KR20050066950A - Apparatus and method of the hierarchical transmission of a multimedia data ts for preventing the jitter of timing information, and apparatus and method of recovering a multimedia data ts transmitted hierarchically - Google Patents

Abstract

1. TECHNICAL FIELD OF THE INVENTION

The present invention relates to a hierarchical transmission apparatus and method for transmitting a multimedia data transport stream for preventing timing information jitter, and to a restoration apparatus and method for a hierarchically transmitted multimedia data transmission stream.

2. The technical problem to be solved by the invention

According to the present invention, a user packet in a multimedia data transport stream (for example, MPEG TS) is transmitted in a hierarchical manner according to priority, and a user packet having timing information (for example, PCR) is transmitted at the transmitting side. Higher priority (HP) layer packets including location information are transmitted together with location information (e.g., serial number, etc.), and at the receiving end, the location information is used to transmit a higher level in the original multimedia data transmission stream. By accurately restoring the positions of the layer packets, it is possible to prevent the generation of timing information jitter, to enable selective reception according to each layer through a general demultiplexer, and to increase the reception rate even in a poor transport channel situation. Hierarchical transmission apparatus and method for transmitting multimedia data transmission stream for preventing timing information jitter To provide a reconstructed device of a multimedia data stream and a method that are sent to the purpose.

3. Summary of the Solution of the Invention

According to an aspect of the present invention, there is provided a hierarchical transmission apparatus for transmitting a multimedia data transmission stream (TS), comprising: input matching means for receiving an encoded multimedia data transmission stream from the outside and classifying the data into packet units; Serial number inserting means for inserting serial numbers in accordance with an input order for each multimedia data transport stream (TS) packet outputted from said input matching means; Error detection code insertion means for generating a user packet by inserting an error detection code into the multimedia data transmission stream (TS) packet inserted with the serial number; Hierarchical information storage means for storing hierarchical information about a packet designated by a user; Hierarchical separation means for hierarchically separating the user packet output from the error detection code insertion means by using the stored hierarchical information; Hierarchical storage means for dividing and storing the hierarchically separated user packets by layers; And forming a hierarchical transmission frame by combining a predetermined number of the stored user packets and corresponding layer information for each layer, and transmitting the configured hierarchical transmission frame in different transmission schemes for each layer. Including means.

4. Important uses of the invention

The present invention is used to transmit / restore multimedia streams to prevent PCR jitter.

Description

Apparatus and method of the hierarchical transmission of a multimedia data TS for preventing a hierarchical transmission apparatus and method thereof for multimedia data transmission stream for preventing timing information jitter the jitter of timing information, and Apparatus and Method of recovering a multimedia data TS transmitted hierarchically}

The present invention relates to a hierarchical transmission of a multimedia data transport stream and a restoration technology of a multimedia data transport stream transmitted hierarchically, and more particularly, in a transmitting side, a multimedia data transport stream (eg, MPEG TS) is provided. User packets are separated and transmitted hierarchically according to priority, and location information (for example, high priority) packets including user packets with timing information (for example, PCR) are included. For example, the serial number, etc.) are transmitted together, and the receiving side uses the position information to accurately restore the position of higher layer packets in the original multimedia data transport stream. Transmission device and method thereof, and the hierarchically transmitted multimedia data transmission stream. Source to an apparatus and a method thereof.

Recently, in terrestrial digital video broadcasting (DVB-T: Terrestrial) or satellite digital video broadcasting (DVB-S2: Digital Video Broadcasting-Satellite 2), data to be transmitted is classified and transmitted according to the content, or a channel. There is an active standardization of how to receive some or all of the transmitted data according to the situation.

In such a recent situation, a hierarchical transmission scheme in which a broadcast service or a data communication service can be provided in various channel environments is considered as a basic structure of next generation broadcast / communication convergence.

In the conventional hierarchical transmission schemes, most hierarchical channel coding / decoding and modulation / demodulation schemes focus on the other hand, but do not specifically mention the peripheral devices required when such schemes are used.

In addition, most of the hierarchical transmission schemes that have been proposed in the past are not actually used. One of the reasons is that when the channel is in a bad state or when only the desired layer is received, only the packets of the corresponding layer are used for the MPEG-2 inverse. It was difficult to restore the MPEG transport stream to the multiplexer.

In particular, one of serious problems in the conventional hierarchical transmission scheme is that the MPEG transport stream (MPEG TS) transmitted in the hierarchical transmission system is not restored to its original state at the receiver side, and also the MPEG transport stream (MPEG TS). This is because jitter occurs because the location of the packet with PCR information in the network changes.

As a conventional method for solving the above problems, a method of transmitting a separate hierarchically separated (MPEG TS) for each independent MPEG transport stream (MPEG TS) has been proposed, but in this case hierarchical transmission The implementation of the system is complicated and expensive, and there is a problem in that the receiving side requires a special demultiplexer composed of a plurality of MPEG TS demultiplexers rather than a general MPEG TS demultiplexer for selective reception according to each layer.

That is, one of the problems in transmitting the actual MPEG-2 TS by using the hierarchical transmission method is to separate the layers, transmit the separated layers in different transmission methods, and then restore the MPEG-2 TS. Jitter occurs in the process. This is because a packet having timing information PCR of an MPEG transport stream deviates from the position of the original MPEG transport stream MPEG TS. Therefore, when the MPEG TS is divided into layers using a hierarchical structure and then transmitted, the receiver receives the corresponding layer and outputs the MPEG TS to the receiver to selectively select the reception layer. In this case, it should be restored to a complete MPEG transport stream (MPEG TS) including timing information. For this function, a separate system, such as a remultiplexer, must be used on the transmitting side to generate an MPEG transport stream (MPEG TS) including new timing information for each layer. In addition, even when using the remultiplexer, there is a problem that it is difficult to receive several layers at the same time in the receiver.

On the other hand, another conventional method for eliminating jitter as described above is a method of correcting a PCR value in an MPEG transport stream (MPEG TS) in accordance with an MPEG transport stream (MPEG TS) newly configured at the reception side (solution at the reception side). How). However, in order to accurately correct the PCR value in order to eliminate the PCR jitter, there is a problem that it is necessary to add a new circuit to the receiver and apply a complex algorithm.

