CN107277648B - A kind of video transmission method of subway train LCD screen - Google Patents
A kind of video transmission method of subway train LCD screen Download PDFInfo
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- CN107277648B CN107277648B CN201710105519.XA CN201710105519A CN107277648B CN 107277648 B CN107277648 B CN 107277648B CN 201710105519 A CN201710105519 A CN 201710105519A CN 107277648 B CN107277648 B CN 107277648B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
- H04N21/60—Network structure or processes for video distribution between server and client or between remote clients; Control signalling between clients, server and network components; Transmission of management data between server and client, e.g. sending from server to client commands for recording incoming content stream; Communication details between server and client
- H04N21/63—Control signaling related to video distribution between client, server and network components; Network processes for video distribution between server and clients or between remote clients, e.g. transmitting basic layer and enhancement layers over different transmission paths, setting up a peer-to-peer communication via Internet between remote STB's; Communication protocols; Addressing
- H04N21/647—Control signaling between network components and server or clients; Network processes for video distribution between server and clients, e.g. controlling the quality of the video stream, by dropping packets, protecting content from unauthorised alteration within the network, monitoring of network load, bridging between two different networks, e.g. between IP and wireless
- H04N21/64723—Monitoring of network processes or resources, e.g. monitoring of network load
- H04N21/6473—Monitoring network processes errors
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L47/00—Traffic control in data switching networks
- H04L47/10—Flow control; Congestion control
- H04L47/25—Flow control; Congestion control with rate being modified by the source upon detecting a change of network conditions
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
- H04N21/60—Network structure or processes for video distribution between server and client or between remote clients; Control signalling between clients, server and network components; Transmission of management data between server and client, e.g. sending from server to client commands for recording incoming content stream; Communication details between server and client
- H04N21/63—Control signaling related to video distribution between client, server and network components; Network processes for video distribution between server and clients or between remote clients, e.g. transmitting basic layer and enhancement layers over different transmission paths, setting up a peer-to-peer communication via Internet between remote STB's; Communication protocols; Addressing
- H04N21/64—Addressing
- H04N21/6405—Multicasting
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
- H04N21/60—Network structure or processes for video distribution between server and client or between remote clients; Control signalling between clients, server and network components; Transmission of management data between server and client, e.g. sending from server to client commands for recording incoming content stream; Communication details between server and client
- H04N21/63—Control signaling related to video distribution between client, server and network components; Network processes for video distribution between server and clients or between remote clients, e.g. transmitting basic layer and enhancement layers over different transmission paths, setting up a peer-to-peer communication via Internet between remote STB's; Communication protocols; Addressing
- H04N21/647—Control signaling between network components and server or clients; Network processes for video distribution between server and clients, e.g. controlling the quality of the video stream, by dropping packets, protecting content from unauthorised alteration within the network, monitoring of network load, bridging between two different networks, e.g. between IP and wireless
- H04N21/64723—Monitoring of network processes or resources, e.g. monitoring of network load
- H04N21/64738—Monitoring network characteristics, e.g. bandwidth, congestion level
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
- H04N21/60—Network structure or processes for video distribution between server and client or between remote clients; Control signalling between clients, server and network components; Transmission of management data between server and client, e.g. sending from server to client commands for recording incoming content stream; Communication details between server and client
- H04N21/63—Control signaling related to video distribution between client, server and network components; Network processes for video distribution between server and clients or between remote clients, e.g. transmitting basic layer and enhancement layers over different transmission paths, setting up a peer-to-peer communication via Internet between remote STB's; Communication protocols; Addressing
- H04N21/647—Control signaling between network components and server or clients; Network processes for video distribution between server and clients, e.g. controlling the quality of the video stream, by dropping packets, protecting content from unauthorised alteration within the network, monitoring of network load, bridging between two different networks, e.g. between IP and wireless
- H04N21/64784—Data processing by the network
- H04N21/64792—Controlling the complexity of the content stream, e.g. by dropping packets
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N7/00—Television systems
- H04N7/18—Closed-circuit television [CCTV] systems, i.e. systems in which the video signal is not broadcast
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- Engineering & Computer Science (AREA)
- Signal Processing (AREA)
- Multimedia (AREA)
- Computer Networks & Wireless Communication (AREA)
- Computer Security & Cryptography (AREA)
- Data Exchanges In Wide-Area Networks (AREA)
- Two-Way Televisions, Distribution Of Moving Picture Or The Like (AREA)
Abstract
The invention discloses a kind of video transmission methods of subway train LCD screen, belong to embedded computer field.This method is made of 3 modules, respectively video server modules, exchanging network module and video consumer end module.Video server modules are responsible for video signal collection, coding output and wrong data and are retransmitted, and according to current network state information, carry out congestion control；Exchanging network module is responsible for the packets forwarding of data, real-time statistics port flow and number of dropped packets, feeds back current network state information to video server；Video consumer end module is responsible for decoding broadcasting and packet loss detection, and loses data according to whether network topology decision requests video server to retransmit.The present invention can improve display effect when LCD screen plays media video information, improve the aesthetic quality of passenger.
