Control method, reproduction method, and computer program

Abstract

The present invention simplifies a process related to content reproduction. This control method includes causing a computation circuit to: transmit, to each of first and second reproduction devices, a request for requesting transmission of the time being counted; receive the time of day of a first internal clock from the first reproduction device that has responded to the request and derive a first difference that is the difference in the time of day between the first internal clock and a third internal clock; receive the time of day of a second internal clock from the second reproduction device that has responded to the request and derive a second difference that is the difference in the time of day between the second internal clock and the third internal clock; transmit, to the first reproduction device, a first control signal for reproducing first content at a first reproduction start time; and transmit, to the second reproduction device, a second control signal for reproducing second content at a second reproduction start time.

Description

Control Method, Reproduction Method, and Computer Program

[0001] The present disclosure relates to a control method for controlling content playback, a reproduction method for reproducing content according to the control, and a computer program.

[0002] There is a playback system for playing content such as video and audio. In such a content playback system, a playlist indicating the order of playing a plurality of contents is generated and played according to the playlist.

[0003] Japanese Patent Application Laid-Open No. 2015-139159

[0004] However, in a content playback system, since a plurality of devices are used for playlist generation and content playback using the playlist, the processing is complicated and cannot be easily executed. Also, playlist generation itself in a content playback system is complicated and cannot be easily executed.

[0005] The control method, reproduction method, and computer program according to the present disclosure can simplify the processing related to content playback.

[0006] The first control method of this disclosure controls the playback of content by first and second playback devices using a control device. The first playback device includes a first internal clock for timekeeping. The second playback device includes a second internal clock for timekeeping. The control device includes an arithmetic circuit and a third internal clock for timekeeping. The control method involves causing the control device's arithmetic circuit to perform the following actions: send a request to each of the first and second playback devices to transmit the time being measured; receive the time of the first internal clock from the first playback device in response to the request and determine a first difference, which is the difference between the times of the first and third internal clocks; receive the time of the second internal clock from the second playback device in response to the request and determine a second difference, which is the difference between the times of the second and third internal clocks; and, upon receiving a playback operation including a playback start time, transmit a first control signal to the first playback device to play the first content at the first playback start time, wherein the first playback start time is determined using the first difference relative to the playback start time; and transmit a second control signal to the second playback device to play the second content at the second playback start time, wherein the second playback start time is determined using the second difference relative to the playback start time.

[0007] A second control method of this disclosure controls the playback of first and second content by a playback device using a control device. The control device includes an arithmetic circuit accessible to a display device. The control method causes the arithmetic circuit of the control device to transmit the first and second content to the playback device, to display on the display device an arbitrary point on the time axis in which the first content is played back, and, upon receiving the arbitrary point in the display, to calculate the elapsed time from the start of the first content to the arbitrary point, to stop the playback of the first content at the arbitrary point, and to transmit a control signal to the playback device to start the second content from the point where the elapsed time has elapsed from the start.

[0008] Such general and specific embodiments may be implemented by systems, methods, and computer programs, or combinations thereof.

[0009] The control method, playback method, and computer program disclosed herein can simplify the processing related to content playback.

[0010] This is a schematic diagram showing a playback system according to the first embodiment. This is a block diagram showing a control device used in the playback system of Figure 1. This is a block diagram showing a playback device used in the playback system of Figure 1. This is a block diagram showing a display device used in the playback system of Figure 1. This is a sequence diagram explaining the process performed by the playback system according to the first embodiment. This is a flowchart explaining the process performed by the control device according to the first embodiment. This is a flowchart explaining the process performed by the control device following Figure 6A. This is a flowchart explaining the process performed by the playback device according to the first embodiment. This is a schematic diagram showing a playback system according to the second embodiment. This is a sequence diagram explaining the process performed by the playback system according to the second embodiment. This is a schematic diagram explaining the switching performed by the playback system according to the second embodiment. This is a flowchart explaining the process performed by the control device according to the second embodiment. This is a flowchart explaining the process performed by the control device following Figure 11A. This is a flowchart explaining the process performed by the playback device according to the second embodiment. This is an example of a display screen displayed by the control device according to the second embodiment. This is an example of a display screen after the playlist has been switched from the display screen of Figure 13A. This is a sequence diagram explaining the process performed in a modified example of the playback system according to the second embodiment.

