KR20080049876A - Apparatus and method for processing jitter and rearranging packet sequence in network based on udp/rtp - Google Patents

Abstract

An apparatus and a method for rearranging a packet sequence for jitter processing on a network based on UDP/RTP(User Datagram Protocol/Real-time Transport Protocol) are provided to operate the buffer of a receiving terminal dynamically and rearrange the order of RTP packets transmitted from a network such as the Internet, thereby improving the transmission quality of data suitably for a VoIP(Voice over Internet Protocol) service. A buffer(50) stores data satisfying a first standard out of data from a network and plays out data satisfying a second standard out of the stored data. A data processing block(54) determines whether the receiving data satisfy the first standard and the second standard, and transfers the satisfied data to the buffer. A descriptor block(58) provides data including the parameters of the data processing block, the standards of the determination, to the data processing block.

Description

JAPTER AND METHOD FOR PROCESSING JITTER AND REARRANGING PACKET SEQUENCE IN NETWORK BASED ON UDP / RTP}

1 illustrates a UDP packet format.

2 is a voice flowchart of a VoIP network.

3 illustrates an RTP header format.

4 is a view schematically showing the structure of a conventional buffer.

5 schematically illustrates one embodiment of the structure of a buffer;

6 illustrates one embodiment of a format of a descriptor.

7 is a data processing flow diagram according to one embodiment.

<Explanation of symbols for the main parts of the drawings>

40, 50: buffer 44: buffer control memory

54: incoming data processing block 58: descriptor block

The present invention relates to jitter processing and packet order rearrangement in a network for transmitting voice, video and data using User Datagram Protocol / Real-time Transport Protocol (UDP / RTP).

UDP (User Datagram Protocol) is a communication protocol that unilaterally transmits data on the sender's side without going through a procedure of transmitting or receiving a signal to send or receive information. In Transmission Control Protocol / Internet Protocol (TCP / IP), data is exchanged by combining any one of IP, a network layer protocol corresponding to the third layer, and TCP or UDP, a transport layer protocol corresponding to the fourth layer. Communication is started after establishing a session. However, UDP does not establish a session and sends data to the other address and does not perform data recovery. Therefore, UDP is less reliable than TCP, but protocol processing speed is much faster. fast. UDP provides an IP service with process-to-process communication in addition to host-to-host communication. As shown in FIG. 1, UDP is a very simple protocol that adds minimal overhead to a data field of a data packet. In general, if a process wants to send a small message and not worry about its reliability, it uses UDP rather than TCP to send a small message.

On the other hand, real-time data services such as Voice over Internet Protocol (VoIP), a communication service technology that converts voice data into Internet Protocol (IP) data packets to enable calls over general telephone networks, is based on UDP-based RTP / RTCP (Real-time). Transport Protocol / RTP Control Protocol) is widely used. 2 is a flowchart of voice data in a basic VoIP network, which may be applied to a real-time data service for processing video and data using UDP / RTP. Referring to FIG. 2, a voice is converted into an analog signal by a voice input device and then digitized by a codec. The digitized voice is compressed by a suitable compression scheme selected, and when the mute removal function is selected during compression, the generated traffic can be reduced by eliminating silence in the voice. The compressed voice packet is RTP packetized to be delivered through the Internet. As shown in FIG. 3, the RTP packet has a Timestamp field indicating the time of occurrence of each packet. Synchronization is possible. As the RTP packet passes through the Internet, propagation delays, delay variations, and packet loss may occur. The propagation delay means the absolute Internet pass delay, and the delay variation, or jitter, is defined as the difference between the maximum propagation delay and the minimum propagation delay. Since each packet has a different propagation delay, a delay variation occurs. Since this delay variation adversely affects voice quality, a buffer is used at the receiving end to absorb the delay variation between RTP packets. That is, after storing the RTP packets transmitted through the Internet in a buffer and playing them out in time according to the timestamp value in the RTP packets, data without jitter is output.

FIG. 4 illustrates the structure of a buffer located at the receiving end of the flowchart of FIG. 2. As shown in FIG. 4, a packet introduced from the Internet is first stored in a buffer 40, and an address or location information of the stored buffer and an RTP Sequence Number (SN) of the incoming packet are stored. ) Is stored in the buffer control memory 44 assigned to the connection. When it is time to read the packet stored in the buffer according to the timestamp value of the RTP packet, the address value having the smallest sequence number among all the location information stored in the buffer control memory is selected, and the packet stored in the corresponding buffer is played out. . When the buffer read process is completed, the location information is cleared and the buffer is switched to the ready state for the next incoming packet.