Description
Technical field
The invention belongs to embedded computer fields, are related to a kind of video transmission method of subway train LCD screen.
Background technique
As the continuous development in city and the size of population persistently increase, subway is as the best side for alleviating traffic above-ground pressure
Formula, operation mode centered on vehicle gradually by being turned to centered on passenger.The appearance of PIS (passenger information system) is just met
The demand of this novel operation mode, it relies on network technology, multimedia technology and the display technology of modern science and technology mature and reliable
Carry out the display of Diversity of information.It is shown by setting up dynamic Customer information in Metro Space, even if passenger is allowed to be in ground
Down space still is able to keep the information interchange with the external world constantly.PIS provides information resources abundant for passenger,
Through becoming subway train inalienable part.
Important component of the LCD screen as PIS can provide train operation state, site information and media for passenger
Video information.Currently, the displaying scheme of subway train LCD screen is based on difference VGA technology more, regarded by VGA analog signal
Keep pouring in defeated, but this method is not able to satisfy high definition requirement, and poor anti jamming capability during long distance transmission.With video
Raising of the development and passenger of technology to information requirement, the requirement to vehicle-mounted LCD screen display effect is also higher and higher, this method
Be no longer satisfied requirement.
With the development of network technology, stream media technology is as one based on Ethernet digital media technology displaying scheme
Kind, it is gradually applied in built-in field.Streaming Media scheme is used on subway train, is generally basede on UDP multicast mode to institute
There is LCD screen to carry out transmission of video.The structure in subway train drivers' cab compartment is as shown in Figure 1, by a cabinet, a media control
Device and a touch screen composition, cabinet is interior to contain three equipment such as video server, sound broadcast controller and interchanger.Media
Controller is that a tool statistics have shown the equipment of output function, and touch screen is for checking that train monitors information in real time.Subway column
Vehicle guest room carriage body construction has been all connected with five LCD screens and two cameras as shown in Fig. 2, be made of interchanger a and interchanger b,
Interchanger a is also connected with a DVR (hard disk video recorder).For the port utilization for improving guest room compartment interchanger, 5 LCD screens
It is suspended on the same port of interchanger by ethernet line cascade, is distinguished according to the numerical value of toggle switch in LCD screen.
Such as it is 2 that LCDa1 toggle switch numerical value, which is 1, LCDa2 toggle switch numerical value, and so on.Interchanger in each compartment is mutual
A local looped network is connected and composed, the network topological diagram of subway train entirety is as shown in Figure 3.
In a column subway, the number of devices such as LCD screen, camera, DVR are all more, and when use can occupy a part of communication
Bandwidth, when the real time monitoring for needing to check by touch screen on train in drivers' cab, the camera in all guest room compartments is all
Data can be sent on network.Meanwhile video server is also sending LCD screen 1080P HD video data to, these bandwidth disappear
Consumption can all aggravate the load of train network, be easy to cause network instantaneous congestion and cause loss of data.Since LCD screen is using cascade
Mode connect, when in train network there is a phenomenon where when loss of data, if the LCD screen near switch port is not received
To data, then cascade screen will not receive the data below.And stream media technology use service model have do one's best
The characteristics of, it does not ensure that the reliable transmission of data, not can be carried out web impact factor, the data of loss can not be retransmitted, this
It will cause LCD screen and the problem of mosaic and Caton occur, influence the display effect of LCD screen, reduce passenger to the seating body of subway
It tests.For this status, set forth herein a kind of new LCD screen video transmission methods.
