JP2009048525A - Content reproduction device, control program, recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reproduction device which does not make a user feel increase of wait time as much as possible by alteration check of content. <P>SOLUTION: When a disk is inserted, disk mount processing is performed first (S30a). Then, a program file and an image data file are read from an optical disk (S30b), and an initialization command is transmitted to an image management section (S30c). Decoding of compression image data is started in the image management section and concurrently content verification is directed to an alteration check section (S30d). In the alteration check section, verification is performed using a hash unit from the optical disk. If verification is successful (Yes in S30e), normal title reproduction process is started (S30g) after waiting for end of decoding (S30f). If verification is failed (No in S30e), a decoding result is canceled (S30h) and the user is notified of a failure of verification or in other words, reproduction is not possible (S30i). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a content playback apparatus, and more particularly to a playback apparatus that controls video playback by computer software.

  Content and players based on next-generation video disc standards such as Blu-ray Disc (BD) and HD DVD are on the market.

  In these standards, a new copyright protection system called AACS (Advanced Access Content System) is adopted as a mechanism for protecting the copyright of content. In addition to the conventional illegal copy prevention function, AACS has a function for detecting content falsification and stopping its reproduction.

  The content falsification detection function in AACS will be described with reference to FIG. As shown in FIG. 10, in content alteration detection, (a) content certificate, (b) content hash table, and (c) content are used. (C) The content is a target for falsification detection. (C) A plurality of fixed-length blocks randomly selected in advance in the content are called hash units. Although not shown, position information of all hash units is also prepared. (B) The content hash table is a table storing hash values of the hash units. The (a) content certificate stores the hash value of the (b) content hash table, and (a) an electronic signature based on public key cryptography is verified so that the content certificate itself can be verified. include.

  To verify whether or not tampering has occurred, first, using the position information of the hash unit described above, (c) a randomly selected hash unit is read out from the content, each hash value is calculated, and (b) a content hash table Compare with the value of. If they do not match, (c) the content is assumed to be falsified and playback is stopped.

  (B) In order to verify whether the content hash table itself has been tampered with, (a) after verifying the content certificate itself using an electronic signature, (b) calculating the hash value of the content hash table (A) The hash digest included in the content certificate is compared. If they do not match, (b) the content hash table is assumed to be falsified and playback is stopped.

  The AACS rule requires that these processes be performed before content playback or during the first 30 seconds or 300 seconds after content playback starts (depending on how hash units are selected).

JP 2007-79989 A

  As described above, the content falsification detection function can prevent the distribution of falsified content.

  However, in an optical disc medium such as a BD or HD DVD, reading a hash unit involves moving the pickup, and therefore requires several seconds. During this time, no content is displayed, which makes the user wait.

  Furthermore, a large amount of high-resolution image data is used for BD and HD DVD content in order to provide a rich and high-quality user interface. These image data use a compression format such as Portable Network Graphics (PNG), and it takes several seconds for the decoding process. Therefore, compared to conventional DVD, the user can start actual content playback. You will have to wait for a long time.

  Although it may be possible to reduce the waiting time by performing content alteration detection after starting the content playback, it is necessary to read the hash unit by video playback and time-sharing. Detrimental effects such as increase and complicated control are great.

  An object of the present invention is to provide a playback apparatus capable of visually reducing the content falsification detection function and the image decoding processing time.

  According to an aspect of the present invention, a data acquisition unit that acquires content data and a program, a content verification unit that verifies whether the content data has been tampered with, a program execution unit that executes the acquired program, and the acquisition The content playback unit that plays back the content and the program executes the first step group out of the first step group that takes time to execute and the other second step group in parallel with the content verification process. And a control unit that performs control to be executed.

  With the above configuration, an increase in the waiting time of the user accompanying content verification can be apparently reduced.

  The data acquisition unit acquires at least one of image data, audio data, and moving image data used by the program as auxiliary data, the auxiliary data decoding unit, and the decoded auxiliary data It is preferable that the first step group is decoded by the auxiliary data decoding unit. With the above configuration, the auxiliary data decoding time can be apparently reduced.

  The auxiliary data acquisition process by the data acquisition unit is performed before the content verification process.

  With the above configuration, content data acquisition and auxiliary data acquisition associated with content verification processing do not occur at the same time, so exclusive control of both and seek processing are unnecessary, and content verification processing can be performed smoothly. .

