CN107347153B - The quality evaluating method of longitude and latitude figure panoramic video - Google Patents

The quality evaluating method of longitude and latitude figure panoramic video Download PDF

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CN107347153B
CN107347153B CN201610916893.3A CN201610916893A CN107347153B CN 107347153 B CN107347153 B CN 107347153B CN 201610916893 A CN201610916893 A CN 201610916893A CN 107347153 B CN107347153 B CN 107347153B
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latitude
frame
longitude
quality
panoramic video
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CN107347153A (en
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刘�东
吴仕林
陈志波
李厚强
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University of Science and Technology of China USTC
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/42—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals characterised by implementation details or hardware specially adapted for video compression or decompression, e.g. dedicated software implementation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N17/00—Diagnosis, testing or measuring for television systems or their details
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/134—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the element, parameter or criterion affecting or controlling the adaptive coding
    • H04N19/154—Measured or subjectively estimated visual quality after decoding, e.g. measurement of distortion
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/30—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using hierarchical techniques, e.g. scalability
    • H04N19/36—Scalability techniques involving formatting the layers as a function of picture distortion after decoding, e.g. signal-to-noise [SNR] scalability

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Health & Medical Sciences (AREA)
  • Biomedical Technology (AREA)
  • General Health & Medical Sciences (AREA)
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Abstract

The invention discloses a kind of quality evaluating methods of longitude and latitude figure panoramic video, comprising: for the panoramic video to be evaluated with two longitude and latitude bitmap-formats as reference, carries out each frame respectively and divides latitude down-sampling, obtain corresponding two irregular shape videos；Mean square error, the quality and overall quality frame by frame between two irregular shape videos are calculated frame by frame, to realize the quality evaluation of longitude and latitude figure panoramic video.The advantages of above method is: 1. consider the geometry deformation converted between spherical surface and longitude and latitude figure；2. considering all information on longitude and latitude figure as far as possible.Therefore, the present invention is better than traditional PSNR and S-PSNR.

