CN104270634B

CN104270634B - Quality-self-adapting wireless video coding method

Info

Publication number: CN104270634B
Application number: CN201410536019.8A
Authority: CN
Inventors: 王中元; 朱婧雅; 胡孟凌
Original assignee: Wuhan University WHU
Current assignee: Chengdu Suirui cloud Technology Co. Ltd.
Priority date: 2014-10-11
Filing date: 2014-10-11
Publication date: 2017-05-10
Anticipated expiration: 2034-10-11
Also published as: CN104270634A

Abstract

The invention discloses a quality-self-adapting wireless video coding method. Firstly, the dynamic texture synthesis method is adopted, a virtual reconstruction frame of a frame to be coded is constructed through a reconstruction frame of a coded image, then with the SSIM being used as the index, a threshold value is set to determine low-quality macro blocks in the virtual reconstruction frame, and finally, coding parameters of the low-quality macro blocks are regulated, and the macro blocks are coded more finely in the coding process, so that complex textures and marginal area macro blocks are better processed, and the user experience quality of the whole image is improved.

Description

A kind of wireless video coded method of quality adaptation

Technical field

The invention belongs to digital video technology field, is related to a kind of method for video coding, and in particular to a kind of quality is adaptive The wireless video coded method answered.

Background technology

With popularization and the high speed development of 4G networks of 3G network, mobile multi-media service there has also been sharp increase, strictly according to the facts When video calling, network video-on-demand, mobile TV etc., user experience quality (Quality-of- of these scenes to video Experience, QoE) there is very high requirement.Meanwhile, the restriction of mobile network's bandwidth and the complexity of applied environment are also to video The code check and real-time of stream proposes high requirement.H.264/AVC it is most widely used international Video coding One of standard, compares old plant, and it can provide high-quality video under lower code check.However, processing with complex texture or During the macro block that marginal information is enriched, traditional H.264 content-adaptive method not can overcome the disadvantages that the impact that complex contents bring, and lead Cause macroblock coding quality relatively low.Meanwhile, according to human visual perception characteristic, image texture and marginal information be human eye more Sensitive region, the distortion of these macro blocks often have influence on human eye aesthetic quality to entire image visually.Therefore, how Adaptive adjustment video coding parameter, improving video quality becomes problem demanding prompt solution.

Most of research with regard to mobile video QoE at present all concentrates on the direction of improvement of network performance, and less focuses on Self-adaptive encoding method based on video content is improved.

The content of the invention

In order to solve above-mentioned technical problem, it is an object of the invention to provide a kind of wireless video of quality adaptation is compiled Code method.The method can lift user experience quality with the coding parameter of low quality macro block in adaptive adjustment video.

Using technical scheme be：The wireless video coded method of a kind of quality adaptation, it is characterised in that including following Step：

Step 1：Obtain reconstruction frames P of encoded image_i～P_n(1≤i≤n)；

Step 2：Synthesize the Virtual Reconstruction frame P ' of the (n+1)th two field picture using the reconstruction frames of encoded image_n+1；

Step 3：Calculate the SSIM values of each sampling window in Virtual Reconstruction frame；

Step 4：Credit rating threshold value T of macro block in sampling window is calculated using maximum entropy method；

Step 5：Obtain the (n+1)th two field picture；

Step 6：Judge whether overlap between each coded macroblocks and SSIM values and the sampling block less than T, overlapping positions Macro block is judged to low quality macro block；

Step 7：Quantization parameter (Quantization Parameter, the QP) value of adjustment low quality macro block；

Step 8：(n+1)th two field picture is encoded；

Step 9：1～step 8 of repeat step, until video sequence coding is finished.

Preferably, the Virtual Reconstruction frame P ' of the (n+1)th two field picture of synthesis described in step 2_n+1, it is to utilize dynamic texture Model synthesizes Virtual Reconstruction frame.

Preferably, the SSIM values for calculating each sampling window in Virtual Reconstruction frame described in step 3, are to adopt The sampling window of 16x16 pixels, with 4 pixel steppings, counts the SSIM values of each sampling window.

Preferably, the use maximum entropy method described in step 4 calculates the credit rating threshold value of macro block in sampling window T, it is to utilize formula which implements

T '=arg mx { E_l(t)+E_m(t)}；

Wherein E_l(t) and E_mT () represents that SSIM values are less than the sampling of given threshold T and the probability higher than given threshold T respectively The entropy definition of window, and：

Wherein P_l、P_mRespectively SSIM values are less than T and the probability higher than T, and t is the credit rating variable of macro block.

Preferably, adjustment low quality macro block described in step 7 quantization parameter (Quantization Parameter, QP) value, its Adjustable calculation formula is：

QP=QP- δ (δ>0)；

Wherein, δ is the empirical value according to the concrete SSIM values setting of current macro, according to threshold value T ' comment with current macro SSIM The size of the difference value divided.

