CN104661111A - Method and device for transmitting I-frame analysis method uplink multicast data - Google Patents
Method and device for transmitting I-frame analysis method uplink multicast data Download PDFInfo
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Abstract
The invention discloses a method and a device for transmitting I-frame analysis method uplink multicast data. Before transmitting the data, a specified frame synchronization code element sequence has to be added at the beginning of each frame; after a receiving end detects a mark of the sequence, the beginning of the frame is determined, the synchronization of both parties is established; the receiving end DCE extracts a bit timing signal from the received sequence so as to achieve the synchronization of bits (code elements). According to the invention, the synchronous transmission needs no beginning signal and ending signal, the transmission efficiency is high, and the method and device are suitable for the transmission of data above 2,400 bit/s, but the technology is complex.
Description
Method and the device of the transmission of a kind of I frame of the present invention analytic method uplink multicast data belong to electronic information field.
Multicast (Multicast) transmits: between sender and each recipient, realize point-to-point configuration connect.
If a sender transmits identical data to multiple recipients simultaneously, also only a identical data packet need be copied.
Which increase data-transmission efficiency.
Decrease backbone network and occur congested possibility.
I frame (I frame) is also called Intra pictures (intra picture), a kind of video compression technology that the normally each GOP(MPEG of I frame uses) first frame, through moderately compressing, as the reference point of random access, can resemble as one.
In the process of mpeg encoded, partial video frame sequence is collapsed into I frame; Partial shrinkage becomes P frame; Partial shrinkage is also had to become B frame.
I frame method is frame data compression method, also referred to as " key frame " compression method.
I frame method is the compress technique based on discrete cosine transform (Discrete Cosine Transform), this algorithm and JPEG compression algorithm similar.
The compression of employing I frame can reach the compression ratio of 1/6 and nothing significantly compresses vestige.
Transfer of data (data transmission) is exactly according to suitable code, through one or more link, transmits the process of data between data source and data sink.
Also the operation by the signal on channel, data being sent to another place from is represented.
(1) definition and application
Transfer of data (data transmission) is exactly according to suitable code, through one or more link, transmits the process of data between data source and data sink.
Also the operation by the signal on channel, data being sent to another place from is represented.
Transfer of data can realize the transmission of telefile and multimedia messages easily.
A kind of communication mode.
The communication mode of " one to one group " between main frame, the main frame namely adding same group can receive all data in this group, and the switch in network and router are only to having demander to copy and forwarding its desired data.
Main frame can add to router solicitation or exit certain group, and the router in network and switch selectively copy and transmit data, namely only data in group is transferred to those main frames adding group.
Once can transfer data to multiple main frame having needs (adding group) like this, can ensure again not affect other other communications not needing the main frame of (not adding group).
Multicast application in a network:
In multicast mode, the sender of information is called " multicast source ", and information receiver is called " multicast group " of this information, supports that the all-router of multicast information transmission is called " multicast router ".International Telecommunication Union's Radiocommunications is also reached common understanding, and mobile communication system will be combined with other system, is that data transmission rate reaches 100Mbps before 2010.For more senior 3G system, ITU determines two standards simultaneously developing IMT-2000---improving the transmission rate of packet and audio files---by the WCDMA of Japanese NTT DoCoMo and J-Phone two company employing by the maximum downloading rate reaching 8Mbps of energy, and CDMA2000 system also will reach the speed of 2.4Mbps.Simultaneously externally the issue a statement frequency range of forth generation mobile communication of ITU not yet comes into question and formulation, but will be based on high band frequency spectrum in principle, also will use the relevant technology of microwave and frequency range in addition.
Forth generation mobile communication system should possess following several fundamental characteristics:
(1) service in complete set: every business such as personal communication, information system, broadcast and amusement will be combined into an entirety, and being supplied to user serves widely than ever and apply; The use of system will be more safe, convenient and more look after the individual character of user.
(2) immanent mobile access: in a 4 g system, the main access way that mobile access will be to provide the business such as speech, high speed information business, broadcast and amusement, people can be linked in system at any time, everywhere.
(3) subscriber equipment miscellaneous: mobile device miscellaneous for use is linked into 4G system by user.Exchanging between equipment with people is no longer only simply listen, say, see, can also be exchanged by other approach with user.This will be large easy for people to use, the particularly use of some disabled user.
(4) autonomous network configuration: the network of 4G system will be a Complete autonomy, adaptive network, and it can manage automatically, dynamically change the structure of oneself to meet the requirement of system change and development.
Access way is according to different applied environments, and the topological structure that WLAN (wireless local area network) adopts mainly contains four kinds, bridge connecting-type, access node connecting-type, HUB access type and non-stop layer type.