Description

The quality evaluating method of longitude and latitude figure panoramic video
Technical field
The present invention relates to video quality evaluation technical field more particularly to a kind of quality evaluation sides of longitude and latitude figure panoramic video Method.
Background technique
With the progress of video acquisition and processing technique, panoramic video starts to step into people's lives.Panoramic video It is the video obtained from the scenery at each visual angle is carried out while being recorded centered on video camera.People are in viewing panoramic video When, it can arbitrarily switch visual angle, it is seemingly on the spot in person.Compared with traditional two-dimensional surface video, panoramic video can give user Preferably experience and feeling of immersion are brought, is the indispensable a part of the following virtual reality technology.
But the original data volume of panoramic video is more much bigger than conventional two-dimensional planar video, there is an urgent need to efficient videos Compression method.The difference between video in order to measure the performance of video compress, before needing more compressed video and compression (distortion) carries out quality evaluation by the compressed video of reference pair of the video before compressing.
Substantially, what panoramic video recorded is the video information on spherical surface.Since spherical surface is not easy to indicate, panoramic video is general It is expressed using longitude and latitude bitmap-format.Longitude and latitude figure by the point of spherical surface according to its longitude, dimension map to two-dimensional surface, for example, through Degree is mapped as column coordinate, latitude is mapped as row coordinate, to be rectangle plane by development of a sphere.The video of longitude and latitude bitmap-format can be with The encoder for directlying adopt traditional two-dimensional surface video carries out compressed encoding.
For conventional two-dimensional planar video, there is reference mass evaluation commonly using Y-PSNR (PSNR).But PSNR pairs The video of longitude and latitude bitmap-format is less reasonable, because very big geometry deformation has occurred compared to spherical surface in longitude and latitude figure, closer to the two poles of the earth Region is stretched bigger, and PSNR gives same weight for different location in plane, cannot accurately embody spherical surface The distortion of itself.
A kind of improved spherical surface Y-PSNR (S-PSNR) is researched and proposed, this method equably takes one on spherical surface These positions are mapped on longitude and latitude figure by a little positions, and only calculate the original video on these positions and compressed video it Between distortion.It solves the problems, such as geometry deformation although doing so, limited click-through on spherical surface has only been taken due to S-PSNR Row calculates, and has in fact only used a part of region on longitude and latitude figure, and ignores the distortion in other regions.
Summary of the invention
The object of the present invention is to provide a kind of quality evaluating method of longitude and latitude figure panoramic video, thus pair warp and weft bitmap-format Panoramic video carries out objective metric with the difference (distortion) before compression upon compression, and then helps to optimize panoramic video compression.
The purpose of the present invention is what is be achieved through the following technical solutions:
A kind of quality evaluating method of longitude and latitude figure panoramic video, comprising:
For the panoramic video to be evaluated with two longitude and latitude bitmap-formats as reference, each frame is carried out respectively and divides latitude Down-sampling obtains corresponding two irregular shape videos；
Mean square error, the quality and overall quality frame by frame between two irregular shape videos are calculated frame by frame, thus real The quality evaluation of existing longitude and latitude figure panoramic video.
Carrying out each frame divides the latitude down-sampling to include:
According to spherical surface to the mapping relations of longitude and latitude figure, the over-sampling rate of every latitude is calculated, further according to over-sampling rate Inverse carries out down-sampling to every latitude.
The step of over-sampling rate for calculating every latitude includes:
With row coordinate representation latitude, branch's down-sampling is carried out；Assuming that the height of longitude and latitude figure be N, latitude be from -90 degree to+ 90 degree, then the corresponding latitude θ of the i-th rowiAre as follows:
θi=(180 × i-90 × N-90)/(N-1), i=1,2 ..., N
Assuming that the sample rate of position is 1 under the line, then in latitude θiPosition, over-sampling rate be 1/cos (θi)。
It is described to include: to every latitude progress down-sampling according to the reciprocal of over-sampling rate
Assuming that the width of longitude and latitude figure is M, then need for M pixel to be down sampled to round (M*cos (θi)) a pixel, Middle round indicates to be rounded；
Down-sampling is realized by linear interpolation or cubic interpolation；Wherein, linear interpolation process is as follows:
It enables, K=round (M*cos (θi)), the value of original M pixel is respectively (1) x ..., x (M), the value after interpolation point Not Wei y (1) ..., y (K) then has:
Y (j)=x (j × M/K), j=1,2 ..., K；
If j × M/K is integer, known to corresponding value；
Otherwise, it enables a=floor (j × M/K), b=ceil (j × M/K), floor and ceil are to remove whole and take respectively It is whole, then have:
Y (j)=(j × M/K-a) × x (b)+(b-j × M/K) × x (a).
Mean square error, quality frame by frame and the overall quality between two irregular shape videos of calculating include: frame by frame
Assuming that in the current frame, the difference that the i-th row jth of two irregular shape videos arranges corresponding pixel value is dij；
Then mean square error RMSE are as follows:
RMSE=sqrt ((ΣI=1..NΣJ=1..round (M*cos (θi))dij 2)/(ΣI=1..Nround(M*cos(θi))))
Wherein, sqrt indicates extraction of square root, θiFor the corresponding latitude value of the i-th row；
The then corresponding quality Q of present frame are as follows:
Q=10*log10(c2/RMSE)；
Wherein, c is constant；
Then the overall quality of video is averaging to obtain by quality frame by frame；Alternatively, being averaging mean square error by mean square error frame by frame Difference, then bring above-mentioned quality into and seek formula to calculate overall quality.
As seen from the above technical solution provided by the invention, the invention has the advantages that 1. consider spherical surface and longitude and latitude The geometry deformation converted between figure；2. considering all information on longitude and latitude figure as far as possible.Therefore, the present invention is better than traditional PSNR and S-PSNR.
Detailed description of the invention
In order to illustrate the technical solution of the embodiments of the present invention more clearly, required use in being described below to embodiment Attached drawing be briefly described, it should be apparent that, drawings in the following description are only some embodiments of the invention, for this For the those of ordinary skill in field, without creative efforts, it can also be obtained according to these attached drawings other Attached drawing.
