JP2003228913A - Device and method for data stream recording, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a data stream recording device for sufficiently protecting data. <P>SOLUTION: A reception unit 3 sends a data stream obtained by receiving a digital broadcasting, to a motherboard 1. The motherboard 1 divides TS packets included in the data stream into two and stores one in an internal memory 33 for contents storage in the form of a packet collection file. Further, the motherboard 1 stores a data stream, obtained by substituting dummy packets for the TS packets of the data stream stored in the internal memory 33 for contents storage, in a storage 2 for the motherboard. The dummy packets each include a packet number indicating the position of a packet replaced with the dummy packet in the packet collection file. In reproduction, the data stream is restored by substituting packets to be thinned out for the dummy packets in the substituted data stream. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data stream recording device, a data stream recording method and a program.

[0002]

2. Description of the Related Art Digital broadcasting is used in which contents such as images and sounds are broadcast in the form of a data stream consisting of a series of packets containing data representing the contents.

Digitally broadcast contents can be stored in a storage device as digital format data,
It is very unlikely that data will be deteriorated during storage. For this reason, a technique is used to protect the rights such as the copyright of the digitally broadcast content. Specifically, there is a method of encrypting data representing content and storing the data.

[0004]

However, if the encryption method is not sufficiently strong against an attack, the encrypted data can be easily decrypted by a person who does not know the decryption key. , Data cannot be protected enough.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a data stream recording device and a data stream recording method for sufficiently protecting data.

[0006]

[Means for Solving the Problems] In order to achieve the above object,
A data stream recording apparatus according to a first aspect of the present invention includes a thinning means for acquiring a data stream and distributing a plurality of packets constituting the acquired data stream into a plurality of groups according to a predetermined rule, and a means other than the thinning means. A first storage unit having a first storage area that substantially blocks access to the second storage unit and a second storage unit having a second storage area, and the thinning unit is provided in a part of the group. The belonging packet is stored in the first storage area, the acquired data stream is converted into a replaced data stream in which the packets distributed to the partial group are replaced with dummy packets, and the converted data stream is converted into the replaced data stream. The dummy packets are stored in the second storage area, and the dummy packets are the thinning target packets replaced by the dummy packets. It includes identification information for identifying the Tsu bets, characterized in that.

The thinning-out means may generate collective data representing a combination of packets belonging to the partial group and store the collective data in the first storage area. In this case, the identification information may include information indicating a logical position occupied in the aggregate data by the packet replaced by the dummy packet including the identification information.

As the identification information, a packet replaced by a dummy packet containing the identification information is the first packet.
May include information indicating a logical position occupied in the storage area.

The packets forming the data stream acquired by the thinning means and the dummy packets are, for example, TS (Transport Stream) packets. In this case, the identification information is, for example, in the payload portion of the TS packet. It need only be included.

The thinning means may include a synthesizing means for reading the packets distributed to the plurality of groups from the first and second storage areas and restoring the data stream based on the read packets. .

The thinning means may include a processor. In this case, the processor may access the first storage area by executing a predetermined program.

The first storage means and the thinning means may be connected to each other via a bus which enables data transmission by the processor executing a predetermined program.

The thinning means may encrypt the packets distributed to the partial group and / or the other group and store the encrypted packets in the first and / or second storage areas.

A data stream recording method according to a second aspect of the present invention acquires a data stream,
A plurality of packets forming the acquired data stream are distributed to a plurality of groups according to a predetermined rule, and packets belonging to a part of the groups are stored in a first storage area that substantially blocks access from other than a predetermined access device. A data stream recording method for storing and acquiring the obtained data stream, converting it into a replaced data stream in which the packets distributed to the partial groups are replaced with dummy packets and storing the converted data stream in a second storage area. The dummy packet includes identification information for identifying the thinning target packet replaced by the dummy packet.

Packets belonging to the partial group are
The packets may be stored in the first storage area as aggregated data indicating that the packets are combined with each other. In this case, the identification information may include information indicating a logical position occupied in the aggregate data by the packet replaced by the dummy packet including the identification information.