1, bridge connecting-type.This structure is mainly used in the interconnection between wireless or cable LAN.When two local area network (LAN)s cannot realize wired connection or use wired connection to have difficulties, bridge connecting-type can be used to realize point-to-point connection.Communication in such an embodiment between local area network (LAN) is realized by respective wireless bridge, and wireless bridge serves the effect of network path selection and protocol conversion.
2, access node connecting-type.This structure adopts mobile cellular communication net access way, communication between each mobile site is first got off by receives information by wireless receiving station (access node: AP) nearby, then the information received is passed to " mobile switching centre " by wired network, then is sent on all wireless receiving stations by mobile switching centre.At this moment in network coverage, this signal can be received Anywhere, and can roaming communication be realized.
3, HUB access type.In cable LAN, utilize HUB can set up Star Network structure.Wireless aps equally also can be utilized to set up the WLAN (wireless local area network) of hub-and-spoke configuration, and its working method is very similar with wired hub-and-spoke configuration.But General Requirements wireless aps should have function of exchange in simple net in a wireless local area network.
4, non-stop layer type structure.The operation principle of this structure is similar to the working method of wired peer-to-peer network.It requires all directly to carry out information exchange between any two websites in net.Namely each website is work station, is also server.
Networking products radio network product.
Wireless
1, versatility--the single platform of multiple Presence Protocol and application can be supported simultaneously;
The system of 2, simplification--easy to understand, operation and maintenance;
3, validity--save the extendible network of frequency spectrum and power.
Above key characteristic brings following advantage:
Total ownership cost can drop to minimum by the single wireless facility 1, being applied to whole factory;
2, connect multinomial mounted industrial protocol (as HART, OPC, Modbus etc.) simultaneously;
3, with existing industrial safety Realization of Product Seamless integration-;
4, the most reliable network--the longest uptime can be provided through on-site verification;
5, current the most scalable factory wireless system.
WLAN
WLAN communication system is selected generally to be used in same seat building as the another kind beyond wired lan.WLAN uses ISM (Industrial, Scientific, Medical) radio broadcasting band communication.The 802.11a standard of WLAN uses 5 GHz frequency ranges, and the maximal rate of support is 54 Mbps, and 802.11b and 802.11g standard uses 2.4 GHz frequency ranges, supports the speed of maximum 11 Mbps and 54 Mbps respectively.
WLAN is similar to wired ethernet, and they are all distribute MAC (Media Access Control) address from same address pool, and are all the network equipment layers appearing at operating system as ethernet device.Such as, ARP (Address Resolution Protocol) table is filled with WLAN MAC address and ethernet mac address.But WLAN and wired ethernet make a big difference at link layer.Such as, 802.11 standards use conflict avoidance (CSMA/CA) to replace the collision detection (CSMA/CD) of wired ethernet.And, with ethernet frame unlike, WLAN frame is identified.
Due to the smeared out boundary between WLAN work station, WLAN link layer has the agreement removing a region before transmission.For security consideration, Wired Equivalent Privacy (WEP) encryption mechanism of WLAN provides the level of security identical with cable network.40 bits or 104 bit keys and 24 random bit initial vectors combine in order to encryption and decryption data by WEP.WLAN supports two kinds of communication patterns: Ad Hoc pattern is used for need not using between small group work station the interior communication of the short time of accessing points, and all communications of Infrastructure pattern must pass through accessing points.Accessing points periodically broadcasts a service set identifier (SSID), and SSID is used for a wlan network and other networks to distinguish to come.
Most of available WLAN card is based on Intersil Prism or Lucent Hermes chipset.Compaq, Nokia, Linksys and D-Link card uses Prism chipset, and Lucent Orinoco card and Apple Airport use Hermes chipset.
Linux WLAN supports to be realized becoming with WLAN set of device drivers by WLAN API.There is the WLAN API that two Linux project definitions are general, and provide instrument by user space application configuration parameter and the information of access from WLAN device driver.Wireless Extensions project provides public Linux user's space interface for different wireless network cards.The instrument of this project comprises iwconfig in order to configuration parameter (the WEP keyword in such as WLAN driver and SSID).Linux-wlan project, as a Wireless Extensions project part, is also supported a series of for from user's space and the mutual instrument of WLAN device driver.Different from the instrument based on Wireless Extensions, these instruments use the grammer being similar to SNMP (Simple Network Management Protocol) MIB (Management Information Base), this grammer reflection IEEE 802.11 specification.Continue device driver is discussed, support that the Linux device driver package of popular WLAN card is drawn together:
Orinoco WLAN driver: the part being linux kernel source code, supports based on the card of Hermes and the card based on Intersil Prism.Orinoco_cs module provides the service support of PCMCIA and CF card necessary PCMCIA card.
The linux-wlan-ng driver of linux-wlan project: support the multiple card based on Prism chipset.This driver supports linux-wlan API and part supports Wireless Extensions.