The present invention has been proposed to solve the above problems, and at the transmitting side, user packets in one multimedia data transport stream (for example, MPEG TS) are separated and transmitted hierarchically according to priority, and also timing Location information (e.g., serial number, etc.) is transmitted together with high priority (HP) layer packets including user packets with information (e.g., PCR), and the receiving side transmits the location information. By precisely restoring the positions of upper layer packets in the original multimedia data transport stream, it prevents the occurrence of timing information jitter, and enables selective reception according to each layer through a general demultiplexer. It is a multimedia for preventing jitter of timing information, which can increase the reception rate even in a poor transmission channel situation. It provides a foundation hierarchical transmission unit of a transport stream and a method and a recovery apparatus in the multimedia data stream transmitted in a hierarchical way and that it is an object.

Other objects and advantages of the present invention can be understood by the following description, and will be more clearly understood by the embodiments of the present invention. Also, it will be readily appreciated that the objects and advantages of the present invention may be realized by the means and combinations thereof indicated in the claims.

According to an aspect of the present invention, there is provided a hierarchical transmission apparatus for a multimedia data transport stream (TS), comprising: input matching means for receiving an externally encoded multimedia data transport stream in packet units; Serial number inserting means for inserting serial numbers in accordance with an input order for each multimedia data transport stream (TS) packet outputted from said input matching means; Error detection code insertion means for inserting an error check code into the multimedia data transmission stream (TS) packet having the serial number inserted therein to generate a user packet; Hierarchical information storage means for storing hierarchical information about a packet designated by a user; Hierarchical separation means for hierarchically separating the user packet output from the error detection code insertion means by using the stored hierarchical information; Hierarchical storage means for dividing and storing the hierarchically separated user packets by layers; And forming a hierarchical transmission frame by combining a predetermined number of the stored user packets and corresponding layer information for each layer, and transmitting the configured hierarchical transmission frame in different transmission schemes for each layer. Means;

On the other hand, the present invention, in the multimedia data transport stream recovery apparatus, receiving hierarchical transport frames transmitted through a transport channel, hierarchical frame reception and user for extracting user packets and hierarchical information from the received transport frame Packet extraction means; Error packet removal and layer separation means for removing a user packet having an error during transmission by using an error detection code in the extracted user packet, and separating user packets without errors by layers using the extracted layer information. ; Hierarchical storage means for separately storing user packets outputted from the error packet removing means for each hierarchical layer; Scheduling means for restoring user packets stored for each layer in the hierarchical storage means in the order of the original multimedia data transport stream using location information in the user packet; Error detection code / location information removal means for restoring a multimedia data transport stream (TS) packet by removing the error detection code and location information from the scheduled and restored original user packet; And an output matching means for receiving the restored multimedia data transport stream (TS) packet, converting a data rate, and outputting the converted data to the multimedia data transport stream TS.

The present invention provides a hierarchical transmission method of a multimedia data transport stream, comprising: an input matching step of receiving a multimedia data transport stream (TS) encoded from the outside and classifying the data into packet units; A serial number is inserted according to the input order for each multimedia data transmission stream (TS) packet classified in the input matching step, and an error check code is inserted into the multimedia data transmission stream (TS) packet in which the serial number is inserted. Inserting a serial number / error detection code to insert a code) to generate a user packet; A hierarchical separation step of hierarchically separating and storing the user packets into which the serial number and the error detection code are inserted, using the hierarchical information on the packet designated by the user; And forming a hierarchical transmission frame by tying a predetermined number of the stored user packets and corresponding layer information for each layer, and transmitting the configured hierarchical transmission frame by different transmission methods for each layer. It includes.

On the other hand, the present invention, in the MPEG transport stream recovery method, receiving hierarchical transport frames transmitted through a transport channel, hierarchical frame reception and user packet extraction for extracting user packets and layer information from the received transport frame step; Eliminates an error packet generated during transmission by using an error detection code in the extracted user packet, and removes an error packet that separates and stores error-free user packets for each layer using the extracted layer information. And storing by layer; A scheduling step of restoring the user packet stored for each layer in order of the original multimedia data transport stream (TS) through scheduling using location information in the user packet; An error detection code / location information removal step of restoring a multimedia data transmission stream (TS) packet by removing the error detection code and location information from the user packets restored in the original order by the scheduling step; And an output matching step of converting a transmission rate for the restored multimedia data transport stream (TS) packet and outputting the multimedia data transport stream (TS).

The above objects, features and advantages will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, whereby those skilled in the art may easily implement the technical idea of the present invention. There will be. In addition, in describing the present invention, when it is determined that the detailed description of the known technology related to the present invention may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a configuration diagram of a hierarchical transmission apparatus of a multimedia data transmission stream and a restoration apparatus of a hierarchically transmitted multimedia data transmission stream for preventing timing information jitter according to the present invention. It shows the process of separating / transmitting / restoring into multiple layers. Here, the multimedia data transport stream is a concept including an MPEG transport stream (MPEG TS) and the like. Hereinafter, an MPEG transport stream (MPEG TS) and PCR, which is timing information thereof, will be described.

The present invention relates to a technology for transmitting MPEG TSs generated for broadcasting or communication according to contents and transmitting them to different layers, based on MPEG-2 TS in a transmission channel environment in which an error may occur. It solves the PCR jitter problem that occurs during hierarchical classification / transmission / restore of one MPEG TS during broadcast or communication using hierarchical transmission.

First, a hierarchical transmission apparatus 100 for an MPEG transport stream in a digital broadcasting transmission system will be described.

MPEG transmission stream (MPEG TS) input matching unit 101 classifies the MPEG transmission stream (TS) output from the MPEG-2 multiplexer (not shown in FIG. 1) of the encoding apparatus and inputs it in packet units, and distinguishes each segment. The time stamp may be inserted into the packet so that the MPEG TS output matching unit 127 may adjust the transmission rate. Here, each packet is composed of a payload and a sync byte (SYNC). Although the case where the time stamp is inserted in the MPEG TS input matcher 101 so that the bit rate is adjusted by using the time stamp in the MPEG TS output matcher 127 has been described as an embodiment, Since the transmission rate can be adjusted using various existing techniques without using time stamps, time stamps are not shown in the MPEG TS packet of FIG.

When the serial number inserting unit 102 inserts and inserts a sequence number in 188 byte unit MPEG Transport Stream (MPEG TS) packet according to the input order, the error detecting code inserting unit 103 generates an error detecting code ( Error Check Code) is inserted to generate one user packet.

