CN107040771A - A kind of Encoding Optimization for panoramic video - Google Patents
A kind of Encoding Optimization for panoramic video Download PDFInfo
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- CN107040771A CN107040771A CN201710193359.9A CN201710193359A CN107040771A CN 107040771 A CN107040771 A CN 107040771A CN 201710193359 A CN201710193359 A CN 201710193359A CN 107040771 A CN107040771 A CN 107040771A
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N13/00—Stereoscopic video systems; Multi-view video systems; Details thereof
- H04N13/10—Processing, recording or transmission of stereoscopic or multi-view image signals
- H04N13/106—Processing image signals
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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
- H04N19/10—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
- H04N19/146—Data rate or code amount at the encoder output
- H04N19/147—Data rate or code amount at the encoder output according to rate distortion criteria
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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
- H04N19/10—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
- H04N19/146—Data rate or code amount at the encoder output
- H04N19/149—Data rate or code amount at the encoder output by estimating the code amount by means of a model, e.g. mathematical model or statistical model
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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
- H04N19/10—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
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Abstract
The invention provides a kind of Encoding Optimization for panoramic video, belong to field of video encoding.The inventive method be primarily based on sphere distortion set up panoramic video rate control module optimization aim, fit sphere distortion and the hyperbolic model of code check relation are wherein obtained by statistical method, then solving-optimizing equation obtains optimal rate-allocation result, quantization step is calculated finally according to the result, present frame is encoded, while needing to update the parameter in hyperbolic model.A kind of Rate Control scheme for panoramic video characteristic of the invention so that the coding of panoramic video has the Data Rate Distribution mechanism more optimized, so as to further improve code efficiency, improves the quality of compression rear video.
Description
Technical field
The invention belongs to field of video encoding, a kind of bit rate control method for panoramic video characteristic of specific design, from
And further lift code efficiency.
Background technology
With developing rapidly for information technology in recent years, the panoramic video of various visual angles due to the virtual experience of its immersion,
Significantly come into vogue in virtual reality (Virtual Reality, VR) field.However, panoramic video requires high-resolution
(4K and more than) supports wide in range visual angle, but network is only capable of providing limited bandwidth at present.Even if in addition, two-dimensional video is encoded
Standard is as H.265/HEVC, and H.264/AVC, AVS/AVS+/AVS2 etc. is quickly grown, but they are still difficult to solve aphorama
The problems of frequency coding, especially code efficiency.
Further, since coding techniques is limited, the coding of panoramic video needs the video on sphere being mapped to plane progress
Coding.But sphere inevitably results in the distortion and stretching of picture to the mapping of plane.Mapped in nowadays the most frequently used longitude and latitude figure
In mode, the area maps at the two poles of the earth are more inclined on sphere more to be needed to carry out extra interpolation to plane.However, panoramic video is flat
The part of interpolation is in sphere in face and is not present, and but needs to consume coding resource in coding, and the code check of traditional algorithm point
Match somebody with somebody and unreasonable.
Reference paper [1] proposition is a kind of based on panorama video code prioritization scheme H.264/AVC, and it is adaptively used
The piece (Tile) of different size and different code checks is separately encoded, so as to strengthen the total quality of panoramic video under cbr (constant bit rate).
Reference paper [2] is with carrying out region adaptivity smooth to video before panorama video code, so the region near limit can
To save more code checks.The two is provided to after panoramic video maps, and the low limit near zone of sampling point density is saved
Code check, but all excessively coarse and uncontrollable code check, and when there is enough code checks, the panoramic video of compression is difficult to return to
Original quality.
Reference paper [1]：Matt Yu,Haricharan Lakshman,and Bernd Girod,“Content
adaptive representations of omnidirectional videos for cinematic virtual
reality,”in Proceedings of the 3rd International Workshop on Immersive Media
Experiences.ACM,2015,pp.1–6.
Reference paper [2]：Madhukar Budagavi,John Furton,Guoxin Jin,Ankur Saxena,
Jeffrey Wilkinson,and Andrew Dickerson,“360degrees video coding using region
adaptive smoothing,”in IEEE International Conference on Image Processing
(ICIP).IEEE,2015,pp.750–754.
The content of the invention
The present invention is directed to the characteristic of panoramic video there is provided a kind of Encoding Optimization for panoramic video, passes through reality
The Rate Control of sphere Y-PSNR (S-PSNR) is now based on, to improve the quality of compression rear video, so as to lift aphorama
Frequency code efficiency.