Host AP device driver: the AP pattern supporting Prism chipset, can make WLAN main frame play accessing points.
Linux Symbol Spectrum device driver: support Symbol PCMCIA card.Be different from PCMCIA card, Symbol CF card lacks plate and carries firmware, and it relies on device driver to carry out download firmware.An independent version of this driver is applicable to CF card.Symbol PCMCIA card is repacked as Intel PRO/Wireless card by Intel, and Symbol CF card has been repacked in Socket communication.
Atmel USB WLAN driver: utilize Atmel chipset to support much USB WLAN equipment.
The recipient member adding same multicast group can extensively distribute in a network Anywhere, and namely " multicast group " does not have region to limit.
It should be noted that multicast source not necessarily belongs to multicast group, it sends data to multicast group, and oneself is recipient not necessarily.
Multiple multicast source can send message to a multicast group simultaneously, and frame is the base unit of a kind of picture of composition video.
Key frame is also I frame, and it is the important frame in interframe compression coding; It is the coded frame of a full frame compression; Only use the data of I frame with regard to restructural complete a kind of picture during decoding; I frame does not need with reference to other pictures and generates.
Video file is made up of a kind of sheet of multiple continuous print.
In video conferencing system, terminal sends to MCU(or MCU to send to terminal) one picture, be not each all a kind of for complete width width sheet is sent to far-end, and just send the part that a rear width picture changes on last width field basis.
If when network condition is bad, the reception far-end of terminal or send to long-range picture just to have packet loss and there is a kind of picture flower screen, phenomenon that a kind of picture card pauses, if do not have I frame mechanism again send out the new complete one picture of a width to local (or the new complete one picture of a width is sent out again to far-end in this locality) to allow far-end in this case, flower screen, the Caton phenomenon of a kind of picture of output of terminal can be more and more serious, thus cause meeting normally to carry out.
In video pictures playing process, if I LOF, then P frame below also just along with solution not out, just there will be the phenomenon of video pictures blank screen; If P LOF, then video pictures there will be the phenomenons such as flower screen, mosaic.
Occur in the bandwidth that I frame only can limit in meeting in video conferencing system, meeting bandwidth can not be surmounted and come into force.
I frame mechanism does not exist only in MCU, exists in television wall server, recorded broadcast server yet.
Exactly in order to solve when network condition is bad, the packet loss of appearance and cause as a kind of picture flower screen, card, and impact can parliament normally be carried out.
IP multicast (also claim multi-address broadcast or multicast) technology is that a kind of one or more main frame (multicast source) that allows sends the TCP/IP network technology of single packet to multiple host (while of once).
Multicast, as the communication of point to multi--point, is one of effective ways saving the network bandwidth.
In the application of network audio/video broadcasting, when needing the signal of a node to be sent to multiple node, being no matter adopt to repeat point-to-point communication mode, or adopting broadcast mode, all can the serious waste network bandwidth, only have multicast to be only best selection.
Multicast can make one or more multicast source only Packet Generation to specific multicast group, and the main frame only adding this multicast group just can receive packet.
At present, IP multicasting technology is widely used in the aspects such as network audio/video broadcasting, AOD/VOD, the network teleconference, multimedia remote education, " push " technology (as stock market etc.) and reality-virtualizing game.
IP cast communication must depend on IP multicast address, and in IPv4, it is a Class D IP address, and scope from 224.0.0.0 to 239.255.255.255, and is divided into local link multicast address, reserved multicast address and administration authority multicast address three class.
Wherein, local link multicast address range is at 224.0.0.0 ~ 224.0.0.255, and this is the address for Routing Protocol and other purposes retain, and router does not forward the IP bag belonging to this scope; Reserved multicast address is 224.0.1.0 ~ 238.255.255.255, can be used for global range (as Internet) or procotol.
Administration authority multicast address 239.0.0.0 ~ 239.255.255.255, for organization internal, can be similar to private IP address, can not be used for Internet, can limit multicast scope.
The All hosts of same IP multicast address receive multicast packet is used to constitute a host groups, also referred to as multicast group.
The member of a multicast group changes at any time, and a main frame can add at any time or leave multicast group, the number of multicast member and the geographical position at place also unrestricted, a main frame also can belong to several multicast group.
In addition, the main frame not belonging to some multicast group also can send packet to this multicast group.
In order to transmit multicast packet to all Receiving Hosts, with multicast distributed tree, the path that IP multicast transmits in a network is described.Multicast distributed tree has two fundamental types: active tree and shared tree.
Active tree is the root using multicast source as active tree, and the branch of active tree forms the distribution tree being arrived Receiving Host by network, because active tree runs through network with the shortest path, so be also often called shortest path tree (SPT).
The common root as shared tree of shared tree in multicast network in some selectable Multicast Routing, this velamen is called point (RP).