After the above process, a general hierarchical transmission process is performed. That is, the hierarchical splitter 105 uses the information contained in the header of the MPEG TS to separate individual user packets from the upper (HP) layer according to the hierarchical information stored in the hierarchical information table storage 104. It is divided into layers such as LP layer. Here, the layer separation may be divided into two layers (that is, the upper (HP) layer, the lower (LP) layer), or may be further divided into three or more layers.

When the MPEG TS stream packet is divided into layers by the layer separation unit 105, the packet including the PCR in the TS must be classified and transmitted as the most stable transport layer (ie, the highest layer). . For example, in the case of the second layer, it must be classified and transmitted as HP (High Prority). This is because the PCR value is clock information transmitted from the transmitter to the receiver, and is a value necessary for demultiplexing in the receiver. PCR is included in an adaptation field of an MPEG transport stream (MPEG TS), and the presence or absence of this region can be determined by 2 bits of adaptation field control information.

Meanwhile, the layer information table storage unit 104 stores layer information about each user packet designated by a user according to priority, that is, information on which layer each user packet belongs to. .

Each layer buffer (106, 107) stores the user packet belonging to each layer for a certain time, hierarchical framing and transmission unit 108 to transmit the user packet stored for a predetermined time frame by frame After framing, each frame is transmitted through the transmission channel 110 according to the transmission scheme assigned to each layer.

In this case, the transport frame configuration process detects the number of user packets stored in each layer buffer 106 for a predetermined time, and detects the user packets arriving at the layer buffers 106 and 107 for the predetermined time and the user packets. A process of forming a single transport frame by combining hierarchical information and a frame header.

The transmission channel 110 may have an error, and may correspond to a wireless channel including a satellite communication channel and a mobile communication channel, and a wired channel through which packet loss may occur.

Next, when the MPEG transmission stream restoration apparatus 120 on the receiving side is removed, it is as follows.

The hierarchical frame receiving and user packet extracting unit 121 receives a hierarchical transmission frame transmitted in a different transmission method for each layer and removes a header from the received transmission frame. ) And hierarchical information is extracted.

The error packet removal and layer separation unit 122 removes an error packet that has an error during hierarchical transmission by using an error detection code (ECC) in the user packet, and user packets without errors are hierarchical frames. The layer information extracted by the reception and user packet extracting unit 121 is separated into layers and stored in the layer buffers 123 and 124.

The scheduler 125 restores the user packets stored in the buffers 123 and 124 of each layer in the original order using location information such as serial numbers and outputs them to the error detection code / serial number removal unit 126.

Then, the error detection code / serial number removal unit 126 removes the error detection code (ECC) and serial number inserted in the packet for each of the restored MPEG TS packets.

The MPEG TS output matching unit 127 outputs the MPEG TS from which the error detection code / serial number has been removed to the outside (i.e., the decoding device), wherein the final output rate of the MPEG TS is transmitted in a hierarchical manner of the transmitting MPEG transport stream. The output is matched with the input transmission rate input to the transmission device (more precisely, the MPEG TS input matching unit) 100. Here, the data rate is adjusted using time stamps embedded in the MPEG TS.

FIG. 2 is a diagram illustrating an embodiment of the serial number inserter and the error detection code inserter of FIG. 1 according to the present invention. FIG. 2 shows a serial number and an error detection code in each MPEG TS stream packet for hierarchical transmission. Indicates how to insert it.

The serial number inserting unit 102 inserts an additional few bytes of the serial number (seq_no) 202 for restoring the transmitted MPEG Transport Stream (MPEG TS) packet at the receiver before classifying the layer for hierarchical transmission. The error detection code insertion unit 103 additionally inserts an error detection code 203 to check whether an error has occurred in the serial number and the MPEG transport stream (MPEG TS).

The serial number inserting unit 102 includes a counter 211 and a serial number inserter 212, and the counter 211 (for example, Modulo 2 ¹⁶ Counter) can receive one MPEG transport stream (MPEG TS). If the counter value is incremented each time, the serial number inserter 212 adds a serial number 202 corresponding to the count value after the MPEG TS Payload 201.

On the other hand, the error detection code insertion unit 103 is composed of an error detection code calculator 221 and an error detection code inserter 222, the error detection code calculator 221 serial number and the corresponding MPEG transport stream (MPEG TS) When calculating an error check code for checking whether an error has occurred in the packet, the error detection code inserter 222 inserts the calculated error detection code (ECC) after the serial number.

After the above process, the user packet is composed of the original MPEG transport stream (MPEG TS) payload 201, the serial number 202, the error detection code 203, and the like.

Hereinafter, a process of inserting the serial number 202 and the error detection code (ECC) 203 for each MPEG TS packet will be described in detail.

The maximum value of the serial number may vary depending on the size of bytes allocated for the serial number. For example, when 2 bytes are used, values of 0 to 65535 are sequentially used, and when 1 byte is used, values of 0 to 255 are used. In addition, a code for error detection is inserted into a packet including each serial number.

The code for error detection may use a general cyclic redundancy check-8 (CRC-8) or cyclic redundancy check-16 (CRC-16) code. In the case of using the CRC-8, the CRC-8 code may be inserted at the position of the SYNC byte of the next MPEG TS packet or may be added after the serial number as a separate byte.

After the above process, the 188-byte MPEG TS packet becomes a user packet in which a serial number and an error detection code are inserted.

FIG. 3 is an explanatory diagram of PCR jitter generation due to a hierarchical transmission method. When only two layers, a high priority (HP) and a low priority (LP), exist, the packet is a general multiplexing technique. When the jitter is restored, a phenomenon in which PCR jitter occurs is shown.

Unlike the conventional hierarchical transmission method in which hierarchically separated MPEG MPEG transport streams are transmitted, the present invention is to transmit one MPEG transport stream hierarchically separated by PCR jitter. (jitter) may occur, and in order to solve the problem, the present invention inserts and transmits a serial number and the like, as shown in FIGS. 4 to 6, and the receiving side restores the MPEG TS using the same. .

Hereinafter, the PCR jitter problem in the hierarchical transmission method without inserting a serial number or the like will be described.

In the hierarchical transmission scheme according to the present invention, one MPEG transport stream (MPEG TS) is divided into several layers according to its contents and transmitted in different ways. However, when only two layers such as HP (Low Priority) and LP (Low Priority) exist, PCR jitter may occur as shown in FIG. 3 when the packet is recovered by a general multiplexing scheme.