However, if the timing of playing out the data stored in the buffer depends only on the timestamp value of the RTP, accurate buffer playout according to the timestamp value can be performed when the accuracy of the buffer read clock is low. none. That is, if a little bit delay occurs continuously, one packet may be delayed someday. In addition, if a packet with a sequence number lower than the sequence number already played out from the buffer is introduced, unnecessary processing may be performed once more, which may affect system performance, and reading and writing the buffer and the buffer control memory simultaneously ( synchronous) can cause problems with packet processing performance.

The present invention is to solve the problems of the prior art, by dynamically operating the buffer of the receiver to reduce the delay variation in a network using UDP / RTP, by rearranging the order of the RTP packet transmitted through the network, The purpose of the present invention is to improve the transmission quality of data to be suitable for real-time data transmission services such as VoIP.

According to one embodiment, a jitter processing and packet order rearrangement apparatus in a network using UDP / RTP (User Datagram Protocol / Real-time Transport Protocol) is provided. The apparatus stores a data satisfying a first criterion among data flowing from the network, and a buffer for playing out data satisfying a second criterion among the stored data, wherein the incoming data includes the first criterion and the first data. An inflow data processing block that determines whether two criteria are satisfied and delivers the buffer to the buffer, and a descriptor block that provides the inflow data processing block to the inflow data processing block, including parameters that are criteria for the determination of the inflow data processing block. .

According to another embodiment, a jitter processing and packet order rearrangement method in a network using UDP / RTP is provided. According to the method, the incoming data processing block reads the descriptor to check whether the connection of the incoming data from the network is valid, and if the connection of the incoming data is valid, whether the number of data stored in the buffer is within the allowable range. If the data stored in the buffer is within the allowable range, the number of the introduced data is compared with the playout threshold of the buffer. The inflow data processing block updates the descriptor according to the comparison result, and if the number of the inflow data is equal to the playout threshold of the buffer, play the data from the buffer according to the timestamp value of the inflow data. Out and update the descriptor accordingly.

The present invention provides an apparatus and method for jitter processing and packet order rearrangement in a network using UDP / RTP. EMBODIMENT OF THE INVENTION Hereinafter, with reference to an accompanying drawing, embodiment of this invention is described in detail.

Figure 5 shows an embodiment of the structure of the buffer of the receiving end. As shown in FIG. 5, data flowing from a network such as the Internet is stored in the data storage buffer 50 in the form of data from which IP header is removed, only data suitable for a user criterion through the inflow data processing block 54. do. The determination of whether to receive or discard the data flowing through the incoming data processing block 54 is made by reading the contents of the descriptor block 58. As shown in FIG. 6, the descriptor includes V, F, PacketNo, BaseBITMAP_D, BaseBITMAP, BITMAP, BaseSN, FirstRxSN, and RoundCount fields. V is a valid bit that indicates whether a normal connection is established to data flowing from the network. If the V field is set to '0', the incoming data is discarded. The F field is a flag bit and is set to '1' if the number of data stored in the buffer coincides with the buffer playout threshold determined by the user, which means that the buffer is ready to be read. The PacketNo field indicates the number of packets stored per connection. The BITMAP field is a parameter indicating the position of data stored in the buffer. If the data is stored in the buffer, the bit of the corresponding position is set to '1', and if the BITMAP field is '0', it means that no packet is stored. The BaseBITMAP field is a parameter that indicates the position to be read most quickly in the BITMAP field. The position of '1' which is the same as or closest to the position of '1' in this parameter is determined as the buffer to be read next. The BaseBITMAP_D field is the binary value of the position of '1' in the BaseBITMAP field. If bit 0 is 1, it is '0', bit 1 is '1', and bit 2 is '10'. . The BaseSN field is a parameter representing a sequence number that is a criterion for determining whether to receive or discard incoming data. If the value is smaller than the BaseSN field, it is discarded. The FirstRxSN field is a parameter indicating the sequence number of the first played out data. The RoundCount field is a parameter indicating how many times the descriptor has been read in a predetermined time unit, for example, 5 ms, and the predetermined time unit may be determined by the user. The time to play out the data stored in the buffer is determined by the RoundCount field value and the F bit. For example, in the case of the AMR codec, since the time stamp is 20 ms, when the descriptor is read in 5 ms units, when the F bit is '1' and the RoundCount field value is '3', the data stored in the buffer is played out. .