Shared tree can be divided into unidirectional shared tree and bidirectional sharing tree again.Unidirectional shared tree refers to that multicast traffic stream has to pass through shared tree and is sent to multicast receiver from root.
Bidirectional sharing tree refers to that multicast traffic stream can without shared tree.
Inverse path forwards the basis that (RPF) is transmitting multicast data process in multicast routing protocol, its working mechanism is when multicast information is by active tree, the multicast source address of the multicast packet that multicast router inspection arrives, with determine this multicast packet the interface of process whether in active branch, if, then rpf check success, multicast packet is forwarded; If rpf check failure, then abandon this multicast packet.
With being interconnected, Internet multicast trunk (MBONE) network supports that the router of IP multicast forms by a series of interconnective sub network host computer.
It can regard the virtual net of a framework on Internet physical network upper strata as, in this virtual net, the multicast information stream that multicast source sends can directly transmit between the groups of routers supporting IP multicast, and will be transmitted by point-to-point tunneling technology between multicast router group and non-multicast groups of routers.
Along with the fast development of Global Internet (Internet), number of netizens just increases fast with geometric progression, the ratio of the data communication of taking as the leading factor with technique of internet in communication service total amount arranges rapid rising, the field that internet service has become with the fastest developing speed in multimedia communication industry, competition is the fiercest.
Internet network transmission and the significantly raising of disposal ability, make web-based applications business get more and more, and particularly the development of video and audio compress technology and maturation, make online video and audio business become one of most important business in Internet.
The video and audio business such as video request program (VOD), video telephone, video conference realized on internet is compared with general business, has the features such as data volume is large, delay sensitive is strong, the duration is long.
Therefore adopt the minimum time, minimum space transmits and solve the problem that network utilization is high, transmission speed is fast, real-time required by video and audio business, will adopt and be different from traditional unicast, the retransmission technique of broadcast mechanism and QoS service pledge system and realize, and in the process that IP multicasting technology is the key technology that addresses these problems to be developed in Internet network, multicast is Geju City concept instead of new ideas.
But it due to a variety of causes development slower.
The concept of IP multicast appeared at the earliest in 1988
steve Deeringthesis for the doctorate in, in 1989
stevedeering expands standard IP network layer protocol, proposes IP multicast specification; First time in March, 1992 sets up Multicast backbone MBone, and IETF has also successfully held a meeting in multicast network, just causes the extensive concern of people.
And first WWW browser appears at nineteen ninety, 100 WWW websites have been developed into by 1993, so though multicast and WWW are in contemporaneity, but the development of multicast is much more slowly than WWW, main cause is the router that IP multicast communication mode needs suitable state and complexity, require that router can provide the information state in each group and each source, and bring difficulty to the further development of multicast along with becoming increasingly complex of Internet network.
Afterwards, occurred the multicast routing protocol (as PIM-DM, PIM-SM) of some deft designs, and multicast IP had been wrapped and correctly and promptly can send to thousands of recipient, the technology of IP multicast and application start fast-developing.
At present, IP multicast may operate on the network of any configuration, comprise internet, ATM, frame relay, SMDS and satellite, relate to many fields of network, video can be applied in and teleconference, multimedia kind, news briefing and those remote lives from space are broadcasted.
Multicasting technology is one of IP network transfer of data three kinds of modes, before introducing IP multicasting technology, first does one to the clean culture of IP network transfer of data, multicast and broadcast mode and simply introduces
Clean culture (Unicast) is transmitted: between sender and each recipient, realize point to point network connect.
If a sender transmits identical data to multiple recipients simultaneously, the identical data packet of many parts also must be copied accordingly.
If when having a large amount of main frame to wish the same portion copy obtaining packet, overburden, postpone long, network congestion will to cause sender; For ensureing that certain service quality need increase hardware and bandwidth.
Multicast (Multicast) transmits: between sender and each recipient, realize point-to-point configuration connect.
If a sender transmits identical data to multiple recipients simultaneously, also only a identical data packet need be copied.
Which increase data-transmission efficiency.
Decrease backbone network and occur congested possibility.
Broadcast (Broadcast) transmission: refer to broadcast data packet in IP subnet, all main frames in subnet inside all will receive these packets.
Broadcast means that network delivers a packet to each main frame of subnet, no matter whether these main frames are happy to receive this packet.
So the scope of application of broadcast is very little, only effective in local subnet, control broadcasting transmitting by router and the network equipment.
Multicast solves clean culture and the inefficient problem of broadcast mode.
When certain user's demand customizing messages in network, multicast source (i.e. multicast information sender) only sends primary information, multicast router is that multicast packet sets up tree-shaped route by multicast routing protocol, and the information be passed just starts to copy and distribute in fork on the road far away as far as possible.
