JP2002185960A - Method and circuit for section filtering - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the respective storage capacities of the reference register and the mask register of the section filtering circuit of a transport stream. SOLUTION: The storage capacities of the reference register 7 and the mask register 8 are made to be several bites and a comparing position information part 6 is provided for storing the comparing position of reference data by a comparing part 5. A data strobe signal from a section start detection part 3 and a counter value from a section byte counter 4 inputting a reset signal are outputted to the part 5. The part 5 outputs the coincidence/noncoincidence of the reference data and section data to a RAM interface 9 at a rear stage and filtering is performed by address control.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and a circuit for section filtering, and in particular, to the International Standards Organization (ISO).
And a section filtering method for extracting a desired section from an MPEG2 transport stream packet specified by the Moving Picture Coding Committee (PEG2).

[0002]

2. Description of the Related Art A conventional technique relating to a data separation method for extracting a desired section from an MPEG-2 transport stream packet defined by ISO PEG2 is disclosed in, for example, JP-A-10-341419. ", JP-A-10-
This is disclosed in, for example, "MPEG2 Data Reproducing Apparatus" of JP-A-23399 and "MPEG2 Transport Stream Transmission Rate Converter" of JP-A-11-205789.

A method of transmitting program-specific information (hereinafter abbreviated to PSI) in an MPEG2 transport stream (hereinafter abbreviated to TS) is described in ISO / IEC13818.
1 standard. As shown in FIG. 5, ISO / IEC
The TS packet specified in 1388.1 is 18
It has a fixed length of 8 bytes. Different PIDs (Packet I
TS packets having D) are temporally multiplexed to form one data stream. When transmitting a PSI in a TS, the PSI is divided into sections and inserted into TS packets. The section filter compares the section data in the TS packet filtered by the PID, and extracts only the TS packet or the section data having the matching data. This reduces the capacity of the storage means for storing the data at a later stage.

[0004] As a method for extracting a TS packet or section data, when a 13-bit PID included in a header portion of a TS packet matches a reference PID value, the first n of a section included in the TS packet is referred to. It is determined whether or not the byte matches the logical sum of n bytes of the reference data and n bytes of the mask data. If the determination results match, only the TS packet or section is transferred to the subsequent RA.
M (random access memory).

[0005] An example of this section filter is disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 10-341419.
FIG. 6 shows a method disclosed in this prior art document.
The conventional circuit of FIG. 6 includes a PID filter 60, a section filter 61, and a RAM interface 67. The section filter 61 includes a section start detection unit 62, a comparison unit 63, a reference register 64, a mask register 65, and a comparison status register 66. Further, the RAM interface 67 includes a write strobe generating section 68, a data latch 69, and an address generating section 70.

The function of each of the components 60 to 65 in FIG. 6 will be described. The PID filter 60 determines the PID of the TS packet.
Is compared with the reference PID, and if they match, the TS packet is passed to the subsequent stage. The section start detection unit 62 in the section filter 61 includes:
Detect section start. Reference register 64
Stores n bytes of reference data to be matched with the section data. The mask register 65
Stores n bytes of mask data of reference data. The comparing unit 63 compares the TS data with the reference data. When the n bytes at the head of the section are not included in one TS packet, the comparison status register 66 holds the comparison position up to the present and the matching status.

Next, the operation of the conventional circuit shown in FIG. 6 will be described. T that has passed the filtering of the PID filter 60
The S packet is sent to the section start detector 62. The section start detection section 62 detects the head of the section in the TS packet and notifies the comparison section 63 of the subsequent stage of a start signal. The comparison unit 63 outputs the section data to the subsequent stage until the determination of the match / mismatch of the section information is completed, regardless of whether the determination is successful or not. Further, it is determined whether the header data of the first n bytes of the section includes all n bytes or is cut off in the middle. First n
When a byte is included in one TS packet, the byte is compared with reference data registered in the reference register 64. If the first n bytes are not completed and are cut off halfway, the position of the cut byte and the match / mismatch status are held in the comparison status register 66.

Thereafter, when a subsequent TS packet arrives, the comparing unit 6 compares the n-byte position in the comparison status register 66 with the matching / mismatching status.
3 and restart comparison with the reference data from the reference register 64. When all the comparisons between the header data of the first n bytes of the section and the reference register are completed, the comparing section 63 continues to output the data when they match. On the other hand, if they do not match, an address reset signal is sent to the subsequent RAM interface 67 to request clearing of the section data already output.

[0009]

The above-mentioned prior art requires a storage circuit of 2 × 8 × n bits for storing n-byte reference data and n-byte mask data. The comparison in the unmasked state at a value close to n is sufficiently effective. However, when the mask is released with a value sufficiently smaller than n, for example, when filtering is performed on only one byte of the table ID of the section, there is a problem that most of the storage circuits for the reference data and the mask data are wasted.

[0010]

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a section filtering method and circuit capable of reducing the storage circuit (capacity) of a reference register and a mask register of a conventional section filtering circuit.

