CN104539593B - H.245 message resolution method - Google Patents
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Abstract
The present invention relates to a kind of H.245 message resolution method, contain the following steps：1st, the H.245 structure of Xie Maxinlingshu；2nd, message definition, mapping；3rd, decode：Corresponding decoding functions are write to each message structure, the corresponding source codec function in decoding functions storehouse is called, decoding effort is completed；4th, message bit is extracted；5th, the H.245 data filling of signaling tree：For every control information, taken bit value is returned to by calling the decoding functions of oneself, be filled into corresponding numerical value on the corresponding node of this message by decoding functions；6th, decoded result output：Output display module is called, the signaling tree to this message travels through, the data value filled on each node layer is read step by step, and carry out visualization output, verify the correctness of decoding；The present invention can provide key parameter and function interface for the multiplexing of visual telephone service data frame.
Description
（One）, technical field：The present invention relates to a kind of message resolution method, more particularly to a kind of H.245 message parsing
Method.
（Two）, background technology：H.245 agreement（Control protocol for multimedia
communication）It is H.323 in protocol suite for the agreement of media channel control, it is main to complete each in multimedia communication
Foundation, maintenance and the release of logical channel, specifically include opening and closing, parameter setting, the energy of receiving-transmitting sides of logical channel
The control functions such as power negotiation, while it will also complete the cooperation control function of logic channel in multipoint conference calling.H.245 define
The syntax and semantics of interaction message in communication process, the interaction to primary message is described, and it is to message language
The definition of method is using a kind of successively nested message structure.
H.245 belong to application layer protocol in OSI frameworks, its function determine H.245 message to use it is extremely complex
Signaling, therefore the type and form of signaling are defined using ASN ASN.1, rule are encoded using the deflation of non-alignment
Then（PER, Packet Encoding Rules）To be indicated.Because PER is bitwise encoded, and each is believed
Without filling between interest statement unit, therefore implement more complicated.
（Three）, the content of the invention：
The technical problem to be solved in the present invention is：A kind of H.245 message resolution method is provided, the method can be can
The multiplexing of phonovision business data frame provides key parameter and function interface.
Technical scheme：
A kind of H.245 message resolution method, contains the following steps：
The structure of step 1, H.245 Xie Maxinlingshu：
H.245 the top layer of message is the control message of multimedia system（Multimedia System Control
Message）, the control message of multimedia system contains four types：Recipient need to respond and response request message
（Request Message）, response request message（Request Message）Response message（Response Message）、
Recipient need to respond but without the command messages of response（Command Message）, recipient is not responding to and without the finger of response
Show message（Indication Message）；The message of these four types is the first order type of message of H.245 control protocol, often
Type message structure contains N seed type of messages again, by that analogy, nested according to layer as next straton tree, ultimately forms
H.245 overall signaling message；According to the level nested structure of H.245 overall signaling message, its whole protocol message is defined
It is a tree-like structure type；For H.245 signaling tree construction, a control message unit may have very in tree structure
Mulitpath can be reached, but for bit stream to be decoded, have every time and an only paths are effective, can be reached.Will
The information of bottom layer node is obtained, it is necessary to cover the node on upper strata, so in decoding, it is necessary to consider all roads being likely to occur
Footpath, just can guarantee that the correctness of decoding.
Step 2, message definition, mapping：
H.245 data type and corresponding message structure that description is defined with ASN.1 PER are defined, program word is mapped as
The data structure file of description is sayed, this is the basis of decoding；There is structure after mapping enough information to be encoded or be had
There are enough domains to deposit decoded data；It is to be mapped to every kind of data type that ASN.1 is described to map the function of completing
In its corresponding decoding functions, these decoding functions recall the decoding function that the corresponding decoding functions of lower floor realize message.
Step 3, decoding：
Next it is exactly to be solved using decoding functions storehouse after data type and message structure are mapped to program file
Code, decoding functions storehouse is the core for H.245 parsing；According to H.245 signaling table structure, it is necessary to which each message structure is compiled
Write corresponding decoding functions；Because the decoding functions of H.245 message are included for basic data type and compound data structure
Call, so for basic data type and compound data structure, it is also desirable to corresponding decoding functions storehouse；Decoding functions portion
Point with api interface to other modules provide calling interface, itself also docking port module it is transparent, the decoding functions of message must be true
Determine the bit number acquired by it, and initialize two pointer positions of buffering area byte and bit, be transmitted to bit extraction function；Pass through
Interface section is received by the H.245 data flow after ASN.1 PER codings, then calls the corresponding source codec in decoding functions storehouse
Function, completes decoding effort, and result is sent out by interface section；
Step 4, message bit are extracted：
For H.245 signaling tree, even if required unit is essential unit and bit number fixing, still need to by bit according to
Tree structure go to information where node.Therefore, one is designed in parsing module neatly takes out any from bit stream
The function of bit, this function receives calling for decoding functions, extracts corresponding information flow bit, and numerical value is returned into decoding
Function；Function itself returns to the digit for taking bit, and the correctness of bit quantity is extracted to verify, and according to taken bit
The position of the double pointers of digit adjustment；So, even if information layer layer H.245 is nested, it is also possible to by calling this function reality repeatedly
Now to the extraction of information unit.