As shown in figure 4, subway train video server uses the digital media processor based on ARM framework, and connect
One digital visual interface-d interface, two panels DDR3 caching, one piece of video signal collection chip and 100,000,000 network switch.
All interchangers and each node device in subway train collectively form a ring local-area network.Interchanger uses
Based on the processor of ARM+FPGA framework, as shown in figure 5, two pieces of Ethernet switch processing chips of connection and a hardware are guarded the gate
Dog.Node device handles chip by the network interface connection on switchboard panel and backboard to Ethernet switch.
Subway train LCD screen is controlled, as shown in Figure 6 as videoconference client by LCD screen controller.LCD screen control
Device uses the multi-core processor based on ARM framework as control core, and connects a piece of Nor Flash memory, a piece of DDR3
Caching, a Video Decoder, 100,000,000 network switch, a toggle switch and a LCD liquid crystal display.
Video server is connect by digital visual interface-d interface with the media controller of train operator room.When subway train operation,
Video server acquires digital video signal by digital visual interface-d interface, in inside according to H264 said shank.Video data is sent
Before, it is packaged according to RTP (real-time transport protocol) format, multicast mode is sent to Ethernet.Interchanger in compartment is to video counts
According to forwarding is grouped, all LCD screens being added in designated multicast group all can receive video data.LCD screen and view
Frequency server establishes RTSP (real time streaming transport protocol) connection, creates buffer area, the video data received is stored to buffering
Video data feeding video tube is decoded broadcasting later by area.
Summary of the invention
The technical problem to be solved by the present invention is to a kind of video transmission methods of subway train LCD screen, improve subway train
LCD screen plays display effect when media video information, improves the aesthetic quality of passenger.
Technical solution of the present invention:
The video transmission method of subway train LCD screen, including video server modules, exchanging network module and video consumer
End module, as shown in Figure 7.
Video server modules are divided into three threads: network state obtains thread, original video data processing thread and mistake
Accidentally restore thread.Network state obtains one timer of thread creation, if reaching timing, asks to exchanging network module
It asks and obtains Network Packet Loss number and port flow, otherwise continue timing.According to the specific value that exchanging network module is fed back, analysis
Network state, dynamic adjust video stream code rate and continue waiting for the arrival of timing later to alleviate network pressure.It is former
Beginning video data processing thread will create one for sending the multicast group 1 of original video data, be adopted in real time by digital visual interface-d interface
Collection vision signal simultaneously encodes.Whether detection frame size of data is more than the MTU (maximum transmission unit) of Ethernet after coding, if surpassed
It crosses, then first carries out operation of unpacking, then carry out RTP package, if be not above, directly carry out RTP package.Package terminates
Afterwards, data are stored to local cache.Interval of giving out a contract for a project is adjusted according to the size of frame dynamic, slows down the temporary impact to network, presses
Inter-packet gap multicast approved for distribution is sent to Ethernet, then proceedes to acquisition vision signal.Fault recovery thread will create one for connecing
The multicast group 2 of NAK (not replying) and erroneous retransmissions is received, includes the sequence number of videoconference client requesting retransmission data in NAK.Such as
Fruit does not receive the NAK from client, then continues waiting for, if received, parses packet sequence number to be retransmitted, In
The data there are the sequence number are searched whether in local cache.If it is present retransmitting the data multicast to all video visitors
Family end, continues waiting for receiving NAK later, continues waiting for next new NAK if it does not exist, then returning.
Exchanging network module is divided into two threads: data grouping forwards thread, network state feedback thread.Data grouping turns
Hair line journey is first turned on all of the port of switch processes chip, initiating port state, buffer status and MDIO (management number
According to input and output) bus.Equal pending datas enter exchanging network module later, if entered without data, continue waiting for, if
Have, switch processes chip carries out the packets forwarding of data according to mac address table, continues waiting for data entrance later.It is network-like
State feeds back thread creation UDP socket, and bundling port number waits and obtains Network Packet Loss number and end from video server modules
The request of mouth flow.If not receiving solicited message, continue waiting for, if received, reads register and obtain currently
Number of dropped packets and port flow obtain local zone time.It encapsulates and is packaged according to the format of network state message, by number of dropped packets, port flow
Three amount, time information feed back to video server modules together, continue waiting for the request from video server modules later.