For example, in the case where the audio / video constituting one broadcast program has one transmission form (301), in the case of audio, QPSK (Quadrature Phase Shift) can be used to reproduce only audio even in an error-prone environment. Key transmission (302), and in the case of video can be transmitted in 8Phase Shift Keying (8PSK) method with high transmission efficiency to effectively process a large amount of data (303).

In this case, in case of separately transmitting audio and video, in order to correctly receive an MPEG transport stream (MPEG TS) to which the MPEG demultiplexer of the receiver is transmitted, the original MPEG transport stream (MPEG TS) must be restored.

However, in the general hierarchical structure, when there is no location information for each packet, jitter may occur in the process of making packets of two layers into one stream even in an environment in which no error occurs (304). . If only HP packets can be received, the jitter becomes more serious (305).

FIG. 4 is an exemplary explanatory diagram of a method for restoring an MPEG transport stream in a case where both the upper (HP) and lower (LP) layers are received at the receiving side according to the present invention. FIG. A reception scheduling method is used. Here, the numbers 1, 2, 3, ... represent serial numbers inserted into MPEG transport stream (TS) packets.

When the receiver can receive both layers (HP, LP) according to the state of the transmission channel, the MPEG transport stream 401 outputted from the MPEG TS multiplexer of the transmitter and input to the hierarchical transmission device 100 of the MPEG transport stream. ) And the order should be restored to the same form.

When the hierarchical transmission apparatus 100 of the MPEG transport stream transmits the user packets 401 having the serial number and the error detection code inserted into the MPEG TS packet to the HP layer 402 and the LP layer 403, The MPEG transmission frame recovery apparatus 120 of the receiver uses the serial numbers included in the user packet to match the user packets stored in the buffers of HP and LP according to the order of the original MPEG transmission stream (the order of "401"). Restore (404). At this time, as a result of the error detection, an empty packet "null" (serial number "10" in the drawing) defined by the MPEG system is inserted in place of the packet "V2" discarded due to an error.

FIG. 5 is an exemplary explanatory diagram of restoration of an MPEG transport stream in a case where only the upper (HP) layer is received by the receiving side according to the present invention. The specific restoration method uses the reception scheduling method of FIG.

If only HP is received, the status of the channel means that LP cannot be received (503), but HP is able to receive (502). An empty packet ( PID = 0x1FFF) is inserted and restored (504).

FIG. 6 is a diagram for explaining a method of transmitting location information in the hierarchical framing and transmission unit of FIG. 1 according to the present invention.

Exemplary embodiments of a structure including location information in an MPEG transport stream (MPEG TS) such as a serial number differently from a layer having PCR most basic information in an MPEG transport stream (MPEG TS).

FIG. 6 illustrates a structure in which location information is included in an MPEG transport stream (MPEG TS) such as a serial number only in a layer having the most basic information in the MPEG transport stream (MPEG TS).

Some applications based on MPEG TS provide data services such as IP (Internet Protocol) in addition to video / audio transmission services. Data services, unlike real-time services such as audio / video, are not sensitive to transmission delays per individual program.

Therefore, if the MPEG TS is transmitted in a demultiplexer of the receiver so that it can be interpreted normally, packet processing in a subsequent stage is normally performed, and thus there is no effect on the service. Therefore, when an individual program is not sensitive to transmission delay, the serial number or only in a layer (that is, a higher layer) classified as a packet having the most basic information such as timing information (PCR) among MPEG transport streams (MPEG TS) By imposing corresponding location information, the location of higher layer packets in the MPEG TS may not be changed. Here, the location information corresponding to the serial number refers to a difference value between adjacent serial numbers imposed instead of the serial number.

On the other hand, if the position information (ie, serial number, etc.) in the MPEG TS is not inserted into all layers, only the upper layer (HP) layer packet is inserted and transmitted, and the higher bandwidth efficiency is achieved. Can be obtained.

In FIG. 6, the third layer is described as an example. However, since the number of layers is not limited in applying the present method, the layers may be separated.

Hereinafter, FIG. 6 will be described in detail.

User packets during the first one frame period are divided into three layers according to a predetermined rule (601). At this time, in the hierarchical transmission, the serial number is inserted and transmitted only in the packet corresponding to the layer 1 (highest layer) having the highest transmission quality, rather than the form 602 in which the serial number is inserted into all packets. (603). "1", "2", and "3" in "603" represent hierarchical rankings, and "1", "6" and "12" represent serial numbers.

On the transmitting side, the serial number ("1", "6", "12") 603 or between serial numbers that are adjacent in the corresponding layer is transmitted so that PCR jitter does not occur in the process of being transmitted hierarchically and restored on the receiving side. The difference values "0", "5", and "6" are sent together (604).

Therefore, since the receiver knows the position information about the packet including the most basic information (PCR, etc.) in the MPEG transport stream (MPEG TS), the PCR jitter problem can be solved.

7 is a flowchart illustrating a hierarchical transmission method of a multimedia data transport stream for preventing timing information jitter according to the present invention. Hereinafter, an MPEG transport stream and PCR, which is timing information thereof, will be described as an example. .

While the hierarchical transmission device 100 of the MPEG transport stream has been described with reference to FIG. 1, the hierarchical transmission method of the MPEG transport stream has been described together, but here, the MPEG applied to the hierarchical transmission device 100 of the MPEG transport stream is described. Only the hierarchical transmission method of the transport stream will be described separately.

First, the hierarchical transmission apparatus 100 receives an MPEG transport stream (MPEG TS) encoded from the outside (that is, the MPEG-2 multiplexer of the transmitter encoding apparatus) and divides the MPEG transmission stream into packet units (701).

Then, the hierarchical transmission apparatus 100 inserts a serial number for each divided MPEG TS packet in the input order (702), and an error check code is inserted into the MPEG TS packet having the serial number inserted therein. C) to generate a user packet (703).

Next, the hierarchical transmission device 100 hierarchically separates user packets in which a serial number and an error detection code are inserted and stores them in a corresponding layer buffer by using hierarchical information on a packet designated by a user. (704). In this case, the layer separation process may be performed by hierarchically separating user packets using hierarchical information designated by a user. However, if a user packet including a program clock reference (PCR) is separated into a higher layer (if three or more layers are separated) Layered).