[0011] Embodiments of this disclosure will be described below with reference to the drawings as appropriate. However, unnecessary parts of the description of the prior art and substantially identical configurations may be omitted in the detailed description. This is for the sake of simplicity. Furthermore, the following description and accompanying drawings are disclosed so that a person skilled in the art can fully understand this disclosure and are not intended to limit the subject matter of the claims.

[0012] The control method, playback method, and computer program relating to this disclosure are used in various processes related to content playback. Specifically, the control method, playback method, and computer program relating to this disclosure can be used to generate playlists used for content playback. Furthermore, the control method, playback method, and computer program relating to this disclosure can be used for playback of content that utilizes playlists.

[0013] [First Embodiment] <Playback System> As shown in Figure 1, the playback system 1A according to the first embodiment includes a control device 10A, a plurality of playback devices 20A, 20B, a plurality of display devices 30A, 30B, and a network 40. The playback devices 20A, 20B are devices that control the display of images by the display devices, and are, for example, media players. Each display device 30A, 30B is, for example, a projection device that can project images onto a screen under the control of each playback device 20A, 20B.

[0014] The images displayed by each display device 30A, 30B may be the same image or different images that are displayed in sync. In the playback system 1A, the control device 10A controls each playback device 20A, 20B so that each display device 30A, 30B displays its respective image in sync.

[0015] For example, the same image may be projected by the first display device 30A and the second display device 30B. Alternatively, different images may be projected by the first display device 30A and the second display device 30B, so that they form a single image together. In this case, if the images projected by the first display device 30A and the second display device 30B cannot be synchronized, and a time lag occurs in the images displayed by each display device 30A and 30B, the playback will not be as desired by the user. For example, even if the same image is to be projected by each display device 30A and 30B, if a time lag occurs, the same frames will not be displayed simultaneously. Also, even if the images displayed by each display device 30A and 30B are to be combined into a single image, if a time lag occurs, it will not be possible to display the entire image as desired.

[0016] The playback system 1A according to the first embodiment can prevent time lags in the content played by each playback device 20A, 20B when playing content using multiple playback devices 20A, 20B, and can play the content in a synchronized manner.

[0017] In the example shown in Figure 1, the playback system 1A includes a first playback device 20A and a second playback device 20B, and a first display device 30A and a second display device 30B. However, the number of playback devices and display devices included in the playback system 1A is not limited. Furthermore, when playback devices 20A and 20B are not distinguished, they will simply be described as playback device 20. In addition, when display devices 30A and 30B are not distinguished, they will simply be described as display device 30.

[0018] In this embodiment, the playback device 20 is described in an example where it plays video content on the display device 30. The display device 30 is described in an example where it is a projection device that projects video content onto a screen. However, the playback device controlled by the playback device 20 is not limited to the display device 30 that displays video content. Therefore, the content played back by the playback device 20 is not limited to video content. For example, the content controlled by the playback device 20 may be audio content. Furthermore, the content controlled by the playback device 20 may be a combination of video and audio. Also, the display device 30 is not limited to a projection device. For example, the display device 30 may be a display such as a liquid crystal display.

[0019] <Control device> The control device 10A controls the playback of content by the first and second playback devices 20A and 20B. As shown in Figure 2, the control device 10A is an information processing device that includes an arithmetic circuit 11, a storage device 12, an input device 13, a monitor 14, a communication circuit 15, and an internal clock 16, etc. The control device 10A can generate a playlist of content to be played back by the playback system 1A and provide it to the playback device 20. The control device 10A can also control the playback device 20 to play back the content.

[0020] The arithmetic circuit 11 is a controller that oversees the control of the entire control device 10A. For example, the arithmetic circuit 11 reads and executes the control program P1 stored in the storage device 12, thereby realizing various processes such as playlist generation and content playback instructions to the playback device 20. Specifically, the arithmetic circuit 11 performs processes such as content reception processing, playlist generation processing, playlist selection processing, playback start position storage processing, control signal generation processing, and transmission processing. The arithmetic circuit 11 may be a CPU, MPU, GPU, FPGA, DSP, ASIC, or other various processors or a specially designed hardware circuit.