Baseband transmission refers to that the signal of telecommunication of binary one or " 0 " sent by data terminal equipment (DTE) directly delivers to the transmission means of circuit.
Baseband signal non-modulated, directly can transmit after code fractal transform (or waveform transformation) carries out driving.
The feature of baseband signal is containing direct current, low frequency and high fdrequency component in frequency spectrum, and along with frequency raises, the corresponding reduction of its amplitude, finally goes to zero.
Baseband transmission is multiplex in short-range transfer of data, as being the transfer of data of medium with twisted-pair feeder or coaxial cable in the data communication of short range intercomputer or local area network (LAN).
Most of transmission channel is bandpass-type characteristic, and baseband signal can't pass.
Adopt modulator approach to transmit within the scope of modulates baseband signals to channel width, receiving terminal restores out the mode of baseband signal by demodulation method, is called frequency band transmission.
This mode can realize remote data communication, such as, utilize telephone network can realize the data communication of the whole nation or global range.
Digital data transfer is a kind of mode utilizing digital speech path transmission of data signals.
Utilize PCM(pulse code modulation) digital telephone path, each speech channel can transmit the data-signal of 64kbit/s, and do not need modulation, efficiency is high, and transmission quality is good, is the good a kind of transmission means of data communication.
Parallel transmission is the mode that the binary code forming character transmits on a parallel channel simultaneously.
8 Unit code characters, 8 channel parallel transmit simultaneously, and once can pass a character, sending and receiving both sides do not exist character synchronization problem, and speed is fast, but channel is many, investment large, seldom adopts in transfer of data.
Be unsuitable for the communication doing longer distance, be usually used in computer-internal or the communication of equipment room in same system.
Serial transmission be form the binary code of character on a channel with position (code element) for unit, the mode transmitted by turn in chronological order.
Step-by-step sends, and receives by turn, also wants acknowledge character simultaneously, so will take synchronisation measures.Though speed is slow, only needs a transmission channel, invest little, be easy to realize, being the prevailing transmission mode that transfer of data adopts, is also a kind of major way that compunication is taked.
Asynchronous transmission is the mode of character synchronization transmission, synchronous also known as start-stop type.
When a transmission character code, will add " a rising " signal before character, length is that 1 code element is wide, and polarity is " 0 ", i.e. spacing polarity; And add " a stopping " signal distributing after a character, when length is 1,1.5(international No. 2 codes with) or 2 code elements wide, polarity is " 1 ", i.e. mark polarity.Receiving terminal by detecting, stop signal, transmitted character can be distinguished.
Character can send continuously, also can send separately, when not sending character, sends stop signal continuously.
Each character initial time can be arbitrary, and in a character, Baud Length is equal, and receiving terminal detects the beginning of a fresh character to the saltus step (" 1 " " 0 ") of signal by stop signal.
Which is simple, and sending and receiving both sides clock signal does not need precise synchronization.Shortcoming be increase, stop signal, efficiency is low, is used in slow data transmission.
Synchronous transmission is position (code element) Synchronous Transfer Mode.
Which must set up accurate bit timing signal sending and receiving both sides, distinguishes the bits per inch number of it is believed that so that correct.
In the transmission, data will be divided in groups (or claiming frame), and a frame is containing multiple character code or multiple independent code element.
Before transmission data, start the frame swynchronization code metasequence that must add regulation, after receiving terminal detects this sequence flag, determine the beginning of frame at every frame, it is synchronous to set up both sides.
Receiving terminal DCE extracts bit timing signal from receiving sequence, thus it is synchronous to reach position (code element).
Synchronous transmission has not added, stop signal, and efficiency of transmission is high, be used in 2 400 more than bit/s transfer of data, but Technical comparing is complicated.
Single work transmission index is according to sending by single direction and receive; Half-duplex transmission index is according to can transmit in both direction but can not carry out, be i.e. alternately sending and receiving simultaneously; Full duplex transmission index, according to can transmit in both direction simultaneously, is namely received simultaneously and sends out.
General four-wire circuit is full-duplex data transmission, and two-wire line can realize full-duplex data transmission.