Subsequently, the hierarchical transmission apparatus 100 configures a hierarchical transmission frame by combining a predetermined number of user packets (user packets stored in a layer buffer) and corresponding layer information for each layer (705). Different transmission schemes are transmitted for each layer (706). Here, the hierarchical transmission frame is configured to remove the inserted serial number for the user packets of the lower layer and to insert the already inserted serial number for the user packets of the upper layer. Also, the inserted frame number may be removed for each user packet of the upper layer, and the transport frame may be configured after inserting the difference of the serial number from the adjacent user packet.

8 is a flowchart illustrating a method of recovering a multimedia data transport stream hierarchically transmitted according to the present invention. Hereinafter, an MPEG transport stream and PCR as timing information thereof will be described as an example.

Although the restoration method of the MPEG transport stream has been described with reference to FIG. 1, the restoration method of the MPEG transport stream has already been described together with the present invention. It will be described separately.

First, when the restoration apparatus 120 of the MPEG transport stream receives hierarchical transport frames transmitted through a transport channel, the apparatus 120 extracts user packets and hierarchical information from the received transport frame (801).

Then, the restoration apparatus 120 of the MPEG transport stream removes packets having errors during transmission by using the error detection code in the user packets, and extracts the user packets without errors. In operation 802, the information is divided and stored in layers.

Next, the restoration apparatus 120 of the MPEG transport stream restores the user packet stored for each layer in the order of the original MPEG transport stream through scheduling using the location information in the user packet (803), and then in the original order. The MPEG TS is restored by removing the error detection code and the location information from each recovered user packet (step 804).

Here, the scheduling process of "803", using the location information in the user packet to restore the user packets stored in each layer in the order of the original MPEG transport stream, the user packet that was removed due to an error or lost during transmission At the location of the user packet, an empty packet ("null") is output instead. In addition, the positional information here means the serial number of a user packet or the serial number difference value with an adjacent user packet.

Subsequently, the apparatus 120 for restoring the MPEG transport stream converts the transmission rate of the MPEG transport stream (MPEG TS) packet and externally outputs it to the MPEG transport stream (805).

FIG. 9 is a detailed flowchart illustrating a method for reconstructing an MPEG transport stream in the scheduler of FIG. 1 when both the upper (HP) and lower (LP) layers are received by the receiving side according to the present invention.

The main process in the restoration unit 120 of the MPEG transport stream includes user error stored in each layer using location information such as an error detection process using an error detection code (ECC), a packet storing process for each layer, and a serial number. Restoration is performed in the order of the original MPEG transport stream (MPEG TS). Here, the configuration of the user packet is as shown in FIG.

The error packet removal and layer separation unit 122 checks whether an error has occurred by using an error detection code (ECC) for each received user packet. At this time, an error user packet is no longer transmitted to the next stage, which means that the error detection code (ECC) alone does not know where the error occurred, so that the serial number added after the MPEG TS is correct. If the error occurs in the above two informations (ie error detection code and serial number), the receiver may not operate correctly later.

On the other hand, if there is no error as a result of performing the error detection process using the error detection code (ECC), the received user packet is stored in the buffer according to the layer.

Hereinafter, when the receiver can receive both layers of HP / LP, the scheduler 125 will explain in detail how to restore the user packets hierarchically divided and stored into a state that can be interpreted by the receiver. . Hereinafter, the packet in the description process of the flowchart of FIG. 9 means a user packet.

In operation 901, a global system initialization process required for the scheduling process, such as allocation of a global variable for receiving scheduling processing and a storage location for temporarily storing packets for each layer, is performed.

The scheduler 125 waits until a new transmission frame arrives (902), and initializes a variable (903) when a new transmission frame arrives. Here, whether the new frame arrives or not, the hierarchical frame reception and user packet extracting unit 121 informs the scheduler 125.

A detailed description of the variable initialization process is as follows. Read the number of packets in the HP buffer / LP buffer (hereinafter referred to as the total number of HP packets to be processed in the current frame (hp_pkts) and the total number of LP packets to be processed in the current frame (lp_pkts) when a new transmission frame arrives. Set its initial value to its initial value, set the packet count (hp_count, lp_count) for each layer processed from the layer buffer to "0", and set the next packet type (next_read_type) to HP In addition, an alarm signal is periodically generated by setting a time required to process one packet as a timer.

Thereafter, the processor waits until a packet fetch alarm signal is generated (904), and if an alarm signal occurs, determines the type of packet to be fetched from the layer buffer, and obtains the packet of the determined type from the layer buffer (905). (See Figures 10A and 10B for more detailed procedures).

Next, the receiver checks whether the receiver has been reinitialized (906), and if not, the serial number (next_seq) of the packet to be output next (hereinafter, simply referred to as next_seq) is present. Check if the HP packet has the same serial number (hp_seq) (908), and if reinitialized (i.e., if the current process is the first start of the reception scheduling process) then the serial number of the first packet to be output ( That is, after setting the first next output packet number (first next_seq) (907) (see FIG. 11), the process 908 is performed.

If the next output packet number (next_seq) is the same as the serial number of the HP packet (hp_seq), the HP packet is output to the next stage and the next output packet number (next_seq) is set to "1". After incrementing 909, " 913 " On the other hand, if the next output packet number (next_seq) is not the same as the HP packet serial number (hp_seq), check again whether the next output packet number (next_seq) is the same as the serial number (lp_seq) of the LP packet. (910).

If the next output packet number (next_seq) is the same as the serial number (lp_seq) of the current LP packet, the outputted LP packet is output to the next step and the next output packet number (next_seq) is "". After increasing by 1 "(911)," 913 "is performed.

As a result of checking the "910" process, if the next output packet number (next_seq) is not the same as the LP packet serial number (lp_seq), that is, the serial number to be output is not the serial number of the HP packet but the serial number of the LP packet. Otherwise, an empty packet (null) is output to the next stage and the next output packet number "next_seq" is incremented by "1" (912).

Then, it checks whether all packets of the number of packets in the HP and LP frames set at the beginning of the first frame have been processed (913). If not, return to " 904 " and perform the procedure below " 904 ".

The scheduler 125 may output the packets stored in the buffer to the next stage 126 in the original order through the scheduling process as described above.