The program according to the third aspect of the present invention includes a thinning means for causing a computer to acquire a data stream and distribute a plurality of packets constituting the acquired data stream to a plurality of groups according to a predetermined rule. A program for functioning as first storage means having a first storage area that substantially blocks access from other than the thinning means and second storage means having a second storage area. Then, the thinning-out means stores some of the packets belonging to the group in the first storage area, and acquires the acquired data stream,
The packets distributed to the partial group are converted into a replaced data stream in which dummy packets have been replaced, and are stored in the second storage area.
It is characterized in that the dummy packet includes identification information for identifying the thinning target packet replaced by the dummy packet.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.
A description will be given with reference to the drawings. FIG. 1 is a diagram showing a configuration of a digital broadcast recorder according to an embodiment of the present invention.
As shown in the figure, this digital broadcast recorder comprises a motherboard 1, a motherboard storage 2, and a receiving unit 3. The motherboard storage 2 is connected to the motherboard 1, and the receiving unit 3 is connected to the motherboard 1 via the connection bus B.

The motherboard 1 is, for example, a CPU (Ce
ntral Processing Unit) and R
A memory including an AM (Random Access Memory) and the like and a bus controller are provided. The connection bus B is P
It consists of a CI (Peripheral Component Interface) bus. The memory of the motherboard 1 has a storage area that serves as a work area for the processor of the motherboard 1. The bus controller of the motherboard 1 is composed of a control circuit for controlling data exchange between the processor of the motherboard 1 and a device external to the motherboard 1 via the connection bus B.

The mother board 1 reads the broadcast recording / reproducing program stored in the mother board storage 2 and performs the processing described later according to the broadcast recording / reproducing program. The process controlled by the broadcast recording / playback program is
Functionally, it includes a plurality of processing blocks. Specifically, the demultiplexer 1 described later with reference to FIG. 4 and FIG.
A, stream thinning block 1B, stream composition block 1C, storage recording block 1D, MPEG
(Moving Picture Expert Group) Decode block 1
Each processing block of E and the storage read block 1F is included.

The motherboard storage 2 is composed of a hard disk device or the like, and prestores the above-mentioned broadcast recording / playback program. Then, according to the access from the mother board 1, the data supplied by the mother board 1 is stored, or the data stored in itself is read and supplied to the mother board 1.

The receiving unit 3 is a digital broadcast receiving section 3
1, a PCI bus bridge 32, an internal memory 33 for storing contents, an IDE (Intelligent Drive Electron)
ics) bus bridge 34.

The digital broadcast receiving section 31 is composed of a demodulation circuit, and is connected to the PCI bus bridge 32 via an internal bus. The digital broadcast receiving unit 31 restores TS (Transport Stream) packets forming a data stream by inputting and demodulating a modulated wave representing a data stream, which is digitally broadcast from the outside. Then, the restored TS packet is supplied to the motherboard 1 via the PCI bus bridge 32 and the connection bus B. The data stream represented by the modulated wave received by the digital broadcast receiving unit 31 represents content including images and audio, and as shown in FIG.
It consists of packets.

The TS packet is a packet representing an image or a sound which constitutes a content, and has a data structure shown in FIG. That is, the TS packet is composed of a TS packet header and a payload part (adaptation / payload part) following the TS packet header.

The payload part is a part containing data representing the content. As shown in FIG. 3, in each payload part, data containing data forming an image (or the same audio) of the same frame are arranged in the order in which TS packets including these payload parts are arranged. PES (Packetized Elementary Stream) by connecting with each other
Packets can be formed.

If the data stream represents MPEG2 format image data (or image data having substantially the same data structure as MPEG2 format image data), PE
The S packet is one of three types of I picture, B picture, or P picture that is data representing an image forming a moving image.
Contains more than one seed. Among them, the B picture and the P picture represent the difference from the I picture.

Then, as shown in FIG. 3, the PES packet includes a PES header including information for identifying the PES packet and a picture layer including any of an I picture, a B picture and a P picture. .

A PES packet including an I picture includes a sequence header code having a predetermined value, and a PES packet including an I picture includes a PE header.
In addition to the S header and picture layer, a video sequence layer and a GOP (Group Of Picture) layer are included.

As shown in FIG. 2, the TS packet header includes a synchronization byte, TS error data, payload unit start indicator, transport priority data, PID (Program IDentifier), transport scramble control data, and adaptation in order from the beginning. Contains field control data and continuity index.

Of these, the payload unit start indicator indicates whether or not the payload portion of the TS packet including the payload unit start indicator itself includes the head data of the PES packet. Specifically, for example, when the value of the payload unit start indicator is “1”, the T including the payload unit start indicator itself is included.
It indicates that the payload part of the S packet includes the head data of the PES packet, and if it is "0", it indicates that the payload part does not include the head data of the PES packet.