Referring back to FIG. 5, the buffer size and buffer playout threshold must be determined before the incoming data processing block 54 performs normal operation. These two values can be determined by the user to obtain optimal performance. The incoming data processing block 54 operates in precise synchronization with the descriptor block 58. When data comes from a network such as the Internet, the incoming data processing block 54 checks the V bit value of the descriptor of the connection, discards the data if the value is '0', and buffers the data if the value is '1'. 50) and update the contents of the descriptor block 58. Also, if the number of stored packets equals the threshold for playing out data, it sets the F bit of the descriptor to '1' and informs that it is time to read the buffer 50. Upon reading the buffer 50, the incoming data processing block 54 updates the contents of the descriptor accordingly.

7 illustrates an embodiment of a process of processing data flowing from a network. Hereinafter, to help understand the operation of the descriptor, the data coming from the network is voice data having a time stamp of 20 ms, and the buffer can accommodate a delay variation of up to 120 ms (± 60 ms), and play the data stored in the buffer. Assume that the buffer playout threshold for out is three. Under this assumption, only the lower 6 bits (5: 0) are used for the 24-bit BITMAP field and the BaseBITMAP field, and the BaseBITMAP_D field is only counted from 0 to 5.

Referring to FIG. 7, when data flows from the network, the incoming data processing block first reads a descriptor to check whether the connection of the incoming data is valid (s71), discards it if it is not valid, and if it is valid, the number of data stored in the buffer. Check whether is within the allowable range (s72). If the number of data stored in the buffer is outside the allowable range, the incoming data is discarded, and if it is within the allowable range, the data is transferred to the next step.

Thereafter, the incoming data processing block compares the playout threshold set by the user with the PacketNo field value of the descriptor (s73). First, when the PacketNo field value is smaller than the threshold value and the PacketNo field value is '0', that is, when the incoming data is the first data, the FlagNo becomes '0' because the PacketNo field value is smaller than the threshold value. Is stored at the center of the buffer, and the BITMAP field and the BaseBITMAP field indicating the position are "000100", and since the "1" is located in bit 2, the BaseBITMAP_D field is updated to "00010". In addition, the BaseSN / FirstRxSN field to be compared with the sequence number (SN) of incoming data is updated with the sequence number of the incoming data, and since the read and write cycles of the buffer are completely separated, the RoundCount field is a value read from the descriptor. It is used as is. The update results are as follows (see Example 1).

<Example 1>

Flag <= '0';

PacketNo <= '1';

BaseBITMAP_D <= "00010";

BaseBITMAP <= "000100";

BITMAP <= "000100";

BaseSN <= RTP Sequence Number of Incoming Data;

FirstRxSN <= RTP Sequence Number of Incoming Data;

RoundCount <= RoundCount of Descriptor;

If the PacketNo field value is smaller than the threshold value, the PacketNo field value is '1', and the sequence number (SN) is greater than 1 than the BaseSN field, data is introduced. The PacketNo field value is increased by 1 to become '2'. Since the SN of the newly imported data is larger than the BaseSN field, the BaseBITMAP and BaseBITMAP_D fields retain their existing values, and since the SN of the imported data is one greater than the BaseSN field, the new BITMAP field replaces the existing BITMAP and BaseBITMAP fields. It is updated with the ORed value with the value shifted by 1 to the left. The update result is as follows (see Example 2).

<Example 2>

Flag <= '0';

PacketNo <= '2';

BaseBITMAP_D <= "00010";

BaseBITMAP <= "000100";

BITMAP <= "001100";

BaseSN <= FirstRxSN of Descriptor;

FirstRxSN <= FirstRxSN of Descriptor;

RoundCount <= RoundCount of Descriptor;

When the PacketNo field value is smaller than the threshold value, the PacketNo field value is '1', and the sequence number (SN) is 1 smaller than the BaseSN field, Flag is '0', and the PacketNo field value is '2'. Becomes Since the SN of the newly introduced data is smaller than the BaseSN field, the BaseBITMAP field is changed to the position "000010" of the newly introduced data, and since the position of '1' is 1 bit, the BaseBITMAP_D field is updated to "00001". Since the SN of the imported data is one less than the BaseSN field, the new BITMAP field is updated with the ORed value between the existing BITMAP field and the BaseBITMAP field shifted to the right by one. The update results are as follows (see Example 3).