FIG. 10A and FIG. 10B are detailed flowcharts illustrating a process of determining a user packet to be imported among the layer buffers in FIG. 9 according to the present invention. When a receiver can receive both layers of HP / LP, an MPEG transport stream (MPEG TS) ), A process of determining a type of a packet to be fetched next and retrieving a packet of the determined type (905). Hereinafter, the packet in the description process of the flowcharts of FIGS. 10A and 10B means a user packet.

First, check the packet type (next_read_type) to be read from the buffer next time (1001), and in case of HP, retrieve one packet from the HP buffer and store it, and then use the packet's serial number (seq_no). Sets the serial number (hp_seq) of the imported HP packet and the current number of HP packets processed (ie, read) from the buffer (ie, read) (hereinafter, simply referred to as HP_count). Is increased to "1", and the next type (next_read_type) of a packet to be read next is set to LP (1002).

On the other hand, when the check result of "1001" indicates that the next packet to be read (next_read_type) is LP, the packet is retrieved from the LP buffer and stored, and the serial number of the HP packet using the serial number of the packet. To increase the current number of LP packets processed (ie read from the buffer) (lp_count) (hereafter simply referred to as the number of currently processed LP packets (lp_count)) by 1 The type (next_read_type) of the packet to be read is set to HP (1003).

According to the currently processed HP packet count (hp_count) and the currently processed LP packet count (lp_count), there are five cases as follows.

In the first case, that is, if the number of HP packets currently processed (hp_count) or the number of currently processed LP packets (lp_count) is "0" (1004), the next packet type to be read next (next_read type) is set to LP. (1005). This is to read both HP and LP with the new frame first and only the HP packet read first.

In the second case, that is, the number of HP packets currently processed (hp_count) and the number of currently processed LP packets (lp_count) are not "0" (1004), and also the number of currently processed HP packets (hp_count) and the number of currently processed LP packets. If (lp_count) is less than the total number of HP / LP packets (lp_pkts, hp_pkts) to be processed in the current frame (lp_count <lp_pkts and hp_count <hp_pkts) (1006), the next output packet number (next_seq) According to the result of checking whether the packet's serial number) is equal to the HP packet's serial number (hp_seq) or the LP packet's serial number (lp_seq), it is processed as follows.

If the next output packet number (next_seq) is the same as the serial number (hp_seq) of the current HP packet (1007), the next packet type (next_read type) to be read next is set to LP (1008). On the other hand, if the next output packet number (next_seq) is equal to the LP packet serial number (lp_seq) instead of the current HP packet serial number (hp_seq) (1007) (1009), the next type of packet to be read (next_read) type) is set to HP (1011), and if it is not equal to the serial number (lp_seq) of the LP packet (1009), the user is informed that an error (1010).

In the third case (LP), that is, the number of HP packets currently processed (hp_count) and the number of currently processed LP packets (lp_count) are not "0" (1004), and the number of currently processed LP packets (lp_count) is Equal to the total number of LP packets to be processed in the frame (lp_pkts) (lp_count == lp_pkts), and if the number of HP packets currently processed (hp_count) is less than the total number of HP packets to be processed in the current frame (hp_pkts) (hp_count < hp_pkts) (1012), and next_read type is set to HP (1013).

In the fourth case (HP case), that is, the number of HP packets currently processed (hp_count) and lp_count is not "0" (1004), and the number of HP packets currently processed (hp_count) must be processed within the current frame. Equals the total number of hp packets (hp_pkts) (hp_count == hp_pkts), and if the number of LP packets currently processed (lp_count) is less than the number of LP packets to be processed in the current frame (lp_count <lp_pkts) (1014), read next The type of all packets is set to LP (1015).

In the fifth case (both HP and LP), that is, the number of HP packets currently processed (hp_count) and the number of currently processed LP packets (lp_count) are not "0" (1004) and the number of currently processed HP packets ( hp_count) and the number of LP packets currently processed (lp_count) equal to the total number of HP / LP packets (hp_pkts, lp_pkts) to be processed within the current frame (1016), indicating that the processing for all packets within the current frame is complete. Generate a signal (1017).

On the other hand, if none of the above, the user is informed that the error (1018).

FIG. 11 is a detailed flowchart of an embodiment of a first packet (next_seq) determination process 907 to be outputted when re-initializing a receiver in FIG. 9 according to the present invention, in which a receiver may receive both layers of HP / LP. If present, it indicates a method of determining the first packet to be output when re-initializing the receiver from MPEG TS. Hereinafter, the packet in the description process of the flowchart of FIG. 11 refers to a user packet.

The number of HP packets currently processed (hp_count) (ie, the current number of HP packets read and processed from the buffer) or LP packets currently processed (ie, the current number of LP packets taken and processed from the buffer) are " 0 ", and if one is" 0 ", simply go to" 908 "process, and if all are not" 0 ", read the packet of the layer which is not taken from the buffer according to FIG. Perform the process. Therefore, one packet is taken from HP and LP buffers.

Check if the serial number (hp_seq) of the HP packet that is currently imported is greater than the serial number (lp_seq) of the LP packet that is currently imported (1102), if the serial number (hp_seq) of the HP packet is the serial number (lp_seq) of the LP packet. If larger than), the serial number of the first packet to be processed is determined as a packet of LP (1103).

On the other hand, if the HP packet's serial number (hp_seq) is not greater than the LP packet's serial number (lp_seq) (1102), the LP packet's serial number (lp_seq) is again the HP packet's serial number. It is checked whether it is "1" larger than (hp_seq) (1104).

If the check result of "1104" indicates that the LP packet's serial number (lp_seq) is one greater than the HP packet's serial number (hp_seq), the serial number of the first packet to be processed (ie, the first next output). The packet number (first next_seq) is determined as the serial number (hp_seq) of the HP packet (1105).

As a result of the check of "1104", the serial number of the first packet to be processed (that is, the first next message) unless the LP packet serial number (lp_seq) is greater than 1 than the HP packet serial number (hp_seq). The output packet number (first next_seq) is determined as the serial number (lp_seq) of the LP packet (1106).

12A and 12B are detailed flowcharts illustrating an embodiment of a method of restoring an MPEG transport stream in the scheduler of FIG. 1 when only a lower (LP) layer is received by a receiver according to the present invention. As shown in FIG. The restoration process is shown in a specific flowchart. Hereinafter, the packet in the description process of the flowcharts of FIGS. 12A and 12B means a user packet.