Claims (8)
1. a kind of I frame of the present invention analytic method uplink multicast data transmission method and device be also called Intra pictures (intra picture), a kind of video compression technology that the normally each GOP(MPEG of I frame uses) first frame, through moderately compressing, as the reference point of random access, can as image;
In the process of mpeg encoded, partial video frame sequence is collapsed into I frame; Partial shrinkage becomes P frame; Partial shrinkage is also had to become B frame;
I frame method is frame data compression method, also referred to as " key frame " compression method;
Method and the device of the transmission of a kind of I frame of the present invention analytic method uplink multicast data are compress techniques based on discrete cosine transform (Discrete Cosine Transform), this algorithm and JPEG compression algorithm similar;
The compression of employing I frame can reach the compression ratio of 1/6 and nothing significantly compresses vestige;
Transfer of data (data transmission) is exactly according to suitable code, through one or more link, transmits the process of data between data source and data sink;
Also the operation by the signal on channel, data being sent to another place from is represented;
The communication mode of " one to one group " between the method for a kind of I frame of the present invention analytic method uplink multicast data transmission and device main frame, the main frame namely adding same group can receive all data in this group, and the switch in network and router are only to having demander to copy and forwarding its desired data;
Main frame can add to router solicitation or exit certain group, and the router in network and switch selectively copy and transmit data, namely only data in group is transferred to those main frames adding group;
Once can transfer data to multiple main frame having needs (adding group) like this, can ensure again not affect other other communications not needing the main frame of (not adding group);
Multicast application in a network:
In multicast mode, the sender of information is called " multicast source ", and information receiver is called " multicast group " of this information, supports that the all-router of multicast information transmission is called " multicast router ";
The recipient member adding same multicast group can extensively distribute in a network Anywhere, and namely " multicast group " does not have region to limit;
It should be noted that multicast source not necessarily belongs to multicast group, it sends data to multicast group, and oneself is recipient not necessarily;
Multiple multicast source can send message to a multicast group simultaneously, and frame is the base unit of composition video image;
Method and the device key frame of the transmission of a kind of I frame of the present invention analytic method uplink multicast data are also I frame, and it is the important frame in interframe compression coding; It is the coded frame of a full frame compression; Only use the data of I frame with regard to restructural complete image during decoding; I frame does not need with reference to other pictures and generates;
Video file is made up of multiple continuous print picture;
In video conferencing system, terminal sends to MCU(or MCU to send to terminal) image, be not all a complete width width picture is sent to far-end at every turn, and just send the part that a rear width picture changes on last width field basis;
If when network condition is bad, the reception far-end of terminal or send to long-range picture just to have packet loss and there is image flower screen, phenomenon that image card pauses, if do not have I frame mechanism again send out the new complete image of a width to local (or the new complete image of a width is sent out again to far-end in this locality) to allow far-end in this case, flower screen, the Caton phenomenon of the output image of terminal can be more and more serious, thus cause meeting normally to carry out;
In video pictures playing process, if I LOF, then P frame below also just along with solution not out, just there will be the phenomenon of video pictures blank screen; If P LOF, then video pictures there will be the phenomenons such as flower screen, mosaic;
Occur in the bandwidth that I frame only can limit in meeting in video conferencing system, meeting bandwidth can not be surmounted and come into force;
I frame mechanism does not exist only in MCU, exists in television wall server, recorded broadcast server yet;
Exactly in order to solve when network condition is bad, the packet loss of appearance and cause as image flower screen, card, and impact can parliament normally be carried out;
IP multicast (also claim multi-address broadcast or multicast) technology is that a kind of one or more main frame (multicast source) that allows sends the TCP/IP network technology of single packet to multiple host (while of once);
Multicast, as the communication of point to multi--point, is one of effective ways saving the network bandwidth;
In the application of network audio/video broadcasting, when needing the signal of a node to be sent to multiple node, being no matter adopt to repeat point-to-point communication mode, or adopting broadcast mode, all can the serious waste network bandwidth, only have multicast to be only best selection;
Multicast can make one or more multicast source only Packet Generation to specific multicast group, and the main frame only adding this multicast group just can receive packet;
Method and the device of the transmission of a kind of I frame of the present invention analytic method uplink multicast data must depend on IP multicast address, in IPv4, it is a Class D IP address, scope from 224.0.0.0 to 239.255.255.255, and is divided into local link multicast address, reserved multicast address and administration authority multicast address three class;
Wherein, local link multicast address range is at 224.0.0.0 ~ 224.0.0.255, and this is the address for Routing Protocol and other purposes retain, and router does not forward the IP bag belonging to this scope; Reserved multicast address is 224.0.1.0 ~ 238.255.255.255, can be used for global range (as Internet) or procotol;
Administration authority multicast address 239.0.0.0 ~ 239.255.255.255, for organization internal, can be similar to private IP address, can not be used for Internet, can limit multicast scope;
The All hosts of same IP multicast address receive multicast packet is used to constitute a host groups, also referred to as multicast group;
The member of a multicast group changes at any time, and a main frame can add at any time or leave multicast group, the number of multicast member and the geographical position at place also unrestricted, a main frame also can belong to several multicast group;
In addition, the main frame not belonging to some multicast group also can send packet to this multicast group;
In order to transmit multicast packet to all Receiving Hosts, with multicast distributed tree, the path that IP multicast transmits in a network is described; Multicast distributed tree has two fundamental types: active tree and shared tree;
Active tree is the root using multicast source as active tree, and the branch of active tree forms the distribution tree being arrived Receiving Host by network, because active tree runs through network with the shortest path, so be also often called shortest path tree (SPT);
The common root as shared tree of shared tree in multicast network in some selectable Multicast Routing, this velamen is called point (RP);
Shared tree can be divided into unidirectional shared tree and bidirectional sharing tree again; Unidirectional shared tree refers to that multicast traffic stream has to pass through shared tree and is sent to multicast receiver from root;
Bidirectional sharing tree refers to that multicast traffic stream can without shared tree;
Inverse path forwards the basis that (RPF) is transmitting multicast data process in multicast routing protocol, its working mechanism is when multicast information is by active tree, the multicast source address of the multicast packet that multicast router inspection arrives, with determine this multicast packet the interface of process whether in active branch, if, then rpf check success, multicast packet is forwarded; If rpf check failure, then abandon this multicast packet.
