I. Introduction to mobile streaming media
Streaming media first appears in a fixed internet. Methods of multimedia information such as transmitted audio and video on the network are mainly used for download and streaming. For downloading schemes, due to large files often require a large number of storage capacity, it is limited by network bandwidth, and downloads often take a few minutes or even hours, and the delay is large. For streaming, sound, video, or animation, etc., on the edge of the file, when the sound is played, the remainder of the file continues to download from the server from the server in the background, not only makes startup delay Double, a hundred times shortening, and it does not require too much cache capacity, avoiding the shortcomings that users must wait for the entire file to download after downloading online.
Streaming media is a business supported by streaming. In the wireless network, the streaming business is mainly for the wireless packet network for higher bandwidth (100kbps or more), and can be divided into video services and audio services depending on the streaming source. Currently, based on wired VOD, AOD business has been widely welcomed by users. In the wireless network, the increase in air interface bandwidth provides a good foundation for streaming media services, combined with the wireless system is not subject to time and location restrictions, making the mobile streaming media business more attractive.
Based on streaming business applications are very wide, such as the World Cup's wonderful incoming fragment playback, mobile commerce stock indexes and finales, movie wonderful pieces appreciation, pop music appreciation, etc., simultaneously via video card, audio source collection, Live broadcast, TV, CD and other programs. Mobile streaming services can provide mobile users with online uninterrupted sounds, images, or animations, etc., users do not have to download to locally, supported media formats include MOV, MPEG4, MP3, WAV, AVI, AU, Flash, etc. You can play audio, video, and hybrid media format. Mobile streaming can provide video on demand, video live, audio, audio live, including TV, video, entertainment information, sports channel, music appreciation, news, animation, etc.
Second, the technical characteristics of mobile streaming media
The key technique to realize streaming is streaming. The definition of streaming is widely defined, mainly refers to the technical general introduction of media transfer media (such as video, audio) through network.
Flow transmission is divided into sequential streaming and real-time streaming.
Sequential streaming uses sequential download mode, while users can watch online programs while downloading files, at a given moment, users can only watch the part of the downloaded part, and cannot jump to some other parts that have not been downloaded, this way is not like In real time flow transmission, it can be adjusted according to the speed of the user connection during transmission. Sequential streaming is not suitable for long fragments and video programs with random access, such as lectures, speeches, and demonstrations, it does not support live broadcasts. Strictly speaking, it is a disconnection technology.
Real-time flow transmission ensures that the media signal bandwidth matches the network connection, and can watch the program in real time. Real-time flow is different from HTTP streaming, which requires a dedicated streaming server and transport protocol. Real-time streaming is always real-time transmission, especially suitable for on-site events, and support random access, users can quickly forward or retreat to watch content. In theory, the real-time stream is not stopped, but cycle is suspended.
Stream transmission mode usually uses RTP / UDP, RTSP / TCP communication protocols to establish contacts with A / V (AUDIO / Video) Server, redirect the server's output to a client running the A / V Player program. address. As shown in Figure 1, the streaming system generally configures a set of dedicated servers and players.
Third, mobile streaming media transmission protocol
1, real-time transmission protocol RTP, RTCP
RTP (Real-Time Transport Protocol is a transport protocol for multimedia data streams on the Internet, working on one-to-one or more transmission, providing time information and streaming synchronization. RTP usually uses UDP to transmit data or work on TCP or ATM protocol. When the application starts a RTP session, two ports are used, one gives RTP, one to the RTCP. The RTP itself does not provide a reliable transmission mechanism to deliver a packet in order, and does not provide traffic control or congestion control, but rely on RTCP to provide these services. Usually the RTP algorithm does not implement as a separate network layer, but as part of the application code. RTCP (Real-Time Transport Control Protocol) with RTP provides traffic control and congestion control services. During the RTP session, the participant periodically transmits the RTCP package, which contains statistics such as the number of transmitted packets, the number of lost packets, and the server can dynamically change the transmission rate and even change the payload type according to this information. . The use of RTP and RTCP can be effectively feedback, thereby reducing overhead, improving transmission efficiency, and is ideal for real-time data on the network.
