"1 What is IPTV?
IPTV, (Network Protocol TV, Internet Protocol Television), providing a variety of digital media services including TV programs through an Internet protocol.
1.1 The difference between simulation TV, digital TV, OTT and IPTV
Analog TV: After receiving an analog signal from the satellite, put these signals through the broadcast to the user television terminal, and the terminal selects different programs by selecting different frequencies.
Digital TV: The signal is received from the satellite, which is transmitted through the video compression and digitization, and then broadcasts through the QAM modulation to the user terminal. Digital TV and analog TV distinguishes are the ways of transmitting into numbers.
IPTV: The signal received from the satellite, after video compression, then the compressed message is fluidized, turn into IP packets, transferred to the user home through the IP network, so it can make full use of the IP network accessibility And the superiority of IP network transmission efficiency. Be
OTT TV is an abbreviation of "Over the Top TV" means a video service based on open internet, means that serving services above the network, emphasizing the independence of services and physical networks. Video program transmitted via the Internet.
Simply put, the difference between IPTV and OTT is:
1) IPTV uses an independent network, and OTT is superimposed on broadband online;
2) IPTV has QoS protection, and ott is none;
3) IPTV's radio and electricity supply program source, live TV live, and OTT is not.
1.2 IPTV definition and characteristics
All IPTV systems transmit video with IP networks, this is right, but in turn, the system with IP network transfer video is IPTV, that is wrong. Be
IPTV is to deliver traditional broadcast channels to consumers on an IP online to replace ground broadcasting, CATV and satellite services. Although all IP networks are used, it is different from Internet video to spread on public Internet, and IPTV services are almost transmitted through private networks.
From the terminal, the IPTV set-top box is needed, and he transforms the entry IPTV signal into a standard video signal to provide a TV display.
The main features of IPTV are:
Be
1) Continuous video stream: content with professional production (such as television broadcasting network);
2) Channels that do not stop, continuously broadcast;
3) Unified content form (all channel sharing a compression mode and using the same code rate)
4) Transfer in dedicated online;
5) Watch on the home TV through the set top box
2 IPTV industry chain
Up to now, the Radio, Film and Television General Administration has awarded seven Internet TV integration licenses, all of which are gateway, CCTV International CNTV (CCTV for application main body), Hangzhou Huaxia (Zhejiang, Hangzhou TV joint application), Shanghai Wen Guangbaiview (Shanghai TV station is the main body), the Southern Media (Guangdong TV station is the main body), Hunan TV Station, China International Radio Station, and Central People's Radio.
Main cooperation model:
IPTV business model:
• IPTV content carrier is responsible for content integration, providing licenses, self-content and other CP content
• Network operators are responsible for transferring content.
• Two operators cooperate to operate, and their income is divided into.
Therefore, IPTV is a telecommunications network, radio and television network, and Internet integration operations.
3 IPTV network architecture
3.1 IPTV System Deployment Architecture
The IPTV system architecture can be divided into content layer, business layer, carrier layer, and access layer.
• The content layer includes content organization, content production, content integration, content billing, DRM encryption, etc.
• The business layer is responsible for live broadcast, on-demand, look at, time shift, etc., responsible for content distribution, value-added business platform, operational support management, and business management.
• Carrying layer refers to the broadband backbone network of network operators, metropolitan area networks, broadband access networks.
• The access layer refers to a user access device, such as a set top box (STB).
CMS (Content Synthetic Management System) Architecture:
BMS (Business Management System) architecture:
CDN platform architecture:
EPG system architecture:
Terminal management platform:
EPG: Electronic Program Guide.
DRM: Digital copyright management. Content encryption prevents arbitrary distribution; preventing decryption from being arbitrarily replicated or modified; preventing content from being used any. The DRM flow chart is as follows:
3.2 IPTV Network Architecture
Typical network deployment architecture:
Network bearing model:
Flow load model:
3.3 IPTV business process
User Access Process:
Live process:
On-demand process:
4 IPTV basic technical principle
4.1 multicast
To understand multicast, you have to understand unicast and broadcasting.