Therefore, one PES packet is, for example, a TS packet including a payload unit start indicator having a value of "1" in the data stream and the following TS including a payload unit start indicator having a value of "1". It is generated by connecting the payload parts of consecutive TS packets up to the TS packet immediately before the packet.

The PID is data for identifying which content is represented by the payload part of the TS packet containing the PID itself (for example, which image or sound is represented).

The PCI bus bridge 32 is composed of a bus controller and the like, is connected to the mother board 1 via a connection bus B, and is I via an internal bus.
It is connected to the DE bus bridge 34 and the digital broadcast receiver 31. The PCI bus bridge 32 mediates access to the internal memory 33 for content storage, which is performed by the motherboard 1 under the control of the broadcast recording / reproducing program. It also mediates the supply of data from the digital broadcast receiving unit 31 to the internal memory 33 for content storage.

The internal memory 33 for storing contents includes a nonvolatile memory such as a compact flash memory and an IDE.
It is composed of an interface circuit for transmitting data via the bus.

The IDE bus bridge 34 is composed of a bus controller and the like, and is connected to the PCI bus bridge 32 via an internal bus, while being connected to the internal memory 33 for content storage via the IDE bus. I
The DE bus bridge 34 mediates access to the internal memory 33 for content storage, which is performed by the motherboard 1 under the control of the broadcast recording / reproducing program. It should be noted that the PCI bus bridge 32 and the IDE bus bridge 34 substantially block this access even if the motherboard 1 accesses the content storage internal memory 33 without following the control of the broadcast recording / playback program.

(Operation) Next, the operation of the digital broadcast recorder will be described. FIG. 4 is a diagram showing a flow of processing for recording content. FIG. 6 is a diagram showing a flow of processing for reproducing the recorded content.

(Recording of Content) When the modulated wave representing the data stream is supplied to the digital broadcast receiving section 31 of the receiving unit 3, the digital broadcast receiving section 31 restores the data stream by demodulating the modulated wave. Then, the restored data stream is supplied to the mother board 1 via the PCI bus bridge and the connection bus B.

On the other hand, the mother board 1 reads the broadcast recording / reproducing program from the mother board storage 2 and executes it in response to a recording instruction supplied from the outside in accordance with an operation of the operator.

When the mother board 1 which executes the broadcast recording / reproducing program is supplied with the data stream (that is, when the TS packets are sequentially supplied), the PID included in the supplied TS packet according to the control of the demultiplexer 1A. And determines whether or not the specified PID indicates the content to be accumulated. The content to be accumulated may be designated by, for example, data supplied from the outside according to the operation of the operator.

When the motherboard 1 determines that the PID does not indicate the content to be stored, it discards the TS packet including this PID, and when it determines that it indicates, the TS packet including this PID is shown in FIG. As described above, the data is delivered to each processing block of the stream synthesis block 1C and the stream thinning block 1B.

When the TS packet is delivered from the demultiplexer 1A to the stream synthesizing block 1C (that is, when this digital broadcast recorder receives a digital broadcast), the mother board 1 uses the stream synthesizing block 1
Under the control of C, this TS packet is delivered to the MPEG decoding block 1E without any particular processing.

When the TS packet is delivered to the MPEG decoding block 1E, the mother board 1 decodes the image and audio represented by the TS packet under the control of the MPEG decoding block 1E, and as shown in FIG. It is output as content data including a video signal, an audio signal, etc.

On the other hand, the motherboard 1 passes the TS packets successively delivered from the demultiplexer 1A to the stream thinning block 1B to the stream thinning block 1B.
According to the control of, thinning out to meet a certain rule. That is, according to this rule, TS packets are sorted into two groups, TS packets belonging to one group (hereinafter referred to as thinning target packets) are written to the internal memory 33 for content storage of the receiving unit 3, and belong to the other group. The TS packet (hereinafter referred to as a non-thinning target packet) is delivered to the storage recording block 1D. The specific content of the rule is arbitrary.

The motherboard 1 writes the thinning-out target packets to be written in the content storage internal memory 33 in the form of a packet set file composed of serially linked thinning-out target packets as shown in FIG. And The arrangement order of the packets to be thinned out in the packet set file is arbitrary, and, for example, the packets may be arranged in the arrangement order in the original data stream. Also, for each thinning target packet, for example,
A packet number indicating the number of the thinning target packet from the beginning is assigned in the packet set file. Note that in FIG. 5, the packet number "k-1",
5 schematically shows a thinning-out target packet to which “k” and “k + 1” (k is an arbitrary integer of 2 or more) are assigned.

