KR100189351B1 - Circuit for updating information table in mpeg2 decoder - Google Patents

Abstract

The present invention provides an information table in an MPEG2 decoder which stores various information tables (PAT and PMT) necessary for decoding a program by receiving TS packets transmitted by being multiplexed by the MPEG2-system unit and decoding them in each decoder unit. The update control circuit of the present invention relates to a recording control unit (50) in accordance with a predetermined control signal output from a version number processing unit (44) having first and second version number storage units (40, 42) and always storing the latest version information. ) Is to update and store the latest various information tables in the first and second storage units 46 and 48 so as to use them for decoding in each decoder unit.

Description

Update processing circuit of information table in MPEG2 decoder

1 is a block diagram showing an encoder model of MPEG2;

2 is a block diagram showing a decoder model of MPEG2;

3 is a block diagram showing the overall configuration of the update processing circuit of the information table in the MPEG2 decoder according to the present invention;

4 is a flowchart for explaining the operation of the update processing circuit of the information table in the MPEG2 decoder according to the present invention.

* Explanation of symbols for main parts of the drawings

10: video encoder 12: packetizer

14: audio encoder 16: packetizer

18: system clock 20: TS multiplexer

22: TS converter 24: TS demultiplexer

26: video buffer 28: audio buffer

30: system clock 32: video reverse packetizer

34: reverse audio packetizer 36: video decoder

38: audio recorder 40: the first version number storage unit

42: second version number storage unit 44: version number processing unit

46: first information table storage unit 48: second information table storage unit

50: recording control unit

The present invention stores various information tables (PAT and PMT) necessary for receiving TS packets (multiplexed and transmitted) transmitted by the MPEG2-system unit, separating predetermined programs, and decoding them in each decoder unit. The present invention relates to an update table of an information table in an MPEG2 decoder which is updated periodically with a latest information table which is periodically transmitted.

Digital video requires tremendous amount of storage space and bandwidth for storage and transmission due to the large amount of expression information. In order to effectively store and transmit it without distortion, image compression technology is essential, and in order to use it for different applications, it is required to be standardized. WG (Working Group) under the International Organization for Standardization (ISO) Moving Pictures Export Group (MPEG) began developing video and audio standards in 1988.

The MPEG standard proposed here is MPEG-Video, which defines a video signal compression algorithm, MPEG-Audio, which specifies a digital audio signal compression algorithm, and MPEG-system, which specifies the combination of encoded audio and video streams into one data stream. It is composed of subdivisions, and generally divided into MPEG1 and MPEG2 according to the data rate of the application codec. MPEG1 standardizes an algorithm capable of compressing video and related audio at about 1.5 Mbps, thereby encoding these encoded audio and video streams. The standard has many applications in many digital storage media and communication channels, but especially commercial and commercial CD-ROMs with high storage capacity and low cost. It is already used in home appliances.

In addition, MPEG2 standardizes an algorithm that can compress video and related audio signals to about 15Mbps. MPEG2-video uses block-based motion estimation and compensation to reduce temporal redundancy. In order to reduce spatial redundancy, discrete cosine transform (DCT) compression is used. Statistical redundancy is eliminated using entropy coding such as two-dimensional Huffman coding, while visual redundancy is eliminated. Specifies a compression algorithm that is optimized at 15Mbps by eliminating it in the adaptive quantization process.

In addition, MPEG2-Audio can only encode audio signals of up to 12 channels (left and right), whereas MPEG1-Audio can effectively encode multichannel audio signals of two or more channels, enabling more realistic reproduction of realism. The compression algorithm is specified.

The MPEG2-system aims at multiplexing video, audio and additional data and outputting them as one bit stream, which allows multiple program channels to be multiplexed in one bit stream. Layer 2 packet structure of the basic elementary stream (PES) and TS packet (Transport Packet), which is a unit of transmission, and a separate control channel for controlling the entire multiplexing structure and managing system information do.

FIG. 1 shows an encoder model of the MPEG2-system, in which an elementary stream (ES) of video compressed and encoded by the video encoder 10 becomes a video PES packet in the packetizer 12, and audio data Similarly, the basic data stream ES coded by the audio encoder 12 becomes a PES packet in the packetizer 16. The packetizers 12 and 16 are 27 MHz (permissible frequency drift error: +- While the packet is synchronized by timing information of a system clock (STC, system timing clock, 18) using a frequency of 0.005%), each PES packet is one TS packet in the TS multiplexer 20 together with additional data. In this case, TS packets of other programs are also bundled together into one TS packet. At this time, TS packets of other programs are bundled together into one TS packet and multiplexed.

In this case, the TS packet has a total length of 188 bytes consisting of a 4-byte header and a payload of 184 bytes, and the 4-byte header includes a 13-bit PID (Packet IDentifier). Associated with the stream, one TS packet cannot contain more than two types of PES packets, and PSI (Program Specific Information) including information indicating the association between the PIDs of these TS packets and the PES packets is periodically It is loaded on TS packet.