2. with being interconnected, Internet multicast trunk (MBONE) network supports that the router of IP multicast forms by a series of interconnective sub network host computer;
It can regard the virtual net of a framework on Internet physical network upper strata as, in this virtual net, the multicast information stream that multicast source sends can directly transmit between the groups of routers supporting IP multicast, and will be transmitted by point-to-point tunneling technology between multicast router group and non-multicast groups of routers;
Along with the fast development of Global Internet (Internet), number of netizens just increases fast with geometric progression, the ratio of the data communication of taking as the leading factor with technique of internet in communication service total amount arranges rapid rising, the field that internet service has become with the fastest developing speed in multimedia communication industry, competition is the fiercest;
On the method for a kind of I frame of the present invention analytic method uplink multicast data transmission and device, the video and audio business such as video request program (VOD), video telephone, video conference that realizes is compared with general business, has the features such as data volume is large, delay sensitive is strong, the duration is long;
Therefore adopt the minimum time, minimum space transmits and solve the problem that network utilization is high, transmission speed is fast, real-time required by video and audio business, will adopt and be different from traditional unicast, the retransmission technique of broadcast mechanism and QoS service pledge system and realize.
The concept of 3.IP multicast appeared at the earliest in 1988
steve Deeringthesis for the doctorate in, in 1989
stevedeering expands standard IP network layer protocol, proposes IP multicast specification; First time in March, 1992 sets up Multicast backbone MBone, and IETF has also successfully held a meeting in multicast network, just causes the extensive concern of people;
And first WWW browser appears at nineteen ninety, 100 WWW websites have been developed into by 1993, so though multicast and WWW are in contemporaneity, but the development of multicast is much more slowly than WWW, main cause is the router that IP multicast communication mode needs suitable state and complexity, require that router can provide the information state in each group and each source, and bring difficulty to the further development of multicast along with becoming increasingly complex of Internet network;
Afterwards, occurred the multicast routing protocol (as PIM-DM, PIM-SM) of some deft designs, and multicast IP had been wrapped and correctly and promptly can send to thousands of recipient, the technology of IP multicast and application start fast-developing;
At present, IP multicast may operate on the network of any configuration, comprise internet, ATM, frame relay, SMDS and satellite, relate to many fields of network, video can be applied in and teleconference, multimedia kind, news briefing and those remote lives from space are broadcasted;
Multicasting technology is one of IP network transfer of data three kinds of modes, before introducing IP multicasting technology, first does one to the clean culture of IP network transfer of data, multicast and broadcast mode and simply introduces
Clean culture (Unicast) is transmitted: between sender and each recipient, realize point to point network connect;
If a sender transmits identical data to multiple recipients simultaneously, the identical data packet of many parts also must be copied accordingly;
If when having a large amount of main frame to wish the same portion copy obtaining packet, overburden, postpone long, network congestion will to cause sender; For ensureing that certain service quality need increase hardware and bandwidth;
Multicast (Multicast) transmits: between sender and each recipient, realize point-to-point configuration connect.
4., if a sender transmits identical data to multiple recipients simultaneously, also only need copy a identical data packet;
Which increase data-transmission efficiency;
Decrease backbone network and occur congested possibility;
Broadcast (Broadcast) transmission: refer to broadcast data packet in IP subnet, all main frames in subnet inside all will receive these packets;
Broadcast means that network delivers a packet to each main frame of subnet, no matter whether these main frames are happy to receive this packet;
So the scope of application of broadcast is very little, only effective in local subnet, control broadcasting transmitting by router and the network equipment;
Multicast solves clean culture and the inefficient problem of broadcast mode;
The method of a kind of I frame of the present invention analytic method uplink multicast data transmission and device are when certain user's demand customizing messages in network, multicast source (i.e. multicast information sender) only sends primary information, multicast router is that multicast packet sets up tree-shaped route by multicast routing protocol, and the information be passed just starts to copy and distribute in fork on the road far away as far as possible;
Baseband transmission refers to that the signal of telecommunication of binary one or " 0 " sent by data terminal equipment (DTE) directly delivers to the transmission means of circuit.