[0021] The storage device 12 is a recording medium that stores various types of information. The storage device 12 can be implemented as, for example, RAM, ROM, flash memory, SSD (Solid State Drive), hard disk drive, other storage devices, or a combination thereof as appropriate. The storage device 12 stores the control program P1, content data 121, playlist data 122, time data 123, etc.

[0022] The control program P1 is a computer program executed by the arithmetic circuit 11.

[0023] Content data 121 is the target of playback by the playback device 20. Content data 121 may be a group of multiple content items. In this case, content data 121 includes multiple video content items.

[0024] The playlist data 122 is data that includes a playlist indicating the schedule for playing content. The playlist is data that indicates the order in which multiple contents are played sequentially on the playback device 20. The playlist may also include information indicating the time required to play each content, and, when a group of multiple contents is played as a single content, the start position of playback for each content from the start of the series of playback. Content playback is performed by specifying the playlist contained in the playlist data 122. Therefore, in the following description, content playback will be described as playlist playback as necessary.

[0025] Time data 123 is data that includes the time acquired at various timings, the difference between two acquired time points, etc.

[0026] The input device 13 is used for user operation and data input. The input device 13 may be, for example, an operation button, keyboard, mouse, touch panel, microphone, etc. The monitor 14 is used for displaying processing results and data. The monitor 14 may be, for example, a display.

[0027] The communication circuit 15 performs data communication with the playback device 20, the display device 30, etc. Data communication is performed by wire and / or wirelessly, and follows, for example, known communication standards. For example, wired data communication may be performed by using a communication controller of a semiconductor integrated circuit that operates in accordance with the Ethernet (registered trademark) standard and / or the USB (registered trademark) standard as the communication circuit 15. Wireless data communication may be performed by using a communication controller of a semiconductor integrated circuit that operates in accordance with the IEEE 802.11 standard for wireless LAN (Local Area Network) and / or the so-called 4G / 5G / 6G mobile communication systems, etc., as the communication circuit 15.

[0028] The internal clock 16 measures time. For example, the time measured by the internal clock 16 is a time that includes the date and time. Alternatively, the time measured by the internal clock 16 may be the time (counter value) obtained by incrementing time from a certain starting point.

[0029] <<Various processes executed by the arithmetic circuit>> The content reception process is the process of receiving content data 121 from an external storage device (not shown) and storing it in the storage device 12.

[0030] The playlist generation process is a process that creates one or more playlists from the received content data 121 in response to user input. The playlist generation process also stores the one or more generated playlists as playlist data 122 in the storage device 12. Furthermore, the playlist generation process transmits the generated playlists and content to the playback device 20 in response to user input.

[0031] The time management process involves acquiring and storing the time measured by the internal clock 16 of the control device 10A or the internal clocks of the regeneration devices 20A and 20B at any given time. Furthermore, the time management process also involves performing various calculations using the acquired time.

[0032] The playlist selection process is a process that accepts the selection of a playlist from one or more playlists included in the playlist data 122 in response to user input. Specifically, the playlist selection process selects the playlist identifier.

[0033] The playback start position storage process is the process of storing the playback start position of the playlist as start point data 124 in the storage device 12. The playback start position indicates the starting point when playing the content. This start point is indicated as a relative position from the beginning of the playlist.

[0034] The control signal generation process generates a playback control signal that, in response to user input, initiates playback of the playlist with the identifier selected in the playlist selection process. The playback control signal includes the identifier of the playlist to be played and the playback start position. The control signal generation process also generates a stop control signal that, in response to user input, initiates playback of the selected playlist with the identifier stopped.

[0035] The communication process involves transmitting the playback control signal generated in the control signal generation process to the playback device. Furthermore, the communication process also involves sending requests generated in the time management process and receiving responses corresponding to those requests.

[0036] <Playback Device> As shown in Figure 3, the playback device 20A is an information processing device equipped with an arithmetic circuit 21, a storage device 22, a communication circuit 23, an HDMI® communication circuit 24, and an internal clock 25, etc. The playback device 20A controls the display device 30A according to the control signal from the control device 10A to play back content.