A kind of application scenarios of the present invention for mobile video, it is proposed that video coding framework of quality adaptation.First The Virtual Reconstruction frame of frame to be encoded is built according to encoded reconstruction frames, then with structural similarity (Structural Similarity, SSIM) as index, arrange a threshold value to determine the low quality macro block in the Virtual Reconstruction frame, finally adjust The coding parameter of these low quality macro blocks is saved, finer coding is taken to these macro blocks in coding；The present invention has following Advantage and good effect：

1) the inventive method can preferably process complex texture and marginal area is grand relative to traditional H.264 coding Block, lifts user experience quality.

2) the inventive method root code stream poor to binary encoding effect, can be effectively improved coding quality.

Description of the drawings

Fig. 1：Method of the present invention flow chart.

Specific embodiment

Understand for the ease of those of ordinary skill in the art and implement the present invention, below in conjunction with the accompanying drawings and embodiment is to this It is bright to be described in further detail, it will be appreciated that enforcement example described herein is merely to illustrate and explains the present invention, not For limiting the present invention.

Fig. 1 is asked for an interview, the technical solution adopted in the present invention is：A kind of wireless video coded method of quality adaptation, bag Include following steps：

Step 1：Obtain reconstruction frames P of encoded image_i～P_n(1≤i≤n)；

Step 2：Using dynamic texture model, by reconstruction frames P of encoded image_i～P_nSynthesize the void of the (n+1)th two field picture Intend reconstruction frames P '_n+1；

Step 3：Using the sampling window of 16x16 pixels, with 4 pixel steppings, each sample window in Virtual Reconstruction frame is calculated The SSIM values of mouth, finish until the SSIM values of each sampling window are calculated；

Step 4：Credit rating threshold value T of macro block in sampling window is calculated using maximum entropy method；It is profit which implements Use formula

T '=arg mx { E_l(t)+E_m(t)}；

Step 5：Obtain the (n+1)th two field picture；

Step 7：Quantization parameter (Quantization Parameter, the QP) value of adjustment low quality macro block；Its adjustment meter Calculating formula is：

QP=QP- δ (δ>0)；

Wherein, δ is the empirical value according to the concrete SSIM values setting of current macro；

Step 8：(n+1)th two field picture is encoded.

Step 9：1～step 8 of repeat step, until video sequence coding is finished.

The method of the present invention can be with the coding parameter of low quality macro block in adaptive adjustment video, in coding to these Macro block takes finer coding, so as to preferably process complex texture and marginal area macro block, lifts the user of entire image Quality of experience.

It should be appreciated that the part that this specification is not elaborated belongs to prior art.

It should be appreciated that the above-mentioned description for preferred embodiment is more detailed, therefore can not be considered to this The restriction of invention patent protection scope, one of ordinary skill in the art are being weighed without departing from the present invention under the enlightenment of the present invention Under the protected ambit of profit requirement, replacement can also be made or deformed, be each fallen within protection scope of the present invention, this It is bright scope is claimed to be defined by claims.

Claims

1. the wireless video coded method of a kind of quality adaptation, it is characterised in that comprise the following steps：

Step 1：Obtain reconstruction frames P of encoded image_i～P_n, wherein 1≤i≤n；

Step 2：Using the reconstruction frames of encoded image, synthesize the Virtual Reconstruction frame of the (n+1)th two field picture using dynamic texture model P′_n+1；

Step 4：The credit rating threshold value T ' of macro block in sampling window is calculated using maximum entropy method；

T '=arg max { E_l(t)+E_m(t)}；

Wherein E_l(t) and E_mT () represents that SSIM values are less than the sampling window of given threshold T and the probability higher than given threshold T respectively Entropy definition, and：

E_{l} (t) = - Σ_{t = 0}^{T} P_{l} (t) \log P_{l} (t),

E_{m} (t) = - Σ_{t = T + 1}^{M} P_{m} (t) \log P_{m} (t);

Wherein P_l、P_mRespectively SSIM values are less than T and the probability higher than T, and t is the credit rating variable of macro block；

Step 5：Obtain the (n+1)th two field picture；

Step 6：Judge whether overlap between sampling block of each coded macroblocks with SSIM values less than T ', the macro block of intersection is sentenced For low quality macro block；

Step 7：The quantization parameter QP values of adjustment low quality macro block；

QP=QP- δ；

Wherein, δ is the empirical value according to the setting of current macro concrete SSIM values, δ>0；

Step 8：(n+1)th two field picture is encoded；

Step 9：1～step 8 of repeat step, until video sequence coding is finished.

2. the wireless video coded method of quality adaptation according to claim 1, it is characterised in that：Described in step 3 Calculate Virtual Reconstruction frame in each sampling window SSIM values, be the sampling window using 16x16 pixels, with 4 pixel steppings, Count the SSIM values of each sampling window.