The Encoding Optimization for panoramic video that the present invention is provided, specific steps include：
Step 1: the optimization aim of panoramic video rate control module is set up in the distortion based on sphere.
Given target bit rate R, the equation of the optimization aim of panoramic video is expressed as：
Wherein, rmM-th of code tree unit CTU bit number is allocated to, M is total CTU numbers of present frame, dmRepresent m-th of CTU
Distortion；
Drawing erlang day multiplier λ is further introduced into, equation above is converted into the optimization problem of no bound term, equation is represented such as
Under：
Wherein, J is rate distortion costs；
Fit sphere distortion and the hyperbolic model of code check relation are obtained by statistical method, obtained：
Wherein, cmAnd kmFor the parameter of hyperbolic model；
The optimization aim of the rate control module of panoramic video is set up, represents that equation is：
Step 2: solve the equation of the optimization aim for the rate control module set up, obtain distributing to each
CTU target bit rm。
Step 3: obtaining after optimal rate-allocation result, quantization step QP is calculated as the output of rate control module, and
Undated parameter cmAnd km。
Advantages and positive effects of the present invention are：The present invention proposes a kind of Rate Control side for panoramic video characteristic
Case so that the coding of panoramic video has the Data Rate Distribution mechanism more optimized, so as to further improve code efficiency, improves pressure
The quality of contracting rear video.
Brief description of the drawings
Fig. 1 is overview flow chart of the present invention for the Encoding Optimization of panoramic video；
Fig. 2 is with fitting result schematic diagram of the hyperbolic model to aphorama frequency distortion curve；
Fig. 3 realizes block diagram for the present invention for the entirety of the Rate Control of panoramic video；
Fig. 4 illustrates for the panorama video code prioritization scheme result of the present invention.
Embodiment
The invention will be further described with instantiation below in conjunction with the accompanying drawings.
The present invention devises a kind of based on sphere Y-PSNR (Sphere-based Peak Signal to Noise
Ratio, S-PSNR) optimization method carry out Data Rate Distribution, and the solution of the equation is provided, so as to be compiled by panoramic video
The code check optimum allocation of code obtains the optimum quality of video.
The Encoding Optimization for panoramic video that the present invention is provided, including：Panoramic video rate control module optimizes
The proposition of target, the more excellent scheme for finding optimization method solution simultaneously determine new parameter update mode.Specific steps such as Fig. 1
It is shown, illustrate each to realize step below.
Step 1: proposing the optimization aim of panoramic video rate control module.
Step 101, the basic theories encoded according to two-dimensional video, propose the optimization aim of panoramic video.
Similar to two-dimensional video, the main target of rate control module is made to minimize coding in panorama video code
Into distortion, that is, maximize objective quality.For panoramic video, objective quality needs to be calculated on sphere, therefore here
Using S-PSNR as the index for weighing panoramic video quality, calculation formula is as follows：
Wherein, S-MSE refers to the Averaged Square Error of Multivariate (Sphere-based Mean Square Error) based on sphere, N
Represent the sum of sphere sampled point, S (xn,yn) and S ' (xn,yn) it is n-th of sphere sampled point (xn,yn) it is respectively mapped to reference
The pixel value of sequence and distortion sequence.But the mapping of sphere to plane may cause point (xn,yn) it is mapped to the sub-pix of plane
On, and the pixel value on sub-pix is unknown.In order to solve this problem, the present invention uses Lanczos interpolation methods, by closing on
Pixel value comes to S (xn,yn) and S ' (xn,yn) estimated.Finally, it is that can obtain the objective matter of compression video by formula (1)
Measure S-PSNR.
Therefore, this invention address that the S-PSNR of maximum compression video lifts code efficiency.Then, based on sphere
Distortion can be obtained by sampled point mean square error sum：
Wherein CmIt is the pixel set for belonging to m-th of code tree unit (Coding Tree Unit, CTU), dmRepresent m
The distortion of individual code tree unit.Therefore, target bit rate R is given, the final optimization pass target of panoramic video can pass through equation below table
Show：
In formula (3), rmM-th of CTU bit number is allocated to, M is total CTU numbers of present frame.
Step 102, to the further analysis of optimization aim, set up the rate control module optimization method for panoramic video.
Next the panoramic video rate control module optimization aim of the invention to proposition is further analyzed, can so as to set up
Majorization of solutions equation.For optimization aim --- formula (3), in order to be able to solve the equation, present invention introduces drawing erlang day multiplier λ,
Formula (3) is converted into the optimization problem of no bound term：
Herein, it is rate distortion (Rate-Distortion, RD) cost that the present invention, which defines J,.λ is the drawing erlang day multiplier of frame.