[0037] The arithmetic circuit 21, memory device 22, communication circuit 23, HDMI communication circuit 24, and internal clock 25 can be implemented by the same specific means as the arithmetic circuit 11, memory device 12, communication circuit 15, and internal clock 16 described above using Figure 2.

[0038] The HDMI communication circuit 24 enables communication of video signals and audio signals with an external device (for example, a display device 30A).

[0039] By reading and executing the playback program P2 stored in the storage device 22, the arithmetic circuit 21 executes data communication with the control device 10A and the display device 30A, and causes the display device 30A to play back the content.

[0040] The storage device 22 stores content data 221, playlist data 222, and a playback program P2.

[0041] The playback program P2 is a computer program executed by the arithmetic circuit 21.

[0042] The content data 221 is the target to be played back on the first display device 30A. The content data 221 is data transmitted from the control device 10A and may be a part of the content data 121.

[0043] The playlist data 222 is data indicating the schedule of content playback on the first display device 30A. The playlist data 222 is data transmitted from the control device 10A and may be a part of the playlist data 122.

[0044] The internal clock 25 measures time. However, the internal clocks of each device measure time independently. Therefore, the times measured by multiple devices may not exactly match. For example, a deviation may occur between the time measured by the internal clock 25 of the first playback device 20A and the time measured by the internal clock 16 of the control device 10A.

[0045] Since the configuration of the second playback device 20B is the same as that of the first playback device 20A, the description thereof is omitted, and reference is made to FIG. 3 as necessary. In the following description, the internal clock 25 of the first playback device 20A is referred to as the first internal clock. Also, the internal clock 25 of the second playback device 20B is referred to as the second internal clock. Furthermore, as necessary, the internal clock 16 of the control device 10A is referred to as the third internal clock. Also, a deviation may occur between the time measured by the first internal clock 25, the time measured by the second internal clock 25, and the time measured by the third internal clock 16.

[0046] <Display Device> The projection device, which is the first display device 30A, includes an arithmetic circuit 31, a storage device 32, an input device 33, a communication circuit 35, an HDMI communication circuit 36, an optical mechanism 37, etc., as shown in FIG. 4. The first display device 30A projects video content transmitted from an information processing device such as the first playback device 20A onto a screen.

[0047] The arithmetic circuit 31, the storage device 32, the input device 33, and the communication circuit 35 are realized by the same specific means as the arithmetic circuit 11, the storage device 12, the input device 13, and the communication circuit 15 described above using FIG. 2. Also, the HDMI communication circuit 36 is realized by the same specific means as the HDMI communication circuit 24 described above using FIG. 3.

[0048] The optical mechanism 37 projects an image onto a screen. The optical mechanism 37 includes a light source such as a laser diode, an LED, a lamp, etc. Also, the optical mechanism 37 includes an optical unit including a light modulation element such as a liquid crystal element or a DMD (Digital Mirror Device) that modulates the light emitted from the light source, and a projection lens system that guides the video light modulated by the light modulation element to the projection surface.

[0049] Since the configuration of the second display device 30B is the same as that of the first display device 30A, the description is omitted, and reference is made to FIG. 4 as necessary.

[0050] <Processing in the Playback System> Referring to FIG. 5, the processing in the playback system 1A according to the first embodiment will be described. Here, an example will be described in which when the time of the internal clock 16 of the control device 10A is 12:00:00, the time of the internal clock 25 of the first playback device 20A is 12:00:05, and the time of the internal clock 25 of the second playback device 20B is 13:00:00. Therefore, the internal clock 25 of the first playback device 20A is 5 seconds behind the internal clock 16 of the control device 10A. Also, the internal clock 25 of the second playback device 20B is 60 minutes behind the internal clock 16 of the control device 10A. When controlling the playback devices 20A and 20B, the control device 10A generates a control signal using this deviation.

[0051] The control device 10A generates a playlist according to the user's operation (playlist generation process) (S001). If the content to be played on the first and second playback devices 20A and 20B is the same, the control device 10A may generate only one playlist. If the content to be played on the first and second playback devices 20A and 20B is different, the control device 10A generates two playlists. The control device 10A may also generate multiple playlists for each playback device 20 and use the playlist selected from the multiple playlists.