5. baseband signal non-modulated, directly can transmit after code fractal transform (or waveform transformation) carries out driving;
The feature of baseband signal is containing direct current, low frequency and high fdrequency component in frequency spectrum, and along with frequency raises, the corresponding reduction of its amplitude, finally goes to zero;
Baseband transmission is multiplex in short-range transfer of data, as being the transfer of data of medium with twisted-pair feeder or coaxial cable in the data communication of short range intercomputer or local area network (LAN);
Most of transmission channel is bandpass-type characteristic, and baseband signal can't pass;
Adopt modulator approach to transmit within the scope of modulates baseband signals to channel width, receiving terminal restores out the mode of baseband signal by demodulation method, is called frequency band transmission;
This mode can realize remote data communication, such as, utilize telephone network can realize the data communication of the whole nation or global range.
6. digital data transfer is a kind of mode utilizing digital speech path transmission of data signals;
Utilize PCM(pulse code modulation) digital telephone path, each speech channel can transmit the data-signal of 64kbit/s, and do not need modulation, efficiency is high, and transmission quality is good, is the good a kind of transmission means of data communication;
Parallel transmission is the mode that the binary code forming character transmits on a parallel channel simultaneously;
8 Unit code characters, 8 channel parallel transmit simultaneously, and once can pass a character, sending and receiving both sides do not exist character synchronization problem, and speed is fast, but channel is many, investment large, seldom adopts in transfer of data;
Be unsuitable for the communication doing longer distance, be usually used in computer-internal or the communication of equipment room in same system;
Serial transmission be form the binary code of character on a channel with position (code element) for unit, the mode transmitted by turn in chronological order;
Step-by-step sends, and receives by turn, also wants acknowledge character simultaneously, so will take synchronisation measures; Though speed is slow, only needs a transmission channel, invest little, be easy to realize, being the prevailing transmission mode that transfer of data adopts, is also a kind of major way that compunication is taked;
Asynchronous transmission is the mode of character synchronization transmission, synchronous also known as start-stop type;
Will add " a rising " signal before the method for a kind of I frame of the present invention analytic method uplink multicast data transmission and device character, length is that 1 code element is wide, and polarity is " 0 ", i.e. spacing polarity; And add " a stopping " signal distributing after a character, when length is 1,1.5(international No. 2 codes with) or 2 code elements wide, polarity is " 1 ", i.e. mark polarity; Receiving terminal by detecting, stop signal, transmitted character can be distinguished;
Character can send continuously, also can send separately, when not sending character, sends stop signal continuously.
7. each character initial time can be arbitrary, and in a character, Baud Length is equal, and receiving terminal detects the beginning of a fresh character to the saltus step (" 1 " " 0 ") of signal by stop signal;
Method and device which of the transmission of a kind of I frame of the present invention analytic method uplink multicast data are simple, and sending and receiving both sides clock signal does not need precise synchronization; Shortcoming be increase, stop signal, efficiency is low, is used in slow data transmission;
Synchronous transmission is position (code element) Synchronous Transfer Mode;
Which must set up accurate bit timing signal sending and receiving both sides, distinguishes the bits per inch number of it is believed that so that correct;
In the transmission, data will be divided in groups (or claiming frame), and a frame is containing multiple character code or multiple independent code element.
8. the method for a kind of I frame of the present invention analytic method uplink multicast data transmission and device are before transmission data, and start the frame swynchronization code metasequence that must add regulation at every frame, after receiving terminal detects this sequence flag, determine the beginning of frame, it is synchronous to set up both sides;
Receiving terminal DCE extracts bit timing signal from receiving sequence, thus it is synchronous to reach position (code element);
Synchronous transmission has not added, stop signal, and efficiency of transmission is high, be used in 2 400 more than bit/s transfer of data, but Technical comparing is complicated;
The method of a kind of I frame of the present invention analytic method uplink multicast data transmission and device list work transmission index are according to sending by single direction and receive; Half-duplex transmission index is according to can transmit in both direction but can not carry out, be i.e. alternately sending and receiving simultaneously; Full duplex transmission index, according to can transmit in both direction simultaneously, is namely received simultaneously and sends out;
General four-wire circuit is full-duplex data transmission, and two-wire line can realize full-duplex data transmission.
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| CN108632149A (en) * | 2017-03-20 | 2018-10-09 | 北京美讯泰科通信技术有限责任公司 | Satellite frame relay network method of multicasting and route device |
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| CN112235406A (en) * | 2020-10-15 | 2021-01-15 | 儒安物联科技集团有限公司 | Subnet equipment information synchronization method based on multicast and memory backup |
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