  Further, the data acquisition unit acquires information for distinguishing a first program executed before content verification from a second program executed after content verification, and the program execution means executes the first program. It is characterized by being executed before content verification.

  With the above configuration, it becomes possible to use a compression method and encryption method unique to the content. In addition, various processing such as animation display during content verification becomes possible.

  According to another aspect of the present invention, a data acquisition step of acquiring content data and a program, a content verification step of verifying whether or not the content data has been tampered with, a step of executing the acquired program, and the acquired A content playback step for playing back the content, and the program executes the first step group among the first step group that takes time to execute and the other second step group as content verification. Provided is a content reproduction method characterized by performing control executed in parallel. With the above configuration, it is possible to execute arbitrary processing during content verification.

  In addition, the recording medium according to the present invention is provided with a recording medium that records a program and content, and further records information indicating whether or not to start execution of the program before verification of the content. The

  With the above configuration, content data acquisition and auxiliary data acquisition associated with content verification processing do not occur at the same time, so exclusive control of both and seek processing are unnecessary, and content verification processing can be performed smoothly. .

  According to the present invention, it is possible to perform content verification processing smoothly.

  Hereinafter, a content reproduction technique according to an embodiment of the present invention will be described with reference to the drawings. First, the reproduction technique according to the first embodiment of the present invention will be described. In this embodiment, a playback technique using a video disc player will be described. However, the present invention is not limited to this, and the form of a playback device such as a PC (Personal Computer) is not limited.

<System configuration>
FIG. 1 is a functional block diagram showing a configuration example of the video disc player 1 according to the present embodiment.
The video disc player 1 is a device that can reproduce AV data recorded on the optical disc 10. As shown in FIG. 1, the video disc player 1 includes a disc reading unit 20, an overall control unit (CPU) 30 that controls the whole, a falsification check unit 40, a program execution unit 50, an image management unit 60, An image decoding unit 70, a video reproduction unit 80, a buffer memory 90, and a synthesis unit 100 are provided. A solid line arrow indicates a data flow, and a broken line axis arrow indicates the direction of the control signal.

  The disk reading unit 20 reads various files from the optical disk 10 in accordance with instructions from the overall control unit 30 and the like. The overall control unit 30 performs overall control such as initialization after power-on, disc loading, disc ejection, title switching, and the like. When a program is recorded on the optical disc 10, the program execution unit 40 executes the recorded program. By executing the program, the video playback unit 80 and the disc reading unit 20 are controlled. Also, the bitmap data generated by executing the program is sent to the synthesis unit 100.

  The image management unit 60 performs decoding control of compressed image data read from the optical disc 10 and management of uncompressed image data after decoding in accordance with instructions from the overall control unit 30 and the program execution unit 50.

  The image decoding unit 70 performs a decoding process on the compressed image data. The compression formats handled are PNG, GIF, JPEG, and the like.

  The video playback unit 80 decodes the AV data read by the disk reading unit 20 in accordance with an instruction from the overall control unit 30 or the program execution unit 50, and converts it into uncompressed video data and uncompressed audio data (not shown). To do. Uncompressed video data is sent to the synthesis unit 100.

  The buffer memory 90 is a buffer memory for holding programs and image data used by the title to be played back. By reading through the disc reading unit 20 before the title reproduction and holding it in the buffer memory 90, it is possible to prevent the video reproduction process from being interrupted by reading the program and image data from the optical disc 10 during the video reproduction. .

  The synthesizing unit 100 superimposes and synthesizes the uncompressed video data sent from the video reproduction unit 80 and the bitmap data generated by the program execution unit 50, and sends it to the external video output.

<File structure>
AV data, programs, and the like on the optical disc can be accessed as files through the file system.
FIG. 2 is a diagram showing a file / directory structure in the optical disc 10. The file will be briefly described below.

  The AV data file F1 is a file storing AV data. The playlist file F2 is a file that stores attribute information regarding playlists and AV data. The playlist is information on which AV data is reproduced from what to where in what order.

  The program file F4 is a compilation of compiled Java class file groups and image data files used by the program, and uses the JAR (Java ARchive) format.

  The image data file F3 stores compressed image data using any one of PNG, GIF, and JPEG compression formats. As described above, it can be stored in the program file, but can also be stored outside the program file.

  The title information file F5 is a file that stores information on each title in the optical disc 10. The stored information includes reference information of program files used by each title.