<Example 3>

Flag <= '0';

PacketNo <= '2';

BaseBITMAP_D <= "00001";

BaseBITMAP <= "000010";

BITMAP <= "000110";

BaseSN <= RTP Sequence Number of Incoming Data;

FirstRxSN <= RTP Sequence Number of Incoming Data;

RoundCount <= RoundCount of Descriptor;

When new data is introduced while the PacketNo field value is '2', the data with the smallest SN becomes the BaseSN / FirstRxSN field compared to the two data SNs introduced earlier, and the Flag bit indicating that the buffer can be read is Is set to '1'. If data with sequential SNs is introduced, the update result is as follows (see Example 4).

<Example 4>

Flag <= '1';

PacketNo <= '3';

BaseBITMAP_D <= "00010";

BaseBITMAP <= "000100";

BITMAP <= "011100";

BaseSN <= FirstRxSN of Descriptor;

FirstRxSN <= FirstRxSN of Descriptor;

RoundCount <= RoundCount of Descriptor;

Once the Flag bit is set, incoming data with an SN less than the BaseSN field is discarded. In the BITMAP field indicating the location where data is stored, the bit is set to the left based on bit 2, and when the last 5 bits are set, the next incoming data is operated to the location of bit 0.

Descriptors that also indicate when the read playout of a buffer is read are accessed every 5ms per connection, and once accessed, the RoundCount field is incremented by one. If the RoundCount field value is 3 and the Flag bit is '1' (s74), the baseSN, BaseBITMAP, and BaseBITMAP_D field values are read from the position of the data that is the same as or closest to the left of the BaseBITMAP field. The RoundCount field is reinitialized. If the RoundCount field value is 3 and the parameter read from the descriptor is the same as the update contents of <Example 4>, bit 2 is indicated because bit 2 of the BaseBITMAP field and bit 2 of the BITMAP field are located in the same place. Play out the data in the buffer, and the update result is as follows (see Example 5).

<Example 5>

Flag <= '1';

PacketNo <= '2';

BaseBITMAP_D <= "00011";

BaseBITMAP <= "001000";

BITMAP <= "011000";

BaseSN <= FirstRxSN of Descriptor + 1;

FirstRxSN <= FirstRxSN of Descriptor;

RoundCount <= 0;

If the RoundCount field value is 3 and the parameter read from the descriptor is as in <Example 6> below,

<Example 6>

Flag <= '1';

PacketNo <= '3';

BaseBITMAP_D <= "00010";

BaseBITMAP <= "000100";

BITMAP <= "111000";

BaseSN <= FirstRxSN of Descriptor;

FirstRxSN <= FirstRxSN of Descriptor;

RoundCount <= 3;

Bit 2 of the BaseBITMAP field and the bit closest to the left are bit 3 of the BITMAP field, so the update result is as follows (see Example 7).

<Example 7>

Flag <= '1';

PacketNo <= '2';

BaseBITMAP_D <= "00100";

BaseBITMAP <= "010000";

BITMAP <= "110000";

BaseSN <= FirstRxSN of Descriptor + 2;

FirstRxSN <= FirstRxSN of Descriptor;

RoundCount <= 0;

In order to dynamically control the buffer, when the buffer is full (s75), the data stored in the buffer may be read instead of one, thereby providing a space for data to be introduced next. If the number of data stored in the buffer is 2 or more (s76), the process is performed in the same process as in step s74. If the number of data stored in the buffer is 1 (s77), the corresponding data is read and stored in the descriptor. If all the parameters except the V bit are initialized and data is newly introduced, the process starts again from step s73.