By by formula (4) on rmLocal derviation be set to 0, you can J is minimized：
Next, in order to solve equation (5), the present invention is set up on the relation between distortion and code check.First, the present invention is logical
Cross statistical method draw most can fit sphere distortion S-MSE and code check relation be hyperbolic model.Fig. 2, which is illustrated, uses hyperbola
Model is to the fitting result of four cycle tests carry out rate distortion curves, and cycle tests is landscape image sequence respectively
Fengjing_1, physical culture image sequence Tiyu_1, film image sequence D ianying_1, aerial image sequence Hangpai_2.
In Fig. 2, the bit number (bit per pixel, bpp) distributed per pixel is used for the overall code check for representing whole video：
Wherein, f represents frame per second, and W and H represent the wide and height of video respectively.Fig. 2 illustrates that hyperbolic model can be preferably
Fit sphere distortion S-MSE and code check bpp relation, and R side's value (R-square) of matched curve has exceeded 0.99.Cause
This, hyperbolic model is used in the Rate Control scheme of the present invention by the present invention,
Wherein cmAnd kmIt is the parameter of hyperbolic model, and they are in each CTU of the Rate Control scheme code
Need to be updated, the specific step that updates will be illustrated in step 3.
Then, formula (7) can be further converted into
By formula (5) and formula (8), it can continue to obtain below equation：
In addition, by formula (3), there is following constraint：
By formula (9) and formula (10), the Data Rate Distribution for each CTU can be obtained by solving equation below：
Therefore, once solving formula (11), you can obtain distributing to each CTU target bit rm, maximize simultaneously
S-PSNR.
Step 2: for setting up rate control module optimization method, being solved, obtaining the code more excellent than existing algorithm
Rate distribution mechanism.
The present invention uses newest recurrence Taylor expansion method (Recursive Taylor Expansion, RTE) [reference
Document 3:Shengxi Li,Mai Xu,Zulin Wang,and Xiaoyan Sun,“Optimal bit allocation
for ctu level rate control in hevc,”IEEE Transactions on Circuits and Systems
For Video Technology, 2016.] closed solutions are sought formula (11), so approximate solution compared to primal algorithm has more
Accurate Rate Control.The calculating speed of wherein RTE algorithms is very fast, and CTU calculating spends 0.0015ms, therefore this hair
Bright Rate Control scheme does not need extra calculation cost compared to primal algorithm.
Step 3: obtaining after optimal rate-allocation result, quantization step (Quantization Parameter, QP) is calculated
As the output of rate control module, and undated parameter.
Obtain after optimal rate-allocation result, calculate quantization step (Quantization Parameter, QP) and be used as code
The output of rate control module：
QPmFor m-th of CTU quantization step, λmIt is m-th of CTU drawing erlang day multiplier,.According to formula (7) and formula
(12) actual code check r, and used in m-th of CTU codinga,m、λa,mAnd actual distortion da,mC after being updatedm、
km：
Fig. 3 summarize the present invention be directed to panoramic video Rate Control protocol procedures, solving-optimizing target equation obtain most
Excellent Data Rate Distribution, carries out QP estimations, present frame is encoded, and used hyperbola parameter is then updated, for next
The Data Rate Distribution of frame.
Step 4: the result to panorama video code optimization method proposed by the invention carries out simple displaying with examining.
The Encoding Optimization of panoramic video of the present invention to being proposed carries out simple displaying with examining.Random choosing of the invention
Take a certain frame of test video after one of compression to be shown, as shown in figure 4, can obtain it is of the invention in some regions for passing
System algorithm can preferably lift quality.Go out in Fig. 4 for the two region white line collimation marks entered.In fact, present invention design
Panoramic video Rate Control scheme can accomplish under to constant bit rate, optimize compression panoramic video quality.
Inhomogeneities of the panoramic video of the present invention from spherical Map to plane, the rate-allocation procedure to video compress is carried out
It is more suitable for panoramic video and more accurately controls, it is adaptable to panoramic video quality is required but equipment can not be transmitted or stored
In the case of larger bitrate video.Although the present invention be described with reference to embodiment and for example, simultaneously
Do not mean that the present invention is limited to the embodiment of the description.