The format of network state message is defined as follows: the packet header of the first two byte representation message；Two words since third byte
Section indicates the length of message；Four bytes since the 5th byte are timestamps, and expression gets number of dropped packets and port flow
The time of amount, as unit of millisecond；Four byte representation number of dropped packets since the 9th byte, since the 13rd byte
Four byte representation port flows, the packet tail of two byte representation messages since the 17th byte.
Video consumer end module is divided into two threads: original video data receiving thread, error feedback and recovery thread.It is former
After the starting of beginning video data receiving thread, the numerical value of toggle switch is read, video tube is constructed, opens up for storing video data
Buffer area, creation UDP socket be added in multicast group 1, establish RTSP with video server modules and connect, waiting video counts
According to arrival.After receiving data, judge whether to be video data, if not then continuing waiting for, if it is video data, by it
Be placed into buffer area, and detect front and back twice packet sequence number it is whether continuous, if discontinuously, determine occur packet loss, touching
It sends out error feedback and restores thread and carry out corresponding operating, video data is continued waiting for later, if continuously, directly sent data
Enter video tube and be decoded broadcasting, continues waiting for video data later.After error feedback and recovery thread starting, UDP is created
Socket is added in multicast group 2, and is created one and lost the sequence number that queue is used to record lost data packets, always later etc.
It to the generation of packet loss event, if there is no packet loss event, continues waiting for, if triggered by packet loss event, is lost newest
The sequence number update for losing data packet judges whether to need to send NAK into packet loss sequence, and according to the numerical value of toggle switch.If
It needs, then sends NAK into multicast group 2, data are inserted into buffer area after reaching again according to sequence number, and are deleted and lost team
Corresponding sequence number in column returns continue waiting for packet loss event later；If it is not required, then directly waiting the arrival for retransmitting data
.
The beneficial effects of the present invention are interchangers can feed back current network state to video server, so that video takes
Business device can control the size and rate of video data transmission in time, slow down network pressure, reduce packet loss phenomenon.Videoconference client inspection
A LCD screen is only chosen after measuring packet loss generation, on each interchanger and carries out NAK feedback, reduces train backbone network flow, video
Server carries out re-transmission recovery to data after receiving NAK feedback.Interchanger, video server and videoconference client have been worked in coordination
At the congestion control of train network and the Fault recovery of video data, to provide reliable video counts for subway train LCD screen
According to transmission, improve the result of broadcast of screen, improves passenger's sensory experience.
Detailed description of the invention
Fig. 1 is the structure chart in subway train drivers' cab of the present invention compartment.
Fig. 2 is the structure chart in subway train guest room of the present invention compartment.
Fig. 3 is the network topological diagram of subway train of the present invention.
Fig. 4 is video server controller hardware structure figure of the present invention.
Fig. 5 is exchange control unit hardware structure diagram of the present invention.
Fig. 6 is LCD screen controller hardware structure figure of the present invention.
Fig. 7 is design method flow chart of the invention.
Fig. 8 is video server modules flow chart of the present invention.
Fig. 9 is exchanging network module flow chart of the present invention.
Figure 10 is videoconference client module flow diagram of the present invention.
Figure 11 is the video tube structure chart of video consumer end module of the present invention.
Specific embodiment
Below in conjunction with technical solution and attached drawing, the specific embodiment that the present invention will be described in detail.
The present invention includes three modules, video server modules, exchanging network module and video consumer end module altogether.Depending on
Frequency server module is responsible for video signal collection and coding output, and has the function of Fault recovery and congestion control；Exchange
Network module is responsible for data forwarding, monitoring flow and packet loss information, and to video server modules feedback network status information；Depending on
Frequency client modules are responsible for decoding and are played, and after detecting the loss of data, whether send NAK according to network topology decision, to
Framing again after data reach is retransmitted, decodes broadcasting after a whole frame wait receive.