The data filling of step 5, H.245 signaling tree：
For every control information, taken bit value is returned to by calling the decoding functions of oneself, decoding functions will be right
The numerical value answered is filled on the corresponding node of this message, and this level remaining node is not filled with, and it is sky to be worth；
Step 6, decoded result output：
After one H.245 signaling resolution is finished, the corresponding signaling tree filling of message is finished, and calls output display module,
Signaling tree to this message is traveled through, and the data value filled on each node layer is read step by step, and carries out visualization output, is tested
Demonstrate,prove the correctness of decoding.
H.245 data type in step 2 contains fundamental type and compound type.
The position of double pointers is moved in the position according to the double pointers of taken number of bits adjustment in step 4 after referring to.
Before decoding functions storehouse is called, it is necessary to perform initialization operation, the setting to 0 of double pointers, H.245 is completed
Each node of signaling tree empties these operations；
The decoding functions of message must determine the bit number acquired by it, and initialize two fingers of buffering area byte and bit
Pin position, is transmitted to bit extraction function；
After bit extraction function obtains required bit, content is returned into corresponding decoding functions, itself returns to institute
The digit of bit is taken, with proving correctness, and according to the position of the double pointers of taken number of bits adjustment；Double pointers are keys,
Can not location revision easily；
In C language, stored bits position is not corresponded to（Less than 8）Data structure, therefore, the read method of bit value
For：Will be comprising bit to be read（N）Byte taken out from buffering area, first moved to left（Determined by bit pointers）, carry out a left side
Alignment, then carries out Right Aligns, by bit clear 0 before taken bit, completes actual bit position and reads；
The structure definition of every H.245 message is exactly the definition of composite data type, and the decoding functions of each message finally need
The decoding functions of fundamental type are called, return value is inserted into signaling tree corresponding node；
The parameter indefinite for number in H.245 message definition, according to the number of number of parameters in real messages, there is provided no
Same memory allocation scheme；If number of parameters is less, static storage is used；If Static-state Space is not enough to deposit
Parameter is put, then dynamic application space.This method had both adapted to the various situations that protocol definition goes out, again can be in most of message solutions
Guaranteed efficiency during code.
Beneficial effects of the present invention：
1st, the present invention first proposed on the basis of the Packet encoding rules PER of further investigation ASN.l descriptions
PER tree-shaped decodes structure, and design is realized and can be used for the PER decoders of communication system；The present invention is directed to signaling
The corresponding decoding functions of the corresponding message composition of each node in tree, it is nested layer by layer；When to source codec, searched with depth-first
Rope mode is traveled through to signaling tree, and the decoding functions of message call the decoding letter basic corresponding with compound type data for including
Number, extracts corresponding bit value, and data value is successively filled on the corresponding node of message signaling tree, until leafy node knot
Beam.The present invention obtains the particular content of control message to carrying out Decoding Analysis by the message structure after ASN.1 PER codings,
For the multiplexing of visual telephone service data frame provides key parameter and function interface.
（Four）, brief description of the drawings：
Fig. 1 is H.245 signaling tree construction schematic diagram；
Fig. 2 is the H.245 mapping schematic diagram of data type and message structure to C data structured file；
Fig. 3 is decoding program flow chart.
（Five）, specific embodiment：
H.245 message resolution method contains the following steps：
The structure of step 1, H.245 Xie Maxinlingshu：
H.245 the top layer of message is the control message of multimedia system（Multimedia System Control
Message）, the control message of multimedia system contains four types：Recipient need to respond and response request message
（Request Message）, response request message（Request Message）Response message（Response Message）、
Recipient need to respond but without the command messages of response（Command Message）, recipient is not responding to and without the finger of response
Show message（Indication Message）；The message of these four types is the first order type of message of H.245 control protocol, often
Type message structure contains N seed type of messages again, by that analogy, nested according to layer as next straton tree, ultimately forms
H.245 overall signaling message；According to the level nested structure of H.245 overall signaling message, its whole protocol message is defined
It is a tree-like structure type（As shown in Figure 1）；For H.245 signaling tree construction, a control message unit is in tree-like knot
May have many paths in structure can reach, but for bit stream to be decoded, has every time and an only paths are effective,
Can reach.Obtain the information of bottom layer node, it is necessary to cover the node on upper strata, thus decoding when, it is necessary to consider it is all can
The path that can occur, just can guarantee that the correctness of decoding.