Fig. 1 is a kind of flow chart of the quality evaluating method of longitude and latitude figure panoramic video provided in an embodiment of the present invention；
Fig. 2 is panoramic video schematic diagram provided in an embodiment of the present invention；
Fig. 3 is the schematic diagram of a certain frame of panoramic video of longitude and latitude bitmap-format provided in an embodiment of the present invention；
Fig. 4 is that the panoramic video of pair warp and weft bitmap-format provided in an embodiment of the present invention obtain after branch's down-sampling The schematic diagram of a certain frame of irregular shape video.
Specific embodiment
With reference to the attached drawing in the embodiment of the present invention, technical solution in the embodiment of the present invention carries out clear, complete Ground description, it is clear that described embodiments are only a part of the embodiments of the present invention, instead of all the embodiments.Based on this The embodiment of invention, every other implementation obtained by those of ordinary skill in the art without making creative efforts Example, belongs to protection scope of the present invention.
The embodiment of the present invention provides a kind of quality evaluating method of longitude and latitude figure panoramic video, as shown in Figure 1, it is mainly wrapped It includes:
Step 11, for it is to be evaluated with as reference two longitude and latitude bitmap-formats panoramic video, carry out respectively each Frame divides latitude down-sampling, obtains corresponding two irregular shape videos.
In the embodiment of the present invention, according to spherical surface to the mapping relations of longitude and latitude figure, the over-sampling rate of every latitude is calculated, then Reciprocal according to over-sampling rate carries out down-sampling to every latitude.Detailed process is as follows:
1) the step of calculating the over-sampling rate of every latitude include:
With row coordinate representation latitude, branch's down-sampling is carried out；Assuming that the height of longitude and latitude figure be N, latitude be from -90 degree to+ 90 degree, then the corresponding latitude θ of the i-th rowiAre as follows:
θi=(180 × i-90 × N-90)/(N-1), i=1,2 ..., N
According to spherical surface calculation formula, θiThe spherical surface circumference of position is proportional to Rcos (θi), wherein R is the radius of ball；
Assuming that the sample rate of position is 1 under the line, then in latitude θiPosition, over-sampling rate be 1/cos (θi)。
2) include: to every latitude progress down-sampling according to the reciprocal of over-sampling rate
Assuming that the width of longitude and latitude figure is M, then need for M pixel to be down sampled to round (M*cos (θi)) a pixel, Middle round indicates to be rounded；
Down-sampling can be realized by linear interpolation or cubic interpolation；Wherein, linear interpolation process is as follows:
It enables, K=round (M*cos (θi)), the value of original M pixel is respectively (1) x ..., x (M), the value after interpolation point Not Wei y (1) ..., y (K) then has:
Y (j)=x (j × M/K), j=1,2 ..., K；
If j × M/K is integer, known to corresponding value；
Otherwise, it enables a=floor (j × M/K), b=ceil (j × M/K), floor and ceil are to remove whole and take respectively It is whole, then have:
Y (j)=(j × M/K-a) × x (b)+(b-j × M/K) × x (a).
It will be understood to those skilled in the art that in addition to linear interpolation used in the examples or cubic interpolation mode, It can also be using other conventional Downsapling methods.
As shown in Fig. 2, being panoramic video schematic diagram；Fig. 3 is the schematic diagram of a certain frame of panoramic video of longitude and latitude bitmap-format；Figure The signal of a certain frame of the 4 irregular shape videos obtained later for panoramic video progress branch's down-sampling of pair warp and weft bitmap-format Figure.
It will be understood by those skilled in the art that the panoramic video to be evaluated with two longitude and latitude bitmap-formats as reference It is handled using aforesaid way.
It will be understood by those skilled in the art that being used as the longitude and latitude figure panoramic video of reference, longitude and latitude figure usually to be evaluated The original version of panoramic video.For example, the video before compression is used as reference, after compression in the compression of longitude and latitude figure panoramic video The video of reconstruction carries out quality evaluation.
Step 12, the frame by frame mean square error between two irregular shape videos of calculating, quality and overall quality frame by frame, To realize the quality evaluation of longitude and latitude figure panoramic video.
Assuming that in the current frame, the difference that the i-th row jth of two irregular shape videos arranges corresponding pixel value is dij；
Then mean square error RMSE are as follows:
RMSE=sqrt ((ΣI=1..NΣJ=1..round (M*cos (θi))dij 2)/(ΣI=1..Nround(M*cos(θi))))
Wherein, sqrt indicates extraction of square root, θiFor the corresponding latitude value of the i-th row；
The then corresponding quality Q of present frame are as follows:
Q=10*log10(c2/RMSE)；
Wherein, c is constant；
Then the overall quality of video is averaging to obtain by quality frame by frame；Alternatively, being averaging mean square error by mean square error frame by frame Difference, then bring above-mentioned quality into and seek formula to calculate overall quality, i.e., with the RMSE of Averaged Square Error of Multivariate substitution above formula, final meter To Q be expressed as the overall quality of video.
It will be understood to those skilled in the art that the above process can be to two videos after down-sampling, point different face The pixel value of color (such as red, green, blue) calculates separately mean square error and quality, or brightness, coloration is divided to calculate separately mean square error Difference and quality, etc..
Through the above description of the embodiments, those skilled in the art can be understood that above-described embodiment can The mode of necessary general hardware platform can also be added to realize by software by software realization.Based on this understanding, The technical solution of above-described embodiment can be embodied in the form of software products, which can store non-easy at one In the property lost storage medium (can be CD-ROM, USB flash disk, mobile hard disk etc.), including some instructions are with so that a computer is set Standby (can be personal computer, server or the network equipment etc.) executes method described in each embodiment of the present invention.
The foregoing is only a preferred embodiment of the present invention, but scope of protection of the present invention is not limited thereto, Within the technical scope of the present disclosure, any changes or substitutions that can be easily thought of by anyone skilled in the art, It should be covered by the protection scope of the present invention.Therefore, protection scope of the present invention should be with the protection model of claims Subject to enclosing.