[0052] The control device 10A transmits the content and playlist to be used by the first playback device 20A to the first playback device 20A (playlist generation process) (S002). The first playback device 20A stores the received content and playlist in the storage device 22.

[0053] Furthermore, the control device 10A transmits the content and playlist to be used by the second playback device 20B to the second playback device 20B (playlist generation process) (S003). The second playback device 20B stores the received content and playlist in the storage device 22.

[0054] The control device 10A acquires the time Tt of the internal clock 16 and stores it in the storage device 12 (time management processing) (S004). Here, we assume that the time Tt of the internal clock 16 acquired by the control device 10A is 12:00:00. This time Tt will be described below as the transmission time Tt.

[0055] Furthermore, the control device 10A, at the same time as acquiring the transmission time Tt of the internal clock 16, sends a request to the first and second regeneration devices 20A and 20B to transmit the time (time management processing) (S005, S006).

[0056] When the first playback device 20A receives a request, it obtains the time Tt1 measured by the first internal clock 25 and transmits it to the control device 10A (S007). Here, it is assumed that the time Tt1 of the internal clock 25 obtained by the first playback device 20A is 12:00:06. In the following, this time Tt1 will be described as the first transmission time Tt1.

[0057] When the control device 10A receives the first transmission time Tt1, it obtains the time measured by its internal clock 16 (first reception time Tr1). The control device 10A also calculates the first difference Td1, which is the difference between the internal clock 16 of the control device 10A and the first internal clock 25 of the first regeneration device 20A (time management processing) (S008). Here, the control device 10A calculates the first difference Td1 using the first transmission time Tt1 and the first communication time γ1, which is the one-way communication time between the control device 10A and the first regeneration device 20A, as shown in the following equation (1.1). The first communication time γ1 can be calculated using the transmission time Tt and the first reception time Tr1, as shown in the following equation (1.2). Td1 = Tt1 - Tt - γ1 ... (1.1) γ1 = (Tr1 - Tt) / 2 ... (1.2)

[0058] Here, the time from the request transmission time Tt (12:00:00) to the reception time Tr1 (12:00:02) at the first time (first time interval Ti1) is 2 seconds. The control device 10A divides the first time interval Ti1, which is the time required for the round trip of the signal, by 2 to determine the time required for one-way communication of the signal (first communication time γ1). In this example, the control device 10A determines that the first communication time γ1 is 1 second. The control device 10A can also obtain the first difference Td1 by subtracting the transmission time Tt (12:00:00) from the first transmission time Tt1 (12:00:06) and subtracting the first communication time γ1 (1 s). Here, the first difference is 5 seconds. In the examples of equations (1.1) and (1.2) above, when the first difference Td1 is a positive value, the internal clock 25 of the playback device 20 is ahead of the internal clock 16 of the control device 10A. Also, when the first difference Td1 is a negative value, the internal clock 25 of the playback device 20 is behind the internal clock 16 of the control device 10A.

[0059] The second playback device 20B, upon receiving a request, acquires the time Tt2 measured by the second internal clock 25 and transmits it to the control device 10A (S009). Here, it is assumed that the time on the internal clock 25 acquired by the second playback device 20B is 13:00:02. In the following, this time Tt2 will be described as the second transmission time Tt2.

[0060] When the control device 10A receives the second transmission time Tt2, it obtains the time measured by its internal clock 16 (second reception time Tr2). The control device 10A also calculates the second difference Td2, which is the difference between the control device 10A's internal clock 16 and the second internal clock 25 of the second regeneration device 20B (time management processing) (S010). Here, the control device 10B calculates the second difference Td2 using the second transmission time Tt2 and the second communication time γ2, which is the one-way communication time between the control device 10A and the second regeneration device 20B, as shown in the following equation (2.1). The second communication time γ2 can be calculated using the transmission time Tt and the second reception time Tr2, as shown in the following equation (2.2). Td2 = Tt2 - Tt - γ2 ... (2.1) γ2 = (Tr2 - Tt) / 2 ... (2.2)

[0061] Here, the time from the request transmission time Tt (12:00:00) to the reception time Tr2 (12:00:04) at the second time (second time interval Ti2) is 4 seconds. The control device 10A divides the second time interval Ti2, which is the time required for the round trip of the signal, by 2 to determine the time required for one-way communication of the signal (second communication time γ2). In this example, the control device 10A determines that the second communication time γ2 is 2 seconds. The control device 10A can also obtain the second difference Td2 by subtracting the transmission time Tt (12:00:00) from the second transmission time Tt2 (13:00:02) and then subtracting the second communication time γ2 (2s). Here, the second difference is 60 minutes.