Step 2, message definition, mapping：
H.245 data type and corresponding message structure that description is defined with ASN.1 PER are defined, program word is mapped as
Say the data structure file of description（As shown in Figure 2）, this is the basis of decoding；There is structure after mapping enough information to carry out
Coding deposits decoded data with enough domains；It is the every kind of data class for describing ASN.1 to map the function of completing
Type is mapped in its corresponding decoding functions, and these decoding functions recall the corresponding decoding functions of lower floor and realize message
Decoding function.
Step 3, decoding：
Next it is exactly to be decoded using decoding functions storehouse after data type and message structure are mapped to program file
（As shown in Figure 3）, decoding functions storehouse is the core for H.245 parsing；According to H.245 signaling table structure, it is necessary to each
Message structure writes corresponding decoding functions；Because the decoding functions of H.245 message are included for basic data type and multiple
Calling for data structure is closed, so for basic data type and compound data structure, it is also desirable to corresponding decoding functions storehouse；
Decoding functions part with api interface to other modules provide calling interface, itself also docking port module it is transparent, the decoding of message
Function must determine the bit number acquired by it, and initialize two pointer positions of buffering area byte and bit, is transmitted to bit and carries
Take function；H.245 data flow after ASN.1 PER are encoded is received by interface section, decoding functions storehouse pair is then called
The source codec function answered, completes decoding effort, and result is sent out by interface section；
Step 4, message bit are extracted：
For H.245 signaling tree, even if required unit is essential unit and bit number fixing, still need to by bit according to
Tree structure go to information where node.Therefore, one is designed in parsing module neatly takes out any from bit stream
The function of bit, this function receives calling for decoding functions, extracts corresponding information flow bit, and numerical value is returned into decoding
Function；Function itself returns to the digit for taking bit, and the correctness of bit quantity is extracted to verify, and according to taken bit
The position of the double pointers of digit adjustment；So, even if information layer layer H.245 is nested, it is also possible to by calling this function reality repeatedly
Now to the extraction of information unit.
The data filling of step 5, H.245 signaling tree：
For every control information, taken bit value is returned to by calling the decoding functions of oneself, decoding functions will be right
The numerical value answered is filled on the corresponding node of this message, and this level remaining node is not filled with, and it is sky to be worth；
Step 6, decoded result output：
After one H.245 signaling resolution is finished, the corresponding signaling tree filling of message is finished, and calls output display module,
Signaling tree to this message is traveled through, and the data value filled on each node layer is read step by step, and carries out visualization output, is tested
Demonstrate,prove the correctness of decoding.
H.245 data type in step 2 contains fundamental type and compound type.
The position of double pointers is moved in the position according to the double pointers of taken number of bits adjustment in step 4 after referring to.
Before decoding functions storehouse is called, it is necessary to perform initialization operation, the setting to 0 of double pointers, H.245 is completed
Each node of signaling tree empties these operations；
The decoding functions of message must determine the bit number acquired by it, and initialize two fingers of buffering area byte and bit
Pin position, is transmitted to bit extraction function；
After bit extraction function obtains required bit, content is returned into corresponding decoding functions, itself returns to institute
The digit of bit is taken, with proving correctness, and according to the position of the double pointers of taken number of bits adjustment；Double pointers are keys,
Can not location revision easily；
In C language, stored bits position is not corresponded to（Less than 8）Data structure, therefore, the read method of bit value
For：Will be comprising bit to be read（N）Byte taken out from buffering area, first moved to left（Determined by bit pointers）, carry out a left side
Alignment, then carries out Right Aligns, by bit clear 0 before taken bit, completes actual bit position and reads；
The structure definition of every H.245 message is exactly the definition of composite data type, and the decoding functions of each message finally need
The decoding functions of fundamental type are called, return value is inserted into signaling tree corresponding node；
The parameter indefinite for number in H.245 message definition, according to the number of number of parameters in real messages, there is provided no
Same memory allocation scheme；If number of parameters is less, static storage is used；If Static-state Space is not enough to deposit
Parameter is put, then dynamic application space.This method had both adapted to the various situations that protocol definition goes out, again can be in most of message solutions
Guaranteed efficiency during code.