If the transmission channel is in a normal state, both HP and LP can receive, but if the channel is bad, only HP can receive. Hereinafter, if the receiver can only receive HP, the MPEG transmission stream (MPEG) stored in the HP buffer A method of restoring a TS) packet to a state that can be interpreted by the receiver will be described in detail.

First, the scheduler 125 performs an overall initialization process necessary for the scheduling process such as allocating a global variable for receiving scheduling processing and a storage location for temporarily storing one HP packet (1201). In addition, an alarm is generated periodically by setting a time required to process one packet as a timer.

The scheduler 125 waits for a new transmission frame to arrive, and then, when a new transmission frame arrives (1202), the number of HP packets in the buffer at the time the new transmission frame arrives (ie, the HP packets to be processed in the current frame). The total number (hp_pkts) is read and set, and the number (hp_count) of HP packets taken from the current buffer and processed is set to "0".

After that, the scheduler 125 waits until an alarm signal indicating a time for fetching a packet occurs, and when an alarm signal occurs (1204), the number of HP packets to be processed (hp_count) in the current frame is processed. Check if it is less than the total number (hp_pkts) (1205), if it is small, take one packet from the HP buffer, increase the number of currently processed HP packets (hp_count) by "1", and the serial number (seq_no) of the packet. ) Is set to the serial number (hp_seq) of the currently imported HP packet (1207). If the number of currently processed HP packets (hp_count) is not smaller than the total number of HP packets (hp_pkts) to be processed in the current frame (1205), an error is reported (1206).

Next, it is checked whether the receiver has been reinitialized (restarted) (906), if the receiver has been reinitialized (restarted) (ie, if the receiver is restarted and the current processing step is the first start of the reception scheduling process) (1208). Next, the next output packet number next_seq (that is, the serial number of the next packet to be output) is set to the serial number (hp_seq) of the currently obtained HP packet (1209).

On the other hand, as a result of checking whether the receiver is restarted (1208), if the receiver is not restarted, it is checked whether the next output packet number (next_seq) is the same as the serial number (hp_seq) of the currently imported HP (1210), and if it is the same, HP The packet is output and the next output packet number (next_seq) is increased by "1" (1211). If it is not the same, an empty packet is generated and outputted, and the next output packet number (next_seq) is increased by "1" (1212).

Next, it is checked whether the value of the currently processed HP packet count (hp_count) is the same as the number of packets arriving within the current frame (hp_pkts) (1213), and if it is the same, returns to "1202" and is less than "1202". Repeat the process of, and if it is different, return to "1205" and repeat the process of "1205" or less again.

As described above, the method of the present invention may be implemented as a program and stored in a recording medium (CD-ROM, RAM, ROM, floppy disk, hard disk, magneto-optical disk, etc.) in a computer-readable form. Since this process can be easily implemented by those skilled in the art will not be described in more detail.

The present invention described above is capable of various substitutions, modifications, and changes without departing from the technical spirit of the present invention for those skilled in the art to which the present invention pertains. It is not limited by the drawings.

As described above, the present invention classifies and transmits the output (MPP transmission stream) of a general single output MPEG multiplexer on the transmitting side in a hierarchical manner. By enabling selective reception according to a layer, there is an effect that the complexity and cost are significantly reduced in the construction of a broadcast system using a hierarchical structure.

In addition, the present invention is important for timing information (PCR) included in an MPEG transport stream (MPEG TS) when broadcasting or communicating using a hierarchical transmission method based on MPEG-2 TS in an environment where an error may occur. By classifying and transmitting a packet with information into a layer having the highest transmission performance, it is possible to allow a receiver to receive even in the worst channel conditions.

In addition, the present invention transmits the position information (e.g., serial number, etc.) together in a packet having important information such as timing information (PCR), so that the position of the original MPEG transport stream (MPEG TS) at the receiving side can be determined. It is effective to restore accurately and easily so that PCR jitter does not occur.

 1 is a block diagram illustrating a hierarchical transmission apparatus for transmitting multimedia data streams for preventing timing information jitter and an apparatus for restoring a multimedia data transmission stream transmitted hierarchically according to the present invention;

FIG. 2 is a diagram illustrating an embodiment of the serial number insertion unit and the error detection code insertion unit of FIG. 1 according to the present invention; FIG.

3 is an explanatory diagram for PCR jitter generation due to a hierarchical transmission method;

4 is a diagram illustrating an embodiment of a method for restoring an MPEG transport stream when both the upper (HP) and lower (LP) layers are received by the receiving side according to the present invention;

FIG. 5 is a diagram for explaining restoration of an MPEG transport stream in a case where only a higher (HP) layer is received at a receiving side according to the present invention; FIG.

6 is a diagram for explaining a method of transmitting location information in the hierarchical framing and transmission unit of FIG. 1 according to the present invention;

7 is a flowchart illustrating a hierarchical transmission method of a multimedia data transport stream for preventing timing information jitter according to the present invention;

8 is a flowchart illustrating a method for reconstructing a hierarchically transmitted multimedia data transport stream according to the present invention;

FIG. 9 is a detailed flowchart illustrating a method of restoring an MPEG transport stream in the scheduler of FIG. 1 when both the upper (HP) and lower (LP) layers are received by the receiving side according to the present invention;

10A and 10B are detailed flowcharts illustrating an embodiment of a user packet determination process to be imported among the layer buffers of FIG. 9 according to the present invention;

FIG. 11 is a detailed flowchart illustrating an embodiment of determining a first packet (next_seq) to be output when re-initializing a receiver in FIG. 9 according to the present invention; FIG.

12A and 12B are detailed flowcharts illustrating an embodiment of a method for restoring an MPEG transport stream in the scheduler of FIG. 1 when only a lower (LP) layer is received at a receiver according to the present invention.