The motherboard 1 writes the packet set file (that is, the set of packets to be thinned out) to the internal memory 33 for storing contents by the PCI.
This is performed by accessing the internal memory 33 for content storage via the bus bridge 32 and the IDE bus bridge 34. That is, when the motherboard 1 accesses the internal memory 33 for storing contents and the packet set file is supplied to the receiving unit 3, the PCI bus bridge 32 of the receiving unit 3 sends this packet set file to the IDE bus bridge 34. Then, the IDE bus bridge 34 accesses the internal content storage memory 33 and stores this packet set file in the storage area of the internal content storage memory 33.

On the other hand, the mother board 1 which performs the processing of the stream thinning block 1B has the storage recording block 1
The non-thinning target packet to be delivered to D is delivered to the storage recording block 1D in the form of the replaced data stream as shown in FIG. As shown in the figure, the replaced data stream includes a data stream having a data structure corresponding to the original data stream received by the receiving unit 3 in which the thinning-out target packet is replaced with a dummy packet.

As shown in FIG. 5, the payload portion of the dummy packet includes identification data for identifying the thinning target packet replaced by the dummy packet. The identification data may be composed of the above-mentioned packet number as shown in FIG. 5, or may be composed of an address indicating the position of the packet to be thinned out in the packet set file. Note that FIG.
Shows schematically the replaced data stream in which the thinning-out target packet assigned the packet number “k” is replaced with a dummy packet.

The contents of the payload portion of the dummy packet are different from the contents of the payload portion of the thinning-out target packet replaced by the dummy packet. It is desirable that there is substantially no correlation between the content of the payload part of the dummy packet and the content of the payload part of the thinning-out target packet located at the position of the dummy packet.

When the replaced data stream is delivered to the storage recording block 1D, the motherboard 1
Accesses the motherboard storage 2 under the control of the storage recording block 1D and stores the replaced data stream in the storage area of the motherboard storage 2.

(Reproduction of Recorded Content) When reproducing the recorded content, the motherboard 1 responds to a content reproduction instruction supplied from the outside according to an operation of the operator, for example, and executes the broadcast recording / reproduction program for the motherboard. It is read from the storage 2 and executed.

Then, the motherboard 1 reads out the replaced data stream (a set of non-thinning target packets) representing the content to be reproduced from the motherboard storage 2.

Specifically, the mother board 1 stores, for example, information indicating the replaced data stream (for example, a file name, an address of a storage area in which it is stored) from the stream synthesis block 1C to the storage reading block 1F. Hand over to. Then, the motherboard storage 2 is accessed under the control of the storage read block 1F, the replaced data stream indicated by this information is read from the motherboard storage 2, and is delivered to the stream synthesis block 1C.

On the other hand, the motherboard 1 accesses the internal memory 33 for content storage via the PCI bus bridge 32 and the IDE bus bridge 34, and a packet set file representing the contents to be reproduced (that is, a set of packets to be thinned out). Read out. The read packet set file is supplied to the IDE bus bridge 34, the IDE bus bridge 34 transfers the packet set file to the PCI bus bridge 32, and the PCI bus bridge 32 sends the packet set file via the connection bus B. Supply to the motherboard 1. The packet set file to be read may be specified, for example, based on the content of the identification data included in any dummy packet in the replaced data stream representing the content to be reproduced.

As shown in FIG. 6, the mother board 1 stores the packet set file read from the receiving unit 3 into
It is delivered to the stream composition block 1C.

Next, the mother board 1 follows the control of the stream synthesizing block 1C and the stream synthesizing block 1
The replaced data stream passed to C is restored to the original data stream. Then, as shown in FIG. 6, the restored data stream is delivered to the MPEG decoding block 1E.

Specifically, the mother board 1 replaces the dummy packet included in the replaced data stream delivered to the stream synthesizing block 1C with the packet to be thinned out included in the packet set file, thereby reducing the original packet. Restore the data stream. It should be noted that the motherboard 1 specifies which thinning target packet replaces each dummy packet based on the identification data included in the dummy packet.

When the original data stream is delivered to the MPEG decoding block 1E, the motherboard 1 is
Under the control of the PEG decoding block 1E, the image and audio represented by this data stream are decoded and output as content data as shown in FIG.