  The index file F6 is a file that automatically reproduces when a disc is inserted and a file that stores correspondence information between a title number and a title information file.

<Program execution part>
FIG. 3 is a functional block diagram showing a detailed configuration example of the program execution unit 50. The description will be given with reference to FIG. As shown in FIG. 3, the program execution unit 50 includes an I / F 50b with a bus 50a and a disk reading unit 20, a program holding unit 50c, an interpreter unit 50d, an I / F 50e with a playback control unit, a graphics engine 50f, It is comprised including.

  The program read through the disk calling unit 20 is held in the buffer memory 90. The interpreter unit 50d executes the programs held in the buffer memory 90 in order from the top. When the graphics drawing process is included in the program, drawing is performed through the graphic engine 50f, and the drawing result is stored in a frame buffer (not shown) in the synthesis unit 100.

  If the program includes logic for starting / ending AV playback, special playback, etc., the video playback unit 80 is controlled through the I / F 50e with the playback control unit.

<Image management department>
FIG. 4 is a functional block diagram showing a detailed configuration example of the image management unit 60 shown in FIG. As shown in FIG. 4, the image management unit 60 includes a bus 60a, a decoded image holding unit 60b, an image management control unit 60c, an I / F 60d with the overall control unit, an image data management table 60e, and an I with the program execution unit. / F60f and I / F 60g with the image decoding unit.

  The image management unit 60 performs decoding control of compressed image data read from the optical disc 10 and management of uncompressed image data after decoding in accordance with instructions from the overall control unit 30 and the program execution unit 50 as described above.

  The image decoding processing sequence in the image management unit 60 will be described below with reference to FIG. FIG. 5 is a flowchart showing the flow of image decoding processing in the image management unit 60. When the image management process is started by a decode command, first, it is checked whether or not the instructed decode command is an initialization command (S20a). If it is an initialization command (Yes), the compressed image file is loaded from the buffer memory 90 (S20b), and the image decoding unit 70 is instructed to decode (S20c). When decoding is completed, the decoding result is stored in the decoded image holding unit 60b (S20d), and a set of file name and decoded image address information is registered in the image management table (S20e). Here, the image data management table 60e is a table that manages a set of the compressed image file name and the address information of the decoded image, and is registered in S20e.

  In S20a, in the case of a normal decode command instead of an initialization command (No), the image data management table 60e is referred to check whether the designated compressed image data file has been decoded (S20f, S20g). In the data management table 60e, if not decoded (No), the compressed image file is loaded from the buffer memory 90 (S20h), and the image decoding unit 70 is instructed to decode (S20i). Then, the decoded image data is transferred to the command issuer (S20j).

  On the other hand, if it has been decoded (Yes), the image data management table 60e is referenced to obtain the address of the decoded image data (S20k), and the decoded image data at that address is transferred to the command issuer (S20j). ).

  In some cases, the compressed image data stored in the memory may be decoded instead of the compressed image data stored in the file. In this case, only steps S20h to S20j are executed.

<Overall processing>
Next, the overall processing sequence of the video disc player 1 will be described with reference to FIG. FIG. 6 is a flowchart showing the overall flow of the video disc player 1. First, initialization is performed as the power is turned on (S10a). Next, disc insertion is detected (S10b), and disc playback processing is performed (S10c). The disc playback process will be described later. When the disc reproduction is completed, the disc ejection process is performed (S10d), and when the power is turned off (Yes in S10e), the termination process is performed (S10f). Until the power is turned off (No in S10e), the processes from S10b to S10d are repeated.

<Reproduction processing>
Next, the reproduction process in the overall control unit 30 will be described with reference to FIG. FIG. 7 is a flowchart showing a processing flow in the overall control unit 30. When a disc is inserted, first, a disc mount process is performed (S30a). Here, the file system information of the optical disc 10 is read out via the disc reading unit 20 so that the data stored in the optical disc 10 can be handled as a file.

  Next, an image data reading process is performed (S30b). Here, the program file and the image data file are read from the optical disk 10 to the buffer memory 90 via the disk reading unit 20. Further, as for the program file, the JAR file (see FIG. 2) is expanded, and each image data file F3 stored therein is extracted.

  Next, an initialization command for the image data file F3 group is transmitted to the image management unit 60 (S30c). As described above, the image management unit 60 starts decoding the compressed image data in response to the reception of the command.