Unicast
Each video stream in unicast is accurately sent to each receptor. If multiple receptors need the same video, the source will generate separate unicast streams for each user, then these independent streams The signal source flows through the IP network to each audience.
As shown in the figure, there is information sender Source, Usera and Userc present requirements, and the network is transmitted in unicast mode.
Send process:
• A unicast message, use a unicast address as the destination address. Source Send a separate unicast message to each Receiver address. N Receiver needs to send NDPPAP. As shown in the figure: Packets for Usera; Packets for Userc.
• The network establishes a separate data transfer path for each single broadcast. N The unicast page requires an independent transmission path. As shown in the figure: Source → Routerb → Routere → Routerd → Usera; Source → Routerb → Routere → Routerf → Userc.
Broadcast
The IP network also supports the function of broadcasting, where a single package is sent to each device of the LAN, and each device that receives the broadcast package must handle this package, if there is information of this device. But the broadcast package will not be used in the streaming, because even a small stream will fill all the local area networks, and the broadcast package generally does not cause the router to spread from a local area network to another LAN, which means that these conditions are flow Application is undesirable. In real IP multicast, these packages are only taken to particularly need to receive their devices.
As shown in the figure above, there is information sender Source, Usera, and Userc presenting information requirements, and the network uses broadcast mode to transmit information.
Send process: • A broadcast message uses a broadcast address as the destination address. Source is sent to the network broadcast address and only one message is sent. As shown in the figure: Packets for all the network.
• Packets are copied and transferred to each network segment, whether there is a need to ensure that the packet reaches all the routers and users in the network. As shown in the figure: UserBes do not need this message can also receive a copy.
Multicast
In multicast, a separate video stream is sent to multiple users, although the use of special protocols, the network is oriented to copy the video stream for each audience. This replication occurs inside the network instead of the source. Copy is performed on the network point required by the audience.
As shown in the figure, there is information sender Source, Usera, and Userc present requirements, the network is transmitted in multicast mode.
Send process:
• A multicast communication, use a multicast address as a destination address. Source Sends to a multicast address and transmits only a message. As shown in the figure: Packets for all the multicast group
• The multicast protocols deployed in the network create a tree route to this multicast, root connection source, and branch connect all multicast group members. As shown in the figure: Source → Routerb → Routere [→ Routerd → Usera | → Routerf → Userc].
▲ Unicast and data stream in the multicast environment
Multicast advantage
The advantage of multicast in the point-to-multipoint network is obvious: a single information stream is sent along the tree path to a group of users, and the same multicast data stream is only one on each link. Compared to unicast, using multicast mode delivery information, users' increase will not significantly increase the network load, alleviate the load of the server and CPU. Users who do not need this message cannot receive this data. Compared to broadcasting, multicast data is only transferred to a recipient, reducing redundant traffic, saving network bandwidth, reducing network load. Therefore, it is possible to say that multicast technology effectively solves the problem of single-point transmission multi-point reception, and implements high-efficiency data transfer in the IP network.
▲ Live business uses multicast and unicast comparison
If IPTV unicast traffic and user Internet traffic running on broadband network, the access terminal cannot realize QoS quality assurance, IPTV Carton, Internet speed is not up to standard, user use perception decline; the traffic of the metropolitan network OLT to CR It will become very large and easy to appear.
Summary: Multicast solves the unicast mode "package" in the source host, repeat "delivery" on the network, the defect of the extremely consumable server resources and network resources, and also solve the lack of lack of safety ( Only the addition of the group can be received), consumes a defect in the transmission link bandwidth.
