, évaluant des vecteurs candidats d'algorithmes d'enrichissement par utilisation d'une fonction d'erreur avec biais vers une solution à consistance spatio-temporelle au moyen d'une fonction de pénalité. La fonction de pénalité augmente la distance, à la fois temporelle et spatiale, entre le bloc sujet et le bloc pour lequel le vecteur candidat est optimal. Les enrichissements sont ainsi graduels dans le temps et dans l'espace et l'information vidéo améliorée est intrinsèquement débarrassée d'artefacts variés spatio-temporels perceptibles.
EP02716230A 2001-02-08 2002-01-28 Estimation vectorielle recursive 3-d pour amelioration de video Withdrawn EP1360648A2 (fr)

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
US26725601P 2001-02-08 2001-02-08
US267256P 2001-02-08
US09/840,817 US7042945B2 (en) 2001-04-24 2001-04-24 3-D recursive vector estimation for video enhancement
US840817 2001-04-24
PCT/IB2002/000275 WO2002063562A2 (fr) 2001-02-08 2002-01-28 Estimation vectorielle recursive 3-d pour amelioration de video

Publications (1)

Publication Number Publication Date
EP1360648A2 true EP1360648A2 (fr) 2003-11-12

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EP02716230A Withdrawn EP1360648A2 (fr) 2001-02-08 2002-01-28 Estimation vectorielle recursive 3-d pour amelioration de video

Country Status (5)

Country Link
EP (1) EP1360648A2 (fr)
JP (1) JP2004519145A (fr)
KR (1) KR20020087128A (fr)
CN (1) CN1460230A (fr)
WO (1) WO2002063562A2 (fr)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2004073313A1 (fr) * 2003-02-13 2004-08-26 Koninklijke Philips Electronics N.V. Conversion-elevation spatio-temporelle
CN101379827B (zh) * 2006-01-31 2011-07-06 汤姆森许可贸易公司 基于边缘的时空滤波方法和装置

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO02063562A2 *

Also Published As

Publication number Publication date
KR20020087128A (ko) 2002-11-21
WO2002063562A2 (fr) 2002-08-15
CN1460230A (zh) 2003-12-03
WO2002063562A3 (fr) 2002-10-17
JP2004519145A (ja) 2004-06-24

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