While the invention and its various functional components have been described in particular embodiments, the invention may be implemented in hardware, software, firmware, middleware, or a combination thereof, and the system, subsystem, components or sub-configurations thereof. It should be understood that they can be used as elements. If implemented in software, the elements of the invention are instructions / code segments for performing the necessary tasks. The program or code segments may be stored in a machine readable medium, such as a processor readable medium, a computer program product, or via a transmission medium or communication link by a computer data signal embodied in a carrier wave or a signal modulated by a carrier. Can be sent. Machine readable media or processor readable media may include any medium that can store or transmit information in a form readable and executable by a machine (eg, processor, computer, etc.).

Although the above embodiments have been described with reference to the embodiments shown in the drawings for clarity, these are merely exemplary, and various modifications and equivalent other embodiments are possible to those skilled in the art. Will understand. Therefore, the technical protection scope of the present invention will be defined by the appended claims.

According to the above embodiments, the processing of the jitter generated in the network using UDP / RTP dynamically operates the buffer of the receiving end, and rearranges the order of the RTP packets transmitted through the network such as the Internet, The transmission quality of data can be improved to be suitable for the same service. In addition, it is possible to set the size of the buffer and the playout threshold of the buffer according to the user's requirements, thereby adapting to various network characteristics.

Claims (17)

Jitter processing and packet order rearrangement in a network using UDP / RTP (User Datagram Protocol / Real-time Transport Protocol), A buffer for storing data satisfying a first criterion among data flowing from the network, and playing out data satisfying a second criterion among the stored data; An inflow data processing block which determines whether the inflow data satisfies the first criterion and the second criterion, and transmits the inflow data to the buffer; Descriptor block provided to the inflow data processing block including the parameters that are the criteria of the determination of the inflow data processing block Device comprising a. The method of claim 1, And the data coming from the network is RTP packet data. The method of claim 1, The parameters A V parameter indicating whether a normal connection is established to data flowing from the network, An F parameter indicating whether the buffer is ready for playout, PacketNo parameter indicating the number of data stored per connection, A BITMAP parameter indicating a location of data stored in the buffer, A BaseBITMAP parameter indicating a position to be read fastest in the BITMAP parameter, A BaseBITMAP_D parameter representing a position of '1' of the BaseBITMAP parameter in binary, A BaseSN parameter indicating a sequence number as a reference for determining whether to receive or discard data flowing from the network; A FirstRxSN parameter indicating the sequence number of the first played out data, and RoundCount parameter indicating how many times the descriptor block has been read in a predetermined time unit. Device comprising a. The method of claim 1, The parameters are updated by the incoming data processing block. The method of claim 1, Wherein the size of the buffer and the playout threshold of the buffer are determined by a user. The method of claim 1, The first criterion is a condition indicating whether a normal connection is established to data flowing from the network. The method of claim 1, And the second criterion is a condition indicating whether the number of data stored in the buffer is equal to a playout threshold of the buffer. The method of claim 3, And the first criterion is determined based on the V parameter. The method of claim 3, And the second criterion is determined based on the F parameter and the RoundCount parameter. Jitter processing and packet order rearrangement in a network using UDP / RTP, Checking, by the incoming data processing block, the descriptor to confirm that the connection of the incoming data from the network is valid; If the incoming data connection is valid, checking, by the incoming data processing block, whether the number of data stored in the buffer is within an allowable range; If the data stored in the buffer is within an allowable range, the inflow data processing block comparing the number of the inflow data with a playout threshold of the buffer; Updating the descriptor by the incoming data processing block according to the comparison result, and If the number of incoming data is equal to the playout threshold of the buffer, playing out data from the buffer according to the timestamp value of the incoming data, and updating the descriptor accordingly How to include. The method of claim 10, And the size of the buffer and the playout threshold of the buffer are determined by a user. The method of claim 10, If the connection of the incoming data is not valid, further including the inflowing data processing block discarding the incoming data. The method of claim 10, And if the number of data stored in the buffer is outside the allowable range, discarding the introduced data by the incoming data processing block. The method of claim 10, If the number of incoming data is equal to the playout threshold of the buffer, the incoming data processing block further includes discarding incoming data with an order number less than a predetermined reference sequence number. The method of claim 10, If the number of data stored in the buffer is equal to the size of the buffer, playing out two data stored in the buffer and updating the descriptor accordingly. The method of claim 10, And if the number of data stored in the buffer is 1, the data is played out and initializing all parameters except parameters indicating whether the connection is valid in the descriptor. A computer readable storage medium storing computer executable instructions for executing the method of claim 10.

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