This digital broadcasting recorder performing the above-described operation stores a part of TS packets conforming to a certain rule in the content storage internal memory 33. Then, the I-picture head packet is substantially blocked from being accessed even if the I-picture head packet is read out without being controlled by the broadcast recording / reproducing program. Therefore, for example, even if the motherboard storage 2 is separated and an external computer or the like is used to reproduce the content based on the storage content of the motherboard storage 2, the data included in some TS packets cannot be obtained. Therefore, the content cannot be played correctly. As a result, the content is protected. Then, which thinning target packet should replace the dummy packet in the replaced data stream can be easily specified by verifying the identification data included in the dummy packet. Therefore, it is possible to easily restore the data stream without separately preparing a table indicating the positions of the packets to be thinned out in the original data stream.

The configuration of this digital broadcast recorder is not limited to that described above. For example, the data structure of the TS packet does not have to be as described above, and may have any data structure. Further, the dummy packet does not necessarily have to include the identification data in the payload part, and may include the identification data in any other position in the dummy packet. The image data included in the TS packet does not necessarily have to be the MPEG2 format data.
It may be MPEG4 or any other type of data. Further, the reception unit 3 may include a plurality of internal memories 33 for storing contents, and the data stream may be distributed to three or more groups.

The identification data included in the dummy packet may be an address indicating the position of the thinning target packet replaced by the dummy packet in the storage area of the internal memory 33 for content storage. In this case, the thinning-out target packet stored in the content storage internal memory 33 does not necessarily have to take the form of the above-mentioned packet set file.

Further, this digital broadcast recorder may include a video circuit for controlling the display of the image represented by the content data generated by the mother board 1 and a display device such as a liquid crystal panel for displaying the image according to this control. Further, an amplifier circuit for reproducing the sound represented by the content data, a speaker, and the like may be provided. A video circuit and an amplifier circuit may be mounted on the motherboard 1.

The connection bus B is not necessarily limited to the PCI bus and may be a bus complying with any standard. Therefore, the connection bus B may be, for example, a bus conforming to the PC Card Standard, or may be an ISA (Industry Sta.
ndard Architecture) It may consist of a bus. However, when the connection bus B is not the PCI bus, the reception unit 3 is provided with a bus controller or the like that mediates data exchange conforming to the standard with which the connection bus B complies, instead of the PCI bus bridge 32.

The bus connecting the internal memory 33 for content storage and the IDE bus bridge 34 is not necessarily I.
The bus is not limited to the DE bus and may be a bus complying with any standard. Therefore, this bus may comprise, for example, a memory-only bus. However, if this bus is not an IDE bus, the receiving unit 3 will use the IDE bus bridge 34.
Instead of this, a bus controller that mediates data exchange conforming to the standard that this bus complies with is provided, and the interface circuit that the internal memory 33 for storing contents also composes data that conforms to the standard that this bus complies with. Shall mediate exchange.

When recording the content, the mother board 1 encrypts the non-thinning-out target packet and stores the encrypted non-thinning-out target packet in the motherboard storage 2, and when reproducing the recorded content, the encrypted non-thinning-out target packet is recorded. The data stream may be restored after being read and decoded. Similarly, when recording the content, the thinning-out target packet is encrypted and then written to the internal memory 33 for content storage, and when playing back the recorded content, the encrypted thinning-out target packet is read and decrypted before the data. The stream may be restored.

Although the embodiments of the present invention have been described above, the data stream apparatus according to the present invention can be realized by using a normal computer system instead of a dedicated system. For example, by installing the program from a medium (CD-ROM, MO, FD, etc.) storing a program for causing the personal computer to execute the operations of the motherboard 1, the motherboard storage 2 and the receiving unit 3 described above, It is possible to configure a digital broadcast recorder that executes the process of.

Further, for example, a bulletin board (BB of a communication line)
The program may be posted in S) and distributed via a communication line. Alternatively, a carrier wave is modulated by a signal representing the program, the obtained modulated wave is transmitted, and the modulated wave is received. The device may demodulate the modulated wave to restore the program. Then, the above process can be executed by activating the program and executing it under the control of the OS in the same manner as other application programs.

When the OS shares a part of the processing,
Alternatively, when the OS constitutes a part of one component of the present invention, the recording medium may store the program excluding the part. Also in this case, in the present invention, it is assumed that the recording medium stores a program for executing each function or step executed by the computer.

[0067]

As described above, according to the present invention, the data stream recording device and the data stream recording method for sufficiently protecting the data are realized.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a digital broadcast recorder according to an embodiment of the present invention.