(1) video server modules
This module is divided into three threads: network state obtains thread, original video data processing thread and Fault recovery line
Journey, as shown in Figure 8.Network state obtains thread and creates a timer first, if timing does not arrive, continues timing, such as
Fruit timing has arrived, and the request for obtaining Network Packet Loss number and port flow is issued to exchanging network module, waits switching network
Network module feedback network state message.If being not received by the message, continue waiting for, it is right if receiving the message
Message is parsed, and obtains current packet loss quantity, and according to the difference of timestamp in front and back twice message and port flow
Difference calculates transmission rate.If detecting on network that reduction coding is multiple when there is packet loss or excessive network load
Miscellaneous degree and transmission code rate, to alleviate the generation of network pressure and packet loss, if showed there is no packet loss or network load are excessive
As illustrating that current network state is normal, then restoring encoder complexity and transmission code rate to normal level.Adjust encoder complexity
Timer is reset with after transmission code rate, starts the timing of a new round.
Original video data processing thread will create one for sending the multicast group 1 of original video data, pass through DVI-D
Interface acquires vision signal in real time, and according to H264 said shank.The size of frame data, ether if more than after judgement coding
The maximum transmission unit MTU of net then needs to calculate number of unpacking, executes operation of unpacking, RTP package carried out later, if do not had
It is more than that then can directly carry out RTP package.It, can be by packet sequence number, the Information encapsulations such as timestamp when according to RTP format package
Enter, the sequence number of first data packet generates at random, and sequence number successively adds up later, stores data to this after package
Ground caching.When excessive in view of frame data to be sent, number of unpacking is necessarily increased, and causes ethernet traffic that can increase suddenly,
It is likely to result in network instantaneous congestion, so video server modules, before transmitting data to Ethernet, meeting is a according to unpacking
Number dynamic adjusts interval of giving out a contract for a project, and slows down the temporary impact to network.The data packet of RTP format is sent to group according to interval of giving out a contract for a project
Group 1 is broadcast, continues to acquire vision signal later.
Fault recovery thread will create one for receiving the multicast group 2 of NAK and erroneous retransmissions, and setting is for receiving data
Time-out time, whether detection time overtime.If the time is overtime, time-out time is reset, whether continue to test the time overtime,
If be not timed-out, judge whether to receive data；If being not received by any data, continue to judge whether the time surpasses
When, if receiving data, judge whether data are the NAK from videoconference client；If it is not, then resetting timer,
Continue to test whether the time is overtime, if it is, the packet sequence number for including in parsing NAK data packet, in local cache
Search whether the data for having to re-transmission sequence number；If it does, illustrate that the data can be restored, retransmitted in the way of multicast to
All videoconference clients reset time-out time, whether overtime the time are continued to test, if it does not, illustrating data not
It can be resumed, then reset time-out time, whether overtime continue to test the time.
(2) exchanging network module
As shown in figure 9, exchanging network module is divided into two threads: data grouping forwards thread, network state feedback thread.
Data grouping forwarding thread is first turned on all of the port of two pieces of Ethernet switches processing chip, initiating port state and posts
Storage state, opens MAC address learning function, and load driver initializes MDIO bus.If entering exchange network without data
Module then continues waiting for, if there is when data, which enter exchanging network module, to be needed to forward, switch processes chip parses the number
According to recording the source MAC and target MAC (Media Access Control) address of data.MAC address learning is carried out, is inquired later according to target MAC (Media Access Control) address
Mac address table.If the mapping relations of target MAC (Media Access Control) address and outlet can be found in table, forwarded the packet according to corresponding outlet,
Data entrance is continued waiting for later, if not finding corresponding outlet in mac address table, by all in addition to entrance
Other ports are forwarded, and are continued waiting for data later and are entered exchanging network module.
Network state feeds back thread creation UDP socket, and bundling port number waits asking from video server modules
It asks.If not obtaining the request of Network Packet Loss number and port flow from video server modules, continue waiting for, if
Have, then the order for obtaining port flow is written toward traffic statistics operation note using SMI (system management interrupt) interface, then read
Low 16 of the first character section 32 bit data stream amounts of acquisition of traffic statistics operation note are taken, the deposit of flow statistical operation is read
Second byte of device obtains the 16 high of 32 bit data stream amounts, obtains port flow by calculating.It is direct to reuse SMI interface
Low 16 of 32 number of dropped packets are read from low level packet loss counter, reads from high-order packet loss counter 16 high, and calculating obtains
Obtain number of dropped packets.The local zone time for obtaining interchanger, is converted as unit of microsecond, is beaten according still further to the format of network state message
Packet is sent to video server modules, continues waiting for obtaining Network Packet Loss number and port flow from video server modules later
The request of amount.