The PSI includes a program association table (PAT) including PID information of each of the multiplexed programs, a program map table (PMT) including PID information corresponding to video, audio, and additional data of a predetermined program, and a NIT including network information. It consists of Network Information Table (CAT) and Conditional Access Table (CAT), among which PAT and PMT contain PID information for separating predetermined programs in multichannel programs. Since it plays an important role in the decoder, it is important to update the latest information according to the PAT and PMT transmitted periodically.

FIG. 2 illustrates a decoder model of the MPEG2-system. The TS converter 22 receives TS packets including a plurality of programs and receives TS packets including a single program to separate TS packets including only a single program. By reading the header, PID outputs only TS packets that make up the current program channel, and the output TS packets are extracted from respective PES packets, that is, video PES packets and audio PES packets, by the TS demultiplexer 24, and the corresponding buffers ( 26) and 28, wherein the PCR extracted from the TS demultiplexer 24 maintains synchronization with the STC of the encoder by correcting the STC of the system clock unit 30.

On the other hand, the PES input to each of the buffers 26 and 28 is decoded by the corresponding decoder units 36 and 38 via the depacketizers 32 and 34, wherein the timing of the system clock unit 30 is determined. The video signal and the audio signal are synchronized by the information.

In order to separate a TS packet including a predetermined single program by receiving a TS packet including a plurality of programs in the MPEG2 decoder model, the PID of the corresponding program is first known, and the PID corresponding to the PID is read by reading the header of the TS packet. It is necessary to separate only the provided TS packets, and all PID information is carried on the PAT and PMT which are periodically transmitted, and the PAT is mapped to the TS packet whose PID is always PID = 0 to transmit the program number and the program. Program-map-PID information indicating the relationship between PID (PMT-PID) of TS packet is delivered.

The PMT obtained by selecting a matching PID value among TS packets transmitted from the PID value obtained from the Program-map-PID obtained from the PAT provides a mapping between the program number and the basic data stream constituting the program.

The PAT and PMT are provided with a 5-bit version number field and a 1-bit current-next-indicator field. The version number field is special when a characteristic of a TS packet describing information about the PSI is changed. When a program is added or when the configuration of an elementary stream for a given program is changed, new PSI data sends updated information to indicate that the most recently transmitted version of the section indicated by current is always valid.

The decoder checks whether the most recently received section matches an already processed or stored section, and if it does match, the received section is abandoned and if it does not match, the configuration table has changed and the information table needs to be updated. .

Also, the current-next-indicator is an important field that indicates when the PSI is valid at a point in the bitstream. The current-next-indicator digitizes whether each section is currently valid or next valid. This allows the decoder to transmit in advance so that the decoder can receive this in advance and prepare for the information change.

The present invention stores various information tables (PAT and PMT) necessary for receiving TS packets (multiplexed and transmitted) transmitted by the MPEG2-system unit, separating predetermined programs, and decoding them in each decoder unit. It is an object of the present invention to provide an update table for processing an information table in an MPEG2 decoder, which is updated with a latest information table which is periodically transmitted.

In the MPEG2 decoder of the present invention for achieving the above object, the update processing circuit of the information table compares the version number input from the outside with the data stored in the first version number storage unit, and, if the version number entered is large, A version number processing unit which stores data stored in the second version number storage unit and outputs a control signal accordingly, and moves data stored in the second version number storage unit to the first version number storage unit when a current-next-indicator signal is input; ; The information table input from the outside is stored in the first storage unit or the second storage unit by the control signal of the version number processor, and when the current-next-indicator signal is input, the data stored in the second storage unit is stored in the first storage unit. Characterized in that the recording control unit is moved to the storage unit.

The present invention having the above-described configuration stores predetermined PSI information, namely, version numbers and information to be processed next or next to PAT and PMT, and periodically compares the version numbers inputted to the version number processing unit with the stored version numbers. It is updated to the version number of the controller, and the information data inputted to the recording control unit is also updated to the latest information data according to the control signal of the version number processing unit. By changing the information to be made, the information data is always maintained as the information currently being processed.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

3 shows an update processing circuit of an information table in an MPEG2 decoder according to the present invention, which compares a version number input from the outside with data stored in the first version number storage unit 40, and has a large version number. In the case of storing the second version number storage unit 42 and outputting a control signal accordingly, when the current-next-indicator signal is input, the data stored in the second version number storage unit 42 is stored in the first version number. A version number processing unit 44 moved to the storage unit 40; The information table input from the outside is stored in the first storage unit 46 or the second storage unit 48 by the control signal of the version number processing unit 44, and the current-next-indicator signal is inputted. The recording control unit 50 is configured to move data stored in the second storage unit 48 to the first storage unit 46.