  Here, in parallel with the decoding process, the falsification check unit 40 is instructed to verify the content (S30d). Accordingly, the falsification check unit 40 reads the hash unit from the optical disc 10 via the disc reading unit 20 and performs verification as described in FIG.

  If the verification is successful (Yes in S30e), it waits for the end of decoding (S30f), and starts a normal title reproduction process (S30g). If the verification fails (No in S30e), the decoding result is discarded (S30h), and there is a possibility that the content is invalid. Therefore, the verification is failed, that is, the user is notified that the reproduction cannot be performed (S30i). ).

  In FIG. 7, the decoding is awaited (S30f), but the decoding may be stopped once and the title reproduction may be started.

  Since the title reproduction process is general, a description thereof is omitted here. However, in the reproduction processing according to the present embodiment, as described above, since the compressed image data file itself has already been decoded, when the running program tries to decode the image data, it has been decoded. Therefore, there is no waiting time associated with decoding.

  The above relationship will be described with reference to FIG. FIG. 8 is a sequence diagram showing a read relationship between functional blocks from disk insertion to program execution.

  Time T11-T12 (X4) is step S30b (image data read) in FIG. 7, T12 is step S30c (instruction to start decoding to image management unit 60), and T14 is step S30d (instruction for verification to falsification check unit 40). , T17 and after correspond to S30g (title playback instruction). T20-T21 (X8) corresponds to the compressed image decoding process from the program. As shown in FIG. 8, it can be seen that the falsification check processing section (T14-T15: X1) and the image decoding processing section (T13-T16: X2) are in parallel. The image management unit performs image decoding in a short time between T20 and T21 (X8). This is because the part decoded by the image decoding unit 70 in advance in the period from T13 to T16 (X3) is moved to the image management unit 60, and the decoding is completed in a short time after reading the disk. That is, the feature of the reproduction processing according to the present embodiment is that it takes processing time, but the image decoding processing X2 takes advantage of the fact that disk access to the optical disc 10 does not occur. By performing the processing in parallel with the falsification check processing that occurs, the image decoding processing (T20-T21) can be apparently shortened.

  Further, as described above, since the image management unit 60 is provided and the decoded image data is managed, the apparent speed can be increased without rewriting existing contents. That is, the decoding time is hidden in the falsification check processing time, and the processing time is shortened after the disk read processing.

  In this embodiment, all the compressed image files inside and outside the program file are decoded. However, a list of compressed image files to be decoded before starting the title reproduction is provided in the optical disc 10, and By decoding only the compressed image files in the list in parallel with the falsification check, reading and decoding of the compressed image files that do not contribute to time reduction until the start of reproduction can be avoided. It should be noted that any method may be used as long as the player can specify the compressed image file to be decoded before starting the title reproduction. For example, it is conceivable to store in a specific directory, collect in a JAR file with a specific name, or include a specific character string in the file name.

  In this embodiment, it is assumed that a general-purpose program language such as Java language or ECMAScript is used, but it goes without saying that the same effect can be obtained even when a markup language such as HTML is used.

  In the present embodiment, the description corresponding to the encrypted compressed image file is not performed. However, if the encryption / decryption process is added immediately before the image decoding unit 160 or the buffer memory 180, it can be easily handled. Needless to say.

Next, a reproduction technique according to the second embodiment of the present invention will be described with reference to the drawings.
A second embodiment of the present invention will be described with reference to FIG. For convenience of explanation, members having the same functions as those shown in the first embodiment are given the same reference numerals, and explanation thereof is omitted. Further, the terms defined in the first embodiment are used in accordance with the definitions in the present embodiment unless otherwise specified.

  The difference between the second embodiment and the first embodiment is that a special program for decoding the compressed image file is executed instead of decoding the compressed image file during the tampering check. Thus, for example, it is possible to apply content-specific encryption to a compressed image file and prevent unauthorized use. Alternatively, it is possible to increase the compression rate by applying a unique compression method specialized for content.

<System configuration>
Since it is common to the first embodiment, the description is omitted.

<File structure>
Although common to the first embodiment, a difference is that a field for specifying a program to be activated before title reproduction is added to the index file. Hereinafter, the program specified in the field is referred to as a pre-title playback execution program. The pre-title playback execution program has a processing configuration in which all data necessary for processing is first read from the optical disc 10 and notified when the reading is completed.
As will be described later, the video disc player 1 refers to this field, reads the execution program before title reproduction before the falsification check processing, and starts the execution.