FIG. 2 is a diagram showing a data structure of a data stream and a TS packet.

FIG. 3 is a diagram showing a data structure of a PES packet.

FIG. 4 is a diagram showing a flow of processing for recording content.

FIG. 5 is a diagram showing a data structure of a packet set file, a replaced data stream, and a dummy packet.

FIG. 6 is a diagram showing a flow of processing for reproducing recorded content.

[Explanation of symbols]

1 Motherboard 2 Motherboard storage 3 receiving unit 31 Digital Broadcast Receiver 32 PCI bus bridge 33 Internal memory for storing contents 34 IDE Bus Bridge B connection bus

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04N 5/92 H04N 5/91 P (72) Inventor Toshiaki Sakate 1-14-6 Dogenzaka, Shibuya-ku, Tokyo KENWOOD Corporation F-term (reference) 5C052 AA17 AB04 CC11 DD06 DD10 5C053 FA13 FA20 FA23 GB06 GB07 GB08 GB11 GB37 JA01 JA21 5D044 AB05 AB07 DE03 DE22 DE49 DE50 EF05 FG18 GK12 GK17

Claims (11)

[Claims] 1. A thinning-out means for acquiring a data stream and distributing a plurality of packets constituting the acquired data stream into a plurality of groups according to a predetermined rule; and a first means for substantially preventing access from other than the thinning-out means. And a second storage means having a second storage area, wherein the thinning means stores a part of the packets belonging to the group in the first storage area. The stored and acquired data stream is converted into a replaced data stream in which the packets distributed to the part of the groups are replaced with dummy packets and stored in the second storage area. The dummy packet includes identification information for identifying the thinning target packet replaced by the dummy packet. The data stream recording apparatus characterized. 2. The thinning-out means generates aggregated data representing a combination of packets belonging to the partial group and stores the aggregated data in the first storage area, and the identification information is The data stream recording device according to claim 1, wherein the packet replaced by the dummy packet including identification information includes information indicating a logical position occupied in the aggregate data. 3. The first identification information is a packet replaced with a dummy packet containing the identification information.
The data stream recording apparatus according to claim 1, further comprising information indicating a logical position occupied in the storage area of the data stream recording apparatus. 4. The packets constituting the data stream acquired by the thinning means and the dummy packets are TS.
4. The data stream recording device according to claim 1, 2 or 3, wherein the data stream recording device comprises a (Transport Stream) packet, and the identification information is included in a payload portion of the TS packet. 5. The decimating means comprises a synthesizing means for reading the packets distributed to the plurality of groups from the first and second storage areas and restoring the data stream based on the read packets. The data stream recording device according to any one of claims 1 to 4, characterized in that: 6. The thinning means includes a processor, and the processor accesses the first storage area by executing a predetermined program. The data stream recording device according to the paragraph. 7. The first storage means and the thinning-out means are connected to each other via a bus which enables data transmission by the processor executing a predetermined program. The data stream recording device according to claim 6. 8. The thinning means encrypts the packets distributed to the partial group and / or the other group and stores the encrypted packets in the first and / or second storage areas. The data stream recording device according to any one of claims 1 to 7. 9. A data stream is acquired, a plurality of packets constituting the acquired data stream are distributed to a plurality of groups according to a predetermined rule, and packets belonging to a part of the groups are accessed by a device other than a predetermined access device. The data stream obtained by storing the data stream in the first storage area that is substantially blocked is converted into a replaced data stream in which the packets distributed to the partial group are replaced by dummy packets. A data stream recording method for storing in a second storage area, wherein the dummy packet includes identification information for identifying a thinning target packet replaced by the dummy packet. Method. 10. The packets belonging to the part of the groups are stored in the first storage area as aggregated data representing a combination of the packets, and the identification information is the identification information. 10. The data stream recording method according to claim 9, further comprising information indicating a logical position occupied by the packet for dummy including the packet in the aggregate data. 11. A thinning-out means for acquiring a data stream by a computer and distributing a plurality of packets constituting the acquired data stream into a plurality of groups according to a predetermined rule, and substantially preventing access from other than the thinning-out means. A program for causing the first storage means having a first storage area and the second storage means having a second storage area to function, wherein the thinning means is a part of the group. Storing packets belonging to the first storage area, converting the acquired data stream into a replaced data stream in which the packets distributed to the partial group are replaced with dummy packets, and The dummy packet is stored in the second storage area while the dummy packet is replaced by the dummy packet. Includes identification information for identifying the target packet came, program characterized by.