[0011]

SUMMARY OF THE INVENTION A section filtering method according to the present invention compares desired section data in a section, which is a transfer unit, from a transport stream packet with reference data to generate a transport stream packet having a matching section. In the separation method, position information is held in reference data and reference data mask information, and a timing for referring to reference data and mask data is determined based on comparison position information.

A section filtering circuit according to the present invention is arranged between a PID filter and a RAM interface, and is connected to a section start detecting section for detecting a section head from data from the PID filter and an output side of the section start detecting section. A comparison unit, a reference register and a mask register connected to the comparison unit, and the comparison unit determines whether the section information matches / mismatches. A comparison position information section is provided for storing comparison position information on the number of bytes to be compared with. Further, according to a preferred embodiment of the section filtering circuit of the present invention, the section filtering circuit includes a section byte counter which receives a reset signal and a data strobe from the section start detecting section and outputs a counter value to the comparing section. The comparing section refers to the counter value of the section byte counter and the value of the comparison position information section, and compares the reference data and the section data at an appropriate position. Also, the comparison unit
When all the comparisons are completed, the comparison result is output to the RAM interface.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The construction and operation of a preferred embodiment of a section filtering method and circuit according to the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing a configuration example of a preferred embodiment of a section filtering circuit according to the present invention. The section filtering circuit 2 is connected between the PID filter 1 and the RAM interface 9. The section filtering circuit 2 includes a section start detection unit 3, a section byte counter 4, a comparison unit 5, a comparison position information unit 6, a reference (reference) register 7, and a mask register 8. Further, the above-described RAM interface 9 includes a write strobe generating unit 10, a data latch 11, and an address generating unit 12.

First, the function of each of the components 1 to 8 shown in FIG. 1 will be briefly described. The PID filter 1 receives the input T
Only TS packets having a specific PID are extracted from the S data # 1. Then, it outputs TS data # 2 together with Hit information and SUI information to the section filtering circuit 2 at the subsequent stage. Also, it outputs TS data # 3 to the RAM interface 9 together with the Hit information, the TS start signal and the end signal. Section start detector 3 of section filtering circuit 2
Detects the start of the section from the input TS packet, resets the section byte counter 4 and sends out the TS data # 4 to the comparing section 5. The section byte counter 4 receives the reset signal from the section start detector 3 and clears the counter value. Further, the number of bytes is counted up in accordance with the timing at which the section data, that is, the TS data # 4, is input to the comparison unit 5.

On the other hand, the reference register 7 is a circuit for holding m bytes of reference data. The mask register 8 is a circuit that holds m-byte mask information of the reference data output from the reference register 7. The comparison position information section 6 holds information indicating the byte number of the section data with which the reference data and the mask data are compared. Therefore, the comparison position information section 6 is a circuit that holds m bytes of position information. The comparison unit 5 compares the reference data and the section data at an appropriate position with reference to the counter value of the section byte counter 4 and the value of the comparison position information unit 6. Then, when all the comparisons are completed, the comparison unit 5 outputs the comparison result to the RAM interface 9.

Next, the operation of the section filtering circuit 2 will be described. The PID filter 1 has a TID having a specific PID specified from the input TS data.
Pass only S data. When the PID of the TS data # 1 matches the reference value of the PID filter 1, the PID filter 1 does not wait for the matching / mismatch of the section filtering circuit 2 and the RAM interface 9
To the TS together with the Hit signal indicating PID match information
Send data # 3. At the same time, TS data # 2
And a Hit signal from the PID filter 1 are sent to the section filtering circuit 2.

[0018] Also, the Payload Unit Start of the TS data
When the indicator is 1, the SUI signal is sent to the section filtering circuit 2. PID filter 1
Sends the TS start signal when transmitting the first byte (TS header) of the TS data # 3 to the RAM interface 9. When transmitting the 188th byte of TS data # 3, it transmits a TS end signal. When the TS data # 2 is input to the section filtering circuit 2, the section start detection unit 3 starts detecting the head of the section.

Next, the operation of the section start detector 3 in FIG. 1 will be described with reference to the flowchart in FIG.
The section start detection unit 3 first detects T in the input data.
A Hit flag indicating whether or not the S data # 2 matches in the PID filtering 1 is referred to (Step 30). The timing for referring to the Hit flag is determined by the TS data #
2 is a TS header. When the Hit flag is active (valid), this TS data # 2 Payload
It is determined whether the Unit Start Indicator is 1 (step 31). This Payload Unit Start Indica
tor is output from the PID filter 1. Payload Un
When the it Start Indicator is 1, the section start detection unit 3 starts detecting a section start position. After skipping the adaptation field of the TS data # 2 (step 32), the section start detector 3 sends a reset signal to the section byte counter 4 (step 33). Thereafter, the section start detector 3 sends the TS data # 4 to the comparator 5, and outputs the output timing to the section byte counter 4 as a data strobe signal (step 3).
4). Then, it returns to the initial state.

