The Implementation of an Adaptive Mechanism in the RTP Packet in Mobile Video Transmission

Transcription

1 2011 International Conference on Information Management and Engineering (ICIME 2011) IPCSIT vol. 52 (2012) (2012) IACSIT Pre, Singapore DOI: /IPCSIT.2012.V52.91 The Implementation of an Adaptive Mechanim in the RTP Packet in Mobile Video Tranmiion Xiaoyu Ma and Ying Ma 1 Department of Economic and Trade, Henan Intitute Of Engineering, Zhengzhou, China 2 School of Software, Henan Intitute Of Engineering, Zhengzhou, China Abtract. Thi paper firtly decribe the advantage of packing mobile video tream before tranmiion, and then lit two ytem of packet,and analyze two factor of impacting the ize of packet, on thi bai, provide a deign cheme of adaptive packet, and analyze the tranmiion performance of the execute of the deigning cheme in the actual monitoring ytem, The reult how that the deign of the new adaptive packet can improve the efficiency and quality of the video tranmiion. Keyword: RTP, mobile video, packet, implementation. 1. Introduction In any type of callback communication, the ynchronization of ending and receiveing time are two key iue. There are two mode of ynchronization, ynchronou mode and aynchronou mode.aynchronou mode end the data tream by ymbol of the predetermined number of bit, each ymbol ha the tart bit and the parity bit followed, o each ymbol ha 2 bit overhead[1]. In ynchronou mode, Tranmiting character haven t any tart and end flag, in order to detect the tart and end flag in the receiving end, each data egment begin from flag bit of the egment header, and end with the pattern of Potpoitive bit, imilar to the aynchronou ytem.thi kind of data egment. The data egment i the data packet, which can be fixed length, uch a ATM cell,can alo be variable length byte, uch a the IP packet[2]. Fig. 1 i a typical packing flow chart of inputing video ource. Fig. 1: Packing Schematic diagram of the video tream 2. The Advantage of Packing Mobile Video Stream before Tranmiion Firtly, can efficiently ue the bandwidth of network, the buine type of net load i flaged by the type field content of each packet header, a unpacker can fat pack by the type field[3], Therefore, we can achieve multiplexing tranmiion of variety of data tream, and improve the utilization ratio. What more, we can determine the appropriate packet to improve tranmiion efficiency according to network type and condition. Correponding author. Tel.: addre: hnzzmxy@yahoo.com.cn.

2 Secondly, can improve the robutne of video data about error, uing the packet,can make the impact of error and information lo limited to a ingle packet, the video decoder will build up ynchronouly in the followed packet which ha no error, and the MB(macroblock) included in packet can be predicted independently by other MB[4]. Finally, can make the decoder interact dynamically,adjut the bit rate and error mechanim to improve the quality of video. 3. Two Sytem of Packet The MPEG-4 data package packed into the RTP packet, there are two mechanim[5]: (1) MPEG-4 for each i encapulated into a RTP packet, A hown in Fig. 2. Fig. 2: A ingle MPEG-4 packet of each RTP packet (2) Each RTP packet contain multiple MPEG-4 packet A hown in Fig. 3. Fig. 3: Multiple MPEG-4 packet of each RTP packet In comparion, chooing the long packet mean when each RTP packet i damaged, there will be more lo of data, but, at the ame time the packet header ue le packet ratio, can alo reduce the poibility of damage to the header; chooing the hort packet i oppoite. 4. Two Factor of Impacting the Packet of Size Tranmiion of Parameter Set 4.1. Network tatu Uing RTP / RTCP tranmiion of video, RTCP can periodically feedback the information of current network tatu, and end it to the erver.the ratio of packet lo and the time delay of tranmiion are two indexe which can react the tatu of network[6]. In the cae of Good tatu of network, the ratio of packet lo will be reduced,at thi time, uing a long packet can improve the efficiency of tranmiion, and in the cae of bad tatu of network, uing a hort packet, can reduce the lo of maive data which i caued by the lo of the long packet, and alo reduce the error probability of packet Content of video data when the image equence of video run intenely, we can elect the hort packet to improve the quality of video, becaue the error probability of hort packet i reduced, and packet can tranfer data much fater, furthermore,can fater get the feedback information of channel, and adjut the bit rate[7]. when the image equence of video run calmly, we can elect the long packet to improve the efficiency of tranmiion, becaue at thi time the ize of each MPEG-4 packet i relatively mall, packing many hort