[0062] The control device 10A generates a first playback control signal that controls content playback using a first difference, and generates a second playback device control signal that controls content playback using a second difference (control signal generation process) (S011).

[0063] Specifically, the control device 10A calculates a first playback start time T1 for starting content playback on the first playback device 20A. The control device 10A also generates a first playback control signal that includes the first playback start time. Specifically, the control device 10A uses the following equation (1.3) to determine the first playback start time T1 using the playback start time Ts relative to the internal clock 16 and the first difference Td1. In this case, the playback start time Ts is a future time. T1 = Ts + Td1 ... (1.3)

[0064] Furthermore, the control device 10A calculates a second playback start time T2 for initiating content playback on the second playback device 20B. The control device 10A also generates a second playback control signal that includes the second playback start time. Specifically, the control device 10A uses the following equation (2.3) to determine the second playback start time T2 using the playback start time Ts and the second difference Td2: T2 = Ts + Td2 ... (2.3)

[0065] The control device 10A transmits the generated first regeneration control signal to the first regeneration device 20A and transmits the second regeneration control signal to the second regeneration device 20B (communication processing) (S012, S013).

[0066] The first playback device 20A plays the content according to the first playback start time included in the first playback control signal (S014).

[0067] The second playback device 20B plays the content according to the second playback start time included in the second playback control signal (S015).

[0068] As described above, the control device 10A determines the difference Td1 and Td2 between the internal clocks 15 and 25 of each device, corrects the discrepancy, and determines the playback start times T1 and T2 for each playback device 20.

[0069] <Processing in the Control Device> The processing performed by the control device 10A according to the first embodiment will be explained using the flowcharts shown in Figures 6A and 6B.

[0070] The arithmetic circuit 11 generates a playlist (playlist generation process) (S101) according to the user's operation via the input device 13. The arithmetic circuit 11 accepts the selection of one or more contents from multiple contents contained in the content data 121 stored in the storage device 12, and the order in which the selected one or more contents will be played. When only a portion of the contents is to be played, the arithmetic circuit 11 can also accept the start and end points of playback for that content. The arithmetic circuit 11 adds the generated playlist to the playlist data 122. The arithmetic circuit 11 can also generate multiple playlists.

[0071] The arithmetic circuit 11 transmits the content and playlist to each playback device 20 (playlist generation process) (S102). The arithmetic circuit 11 may transmit only the content to be played by each playback device 20 from among the multiple contents included in the content data 121. Alternatively, the arithmetic circuit 11 may transmit only the playlist used by each playback device 20 from among the multiple playlists generated in step S101 to each playback device 20. The content and playlist transmitted to each playback device 20A, 20B do not have to be the same.

[0072] The arithmetic circuit 11 acquires the time from the internal clock 16 (time management processing) (S103). At this time, the arithmetic circuit 11 adds the acquired time to the time data 123 stored in the storage device 12 as the transmission time Tt. Also, when acquiring the time, the arithmetic circuit 11 sends a request to the first and second playback devices 20A and 20B, respectively, to transmit the time being measured (S104).

[0073] In response to the request sent in step S103, the arithmetic circuit 11 receives the first transmission time Tt1 from the first playback device 20A. The arithmetic circuit 11 also receives the second transmission time Tt2 from the second playback device 20B (time management processing) (S105). The arithmetic circuit 11 adds the received first transmission time Tt1 and second transmission time Tt2 to the time data 123 stored in the storage device 12. At this time, the arithmetic circuit 11 adds the time measured by the internal clock 16 when the first transmission time Tt1 is received as the first reception time Tr1 to the time data 123. The arithmetic circuit 11 also adds the time measured by the internal clock 16 when the second transmission time Tt2 is received as the second reception time Tr2 to the time data 123.