Next, referring to the flowchart of FIG.
The operation of the section byte counter 4 in FIG. 1 will be described. First, it is determined whether or not the reset signal to the section byte counter 4 is active (step 40). When the reset signal is active (Step 40: YES)
First, the section byte counter 4 receives the reset signal from the section start detector 3 and clears the section byte counter 4 to 0 (step 41). If the reset signal is not active (step 4
(0: NO), it is determined whether the data strobe to the section byte counter 4 is enabled (step 4).
2). When enabled (step 42: YES), the section byte counter 4 receives the data strobe signal from the section start detector 3 and counts up the counter value by one (step 4).
3). After step 41 or step 43 and when the data strobe is not enabled (step 42: N
In O), the process returns to step 40 described above.

Next, the operation of the comparing section 5 in FIG. 1 will be described with reference to the flowchart in FIG. First, the comparison unit 5
It is determined whether or not the Payload Unit Start Indicator is 1 (step 50). Step 50: If YES,
It is determined whether the counter value of the section byte counter 4 is the same as the comparison position information value (step 51). Step 50: If YES and the counter value of the section byte counter 4 becomes equal to the value of the comparison position information section 6 (Step 51: YES), the value of the reference register 7 and the value of the mask A value obtained by logically ANDing the bits for each bit is compared with a value obtained by logically ANDing the TS data # 4 and the value of the mask register 8 for each bit (step 52). If the two values are the same (step 52: YES), a match is determined and a match flag is output (step 53).
If the values are different (step 52: NO), the non-coincidence flag is output as the determination result of the section filtering circuit 2 (step 54). The result of this determination is
The TS data # 2 for which the yload Unit Start Indicator becomes 1 is held in the section filtering circuit 2 until it is input.

The RAM interface 9 adds a write strobe signal and an address signal for writing to the RAM to the TS data # 3 from the PID filter 1. In the write strobe generation unit 10, referring to the Hit flag,
When the Hit flag is valid, a write strobe signal is generated in synchronization with the input of the TS data # 3. When the Hit flag is invalid, it is not necessary to write the TS data # 3 to the RAM, so that the write strobe signal is not generated.

The data latch section 11 outputs data suitable for the timing of writing to the RAM. The address generation unit 12 refers to the Hit flag, and when the Hit flag is valid, every time TS data # 3 is written to the RAM,
Increment the address value. However, the operation of the address value is performed under the following conditions. First, when the TS start signal is valid, it is stored as a backup value of the current address value. When the TS end signal is valid, the match determination result of the section filtering circuit 2 is referred to, and when the match is determined, the address is left as it is. If a mismatch is determined, the backup value is set as a new address value. That is, the address value is reset for one TS packet.

The configuration and operation of the preferred embodiment of the section filtering method and circuit according to the present invention have been described above in detail. However, it should be noted that such an embodiment is merely an example of the present invention and does not limit the present invention in any way. It will be readily apparent to those skilled in the art that various modifications can be made in accordance with the particular application without departing from the spirit of the invention.

[0025]

As will be understood from the above description, according to the section filtering method and circuit of the present invention,
The following remarkable practical effects can be obtained. First, the circuit size of the section filtering circuit can be reduced, and the cost of hardware can be reduced. The reason is that the number of data held in the reference register and the mask register can be reduced. Second
Second, section filtering can be performed at an arbitrary number of bytes from the beginning. The reason is that by holding the comparison position information, the comparison position of the reference data can be arbitrarily set.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a preferred embodiment of a section filtering circuit according to the present invention.

FIG. 2 is a flowchart showing an operation procedure of a section start detection unit shown in FIG.

FIG. 3 is a flowchart showing an operation procedure of a section byte counter shown in FIG. 1;

FIG. 4 is a flowchart illustrating an operation procedure of a comparison unit illustrated in FIG. 1;

FIG. 5 is a diagram illustrating a configuration of a transport stream (TS).

FIG. 6 is a block diagram showing a circuit configuration of a conventional example of a section filtering circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 PID filter 2 Section filtering circuit 3 Section start detection part 4 Section byte counter 5 Comparison part 6 Comparison position information part 8 Mask register 9 RAM interface 10 Write strobe generation part 11 Data latch 12 Address generation part

Claims (5)

[Claims] 1. A section filtering method for comparing desired section data in a section, which is a transfer unit, from a transport stream packet with reference data and separating a transport stream packet having a matching section, comprising: A section filtering method comprising: holding position information of reference data mask information; and controlling a timing of referring to the reference data and the mask data based on comparison position information. 2. A section start detecting section disposed between a PID filter and a RAM interface for detecting a section head from data from the PID filter, a comparing section connected to an output side of the section start detecting section,
A section filtering circuit that includes a reference register and a mask register connected to the comparing unit, and determines whether the section information matches / mismatches by the comparing unit. A section filtering circuit, comprising: a comparison position information unit that stores comparison position information indicating whether to compare with the comparison position information. 3. The section filtering circuit according to claim 2, further comprising a section byte counter that receives a reset signal and a data strobe from the section start detection section and outputs a counter value to the comparison section. 4. The comparison section references the counter value of the section byte counter and the value of the comparison position information section, and compares the reference data and the section data at an appropriate position. The section filtering circuit according to claim 3. 5. The section filtering circuit according to claim 4, wherein the comparing section outputs a comparison result to the RAM interface when all the comparisons have been completed.