3 packet can reduce the channel ratio of occupied by the protocol header,and increae the efficiency of tranmiion. 5. Deign of the Adaptive Packet The determination of the traditional RTP packet i implemented by the packet lo rate, the advantage i imple to implement, the hortcoming i not with the new video compreion algorithm and the combination of fault-tolerant technology. Packing mechanim baed on video content, i propoed on the bai of MPEG- 4, it i organically integrated with the MPEG-4 object-oriented thinking, and thi i alo the reearch direction of video tranmiion and compreion in future[8]. The advantage of thi packet i that it can improve the error robutne. Combination of the two application,can make up for the hortcoming of each other, thereby enhancing the robutne of video error and the utilization ratio of channel. So,thi article propoe an adaptive ytem of RTP packet, according to current network condition and the content of the current video data to dynamically adjut the ize of packet. The following i the algorithm proce: 5.1. Calculate the Packet lo rate,and determine the network tatu The calculating proce of the Packet lo rate i divided into three tep: Step1: Calculate the number of lot packet of ending time lot L(n): According to the difference of the cumulative number of lot packet included into two receiver report (RR) packet before or after a time lot of the end end i the number of the packet lo of ending time lot, a in (1) L(n)=C(n)-C(n-1) (1) Thereinto,C(n) i the number of lot packet after the nth ending time lot; Step2: Calculate the number of packet received in thi time lot R(n): The difference between expanion of the highet packet equence number in two packet received i the number of packet to be received in thi time lot, a in (2) R(n)=H(n)-H(n-1) (2) Thereinto, H(n) i the highet packet equence number of lot packet after the nth ending time lot; Step3: Calculating packet lo rate in thi time lot F(n):the ratio of L(n)and R(n) i packet lo rate in thi time lot, a in (3) F(n)=L(n)/R(n) (3) Packet lo rate i an important index of ing the condition of network channel,but wo can not directly ue packet lo rate to judge the condition of twork channel,and adjut the ending of video according to it,becaue thi will make ending data change too frequently,and alo make the image quality of receiveing end untable[9].o,before uing packet lo rate to etimate the condition of network channel,we houd firtly make it moothing.we can uppoe that t(n) i the packet lo rate moothed,it moothing relationhip i a in (4): t(n)=(1-a) t(n-1)+a F(n),(0 a 1) (4) When the value of a increae, the current packet lo rate F(n) increae the influence to the moothing reult t (n) ; When the value of a decreae, previou moothing reult t (n-1) increae the influence to the current moothing reult t (n). According to the experimental reult to determine the value of a, the moothing reult will weaken the QoS ocillation of network channel, uing the packet lo rate moothed to judge the condition of network channel i good to reaonably adjut the tranmiion of video. The claification algorithm of network tatu: Set two threhold k1, k2 (the value of tet experience), the moothed RTP packet lo rate i t (n): 1 when t(n)< k1,a a light load; 2 when t(n)> k1,a a full load; 3 when t(n)> k2,a a jam; In order to tet,we can take k1 and k2,and et the value 2% and 4% Calculating the exercie amount of current video equence

4 Each MPEG-4 video packet data ha two part, one i made up of head and motion data, and the other i mainly made up of the texture data. The algorithm of current imple and better exercie mount of video equence i calculating the the firt part proportion for each MPEG-4 packet. Calculated a in (5): Y MB A X MB Y MB (5) Here, the variable A i the proportion of the firt part in group, characterize the exercie amount of video image equence, Y MB i the average number of bit per MB in the firt part, X MB i the average number of bit per MB in the econd part. Similarly, we alo et ome appropriate threhold, which can generally be divided into three interval in the application, and be adjuted concretely according to the different application. We can take 0.1 and 0.4 a the two threhold, the value of A i divided into three interval Determine the appropriate packet ize According to the Packet lo rate baed on the calculated value of t (n) and A value of characterizing exercie amount of video image equence,we can determine the appropriate packet ize, elect a monitoring ytem, value of pecific application are a the table I: Tab. 1: value of determining the appropriate packet ize of the elected monitoring ytem value range of value range of value of L t(n) A 0.1<A< *A 0<t(n)<=0.02 A> A< <A< *A 0.02<t(n)<=0.04 A> A< <A< *A t(n)>0.04 A> A< Thereinto, L i the length of RTP packet, t(n) i the packet lo rate in the time of n,a i the proportion of the firt part in MPEG-4 packet. 6. Analyi of Tranmiion Performance The propoed packet lo rate and video content baed on the adaptive grouping approach, were ued in monitoring ytem teted, According to the experimental reult, we can ee, whether the tranmiion efficiency or the quality of the video i obviouly improved. In the apect of tranmiion efficiency, the ue of adaptive packing tranmiion frame rate i bigger than the other two packing ytem, and the video image are more fluent. In the monitoring ytem teted, the table II i the reult of tatitic about frame rate running in the ten minute: 7. Concluding Remark Tab. 2: frame rate comparion of three Sytem frame rate maximum average Packet lo 6.8frame/ 9 frame/ rate Video content 9frame/ 6.5frame/ adaptive 10frame/ 7.2frame/ Thi paper analyzed factor of impacting the packet of ize,and propoed a deign cheme of adaptive packet, and analyzed the tranmiion performance of the execute of the deign cheme in the actual

5 monitoring ytem, According to the experimental reult, we can ee that the deign of the new adaptive packet can improve the efficiency and quality of the video tranmiion. 8. Reference [1] DAHLMAN E WCDMA - The radio Interface for future mobile multimedia communication [ J ], IEEE Tran. On. Veh. Tech. [2] Third-generation Project, Technical Specification Group, Service and Sytem Apect; Service Apect; Mobile multimedia ervice including mobile intranet and internet ervice, 3G TR , Verion [3] The 3rd Generation Partnerhip Project(3GPP) Available from. [4] MPEG-4 Video Verification Model verion 15.0, ISO/IEC JTC1/SC29/WG11 N3093, Maui, Dec [5] Wiegand T,Sullivan G J,Bjntegaard G,Luthra A.Overview of the H.264/AVC Video Coding Standard. IEEE Tran,Circuit Syt,Video Technol., [6] Xiubo Feng,Yingjian Xie. The new progre of the reearch in fault-tolerant algorithm for wirele video tranmiion, Communication journal, [7] FFC3016. RTP Payload Format for MPEG-4 Audio/Viual Stream[S] [8] Gary J.Sullivan.Thoma Wiegand,Thoma Stockhammer. uing the draft H.26L video coding tandard for mobile application.[j]. Sytem[C].ICIP,2010,10: [9] Vetro and Huifang Sun. An overview of MPEG-4 object-baed encoding algorithm.proceeding of Information Technology: Coding and Computing, p.,2010.6