CN1808964B - Method and system of obtaining clock for H.323 multimedia communication network terminal - Google Patents
Method and system of obtaining clock for H.323 multimedia communication network terminal Download PDFInfo
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- CN1808964B CN1808964B CN 200510002657 CN200510002657A CN1808964B CN 1808964 B CN1808964 B CN 1808964B CN 200510002657 CN200510002657 CN 200510002657 CN 200510002657 A CN200510002657 A CN 200510002657A CN 1808964 B CN1808964 B CN 1808964B
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Abstract
This invention discloses one H.323 multi-media communication network terminal to require clock time, which comprises network gate, transmission network and terminal and the method comprises the following steps: terminal starting network gate to send register requirement message; network gate receiving the said register requirement and determining information to terminal back expansion; terminal getting network net gate system time information according tot eh said expansion register message; setting local clock according the said time information. This invention also discloses one H.323 multi-media communication network terminal, which comprises network gate, transmission network and terminal composed of agreement canalization module and date conversion module.
Description
Technical Field
The invention relates to the technical field of multimedia communication, in particular to a method and a system for acquiring a clock by an H.323 multimedia communication network terminal.
Background
With the rapid development of computer network technology and multimedia communication technology, video conferencing or multimedia conferencing has gained general attention in the industry, and currently, an IP (internet protocol) based h.323 video conferencing system has become a hot spot for research and development. H.323 is a standard established by ITU-T (international telecommunication union, telecommunication standardization sector) for transmitting audio, video and data over packet-switched based networks. It describes services like call signalling and control, multimedia transmission and control, bandwidth control and multipoint conferencing. In the h.323-based conference system, the system mainly includes an MCU (multipoint control unit), a GK (gatekeeper), a service unit, and a terminal, and a typical networking structure is shown in fig. 1. Wherein,
the MCU is used for connecting a plurality of user terminals when a conference is held, simultaneously switching video signals, mixing voice signals and transmitting data signals, assembling the switched video, mixed audio and data signals, and then sending the video, mixed audio and data signals to all the user terminals.
The H.323 terminal is a client end providing one-way or two-way real-time communication, and has the functions of encoding, decoding and displaying video and audio signals, and also has the function of data communication such as transmitting still images, files, sharing application programs and the like.
The gatekeeper is an optional component of the h.323 system, and its function is to provide call control services to the h.323 endpoint. The h.323 gatekeeper must provide 4 basic services in the system: address translation, bandwidth control, admission control and zone management functions. The gatekeeper is logically an endpoint-independent functional unit, but may be included in the terminal, MCU, and gateway when physically implemented.
Because the video, voice, control and indication signals of the video conference are transmitted to each other after compression coding, necessary measures must be taken to achieve synchronization of the video conference network in order to ensure the accuracy of the transmitted signals.
In the h.323 conference system shown in fig. 1, the terminal may not have a clock chip and cannot independently maintain a clock due to cost. In order to make each terminal obtain the clock information correctly, a special clock server is usually used to provide a uniform clock source for each terminal. All terminals acquire clocks to a clock server through a standard NTP (network time protocol) protocol.
The specific flow of the process of acquiring clock information through the NTP protocol is shown in fig. 2:
when the terminal needs the current clock information, sending clock request information to a clock server; and after receiving the information, the clock server acquires the current clock and returns the current clock to the terminal.
This implementation provides clock information for all terminals in the whole system, but requires a dedicated clock server in the system, and also requires an increased communication interface between the terminals and the clock server. Therefore, not only is system resources wasted, but also the complexity of system implementation and the workload of system maintenance are increased.
Disclosure of Invention
The invention aims to provide a method and a system for acquiring a clock by an H.323 multimedia communication network terminal, which overcome the defects of complex realization and large system maintenance amount of the prior art in a clock acquisition mode through an NTP protocol, and simply and reliably acquire time information by utilizing the prior system resources.