(3) video consumer end module
This module is divided into two threads: original video data receiving thread, error feedback and recovery thread, such as Figure 10 institute
Show.Original video data receiving thread is established RTSP with video server modules and is connect, and is added to for sending original video
In the multicast group 1 of data.Read the numerical value of equipment toggle switch and preservation.The buffer area storage video data of 25 2M is opened up,
Prevent because parking space it is inadequate caused by loss of data.Video tube, video tube structural frames are built based on GStreamer frame
Figure passes through src pad as shown in figure 11, by tetra- plug-in units of apprsrc, h264parse, imxvpudec, imxg2dvideosink
(input liner) and sink pad (output liner) connection composition.Appsrc is as source plug-in unit, for receiving complete frame data,
H264parse plug-in unit is pushed data into later, data are parsed according to H264 format, then passes through imxvpudec plug-in unit
Color space is converted into RGB by decoding, gained code stream, to adapt to the media capability of imxg2dvideosink player plug-in, finally
The video flowing of transmission is shown in LCD screen by imxg2dvideosink plug-in unit.After video tube is built successfully, wait waiting
Receive the data from multicast group 1 judge whether to be video data after receiving data, if not then continue waiting for receive number
According to being if it is placed into buffer area, and whether the sequence number for detecting front and back data packet twice is continuous.If continuous explanation
There is no packet loss, then continues to determine whether to have had received a frame partial data, the frame data are if it is taken out from buffer area
It is sent into video tube and is decoded broadcasting, continue waiting for reception data later and returned if not receiving a frame partial data
It continues waiting for receiving data；If packet sequence number is discontinuous, determine that packet loss, triggering error feedback and recovery thread occurs
Corresponding operating is carried out, continues waiting for receiving data later.
Error feedback and recovery thread creation UDP socket, and the multicast group 2 for receiving NAK and erroneous retransmissions is added.
A loss queue is created, for recording the sequence number of lost data packets, waits the triggering of packet loss event always later.If not yet
There is packet loss event, then continue waiting for, if triggered by packet loss event, the packet sequence number of newest loss is updated to
In packet loss sequence.Judge whether it is the LCD screen in network topology near switch port according to the numerical value of toggle switch.If
It is that the NAK with packet loss sequence number is fed back into video server modules, then waits the arrival for retransmitting data, if not
Then no need to send NAK feedbacks, directly wait and retransmit data arrival.If re-transmission data are received, according to data packet
Sequence number inserts it into buffer area on suitable position, and updates loss queue, deletes recovered in loss queue
The sequence number of data packet continues waiting for the generation of packet loss event later；If be not received by, continue waiting for retransmitting data
It reaches.
