On the application of streaming media technology i

  • Detail

Talking about the application of streaming media technology in wireless network

Abstract: the development of wireless technology makes streaming media technology can be applied to wireless terminals. This paper introduces the application of streaming media technology in wireless network, and makes a detailed analysis of mobile streaming media technology rtp/rtcp, RTSP, RSVP and video audio coding format

Keywords: streaming media; Wireless network; 3G

1. Overview of mobile streaming media business

streaming media is a mechanism for media content to be played on the client while it is transmitted to the client through the data network. Streaming media technology first appeared in fixed network communication. The methods of uploading multimedia information such as audio and video on the network mainly adopt download and streaming. For the download method, because large files often require a large amount of storage capacity, and are limited by network bandwidth, the download often takes several minutes or even hours, with great delay. For streaming transmission, files such as sound, video or animation are played while downloading. When time-based media such as sound is played on the client, the rest of the file continues to be downloaded from the server in the background, which not only shortens the start-up delay tenfold or hundredfold, but also does not require too much cache capacity, avoiding the disadvantage that users must wait for the entire file to be downloaded before viewing

in mobile networks, streaming media services are mainly for gprs/edge, UMTS and other wireless packet networks that provide high bandwidth (above 100kbit/s), which can be divided into video services and audio services according to different streaming media sources. At present, VOD and AOD services based on fixed networks have been widely welcomed by users. In wireless networks, the increase of air interface bandwidth provides a good foundation for the development of streaming media services. Combined with the characteristics of wireless systems that are not limited by time and place, mobile streaming media services are more attractive

2. Mobile streaming media business framework

the overall network architecture of mobile streaming media system is roughly the same as that of fixed network streaming media, which is composed of streaming media server, client, corresponding background management system and content caching device. The following figure shows the framework of mobile streaming media business

Figure 1 mobile streaming media business framework

the complete streaming media business is composed of streaming media server, streaming media client, portal, user management system and cache server. For mobile streaming media system, streaming media server is connected with wireless core GGSN through GI interface

portal is a server that provides more convenient access to streaming media content. For example, a portal may provide a content browser and search tools. In the simplest case, it contains only one web/wap page. The streaming media content is stored on the content server, and the streaming media content link list can be located anywhere in the network. At the same time, through the portal, content providers (CPS) publish content to streaming media servers and streaming media caches. The portal provides CP authentication and content publishing interfaces

the management system is used to store user parameters and device function information, and to control how to provide streaming media content to mobile users

the client initiates the streaming media service and connects to the server of its choice. The streaming media server can also send real-time content. When the session is initiated, the streaming media server negotiates with the management system and transmits the streaming media information according to the terminal capacity

3. Key technology analysis

3.1 streaming media transmission protocol

(1) rtp/rtcp protocol

rtp (real time Transport Protocol) is a transmission protocol for multimedia data streams on the Internet. It works in one-to-one or one to many transmission situations, and can provide time information and realize stream synchronization. RTP usually uses UDP to transmit no data, and it can also work on TCP or ATM protocol. When an application starts an RTP session, it will use two ports, one as RTP port and the other as RTCP port. RTP itself does not provide a reliable transmission mechanism for the sequential transmission of data packets, nor does it provide flow control or congestion control, but relies on RTCP to provide these services

rtcp (real time Transport Control Protocol) and RTP jointly provide flow control and congestion control services. During the RTP session, participants periodically transmit RTCP packets, which contain statistical data such as the number of sent packets and the number of lost packets. The server can dynamically change the transmission rate and even the payload type according to these information. The combination of RTP and RTCP can effectively feedback, so as to reduce the overhead and improve the transmission efficiency. It is very suitable for transmitting real-time data

(2) real time streaming protocol (RTSP)