Multicast Basic Concept
Multicast Group: The multicast group uses an IP multicast address identifier. Any user host (or other receiving device) adds a multicast group, which is a member, which can identify and receive an IP packet with the IP multicast address as the destination address. Such as: When you listen to the car radio, when the radio is in FM98.8, you have added a station group, then you receive this channel information.
Multicast Source: Source of sending IP packets is called a multicast source with the source of multicast group addresses. A multicast source can send data to multiple multicast groups simultaneously. Multiple multicast sources can send messages to a multicast The gathering point is the total root of two trees. Under normal circumstances, the full-network device is consistent for the RP address, otherwise the two trees cannot aggregate, resulting in the traffic sent by the source that cannot be reached.
4.2 streaming media
Streaming Media refers to a continuous time base medium such as audio, video, and other multimedia files using streaming technology in the network. Stream media technology generally refers to the video that continuous image and sound information is placed on the streaming media server after compression, so that the user can download, listen, without waiting for the entire compressed file to download to the machine, can watch the video / Audio transmission, codec technology. Streaming media technology is not a single technology, which is a technology established on many basic technologies. Key technologies for streaming media are streaming. The main technical feature of streaming media is to transmit streaming media content to the client through the network.
Streaming media basic network protocol:
• TCP, UDP (transport layer)
• IP protocol (Internet layer).
Streaming media transfer protocol:
• RTP, RTCP, RTP is real-time transport protocol, transmitted through UDP protocol, RTCP is a real-time transmission control protocol, and can be transmitted through TCP protocol, but also through the UDP protocol, but use different port numbers with RTP, separated.
RTP is a real-time transport protocol that provides end-to-end transport services to support single target broadcast and multi-target broadcast network services to transmit real-time data, and real-time data transmission is monitored and controlled by the RTCP protocol.
• RTSP, RTSP is a real-time flow protocol, or it is also a voice control protocol, supporting operational control like VCR, such as pause, fast forward, fast retreat. RTSP is also transmitted via UDP.
• RSVP, RSVP protocols are resource reserved protocols, which are protocols for transport layer ranges, which makes control bandwidth (reserved) requirements for routers along the route to ensure certain signal bandwidth stable requirements.
Network transmission characteristics of streaming media:
• High bandwidth and high compression ratio
• Low transmission delay
• Support multicast mode
• High reliability
• Channel synchronization, video stream, audio stream, and other data streams From different transmission channels to the terminal node via different routes, it is necessary to take a certain mechanism to achieve synchronization problems between heterogeneous data flow, referred to as channel synchronization problems.
4.3 Video Code
Since the videos of video data, uncompressed digital video data amounts for the network whether storing or transmission is pressure, the key issue of digital video is the compression technology of digital video, while video is formed by continuous image frames. Image sequence, due to the limitation of the scene conversion speed, there is a high correlation between adjacent frames, and thus the transform coding is combined with motion compensation techniques, and the main method of sequence image encoding is constituted.
H.264 video encoding:
H.264 is a new generation of digital video compression formats after MPEG4, and the main features of the International Standardization Organization (ISO) and International Telecommunications Union (ITU).
• The low yard ratio: compared with the compression technique such as MPEG2 and MPEG4 ASP, the amount of data compressed by H.264 is only 1/8 of MPEG2 1/8, and MPEG4 is 1/3. Be
• High quality images: H.264 provides continuous, smooth high quality images (DVD quality). Be
• The fault tolerance is strong: H.264 provides the necessary tools that address errors such as packet loss that occurs in unstable network environments.
• Network Adaptability: H.264 provides Network Abstract Layer, so that the File of H.264 can be easily transmitted on different networks.
