Source: http://www.google.com/patents/US7705881?ie=ISO-8859-1&dq=6,373,753
Timestamp: 2015-01-25 16:44:36
Document Index: 604172628

Matched Legal Cases: ['art 11', 'art 35', 'art 35', 'art 41', 'art 41', 'art 41', 'art 41', 'art 42', 'art 43']

Patent US7705881 - Video quality assessing apparatus, video quality assessing method, and video ... - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsA subjective quality estimating part (11) receives an undeteriorated reference video signal (RI) and a deteriorated video signal (PI) produced from the reference video signal, calculates video signal feature values for both the signals, and according to a difference between the calculated video signal...http://www.google.com/patents/US7705881?utm_source=gb-gplus-sharePatent US7705881 - Video quality assessing apparatus, video quality assessing method, and video quality assessing programAdvanced Patent SearchPublication numberUS7705881 B2Publication typeGrantApplication numberUS 10/556,103Publication dateApr 27, 2010Filing dateAug 20, 2004Priority dateAug 22, 2003Fee statusPaidAlso published asCA2525812A1, CA2525812C, CA2646805A1, CA2646805C, CA2646808A1, CA2646808C, EP1622395A1, EP1622395A4, US8253803, US20060276983, US20100157144, WO2005020592A1Publication number10556103, 556103, US 7705881 B2, US 7705881B2, US-B2-7705881, US7705881 B2, US7705881B2InventorsJun Okamoto, Takaaki KuritaOriginal AssigneeNippon Telegraph And Telepone CorporationExport CitationBiBTeX, EndNote, RefManPatent Citations (13), Non-Patent Citations (7), Referenced by (22), Classifications (9), Legal Events (2) External Links: USPTO, USPTO Assignment, EspacenetVideo quality assessing apparatus, video quality assessing method, and video quality assessing programUS 7705881 B2Abstract A subjective quality estimating part (11) receives an undeteriorated reference video signal (RI) and a deteriorated video signal (PI) produced from the reference video signal, calculates video signal feature values for both the signals, and according to a difference between the calculated video signal feature values of the signals, estimates a subjective quality of the deteriorated video signal. A feature value calculating part (12) calculates the video signal feature values of the reference video signal. A correction information storing part (13) stores correction information that corresponds to video signal feature values and is used to correct the subjective quality. A correction calculating part (14) receives the video signal feature values of the reference video signal from the feature value calculating part (12), retrieves correction information corresponding to the received video signal feature values from the correction information storing part (13), and transfers the retrieved correction information to a correcting part (15). According to the transferred correction information, the correcting part (15) corrects the subjective quality estimated by the subjective quality estimating part (11).
TECHNICAL FIELD The present invention relates to a video quality assessing apparatus, a video quality assessing method, and a video quality assessing program that estimate a subjective quality of video images by measuring the physical feature values of a video signal without conducting a subjective quality assessing test in which a human tester actually watches the video images and assesses a quality thereof.
BACKGROUND ART Video information generally deteriorates its quality when subjected to some process such as encoding or transmitting through a network. The degree of deterioration of such deteriorated video information sensed by a person who actually watches the deteriorated video information is called a subjective quality.
A subjective video quality may be accurately estimated from limited video images. (For example, ANSI T1.801.03-1996, �Digital Transport of One-Way Video Signals Parameters for Objective Performance Assessment�; Okamoto and Takahashi, �Study on application of video quality objective assessment technique,� IEICE society conference, September 2002; and Okamoto, Kurita, and Takahashi, �Study on improving the performance of video quality objective assessment,� IEICE society conference, March 2003 can be referred to.) The quality of a given video image is greatly dependent on the characteristics of the video image, and therefore, video images having the same degree of deterioration may be assessed to have different subjective qualities.
The above-mentioned PCT Pub. No. WO99/45715 discloses, as a document showing an example of a temporal aligning process, ITU-T Contribution COM-12-29, �Draft new recommendation on multimedia communication delay, synchronization, and frame rate measurement,� December 1997.
DISCLOSURE OF INVENTION In consideration of the conventional techniques mentioned above, an object of the present invention is to provide a video quality assessing apparatus, a video quality assessing method, and a video quality assessing program, capable of accurately and invariably estimating a subjective quality of optional video images.
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a block diagram showing a video quality assessing apparatus according to a first embodiment of the present invention;
BEST MODE FOR CARRYING OUT THE INVENTION Video quality assessing apparatuses, video quality assessing methods, video quality assessing programs, video aligning apparatuses, video aligning methods, and video aligning programs according to embodiments of the present invention will be explained in detail. The first to third embodiments of the present invention relate to the video quality assessing apparatuses, video quality assessing methods, and video quality assessing programs. The fourth embodiment of the present invention relates to the video aligning apparatus, video aligning method, and video aligning program.
First Embodiment The video quality assessing apparatus according to the first embodiment of the present invention will be explained with reference to FIG. 1. FIG. 1 is a block diagram showing the video quality assessing apparatus according to the first embodiment of the present invention.