RTSP is a protocol jointly proposed by RealNetworks and Netscape, which defines how to make one to many applications effectively transmit multimedia data over IP networks. RTSP is a protocol for establishing and controlling audio and video streams between the server and the client. It acts as a "remote controller" between the server and the client. The client can play, pause, fast forward, locate, record and other operations on the audio and video streams on the server. RTSP is an application layer protocol. It must rely on the underlying RTP, RSVP and other protocols to provide complete streaming media transmission services on the Internet. The underlying RTP or TCP is followed in the selection of data transmission path and transmission mechanism. Now the State Council 46 protocol is firmly implemented nationwide. It can provide high playback performance for streaming multimedia of single point transmission and multi-point transmission. At the same time, it can also be compatible with the applications of sending and receiving ends of different manufacturers

(3) resource reserve protocol (RSVP) RSVP is a resource reservation protocol on the Internet. Using RSVP to reserve some network resources (i.e. bandwidth) can provide QoS for streaming media transmission to a certain extent

rsvp runs on the transport layer and belongs to the transmission control protocol. RSVP consists of sender, receiver and host or route buzzer sounding alarm. The sender is responsible for letting the receiver know that the data will be sent and what kind of QoS is required; The receiver is responsible for sending a notification to the host or router so that they can be ready to receive the incoming data. The host or router is responsible for setting aside all appropriate resources

two important concepts of RSVP protocol are flow and reservation. Flow is the connection feature from the sender to one or more receivers, which is authenticated by the "flow mark" in the IP packet. Before sending a stream, the sender should transmit a path information to the destination receiver, which includes the source IP address, destination IP address and a stream specification. This flow specification is composed of the flow rate and delay. After the receiver realizes the reservation, the receiver based mode can realize a distributed solution

3.2 encoding format

(1) video encoding format

3gpp UMTS video media encoding and decoding technical specification is ITU-T H.263, which is also a video decoder that must be used by PSS. At the same time, it also supports MPEG-4 decoder. In practical applications, two video decoders are optional. The recently proposed H.264 standard has aroused widespread interest in the industry because of its high compression quality, high network adaptability and other characteristics. At present, various manufacturers have launched research on the application of H.264 coding technology, and 3GPP PSS R6 is also actively considering its inclusion in the specification

(2) audio coding format

3gpp UMTS audio media coding and decoding should support extended aac+ or extended AMR-WB, and can support both coding and decoding formats at the same time, as well as MPEG-4 decoder

for CDMA 2000 system, at least 13K should be supported, which is one of qcelp, AAC and amr-nb

4. Application prospect of mobile streaming media technology

in the field of wireless communication, 3G is based on broadband and diversified requirements. It should not only provide high-quality voice, but also provide timely multimedia services. The application of mobile streaming media technology mainly includes the following situations:

(1) mobile music

if 3G has MP3 function, the operator United record company will release pop music charts every week. After listening to the song clips, users can download them to China through small payment, which is equivalent to the operator opening a record store

(2) mobile TV

users watch TV programs through 3G to gain entertainment experience through simple operation. In order to ensure better viewing effect, the bandwidth must be guaranteed at about 100kbit/s. Considering the limitation of air bandwidth and the huge number of users, broadcast mode can be used instead of VOD mode. TV programs can be selected into, cartoons, funny short films, MTV, classic clips, movie trailers, TV program trailers, and wonderful clips to meet the needs of most users and ensure the low cost of the program

(3) live broadcast

below all kinds of sports events, concerts, conferences and other large events are some related requirements of the pressure testing machine printer. In addition, it can also be used in places that need monitoring, such as transportation and families

(4) the integration of various converged business forms

streaming media and MMS, forwarding some video clips between users through MMS; The integration of streaming media and location services shows the road information and road guidance to users in the form of streaming media

the development of mobile streaming media business has brought new hope to mobile value-added services. The development of 2.5G, 3G and ultra 3G wireless networks has also made streaming media technology available to wireless terminal devices. With the application of 3G wireless networks, users' network bandwidth can reach 384kbit/s. On the other hand, the computing power of equipment is getting stronger and stronger. In short, mobile streaming media technology is still developing and improving. (end)

Copyright © 2011 JIN SHI