| In recent years,with the rapid development of mobile communication technology,high-rate video services have become one of its main applications.However,the scarce spectrum resources will be difficult to meet the needs of the development of high-rate video services.How to use the limited spectrum resources to meet the service requirements of the high-rate video services has become one of the main challenges of the current mobile communication system.After years of development,video coding standards have evolved more maturely.Because of the high-efficiency video coding and compression technology,H.264 has high coding and compression efficiency and has been widely recognized by industry and academia.On the basis of the H.264 framework,H.264/SVC(Scalable Video Coding)uses layered coding technology to make the video code stream scalable.This property allows SVC to easily adapt to dynamic networks.SVC uses a picture group as a unit for coding,and the predictive coding technology is used in the picture group to eliminate the redundancy in the video sequence.The increase of the group size will increase the cumulative error,which will affect the video quality;different group structures have different prediction relationships,resulting in different error propagation conditions under the influence of error codes,which affects their effective reception Video quality.In order to make the video service better adapt to the dynamic network environment under the premise of ensuring the quality of the video received by the user.It will be of great significance to study the configuration of the GOP in the case of limited resources.In response to the above problems,this paper studies the optimization of the GOP(Group of Picture)in scalable video coding under the constraints of the network environment based on the architecture of the H.264/SVC video coding standard.On the one hand,it is to study the size of the GOP and obtain the optimal GOP size under the transmission rate constraint by studying the influence of the GOP size on video coding efficiency and the accumulation of errors in the GOP;on the other hand,In the case of considering error propagation,further research on the structure of the GOP is carried out,and the optimal structure of the GOP under the constraint of the bit error rate is obtained.The main research contents of this paper are as follows:(1)Study the optimal size of the GOP under the transmission rate constraint.When performing scalable video coding,parameters need to be continuously adjusted to find video coding parameters that meet the requirements of the network environment.This process is not only complicated,but also requires high performance on the coding end.The GOP size and the quantization parameter are the two main parameters that affect the video encoding result.If traverse the combination of these parameters,the complexity is self-evident.Therefore,under the constraints of transmission rate,this paper studies the video quality of different group size under the influence of quantization,and obtains the optimal group size under the constraints of the network environment.At this time,the video quality of the receiving end is the best,and the encoding end can reduce the complexity of finding the optimal encoding result.(2)Study the optimal structure of the GOP under the constraint of bit error rate.In SVC,the predictive coding technology is used in the GOP to efficiently remove the redundant information in the video,but it can also cause the phenomenon of error propagation.Based on predictive coding technology,this paper studies the error propagation in the temporal,spatial and quality scalable coding GOP structure,and further analyzes the effective received video quality and quality degradation ratio of the three GOP structures under the given error rate constraint.And get the GOP structure least affected by the bit error rate through simulation verification.(3)Study the optimal combine structure of the GOP under the constraint of bit error rate.Based on the temporal,spatial and quality scalable GOP structure,this paper constructs the combined scalable GOP structure,and studies the error propagation phenomenon in the combined GOP structure,and further analyzes the structure of the combined GOP under the constraint of a given bit error rate.Effectively receive the video quality and the quality degradation ratio,and obtain the combined scalable GOP structure that is least affected by the bit error rate through simulation verification.In summary,the optimal GOP size,the optimal structure of the GOP and the optimal structure of the combined GOP for the transmission-oriented video can be obtained through the above research.In this paper,the research on the optimization method of GOP in scalable video coding can make the video service better adapt to the network environment when facing wireless transmission,reduce the complexity of the video coding terminal and ensure the quality of the video received by the user. |
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