The input version number and current-next-indicator are fields commonly configured in PSI (PAT and PMT), and the 5-bit version number field is special when the characteristics of the TS packet describing information about the PSI are changed. When a program is added or the configuration of an elementary stream for a given program is changed, new PSI data sends updated information to indicate that the most recently transmitted version of the section marked current is always valid. The current-next-indicator field of a bit is an important field that tells when the PSI is valid at which point in the bitstream. It indicates whether each section is currently valid or next with a flag signal. The flag signal allows the decoder to transmit the information in advance and receives the information to be changed in advance. Is entered, the next information table can be changed to the current information table.

The version number processing unit 44 includes first and second version number storage units 40 and 42 and receives a version number from the outside to store the currently processed version number in the first version number storage unit 40, The next version number to be processed is stored in the second version number storage section 42. At this time, the input version number is compared to the data stored in the first version number storage unit 40, that is, the version number of the currently being processed section number is different, that is to recognize as the version number of the next section to be processed, the input The stored version number is stored in the second version number storage section 42, and the control signal corresponding thereto is output to the recording controller 50.

In addition, when the current-next-indicator signal is input from the outside, that is, when the currently processed section is updated to the next version, the data of the second version number storage section 42 is stored in the first version number storage section 40. Will be stored in.

The recording controller 50 includes first and second storage units 46 and 48, and receives the first and second storage units 46 and 48 in a predetermined format from an information table that receives a control signal from the version number processing unit. If the control signal is not input to the version number processor 44, the input data is discarded. If the control signal is input to the version number processor 44, the input data is stored. Is input to the second storage unit 48.

In addition, when the current-next-indicator signal is input from the outside, that is, when the currently processed section is updated to the next version, the data of the second storage unit 46 is moved to the first storage unit 48. do.

In addition, the data input to the first storage unit 46 includes the information of the data currently being processed, so that it refers to the information data stored externally in the decoder processing of the program currently being processed.

The operation of the present invention having the above-described configuration will be described below with reference to the flowchart shown in FIG.

When power is first applied to all decoders, a TS packet including an information table is transmitted to the decoder, and when the transmitted TS packet is input to the version number processing unit 44 through a predetermined processing procedure, the version number processing unit 44 Inputs the input version number into the first version number storage unit 42 and stores the information table of the section corresponding to the input version number in the first storage unit 46 through the recording storage unit 50. do.

Subsequently, the TS packet including the information table which is periodically transmitted without changing the information of the program being processed does not change the version number. Therefore, the version number processing unit 44 stores the first version number. If it is the same as the version number entered in the section 42, and give up the version number as it is, and at the same time the information data 50 input to the recording storage unit 50 is also given up as it is.

On the other hand, in the encoder, when a program being transmitted or an additional program is added, an information table having a version field updated in advance is transmitted to a TS packet. After the transmitted TS packet is processed by a decoder through a predetermined procedure, The version field and the information table are input to the version number processing section 44 and the recording control section 50, respectively.

At this time, the version number processor 44 stores the input version number larger than the current version number stored in the first version number storage unit in the second version number storage unit 42 to change information of the next program. In addition, the control signal is output to the recording controller 50.

The recording controller 50 stores the input information table data in the second storage memory according to the control signal input from the version number processing section 44 to prepare for the next program information change.

Subsequently, the encoder transmits the program-changed data being transmitted and simultaneously transmits the current-next-indicator field to the set TS packet. After the TS packet is processed by the decoder through the predetermined procedure, the current-next is processed. The -indicator fields are input to the version number processing section 44 and the recording control section 50, respectively.

At this time, the version number processing section 44 changes the information of the program by moving and storing the version number to be processed in the second version number storage section 42 in the first version number storage section 40. The recording control unit 50 also moves and stores the data stored in the second storage unit 48 to the first storage unit 46 by the input current-next-indicator field signal, thereby storing the information data of the next program. The change is made to the information data.

The embodiments described above are merely illustrative in all respects and should not be construed as limiting, and all modifications that fall within the true spirit and scope of the present invention shall fall within the claims of the present invention.

Claims (1)

When the version number input from the outside is compared with the data stored in the first version number storage unit 40 and the input version number is large, the version number is stored in the second version number storage unit 42 and the control signal is output accordingly. a version number processor 44 for moving data stored in the second version number storage unit 42 to the first version number storage unit 40 when a current-next-indicator signal is input; The information table input from the outside is stored in the first storage unit 46 or the second storage unit 48 by the control signal of the version version processing unit 44 and the current-next-indicator signal is inputted. Update processing circuit of the information table in the MPEG2 decoder composed of the recording control unit 50 which moves the data stored in the storage unit 48 to the first storage unit 46.