Claims (1)
1. a kind of video transmission method of subway train LCD screen, including video server modules, exchanging network module and video visitor
Family end module, it is characterised in that:
Video server modules are divided into three threads: it is extensive that network state obtains thread, original video data processing thread and mistake
Multiple line journey；Network state obtains one timer of thread creation, if reaching timing, obtains to exchanging network module request
Network Packet Loss number and port flow are taken, timing is otherwise continued；According to the specific value that exchanging network module is fed back, network is analyzed
State, dynamic adjust video stream code rate and continue waiting for the arrival of timing later to alleviate network pressure；Original view
Frequency data processing thread creation one, for sending the multicast group 1 of original video data, acquires video by digital visual interface-d interface in real time
Signal simultaneously encodes；Whether detection frame size of data is more than the MTU of Ethernet after coding, if it does, operation of unpacking then first is carried out,
Then RTP package is carried out, if be not above, directly carries out RTP package；After package, data are stored to local slow
It deposits；Adjust interval of giving out a contract for a project according to the size of frame dynamic, slow down the temporary impact to network, according to give out a contract for a project be spaced multicast be sent to
Too net then proceedes to acquisition vision signal；Fault recovery thread creation one is used to receive the multicast group 2 of NAK and erroneous retransmissions,
It include the sequence number of videoconference client requesting retransmission data in NAK；If not receiving the NAK from client, continue
To if received, parse packet sequence number to be retransmitted, the number there are the sequence number is searched whether in local cache
According to；If it is present retransmitting the data multicast to all videoconference clients, continue waiting for receiving NAK later, if do not deposited
It is then returning and is continuing waiting for next new NAK；
Exchanging network module is divided into two threads: data grouping forwards thread and network state feedback thread；Data grouping forwarding
Thread is first turned on all of the port of switch processes chip, initiating port state, buffer status and MDIO bus；It waits
Data enter exchanging network module, if entered without data, continue waiting for, if so, switch processes chip is according to MAC
Address table carries out the packets forwarding of data, continues waiting for data entrance；Network state feeds back thread creation UDP socket, binding
Port numbers wait the request that Network Packet Loss number and port flow are obtained from video server modules；It is asked if do not received
Information is sought, then is continued waiting for, if received, reads register, obtains current Network Packet Loss number and port flow, obtains this
The ground time；It encapsulates and is packaged according to the format of network state message, by three Network Packet Loss number, port flow, local zone time information
Video server modules are fed back to together, continue waiting for the request from video server modules；
The format of network state message is defined as follows: the packet header of the first two byte representation message；Two since third byte
The length of a byte representation message；Four bytes since the 5th byte are timestamps, and expression gets Network Packet Loss number
With the time of port flow, as unit of millisecond；Four byte representation Network Packet Loss numbers since the 9th byte, from the tenth
Four byte representation port flows that three bytes start, the packet of two byte representation messages since the 17th byte
Tail；
Video consumer end module is divided into two threads: original video data receiving thread and error feedback and recovery thread；It is original
After the starting of video data receiving thread, the numerical value of toggle switch is read, video tube is constructed, opens up for storing video data
Buffer area, creation UDP socket are added in multicast group 1, establish RTSP with video server modules and connect, and wait video data
It reaches；After receiving data, judge whether to be video data, if not then continuing waiting for, if it is video data, be put
Set to buffer area, and detect front and back twice packet sequence number it is whether continuous, if discontinuously, determine occur packet loss, triggering
Error feedback and recovery thread carry out corresponding operating, video data are continued waiting for, if continuously, data are directly sent into video
Pipeline is decoded broadcasting, continues waiting for video data；After error feedback and recovery thread starting, creation UDP socket is added
It into multicast group 2, and creates one and loses the sequence number that queue is used to record lost data packets, wait packet loss event always later
Generation continued waiting for if there is no packet loss event, if triggered by packet loss event, by newest lost data packets
Sequence number update judges whether to need to send NAK into packet loss sequence, and according to the numerical value of toggle switch；If it is required, then to
NAK is sent in multicast group 2, data are inserted into buffer area after reaching again according to sequence number, and are deleted to lose and be corresponded in queue
Sequence number, return continue waiting for packet loss event；It is reached if it is not required, then directly waiting and retransmitting data.
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| CN108966038B (en) * | 2017-12-27 | 2021-01-22 | 视联动力信息技术股份有限公司 | Video data processing method and video networking cache server |
| CN108600861A (en) * | 2018-03-26 | 2018-09-28 | 南京地铁建设有限责任公司 | The long method of adjustment of audio, video data packet based on city rail passenger information system |
| CN110149480A (en) * | 2019-05-27 | 2019-08-20 | 南昌大学 | A kind of video image processing and Transmission system |
| CN112134619B (en) * | 2020-09-23 | 2021-08-31 | 北京冠华天视数码科技有限公司 | Method for realizing single-fiber bidirectional transmission between play controller and display terminal |
| CN114401264A (en) * | 2022-01-21 | 2022-04-26 | 厦门海菱科技股份有限公司 | Vehicle-mounted multi-screen different display output method, device, equipment and medium |
| CN117793073A (en) * | 2024-02-23 | 2024-03-29 | 深圳安德空间技术有限公司 | Image data real-time transmission and display method for three-dimensional ground penetrating radar |
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