Claims (3)
1. a kind of Encoding Optimization for panoramic video, it is characterised in that use sphere Y-PSNR S-PSNR conducts
The index of panoramic video quality is weighed, methods described comprises the following steps：
Step 1: the optimization aim of the rate control module of panoramic video is set up in the distortion based on sphere；
Given target bit rate R, the equation of the optimization aim of panoramic video is expressed as：
Wherein, rmM-th of code tree unit CTU bit number is allocated to, M is total CTU numbers of present frame, dmRepresent m-th
CTU distortion；
Drawing erlang day multiplier λ is further introduced into, equation above is converted into the optimization problem of no bound term, represents that equation is as follows：
Wherein, J is rate distortion costs；
Fit sphere distortion and the hyperbolic model of code check relation are obtained by statistical method,
Wherein, cmAnd kmFor the parameter of hyperbolic model；
The final optimization aim for setting up rate control module, represents that equation is as follows：
Step 2: solving the equation of the optimization aim for the rate control module set up, obtain distributing to each CTU's
Target bit rm；
Step 3: outputs of the calculating quantization step QP as rate control module, and undated parameter cmAnd km。
2. Encoding Optimization according to claim 1, it is characterised in that in described step one, dmIt is equal by sampled point
Square error sum is obtained, as follows：
Wherein, CmIt is the pixel set for belonging to m-th of code tree unit, S (xn,yn) it is n-th of sphere sampled point (xn,yn) mapping
To the pixel value of reference sequences, S ' (xn,yn) it is n-th of sphere sampled point (xn,yn) it is mapped to the pixel value of distortion sequence.
3. Encoding Optimization according to claim 1 or 2, it is characterised in that in described step three, parameter updates public
Formula is：
Wherein, da,mFor m-th of CTU actual distortion, ra,mAnd λa,mFor the actual bit rate and La Er used in m-th of CTU coding
Bright day multiplier.
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108076344A (en) * | 2017-11-27 | 2018-05-25 | 上海交通大学 | A kind of VR video code rate control bit distribution methods based on weight graph model |
| CN109874019A (en) * | 2019-03-26 | 2019-06-11 | 深圳大学 | A kind of method of the inequality error protection auxiliary wireless panoramic video of region-of-interest |
| CN110730346A (en) * | 2018-07-17 | 2020-01-24 | 天开数码媒体有限公司 | Video coding rate control method based on coding tree unit distortion optimization |
| CN110944200A (en) * | 2019-12-10 | 2020-03-31 | 南京大学 | Method for evaluating immersive video transcoding scheme |
| CN111277839A (en) * | 2020-03-06 | 2020-06-12 | 北京工业大学 | Self-adaptive QP (quantization parameter) adjustment method for coding cube projection format |
| CN112616014A (en) * | 2020-12-09 | 2021-04-06 | 福州大学 | GAN-based panoramic video adaptive streaming transmission method |
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Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108076344A (en) * | 2017-11-27 | 2018-05-25 | 上海交通大学 | A kind of VR video code rate control bit distribution methods based on weight graph model |
| CN110730346A (en) * | 2018-07-17 | 2020-01-24 | 天开数码媒体有限公司 | Video coding rate control method based on coding tree unit distortion optimization |
| CN110730346B (en) * | 2018-07-17 | 2023-05-23 | 天开数码媒体有限公司 | Video coding rate control method based on coding tree unit distortion optimization |
| CN109874019A (en) * | 2019-03-26 | 2019-06-11 | 深圳大学 | A kind of method of the inequality error protection auxiliary wireless panoramic video of region-of-interest |
| CN110944200A (en) * | 2019-12-10 | 2020-03-31 | 南京大学 | Method for evaluating immersive video transcoding scheme |
| CN110944200B (en) * | 2019-12-10 | 2022-03-15 | 南京大学 | Method for evaluating immersive video transcoding scheme |
| CN111277839A (en) * | 2020-03-06 | 2020-06-12 | 北京工业大学 | Self-adaptive QP (quantization parameter) adjustment method for coding cube projection format |
| CN111277839B (en) * | 2020-03-06 | 2022-03-22 | 北京工业大学 | Self-adaptive QP (quantization parameter) adjustment method for coding cube projection format |
| CN112616014A (en) * | 2020-12-09 | 2021-04-06 | 福州大学 | GAN-based panoramic video adaptive streaming transmission method |
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Inventor after: Xu Mai Inventor after: Liu Yufan Inventor after: Li Chen Inventor after: Tao Xiaoming Inventor after: Liu Shuai Inventor before: Xu Mai Inventor before: Liu Yufan Inventor before: Li Chen Inventor before: Tao Xiaoming |