The maximum advantage of H.264 is to have a high data compression ratio. Under the conditions of the same image quality, the compression ratio of H.264 is 2 times the MPEG-2, which is 1.5 to 2 times the MPEG-4. For example, if the size of the original file is 88GB, it is 3.5GB after compressing the MPEG-2 compression standard, and the compression ratio is 25: 1, and the compression ratio is compressed by the compression standard to 879MB, from 88GB to 879MB, The compression ratio of H.264 is an amazing 102: 1. Low bit rats play an important role in the high compression ratio of H.264, compared to compression technology such as MPEG-2 and MPEG-4 ASP, will greatly save users' download time And data traffic charges. It is particularly worth mentioning that H.264 also has a high quality image while having a high compression ratio, as in this way, after the H.264 compressed video data, less bandwidth required in the network transmission process, It is also more economical.
H.265 video encoding:
High Efficiency Video Coding, referred to as HEVC) is a video compression standard that is considered to be a successor of ITU-T H.264 / MPEG-4 AVC standard. 2004 began by ISO / IEC MOVING PICTURE Experts Group (MPEG) and ITU-T Video Coding Experts Group (VCEG) as ISO / IEC 23008-2 MPEG-H Part 2 or as ITU-T H.265 is started. The first edition of HEVC / H.265 video compression standard was accepted as a formal standard for the International Telecommunication Union (ITU-T) on April 13, 2013.
HEVC is considered not only to improve video quality, but also to reach the compression ratio of the H.264 / MPEG-4 AVC (equivalent to the same picture quality reduction to 50%), support 4K resolution or even a super HD TV. (UHDTV), the highest resolution can reach 8192 × 4320 (8K resolution).
4.4 Broadband
The bandwidth requirements required by the streaming media business in the various services of IPTV are high. Different program types, encoding methods, the demand for network bandwidth is different.
The resolution of the standard clearance is typically 720 × 480. The visual experience is comparable to the DVD. The currently commonly used standard clearance program encoding is MPGE-2 and H.264, and the corresponding bandwidth requirements are 3.75m and 2m, respectively;
The high-definition program is divided into two types of 720p and 1080i. The visual experience is higher than DVD, corresponding to the resolution of 1280 × 720 and 1920 × 1080, MPGE-2 encoding HD program requires 12m, H.264 encoding HD program. The bandwidth is 8m.
For 4K ultra HD IPTV, the physical resolution is 3840 × 2160, and H.265 encoding technology is used, with a bandwidth requirement of approximately 27m.
4.5 Set-top box (STB)
Set-top-box, convert the digital television signal to an analog TV signal.
Main features: Receive digital TV shows, with all broadcast, on-demand, and interactive multimedia application functions.
• Electronic Program Guide (EPG)
• Interactive App: Provide users with video on demand, multicast, and interactive games. Through the application of interactive function, people can make fast forward, rewind, pause like operational houses, and can quickly switch TV channels when multicasting. Through interactive features, people can also interact. Be
• Software online upgrade: Using the set top box intermediate plug-in to provide set top box capabilities, online installation and update set-top box applications. The set top box can identify the version number of the software, receive the software at version different, and update the software saved in the memory. Be
• Internet browsing and other features (VoIP, games, web, email ...)
IPTV set-top box key technologies include: video decoding and play, streaming technology, image, and graphics display technology, middleware technology, and embedded applications.
Set top box hardware architecture:
Set top box software architecture:
The set top box is turned on to enter the EPG interface to the following stages:
1) Network certification phase (0% -7%)
2) Loader top box firmware (7% -52%)
3) Analyze the domain name server (52% -61%)
4) IPTV business account certification (61% -83%)
5) Load EPG (83% -100%)
Therefore, it is possible to determine the cause of the failure according to the failure of the set-top box. For example, stop at 7% when booting, indicating that there may be problems with the network connection.
5 IPTV common faults and maintenance
5.1 live broadcast card, flower screen
1) All live channels, on demand programs
Solution: Check the network! Most of the access network issues, the other node observes whether there is the same carton, and the flower screen. Such fault area, time period, strong continuity, the same user may have problems for a while.
Typical case: Some users have serious carton, and after investigation: OLT uplink bandwidth utilization has reached 100%, and the BAS uplink bandwidth utilization is 80%, which needs to be expanded.