Therefore, the invention provides the following technical scheme:
a method for acquiring a clock by a h.323 multimedia communication network terminal, said network comprising: gatekeeper, transport network and terminal, the method includes:
A. the terminal sends a registration request message to the gatekeeper after starting;
B. after receiving the registration request message, the gatekeeper returns an extended registration confirmation message to the terminal, wherein the extended registration confirmation message comprises the system time of the gatekeeper;
C. the terminal acquires the system time information of the gatekeeper according to the expanded registration confirmation message;
D. and setting a local clock according to the time information.
The step B comprises the following steps:
b1, setting the format of the extended registration confirmation message;
b2, acquiring the system time of the gatekeeper;
b3, generating the extended registration confirmation message according to the acquired system time of the gatekeeper;
b4, sending the extended registration confirmation message to the terminal.
The extended registration confirmation message further comprises: and (4) non-standard identification.
The time information format is an encapsulation format specified by an H221 protocol.
The time information format is a self-defined packaging format.
The step C comprises the following steps:
c1, analyzing the extended registration confirmation message;
and C2, obtaining the system time information in the extended registration confirmation message.
The step D comprises the following steps:
d1, establishing a clock function of the terminal;
d2, generating the local clock by taking the time information as an input parameter of the clock function.
A system for acquiring a clock by an H.323 multimedia communication network terminal comprises: a gatekeeper, a transport network and a terminal,
the terminal includes:
the protocol analysis module is used for analyzing a registration confirmation message which is received when the terminal registers to the gatekeeper and comprises the system time information extension of the gatekeeper, and acquiring the system time information in the message;
and the date conversion module is coupled with the protocol analysis module and used for carrying out date conversion on the system time information obtained by the protocol analysis module and setting the converted date as the system time of the terminal.
The gatekeeper includes:
the system time acquisition module is used for acquiring the system time of the gatekeeper;
and the message generating module is coupled with the system time acquiring module and used for generating an expanded registration confirmation message according to the system time.
It can be seen from the above technical solutions that the present invention fully utilizes the existing resources to extend the standard RCF (registration confirmation) message in the protocol RAS (registration, access permission and status) signaling between the endpoint and the gatekeeper, and add clock information, when the terminal registers with the gatekeeper, the clock information of the gatekeeper can be obtained through the RCF message, and then set as the terminal local time, and the terminal's own clock is established on the basis of the time. Therefore, not only is the system resource saved, but also the realization is simple, and the workload of system maintenance is reduced.
Drawings
FIG. 1 is a schematic diagram of a typical networking architecture of an H.323-based conferencing system;
fig. 2 is a flow of an h.323 terminal acquiring a clock through an NTP protocol in the prior art;
fig. 3 is a schematic diagram of a registration process of an h.323 terminal;
FIG. 4 is a flow chart of an implementation of the method of the present invention;
FIG. 5 is a functional block diagram of a first embodiment of the system of the present invention;
fig. 6 is a functional block diagram of a second embodiment of the system of the present invention.
Detailed Description
The core of the invention lies in that standard RCF (registration confirmation) message in RAS (registration, access permission and status) signaling between an end point and a gatekeeper is expanded, clock information of the gatekeeper is added in the message, when a terminal registers to the gatekeeper, the gatekeeper returns RCF message to the terminal, the terminal obtains time information according to the message, then the time information is set as the local time of the terminal, and a clock of the terminal is established according to the time.
In order that those skilled in the art will better understand the technical solution of the present invention, the following detailed description of the present invention is provided in conjunction with the accompanying drawings and embodiments.
As known to those skilled in the art, the h.323 call setup procedure involves three types of signaling: RAS signaling, h.225.0 call signaling, and h.245 control signaling. Wherein, RAS signaling adopts the message in H.225 to complete the processes of registration, endpoint positioning, call admission, gateway resource query and the like between the terminal and the gatekeeper. The GK (gatekeeper) is an h.323 entity on the network, and mainly provides address translation for h.323 terminals, gateways, and MCUs (multipoint control units), controls network access, and may also provide other services for the terminals, gateways, and MCUs, such as bandwidth management, positioning gateways, and the like.
The endpoint registration process of the terminal is shown in fig. 3, and includes the following two processes:
(1) after the terminal is started, a standard RRQ (registration request) message needs to be sent to the GK, and the terminal registration process is started;
(2) after the GK receives the RRQ message sent by the terminal, if the registration is successful, a standard RCF (registration confirmation) message is returned to the terminal, otherwise, an RRJ (registration rejection) message is returned.