Claims (4)
1. one kind H.245 message resolution method, it is characterized in that：Contain the following steps：
The structure of step 1, H.245 Xie Maxinlingshu：
H.245 the top layer of message is the control message of multimedia system, and the control message of multimedia system contains four types：Connect
Debit need to respond and the request message of response, the response message of response request message, recipient need to be responded but without response
Command messages, recipient are not responding to and without the instruction message of response；The message of these four types is the of H.245 control protocol
First-level message type, each type message structure contains N seed type of messages again, as next straton tree, ultimately forms
H.245 overall signaling message；According to the level nested structure of H.245 overall signaling message, its whole protocol message is defined
It is a tree-like structure type；
Step 2, message definition, mapping：
The H.245 data type and corresponding message structure that description will be defined with ASN.1 PER define, are mapped as program language and retouch
The data structure file stated；After there is structure after mapping enough information to be encoded or be decoded with enough domain storages
Data；
Step 3, decoding：
Corresponding decoding functions are write to each message structure；Because the decoding functions of H.245 message are included for basic
Data type and compound data structure are called, so for basic data type and compound data structure, it is also desirable to correspondence
Decoding functions storehouse；Decoding functions part with api interface to other modules provide calling interface, itself also docking port module it is saturating
Bright, the decoding functions of message must determine the bit number acquired by it, and initialize two pointer positions of buffering area byte and bit
Put, be transmitted to bit extraction function；H.245 data flow after ASN.1 PER are encoded is received by interface section, is then called
The corresponding source codec function in decoding functions storehouse, completes decoding effort, and result is sent out by interface section；
Step 4, message bit are extracted：
A function that any bit is taken out from bit stream is designed in parsing module, this function receives the tune of decoding functions
With, the corresponding information flow bit of extraction, and numerical value is returned into decoding functions；Function itself returns to the digit for taking bit,
The correctness of bit quantity is extracted to verify, and two pointers of buffering area byte and bit are adjusted according to taken number of bits
Position；
The data filling of step 5, H.245 signaling tree：
For every control information, taken bit value is returned to by calling the decoding functions of oneself, decoding functions will be corresponding
Numerical value is filled on the corresponding node of this message, and this level remaining node is not filled with, and it is sky to be worth；
Step 6, decoded result output：
After one H.245 signaling resolution is finished, the corresponding signaling tree filling of message is finished, and output display module is called, to this
The signaling tree of bar message is traveled through, and the data value filled on each node layer is read step by step, and carries out visualization output, checking solution
The correctness of code.
2. H.245 message resolution method according to claim 1, it is characterized in that：H.245 data class in the step 2
Type contains fundamental type and compound type.
3. H.245 message resolution method according to claim 1, it is characterized in that：In the step 4 according to taken bit
Two positions of pointer of buffering area byte and bit are moved in the position of digit adjustment two pointers of buffering area byte and bit after referring to.
4. H.245 message resolution method according to claim 1, it is characterized in that：Before decoding functions storehouse is called, it is necessary to
Perform initialization operation, complete the setting to 0 of two pointers of buffering area byte and bit, H.245 each node of signaling tree empty these and grasp
Make；
The decoding functions of message must determine the bit number acquired by it, and initialize two pointer positions of buffering area byte and bit
Put, be transmitted to bit extraction function；
After bit extraction function obtains required bit, content is returned into corresponding decoding functions, itself returns and takes ratio
Special digit, with proving correctness, and adjusts two positions of pointer of buffering area byte and bit according to taken number of bits；
The read method of bit value is：Byte comprising bit to be read is taken out from buffering area, is first moved to left, carried out
Left-justify, then carries out Right Aligns, by bit clear 0 before taken bit, completes actual bit position and reads；
The structure definition of every H.245 message is exactly the definition of composite data type, and the decoding functions of each message finally need tune
With the decoding functions of fundamental type, return value is inserted into signaling tree corresponding node；
The parameter indefinite for number in H.245 message definition, according to the number of number of parameters in real messages, there is provided different
Memory allocation scheme；If number of parameters is less, static storage is used；If Static-state Space is not enough to storage ginseng
Number, then it is dynamic to apply for space.
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| CN106899377B (en) * | 2015-12-17 | 2019-07-12 | 辰芯科技有限公司 | A kind of channel decoding method and device |
| CN113742294A (en) * | 2021-08-23 | 2021-12-03 | 宜通世纪科技股份有限公司 | Method, system, device and medium for decoding ASN.1-PER signaling message |
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