2) Individual live broadcast channel card, flower screen
Workaround: One is not enough network bandwidth, and user bandwidth is not enough to support users to watch some of the programs that are too high. This phenomenon is that as long as it is a high-definition channel or program card, ordinary very Smooth. The other one is a certain program or channel carton, a flower screen, which is likely to be a program source.
Typical case: CCTV1 HD channel will have a mosaic flower screen every 5 or 6 minutes, and when you look back, you will appear in the same position, and other channels have no phenomenon. After checking is a radio and electricity encoder failure.
5.2 Users cannot log in
1) New installation cannot be logged in
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Solution: Check the network and account, first check if the user's broadband can be accessed normally, then find the access account of the local value-added machine top box and whether the business account is normal.
Typical case: a city, many hotels in a city, can't get a TV, 8:00 to 9:30, open the set top box ITV connection schedule 7%, and the cause of the BAS has a super processing ability. Cutting some users on the board to another BAS, fault elimination.
2) Suddenly unlawful
Solution: Check the network, find the BOSS to check if the business account is owed.
5.3 live black screen
1) HD channel black screen
Solution: Insufficient bandwidth
2) Single channel black screen
Solution: Most of the live broadcast of the live broadcast program.
3) Both black screen
Workaround: If the same PON is in the mouth, change the cat. Replace the set top box, or contact your local live broadcast is normal.
5.4 Home Display and Image Show
Can log in normally, single user home page display and picture display is not full, mostly the set top box problem.
5.5 No image has sound, there is no sound
It may be faulty for the connection of the TV and set-top box.
5.6 Sounds and images are not synchronized
Obstacles may be: a piece source problem or a set top box fault.
Reprinted article HR OPT "group.
Multicast Router: The router that supports multicast function in the network is called "multicast router." Like the unicast router, the function of the multicast router is addressing and forwarding. The multicast router discovers and selects the route through the multicast routing protocol, and finally forms a multicast routing table, and the multicast data is forwarded.
Multicast Tree: Using multicast is "planting" and "maintenance" one or two trees. The most important thing to learn multicast is how these trees are formed, how to converge, how to change, how data is transmitted on the tree. As for a tree or two trees, the key depends on which multicast routing protocol used. The best embodiment of multicast tree on the multicast router is the multicast routing entry (*, g) and (s, g). Common in the multicast is the following two trees: source trees and shared trees.
IGMP: IGMP protocol is a language of multicast communication, corresponding to the OSI model, which is the third layer of multicast protocol, which is the Three-layer multicast protocol.
Multicast Routing Protocol: The multicast routing protocol is a multicast communication language between the multicast router. Like OSPF is the same as the unicast route protocol. The multicast routing protocol can be divided into IGP and EGP according to the range of ranges, which is also the same as the unicast routing protocol.
PIM: PIM is a broader multicast routing protocol, and the PIM (Protocol independent multicast is called the protocol independent multicast. What is the agreement? Simple understanding of PIM is "broughtist", PIM does not discover routing, but uses a route entry in the ready-made unicast routing table, regardless of which unicast routing protocol discovers and passes, This is the meaning of the agreement. PIM utilizes existing unicast routing information, performs RPF (Reverse Path Forwarding) checking for multicast, to create a multicast routing table, and build a group broadcasting tree. PIM does not maintain a special unicast route, nor does it rely on a specific unicast routing protocol, which directly uses the result of unicast routes.
PIM supports two types of multicast routing models: PIM-DM and PIM-SM. PIM-DM is called protocol independent multicast-intensive mode, suitable for smaller, multicast group members relatively densely dense LAN. PIM-SM is called a protocol independent multicast-sparse mode, and the group members suitable for networks are relatively sparse, distributed widely distributed large networks.
RP: RP (Rendezvous Point) is the source tree and shared trees in PIM SM
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