Therefore, the RCF message is expanded to contain the system time information of the gatekeeper, so that the system time information of the gatekeeper can be obtained after the terminal receives the message, and the clock of the terminal is established on the basis.
For example, the RCF message may be extended as follows:
RegistrationConfirm::＝SEQUENCE--(RCF)
{
requestSeqNum RequestSeqNum,// request sequence number
protocol identifier,// protocol identifier
NonStandardData NonStandardParameter OptiONAL,// NonStandardParameter parameter
CallSignalAddress SEQUENCE OF TRANSPORADDRESS,// Call Signaling Address
TerminalAlias SEQUENCE OF AliasAddress OPTIONAL,// terminal
Alias (e.g. number)
...，
}
The content of the non-standard part is as follows:
NonStandardParameter::＝SEQUENCE
{
NonStandardIndustriant,// nonstandard identifier
data OCTET STRING// time data format of
SERVERCLOCK
}
NonStandardIdentifier ::＝CHOICE
{
OBJECT IDENTIFIER,// OBJECT IDENTIFIER
H221NonStandard H221NonStandard,// H221NonStandard
}
H221NonStandard::＝SEQUENCE
{
t35Countrycode INTEGER (0..255),// Country code
t35Extension INTEGER (0..255),// code under Country
manufaturercode INTEGER (0..65535),// vendor code
}
Thus, the time obtained from GK, which is the number of seconds since 1 month 1 day 0 hour 0 minute 0 second 1970, UTC (universal time coordinate) time, is filled in the server clock, and the reference time zone referred to for this number of seconds is the GMT (greenwich time) standard, i.e., the 0 time zone.
Referring to fig. 4, fig. 4 is a flow chart of the implementation of the method of the present invention:
first, in step 401: an extended RCF (registration confirmation) message format is set, and the message format may be the above-described RCF message extended format, but may also be other formats as long as the message format includes the system time information of the gatekeeper.
In the extended registration confirmation message, including: non-standard mark and time information. The non-standard mark describes non-standard information, and the time information is used for filling system time information of the gatekeeper. The system time of the gatekeeper can be filled in the time information field in the message by adopting an encapsulation format specified by an H221 protocol, and the system time of the gatekeeper can also be filled in the time information field in the message by adopting a self-defined encapsulation format.
Step 402: and after the terminal is started, sending a registration request message to the gatekeeper, and starting a terminal registration process. The registration request message is a standard RRQ (registration request) message specified by the h.323 protocol, and includes information to be registered, such as an alias, an address, and the like.
Step 403: and after receiving the registration request message, the gatekeeper acquires the system time of the gatekeeper. The time can be obtained by calling a time acquisition function provided by an operating system where the gatekeeper is located, and is converted into UTC (Universal time coordinate) time. Step 404: and generating an expanded registration confirmation message according to the acquired system time of the gatekeeper.
Then, proceed to step 405: and sending the expanded registration confirmation message to the terminal.
After receiving the message, the terminal proceeds to step 406: and the terminal acquires the system time information of the gatekeeper according to the received expanded registration confirmation message. Namely, the expanded registration confirmation message is analyzed to obtain the time information therein.
Step 407: and setting a local clock according to the acquired time information.
And converting the acquired UTC time into local time by combining the local time zone, calling a system time setting function provided by a terminal operating system to set the local time as a local clock, and then maintaining the time by the system.
FIG. 5 shows a schematic block diagram of the system of the present invention:
the system comprises: gatekeeper S1, transport network S2 and terminal S3.
In order to enable the terminal S3 to obtain the system time of the gatekeeper according to the extended registration confirmation message, the terminal S3 includes: a protocol analysis module S31 and a date conversion module S32.
When the terminal registers to the gatekeeper through the transmission network, if the registration is successful, the gatekeeper returns the expanded RCF message to the terminal, and after the terminal receives the message, the message is firstly analyzed by the protocol analysis module S31 to obtain the time information in the message; then the date conversion module S32 carries out date conversion on the time information obtained by the protocol analysis module, namely, the system time of the gatekeeper is converted into the local time of the terminal operating system; the time is thereafter maintained by the terminal operating system itself with the local time converted by the date conversion module S32 as a starting point.