<Program execution part>
Since it is common to the first embodiment, the description is omitted.

<Image management department>
Since it is common to the first embodiment, the description is omitted.

<Overall processing>
Since it is common to the first embodiment, the description is omitted.

<Reproduction processing>
The reproduction process in the overall control unit 30 will be described with reference to FIG. FIG. 9 is a flowchart showing the flow of processing in the overall control unit 30. As shown in FIG. 9, when a disc is inserted, a disc mount process is first performed (S40a). Here, the file system information of the optical disc 10 is read out via the disc reading unit 20 so that the data stored in the optical disc 10 can be handled as a file.
Next, the index file is read from the optical disc 10, and the pre-title playback execution program is read from the optical disc 10 to the buffer memory 90 (S40b).
Next, the program execution unit 50 is instructed to execute the pre-title playback execution program (S40c). As described above, the title pre-play execution program first reads all necessary data from the optical disc and notifies the end of the data, and waits for it (S40d). Note that the decode command sent from the program execution unit 50 to the image data management unit 60 when the execution program before title reproduction is executed is handled as an initialization command.

  Here, in parallel with the execution of the pre-title playback execution program, the falsification check unit 40 is instructed to verify the content (S40e). Accordingly, the falsification check unit 40 reads the hash unit from the optical disc 10 via the disc reading unit 20 and performs verification as described in the background art.

  If the verification is successful (Yes in S40f), the program waits for the end of the program execution (S40g), and starts a normal title reproduction process (S40h). If the verification fails (No in S40f), the decoding result is discarded (S40i), and there is a possibility that the content is invalid, so that the user is notified that reproduction cannot be performed (S40j).

  By enabling the program to be executed in parallel with the tamper check as in this embodiment, the time can be shortened as in the first embodiment, and the content's unique compression method and encryption There is an advantage that the method can be used.

  Furthermore, by reading data from the optical disc 10 collectively at the beginning of the execution program before the title reproduction, and performing a tampering check after waiting for it, a file used by the program is read during the hash unit reading. There is no need for mutual exclusion control or seek processing, and tampering check processing can be performed smoothly.

  In this embodiment, the title pre-play program is designated by a specific field in the index file, but the present invention is not limited to this. Any player can identify it. For example, it is conceivable to store in a specific directory, to collect a JAR file with a specific name, or to include a specific character string in the file name.

  The execution program before title reproduction may be anything other than reproduction of the AV data file. For example, an animation generated by the program execution unit 50 may be displayed on the screen. This makes it difficult for the user to feel the waiting time for tampering check. However, in this case, the decode command sent from the program execution unit 50 to the image data management unit 60 when the execution program before title reproduction is executed is handled as a normal decode command.

  In the first and second embodiments, the decoding of the compressed image file is targeted. However, the present invention is not limited thereto. For example, the present invention is applicable to decoding of a compressed video file and a compressed audio file. Needless to say. In addition to decoding, any process that requires time for processing, such as verification of an electronic certificate using public key cryptography or communication negotiation, can be applied.

  In the first and second embodiments, it is assumed that the content is read from the optical disc, but the scope of application of the present invention is not limited thereto. For example, content can be applied even if it is obtained through broadcasting or a network.

  Finally, each block of the video disc player 1 in FIG. 1 may be configured by hardware logic, or may be realized by software using a CPU as described below. That is, the video disc player 1 includes a CPU (central processing unit) that executes instructions of a control program that realizes each function, a ROM (read only memory) that stores the program, and a RAM (random access memory) that expands the program. And a storage device (recording medium) such as a memory for storing the program and various data. An object of the present invention is a recording medium on which a program code (execution format program, intermediate code program, source program) of a control program of the video disc player 1 which is software for realizing the above-described functions is recorded so as to be readable by a computer. This can also be achieved by supplying the video disc player 1 and reading and executing the program code recorded on the recording medium by the computer (or CPU or MPU).

  Examples of the recording medium include a tape system such as a magnetic tape and a cassette tape, a magnetic disk such as a floppy (registered trademark) disk / hard disk, and an optical disk such as a CD-ROM / MO / MD / DVD / CD-R. Card system such as IC card, IC card (including memory card) / optical card, or semiconductor memory system such as mask ROM / EPROM / EEPROM / flash ROM.