Claims (5)

1. a kind of quality evaluating method of longitude and latitude figure panoramic video characterized by comprising
For the panoramic video to be evaluated with two longitude and latitude bitmap-formats as reference, carry out each frame respectively and divide under latitude to adopt Sample obtains corresponding two irregular shape videos；
Mean square error, the quality and overall quality frame by frame between two irregular shape videos are calculated frame by frame, to realize warp The quality evaluation of latitude figure panoramic video.
2. the quality evaluating method of longitude and latitude figure panoramic video according to claim 1, which is characterized in that carry out each frame point Latitude down-sampling includes:
According to spherical surface to the mapping relations of longitude and latitude figure, the over-sampling rate of every latitude is calculated, further according to the inverse of over-sampling rate Down-sampling is carried out to every latitude.
3. the quality evaluating method of longitude and latitude figure panoramic video according to claim 2, which is characterized in that described to calculate often The step of over-sampling rate of latitude includes:
With row coordinate representation latitude, branch's down-sampling is carried out；Assuming that the height of longitude and latitude figure is N, latitude is spent from -90 degree to+90, The then corresponding latitude θ of the i-th rowiAre as follows:
θi=(180 × i-90 × N-90)/(N-1), i=1,2 ..., N
Assuming that the sample rate of position is 1 under the line, then in latitude θiPosition, over-sampling rate be 1/cos (θi)。
4. the quality evaluating method of longitude and latitude figure panoramic video according to claim 3, which is characterized in that described to be adopted according to mistake The inverse of sample rate carries out down-sampling to every latitude
Assuming that the width of longitude and latitude figure is M, then need for M pixel to be down sampled to round (M*cos (θi)) a pixel, wherein Round indicates to be rounded；
Down-sampling is realized by linear interpolation or cubic interpolation；Wherein, linear interpolation process is as follows:
It enables, K=round (M*cos (θi)), the value of original M pixel is respectively (1) x ..., x (M), and the value after interpolation is respectively y (1) ..., y (K), then have:
Y (j)=x (j × M/K), j=1,2 ..., K；
If j × M/K is integer, known to corresponding value；
Otherwise, enable a=floor (j × M/K), b=ceil (j × M/K), floor and ceil be respectively remove it is whole and take it is whole, Then have:
Y (j)=(j × M/K-a) × x (b)+(b-j × M/K) × x (a).
5. the quality evaluating method of longitude and latitude figure panoramic video according to claim 1, which is characterized in that calculate two frame by frame Mean square error between irregular shape video, quality frame by frame and overall quality include:
Assuming that in the current frame, the difference that the i-th row jth of two irregular shape videos arranges corresponding pixel value is dij；
Then mean square error RMSE are as follows:
RMSE=sqrt ((ΣI=1..NΣJ=1..round (M*cos (θi))dij 2)/(ΣI=1..Nround(M*cos(θi))))
Wherein, sqrt indicates extraction of square root, θiFor the corresponding latitude value of the i-th row, M is the width of longitude and latitude figure, and N is the height of longitude and latitude figure Degree, round indicate to be rounded；
The then corresponding quality Q of present frame are as follows:
Q=10*log10(c2/RMSE)；
Wherein, c is constant；
Then the overall quality of video is averaging to obtain by quality frame by frame；Alternatively, mean square error is averaging by mean square error frame by frame, then It brings above-mentioned quality into and seeks formula to calculate overall quality.
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CN108271020B (en) * 2018-04-24 2019-08-09 福州大学 A kind of panoramic video quality evaluating method of view-based access control model attention model
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