* Explanation of symbols on the main parts of the drawing

100: hierarchical transmission device of MPEG transport stream 101: MPEG TS input matching unit

102: serial number insertion unit 103: error detection code insertion unit

104: hierarchical information table storage unit 105: hierarchical separation unit

106 and 107: hierarchical buffer 108: hierarchical framing and transmission unit

120: MPEG transmission stream restoration device

121: hierarchical frame receiving and user packet extracting unit

122: Error packet removal and layer separation unit 123, 124: Layer buffer

125: scheduler

126: error detection code / serial number removal unit 127: MPEG TS output matching unit

Claims (15)

In the hierarchical transmission device of the multimedia data transport stream (TS), Input matching means for receiving an encoded multimedia data transport stream from the outside and classifying the packet into packet units; Serial number inserting means for inserting serial numbers in accordance with an input order for each multimedia data transport stream (TS) packet outputted from said input matching means; Error detection code insertion means for inserting an error check code into the multimedia data transmission stream (TS) packet having the serial number inserted therein to generate a user packet; Hierarchical information storage means for storing hierarchical information about a packet designated by a user; Hierarchical separation means for hierarchically separating the user packet output from the error detection code insertion means by using the stored hierarchical information; Hierarchical storage means for dividing and storing the hierarchically separated user packets by layers; And Hierarchical framing and transmission means for combining a predetermined number of stored user packets and corresponding layer information for each layer to form a hierarchical transmission frame, and transmitting the hierarchical transmission frame by different transmission methods for each layer. Hierarchical transmission device of the multimedia data transport stream for preventing timing information jitter comprising a. The method of claim 1, The layer separation process of the layer separation means, And hierarchically separating the user packets using the hierarchical information, and dividing the user packet including timing information into a higher layer. The method according to claim 1 or 2, The hierarchical framing and transmission frame configuration process of the transmission means, The hierarchical transmission apparatus of the multimedia data transport stream for preventing timing information jitter, characterized in that a transport frame is formed by removing the inserted serial number for user packets of a lower layer. The method of claim 3, wherein The hierarchical framing and transmission frame configuration process of the transmission means, Removing the inserted serial number for each user packet of the upper layer, and inserting the difference value of the serial number with the adjacent user packet, multimedia data transport stream for preventing jitter timing information, characterized in that configured as a transport frame Hierarchical transmission device. In the multimedia data transmission stream restoration apparatus, Hierarchical frame receiving and user packet extracting means for receiving hierarchical transport frames transmitted through a transport channel and extracting user packets and hierarchical information from the received transport frame; Error packet removal and layer separation means for removing a user packet having an error during transmission by using an error detection code in the extracted user packet, and separating user packets without errors by layers using the extracted layer information. ; Hierarchical storage means for separately storing user packets outputted from the error packet removing means for each hierarchical layer; Scheduling means for restoring user packets stored for each layer in the hierarchical storage means in the order of the original multimedia data transport stream using location information in the user packet; Error detection code / location information removal means for restoring a multimedia data transport stream (TS) packet by removing the error detection code and location information from the scheduled and restored original user packet; And Output matching means for receiving the restored multimedia data transport stream (TS) packet and converting a data rate to output the multimedia data transport stream (TS); Apparatus for restoring a hierarchically transmitted multimedia data transport stream comprising a. The method of claim 5, The transport stream restoration process in the scheduling means, Output the user packets stored in the hierarchical storage means to the error detection code / serial number removal means using the location information in the user packet so as to match the sequence of the original multimedia data transport stream. And an empty packet ("null") is output at the position of the user packet that has been eliminated and lost during transmission. The method of claim 6, The location information, And a serial number difference value of a user packet or a serial number difference between adjacent user packets. The method according to any one of claims 5 to 7, The rate conversion process of the output matching means, When there is a time stamp in the multimedia data transmission stream (TS) packet, the transmission rate of the multimedia data transmission stream (TS) is converted hierarchically by using the time stamp. Device for restoring a multimedia data transmission stream. In the hierarchical transmission method of the multimedia data transport stream, An input matching step of receiving an encoded multimedia data transport stream (TS) from the outside and classifying the packet into packet units; A serial number is inserted according to the input order for each multimedia data transmission stream (TS) packet classified in the input matching step, and an error check code is inserted into the multimedia data transmission stream (TS) packet in which the serial number is inserted. Inserting a serial number / error detection code to insert a code) to generate a user packet; A hierarchical separation step of hierarchically separating and storing the user packets into which the serial number and the error detection code are inserted, using the hierarchical information on the packet designated by the user; And A hierarchical framing and transmission step of forming a hierarchical transmission frame by combining a predetermined number of stored user packets for each layer and corresponding layer information, and transmitting the configured hierarchical transmission frame by different transmission methods for each layer. Hierarchical transmission method of a multimedia data transport stream for preventing jitter timing information comprising a. The method of claim 9, The layer separation process in the layer separation step, Hierarchically separating the user packets using hierarchical information designated by the user, hierarchically transmitting the multimedia data transport stream for preventing timing information jitter, wherein the user packet including timing information is separated into a higher layer. Way. The method according to claim 9 or 10, The transport frame configuration process in the hierarchical framing and transmission step, A method of hierarchical transmission of a multimedia data transport stream for preventing timing information jitter, characterized in that a transport frame is formed by removing the inserted serial number for user packets of a lower layer. The method of claim 11, The transport frame configuration process in the hierarchical framing and transmission step, Removing the inserted serial number for each user packet of the upper layer, and inserting the difference value of the serial number with the adjacent user packet, multimedia data transport stream for preventing jitter timing information, characterized in that configured as a transport frame Hierarchical Transmission Method. In the multimedia data transmission stream restoration method, Receiving hierarchical transport frames transmitted through a transport channel, and extracting hierarchical frame and hierarchical information from the received transport frame; Eliminates an error packet generated during transmission by using an error detection code in the extracted user packet, and removes an error packet that separates and stores error-free user packets for each layer using the extracted layer information. And storing by layer; A scheduling step of restoring the user packet stored for each layer in order of the original multimedia data transport stream (TS) through scheduling using location information in the user packet; An error detection code / location information removal step of restoring a multimedia data transmission stream (TS) packet by removing the error detection code and location information from the user packets restored in the original order by the scheduling step; And An output matching step of converting a transmission rate for the restored multimedia data transport stream (TS) packet and outputting the multimedia data transport stream (TS); Method of restoring a hierarchically transmitted multimedia data transport stream comprising a. The method of claim 13, Transport stream restoration process in the scheduling step, Using the location information in the user packet, the user packets stored for each layer are restored in the order of the original multimedia data transport stream, but an empty packet is located at the location of the user packet lost due to an error or a user packet lost during transmission. and restoring ("null") instead. The method of claim 14, The location information, And a serial number difference value of a user packet or a serial number difference between adjacent user packets.