  Further, the video disc player 1 may be configured to be connectable to a communication network, and the program code may be supplied via the communication network. The communication network is not particularly limited. For example, the Internet, intranet, extranet, LAN, ISDN, VAN, CATV communication network, virtual private network, telephone line network, mobile communication network, satellite communication. A net or the like is available. Also, the transmission medium constituting the communication network is not particularly limited. For example, even in the case of wired such as IEEE 1394, USB, power line carrier, cable TV line, telephone line, ADSL line, etc., infrared rays such as IrDA and remote control, Bluetooth ( (Registered trademark), 802.11 wireless, HDR, mobile phone network, satellite line, terrestrial digital network, and the like can also be used. The present invention can also be realized in the form of a computer data signal (transmission medium) embedded in a carrier wave in which the program code is embodied by electronic transmission.

  The playback device of the present invention can be suitably used for a video player that combines video playback and a general-purpose program language execution environment.

FIG. 2 is a block diagram showing a schematic configuration example in the first embodiment of the present invention. FIG. 3 is an explanatory diagram showing a file / directory configuration in the first exemplary embodiment of the present invention. FIG. 2 is a block diagram showing a schematic configuration of a program execution unit in the first embodiment of the present invention. FIG. 2 is a block diagram illustrating a schematic configuration of an image management unit in the first embodiment of the present invention. FIG. 5 is a flowchart showing a flow of processing in an image management unit in the first embodiment of the present invention. FIG. 2 is a flowchart showing an overall flow in the first embodiment of the present invention. FIG. 6 is a flowchart showing a flow of disk reproduction processing of the overall control unit in the first embodiment of the present invention. FIG. 5 is a sequence diagram showing a calling relationship between components from disk insertion to program execution in the first exemplary embodiment of the present invention. It is a flowchart figure which shows the flow of the disk reproduction | regeneration processing of the whole control part in the 2nd Embodiment of this invention. It is a figure which shows the data structural schematic example for a content alteration detection.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Video disc player 10 Optical disc 20 Disc reading part 30 Overall control part 40 Tampering check part 50 Program execution part 60 Image management part 60 AV decoding part 70 Image decoding part 80 Video reproduction part 90 Buffer memory 100 Composition part

Claims (11)

A data acquisition unit for acquiring content data and programs;
A content verification unit that verifies whether the content data has been tampered with;
A program execution unit for executing the acquired program;
A content playback unit for playing back the acquired content;
The program includes a control unit that performs control to execute the first step group in parallel with the content verification process among the first step group that takes time to execute and the second step group other than the first step group. A content playback apparatus comprising: The data acquisition unit
At least one of image data, audio data, and video data used by the program is acquired as auxiliary data;
A decoding unit for the auxiliary data; and a management unit for managing the decoded auxiliary data.
The content reproduction apparatus according to claim 1, wherein the first step group is decoded by a decoding unit of the auxiliary data.   The content reproduction apparatus according to claim 2, wherein the auxiliary data acquisition process by the data acquisition unit is performed before the content verification process. The data acquisition unit acquires a list of auxiliary data to be decoded before content verification processing,
The content reproducing apparatus according to claim 2, wherein the auxiliary data decoded in the first step group is auxiliary data described in the list.   The content reproduction apparatus according to claim 1, further comprising a notification unit that notifies a user of a verification result by the content verification unit. The data acquisition unit acquires information for distinguishing between a first program executed before content verification and a second program executed after content verification;
The content reproduction apparatus according to claim 1, wherein the program execution unit executes the first program before content verification. A data acquisition step for acquiring content data and programs;
A content verification step of verifying whether the content data has been tampered with;
Executing the acquired program;
A content playback step of playing back the acquired content,
The program performs control to execute the first step group out of a first step group that takes time to execute and a second step group other than that in parallel with content verification. Content playback method.   A program for executing the steps according to claim 7 on a computer.   A computer-readable recording medium on which the program according to claim 8 is recorded.   A recording medium for recording a program and content, and further recording information indicating whether or not to start execution of the program before verification of the content. The recording medium according to claim 10,
The program executed before the content verification includes a program for causing a computer to execute a process of acquiring data,
The recording medium is characterized in that the process for acquiring the data is included in a head part of the process of the program, and includes a program for executing a process for notifying that when the data acquisition is completed.

Images