For the reference video signal RI and deteriorated video signal PI, the subjective quality estimating part 11 calculates a difference between physical feature values of the signals. The video signal feature values include, for example, spatial information (SI) indicative of a video state of a given frame contained in the video signal and temporal information (TI) indicative of a frame-to-frame video change contained in the video signal. The spatial information SI and temporal information TI are stipulated in, for example, ITU-R Recommendation P.910, �Subjective Video Quality Assessment Methods for Multimedia Applications,� Appendix A.
The function F is beforehand obtained through subjective assessment tests. The edge energy (E) and moving energy (M) are stipulated in ANSI T1.801.03-1996, �Digital Transport of One-Way Video Signals Parameters for Objective Performance Assessment.�
Second Embodiment Components of a video quality assessing apparatus according to the second embodiment of the present invention will be explained with reference to FIG. 4. FIG. 4 is a block diagram showing an arrangement of the video quality assessing apparatus according to the second embodiment of the present invention.
This index quantizes, according to the reference video signal RI and deteriorated video signal PI, a deterioration (such as the degree of blurring) of an edge where brightness suddenly changes in a frame. The second embodiment employs a Sobel filter to enhance an edge according to pixel brightness values and quantize a deterioration of the edge. The edge energy (Ave_EE) to be quantized is stipulated in ANSI T1.801.03-1996, �Digital Transport of One-Way Video Signals Parameters for Objective Performance Assessment.�
SI μ ( m ) = 1 N ∑ i , j { SI h_μ 2 ( i , j , m ) + SI v_μ 2 ( i , j , m ) } - ( 1 N SI h_μ 2 ( i , j , m ) + SI v_μ 2 ( i , j , m ) ) 2 μ = in or out ( 4 ) where SIh � μ(i, j, m) and SIv � μ(i, j, m) are Sobel filters at a position (i, j) in an �m�th frame and are given as follows:
SI h � μ(i,j,m)={−Y α(i−1,j−1,m)−2Y α(i,j−1,m)−Y α(i+1,j−1,m)+Y α(i−1,j+1,m)+2Y α(i,j+1,m)+Y α(i+1,j+1,m)} (5) SI v � μ(i,j,m)={−Y μ(i−1,j−1,m)−Y μ(i+1,j−1,m)−2Y μ(i−1,j,m)+2Y μ(i+1,j,m)−Y μ(i−1,j+1,m)+Y μ(i+1,j+1,m)} (6)
where Yin(i, j, m) is a brightness value (from 0 to 255) of a pixel at a position (i, j) in an �m�th reference video frame, and Yout(i, j, m) is a brightness value (from 0 to 255) of a pixel at a position (i, j) in an �m�th deteriorated video frame.
HVR μ ( m ) = HV μ ( r min , Δθ , m ) + 0.5 HV μ _ ( r min , Δθ , m ) + 0.5 μ = in or out ( 8 ) There is the following definition:
HV μ ( r min , Δθ , m ) = 1 P ∑ i , j SI r_μ ( i , j , m ) μ = in or out ( 9 ) in which the following conditions must be satisfied:
SI r,μ(i,j,m)≧r min>0 (10) k Π/2−Δθ<SI θ,μ(i,j,m)<k Π/2+Δθ(k=0,1,2,3) (11)
where SIθ � μ(i, j, m)=tan−1 [SIv � μ(i, j, m)/SIh � μ(i, j, m)]
SI r � μ(i,j,m)≧r min>0 (13) k Π/2+Δθ<SI θ � Π(i,j,m)<(k+1)Π/2−Δθ(k=0,1,2,3) (14)
Ave_MEB = 1 M ∑ m = 0 M - 1 1 N b ∑ ( k , 1 ) ( TI b _ in ( k , l , m ) - TI b _ out ( k , l , m ) TI b _ in ( k , l , m ) ) 2 ( 15 ) where TIb � μ(k, l, m) is expressed as follows:
TI b_μ ( k , l , m ) = 1 64 ∑ ( i , j ) ( Y μ ( 8 k + i , 8 l + j , m ) - Y μ ( 8 k + i , 8 l + j , m - 1 ) ) 2 μ = in or out ( 16 ) The average moving energy of blocks (Ave_MEB) is a feature value that is capable of catching a motional deterioration occurring in a block area. Such a deterioration is unable to catch with the edge energy (Ave_EE). The index Ave_MEB can sensitively catch the motional block deterioration as will be explained later. The index Ave_MEB is an original measure created to catch a block motion. This index finds a TI value in each block and normalizes the TI value with a TI value of a reference video frame to sensitively catch a block motion.
Third Embodiment Components of a video quality assessing apparatus according to the third embodiment of the present invention will be explained with reference to FIG. 6. FIG. 6 is a block diagram showing an arrangement of the video quality assessing apparatus according to the third embodiment of the present invention.