2, real-time flow protocol RTSP
Real-time flow protocol RTSP (Real-Time Streaming Protocol) is a protocol proposed by RealNetworks, Netscape, which defines how to make a pair of applications to transmit multimedia data through IP networks. RTSP is located on RTP, RTCP on the architecture, which uses TCP or RTP to complete data transmission. Compared to HTTP, RTP is transmitted by multimedia data, while HTTP transmits HTML. When using RTSP, the client and server can issue a request, that is, the RTSP can be two-way services, and the request of HTTP is issued by the client, and the server responds.
3. Resource reservation protocol RSVP
The audio and video data stream is more sensitive to the network's delay, how to transmit high quality audio and video information in the network, in addition to bandwidth requirements, other conditions. RSVP (Resource Reservation Protocol is a developed Internet resource booking protocol, which provides QoS to stream media transmission by taking a part of a part of the network resource (bandwidth) to a certain extent. Some experimental systems, such as the network video conferencing tool Vic integrates RSVP.
The 3GPP UMTS video media codec technology specification is ITU-T H.263 Profile 0 Level 10, which is also a video decoder that PSS must use. In addition, PSS should also support H.263 Profile 3 Level 10 decoder and MPEG-4 Visual Simple Profile Level 0 decoder, in actual applications, two video decoders are optional. Recently, H.264 standards have also caused extensive interest in the industry, and 3GPP PSS R6 is also actively considering its norms.
Fourth, Huawei Mobile Streaming Media Business Solution
1, architecture
Figure 3 is a schematic diagram of Huawei mobile streaming media business solution, which describes the main modules of it.
※ stream Media Server
This is the core part of InfoxTM-OpenStream, mainly for codec, connection management, priority scheduling, session management, etc. It receives the video of the CP / SP to receive the video and audio source of the CP / SP, realize data compression, and transmit media formats in real time, transmits the passage of the GGSN / PDSN network, and the system has high performance processing capabilities.
※ Presentation Server
Implement the portal and navigation features of the user browsing content, you can perform user personalization settings, QoS settings, etc., and enable business recommendation and ranking, business preview, and query interfaces, terminal adaptation, etc., which can provide different types of terminals. Business interface and business collection. ※ Content Storage Content Storage Server
You can provide storage for editing, audio clips, and support high-capacity concurrent user's view and audio processing.
※ DRM Manager Digital Rights Management Module
Responsible for packaging content, generate application license, limit the forwarding of terminal content, and multiple playbacks.
※ Service Publisher Service Release
The business release window is a business release portal for CSP.
※ SP agent
Realize the real-time transmission of the SP stream media program source, and support the billing information of the streaming content to the SP to settle the SP and operators.
2, system characteristics
※ Video, audio, animation, still picture integrated mobile multimedia platform;
※ Compliance with MPEG-4 technical standards;
※ Variable dynamic rate control, from 9.6kbps-384 kbps;
※ The encoding can apply multiple bandwidths at once;
※ Support circuit exchange and package switching network;
※ Media flow mode and download mode are coexist;
※ With a powerful error correction function, special optimization for the mobile environment (10-3 BER);
※ Supports a variety of mobile networks: CDMA, GPRS, CDMA 1x, WCDMA, etc.
V. Main applications of mobile streaming media
Mobile Music, MP3
Operators Joint Record Company released a POP Music list every week. After listening to the songs, you can download to your mobile phone through a small payment, which is equivalent to the operator's record store. This business requires a mobile phone to have an MP3 function.
Mobile TV
The user watches the TV program via the mobile phone to make entertainment experience, which is equivalent to operators to open a TV station. In order to ensure the effect of viewing, the bandwidth must be guaranteed to 100kbps. Taking into account the limited nature of the air bandwidth and the huge number of users, it is recommended that the operator uses a broadcast method without using a VOD method. TV shows can be selected as news, cartoon, humorous movies, MTV, classic pieces, movie trailers, TV programs, wonderful pieces, etc. to meet most users, while ensuring the low cost of the program.
Infotainment on Demand
News, sports, fashion consumption information, idol information, etc.
Live live
Large events of sports events, concerts, conferences, can also be used in places that need to be monitored in traffic, families.
Video advertisement
Advertising, movie advertising, tourism advertising, etc. can be formed through a variety of media (video, images, text).
Video short film
Funny short film, tourist attractions, advertising, corporate image promotion, etc.
Various integration business forms
Fusion streaming media and MMS, forward some video clips through MMS between users; integrated streaming media and location services, traffic conditions, road guidelines, etc., to the user in the form of streaming media.