In order to enable the gatekeeper to generate the extended RCF message containing the system time information of the gatekeeper, the extended RCF message may be preset, and after the RRQ message of the terminal is received, the system time of the gatekeeper is acquired through software and then added to a corresponding field in the extended RCF message. Of course, it can also be implemented by hardware:
referring to fig. 6, fig. 6 shows a functional block diagram of a second embodiment of the system of the present invention:
when the gatekeeper S1 receives the RRQ message sent by the terminal, the system time acquiring module S11 acquires the system time of the gatekeeper, and then the message generating module S12 generates the extended RCF message according to the system time.
Thus, after the registration is successful, the gatekeeper can send the expanded RCF message generated by the message generation module to the terminal, and the terminal establishes a local clock of the terminal according to the message.
While the present invention has been described with respect to the embodiments, those skilled in the art will appreciate that there are numerous variations and permutations of the present invention without departing from the spirit of the invention, and it is intended that the appended claims cover such variations and modifications as fall within the true spirit of the invention.
Claims (9)
1. A method for acquiring a clock by a h.323 multimedia communication network terminal, said network comprising: a gatekeeper, a transport network and a terminal, characterized in that the method comprises:
A. the terminal sends a registration request message to the gatekeeper after starting;
B. after receiving the registration request message, the gatekeeper returns an extended registration confirmation message to the terminal, wherein the extended registration confirmation message comprises system time information of the gatekeeper;
C. the terminal acquires the system time information of the gatekeeper according to the expanded registration confirmation message;
D. and setting a local clock according to the time information.
2. The method of claim 1, wherein step B comprises:
b1, setting the format of the extended registration confirmation message;
b2, acquiring the system time of the gatekeeper;
b3, generating the extended registration confirmation message according to the acquired system time of the gatekeeper;
b4, sending the extended registration confirmation message to the terminal.
3. The method of claim 1, wherein the extended registration confirmation message further comprises: and (4) non-standard identification.
4. The method of claim 3, wherein the time information format is an encapsulation format specified by the H221 protocol.
5. The method of claim 3, wherein the time information format is a custom encapsulation format.
6. The method of claim 1, wherein step C comprises:
c1, analyzing the extended registration confirmation message;
and C2, obtaining the system time information in the extended registration confirmation message.
7. The method of claim 1, wherein step D comprises:
d1, establishing a clock function of the terminal;
d2, generating the local clock by taking the time information as an input parameter of the clock function.
8. A system for acquiring a clock by an H.323 multimedia communication network terminal comprises: gatekeeper, transport network and terminal, its characterized in that, the terminal includes:
the protocol analysis module is used for analyzing a registration confirmation message which is received when the terminal registers to the gatekeeper and comprises the system time information extension of the gatekeeper, and acquiring the system time information in the message;
and the date conversion module is coupled with the protocol analysis module and used for carrying out date conversion on the system time information obtained by the protocol analysis module and setting the converted date as the system time of the terminal.
9. The system of claim 8, wherein the gatekeeper comprises:
the system time acquisition module is used for acquiring the system time of the gatekeeper;
and the message generating module is coupled with the system time acquiring module and used for generating an expanded registration confirmation message according to the system time.
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| KR20030027466A (en) * | 2001-09-28 | 2003-04-07 | 삼성전자주식회사 | Method and apparatus for forwarding call in ip-pcx |
| CN1457198A (en) * | 2002-05-10 | 2003-11-19 | 华为技术有限公司 | Conference dispatching system and method of IP network meeting TV-set |
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| KR20030027466A (en) * | 2001-09-28 | 2003-04-07 | 삼성전자주식회사 | Method and apparatus for forwarding call in ip-pcx |
| CN1457198A (en) * | 2002-05-10 | 2003-11-19 | 华为技术有限公司 | Conference dispatching system and method of IP network meeting TV-set |
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Granted publication date: 20100428 Termination date: 20170121 |