If reference video images have a YUV format of VGA size and if deteriorated video images have an RGB color format that is different from the color format of the reference video images, the format converting part 35 converts the format of the deteriorated video images into that of the reference video images according to a conversion formula stipulated in, for example, Rec. ITU-R BT.601, �STUDIO ENCODING PARAMETERS OF DIGITAL TELEVISION FOR STANDARD 4:3 AND WIDE-SCREEN 16:9 ASPECT RATIOS.� When equalizing the size and aspect ratio between the reference video images and deteriorated video images, the format converting part 35 may carry out conversion simply through an integer multiplication. If this is insufficient, it is necessary to carry out an optional size conversion. In this case, a known technique will be employed. (For example, Muramatsu S. and Kiya H, �Scale Factor of Resolution Conversion Based on Orthogonal Transforms,� IEICE Trans. Fundamentals, E76-A, 7, pp. 1150-1153 (July 1993); and Shogo Matsumura and Hitoshi Takaie, �Resolution conversion method with optional rational number multiplication for changed encoded images,� IEICE Trans. A, Vol. 77-A, No. 3, pp. 369-378, March 1994 may be referred to.) A compressed video signal must be decompressed in advance.
First, subjective assessment data used to verify estimation accuracy and find the weighting factors stored in the weighting factor database 36 will be explained. FIG. 8 shows 36 standard video images (having video sequence names as shown in FIG. 8) according to ITU-R (ITU-R BT. 802-1, �Test Pictures and Sequences for Subjective Assessments of Digital Codecs Conveying Signals Produced According to Recommendation ITU-R BT.601,� 1994; and ITU-R BT.1201-2, �Test materials to be used in subjective assessment,� 2001). In FIG. 8, the standard video images are separated into verification data for verifying the estimation accuracy of a video quality assessment value and learning data for finding the weighting factors.
The subjective assessment data used to verify estimation accuracy is selected in such a way as to minimize the influence of a bias in the characteristics of a reference video image. Namely, the spatial information (SI) and temporal information (TI) stipulated in ITU-T P.910 (ITU-T P.910, �Subjective video quality assessment methods for multimedia applications,� August 1996) are considered, and the same number of video images are selected for each of areas A to D shown in FIG. 9. This allows to use video images having various SI values and TI values as reference video images. The reference video images are deteriorated by carrying out an MPEG4-based encoding in four stages in the range of 256 kbps to 8 Mbps.
As a subjective quality assessing method, a DSCQS method (ITU-R BT.500-10, �Methodology for the subjective assessment of the quality of television pictures,� March 2000) is used on 24 male and female general test subjects ranging from 18 to 40-years old. The DSCQS method is frequently used for MPEG verification and codec performance tests.
Fourth Embodiment A video aligning apparatus, video aligning method, and video aligning program according to embodiments of the present invention will be explained.
Firstly, if the signal formats, sizes, and aspect ratios of the reference video signal and deteriorated video signal differ from each other, the format converting part 41 converts the signal format of the deteriorated video signal (step S1). For example, the data format of the reference video signal is YUV, and that of the deteriorated video signal is uncompressed RGB. In this case, the format of the deteriorated video signal is converted with the use of a conversion formula stipulated in Rec. ITU-R BT.601 �STUDIO ENCODING PARAMETERS OF DIGITAL TELEVISION FOR STANDARD 4:3 AND VIDEO-SCREEN 16:9 ASPECT RATIOS.� If the deteriorated video signal is compressed, the format converting part 41 decompresses the signal. If the sizes and aspect ratios of the signals differ from each other, the format converting part 41 converts them so that the signals may have the same size and aspect ratio. The sizes thereof may be equalized through a simple integer multiplication. If it is insufficient, the sizes must be optionally changed. In this case, a known method is used to change them into proper size. (For example, Muramatsu S. and Kiya H, �Scale Factor of Resolution Conversion Based on Orthogonal Transforms,� IEICE Trans. Fundamentals, E76-A, 7, pp. 1150-1153 (July 1993); and Shogo Matsumura and Hitoshi Takaie, �Resolution conversion method with optional rational number multiplication for changed encoded images,� IEICE Trans. A, Vol. 77-A, No. 3, pp. 369-378, March 1994 may be referred to.) Thereafter, the format converting part 41 transfers the reference video signal and converted deteriorated video signal to the display timing aligning part 42.
It is determined if F1 is �1� or not, i.e., if the reference video frame and deteriorated video frame are asynchronous or not (step S7). If the reference and deteriorated video frames are synchronous (F1=0), step S8 is carried out. If the reference and deteriorated video frames are asynchronous (F1=1), step S16 is carried out.
If the deteriorated video frames are frozen, the synchronizing/position-aligning part 43 sets an asynchronous state (F1=1) and changes a frozen number to �1� (Count=1) (step S10), and step S22 is carried out.
INDUSTRIAL APPLICABILITY The video quality assessing apparatus, video quality assessing method, and video quality assessing program according to the present invention can invariably accurately estimate a subjective quality of optional video frames including unknown reference video frames.
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