[0074] The arithmetic circuit 11 calculates the first communication time γ1 using the transmission time Tt and the first reception time Tr1, as described above in equation (1.2). The arithmetic circuit 11 also calculates the second communication time γ2 using the transmission time Tt and the second reception time Tr2, as described above in equation (2.2) (time management processing) (S106). The arithmetic circuit 11 adds the calculated communication times γ1 and γ2 to the time data 123.

[0075] As described above in equation (1.1), the arithmetic circuit 11 calculates the first difference Td1 using the transmission time Tt, the first transmission time Tt1, and the first communication time γ1. The arithmetic circuit 11 also calculates the second difference Td2 using the transmission time Tt, the second transmission time Tt2, and the second communication time γ2 as described above in equation (2.1) (time management processing) (S107). The arithmetic circuit 11 adds the calculated differences Td1 and Td2 to the time data 123.

[0076] The arithmetic circuit 11 sets (initializes) the playback start position to the beginning of the playlist (playback start position storage processing) (S108).

[0077] The arithmetic circuit 11 accepts the selection of a playlist according to the user's operation input via the input device 13. The arithmetic circuit 11 also transmits the identifier of the selected playlist to the playback device 20 (playlist selection process, communication process) (S109). When the playback operations for the first playback device 20A and the second playback device 20B are different, the arithmetic circuit 11 can accept the selection of a playlist for the first playback device 20A and the selection of a playlist for the second playback device 20B.

[0078] When the arithmetic circuit 11 receives a playback operation in accordance with the user's input via the input device 13 (YES in step S110), it generates first and second playback control signals (control signal generation process) (S111).

[0079] The first playback control signal is a signal that causes the content to be played at a first playback start time T1. The first playback control signal includes the first playback start time T1, which causes the content to be played on the first playback device 20A. The first playback start time T1 is determined using the playback start time Ts received from the user via operation and the first difference Td1, as described above in equation (1.3). Alternatively, the first playback start time T1 may be determined by adding a predetermined time λ required by the first playback device 20A from the reception of the first playback control signal to the playback of the content, as shown in the following equation (1.4). The predetermined time λ is, for example, the time required to start up the playback device 20. T1 = Ts + Td1 + λ ... (1.4) where λ > γ1

[0080] The second playback control signal is a signal that causes the content to be played at the second playback start time T2. The second playback control signal includes the second playback start time T2, which causes the content to be played on the second playback device 20B. The second playback start time T2 is determined using the playback start time Ts received from the user and the second difference Td2, as described above in equation (2.3). Alternatively, the second playback start time T2 may be determined by adding a predetermined time λ required by the second playback device 20B from the reception of the second playback control signal to the playback of the content, as shown in equation (2.4) below. Here, the predetermined time λ is assumed to be the same for each playback device 20A and 20B. However, the predetermined time λ may be different for each playback device 20A and 20B. T2 = Ts + Td2 + λ ... (2.4) where λ > γ2

[0081] The arithmetic circuit 11 transmits the first playback control signal generated in step S110 to the first playback device 20A. The arithmetic circuit 11 also transmits a second playback control signal to the second playback device 20B (communication processing) (S112). As a result, playback of the content begins at the playback start time in each playback device 20. At this point, the arithmetic circuit 11 may display a preview screen on the monitor 14 that includes the content to be played back by the first playback device 20A and the second playback device 20B. At this time, the arithmetic circuit 11 displays a preview screen on the monitor 14 that includes the display corresponding to the playback control signal transmitted in step S112, with a predetermined time λ delay from the operation reception in step S110.

[0082] When the arithmetic circuit 11 receives a playback stop operation from the user via the input device 13 (YES in step S113), it generates first and second playback stop control signals (control signal generation process) (S114). The arithmetic circuit 11 also updates the playback start position, setting the position where playback stops in the content as the new playback start position (playback start position storage process) (S115).

[0083] The arithmetic circuit 11 transmits the first stop control signal generated in step S114 to the first regeneration device 20A. The arithmetic circuit 11 also transmits a second stop control signal to the second regeneration device 20B (control signal generation process) (S116).

[0084] When the user inputs an operation to terminate the series of processes via the input device 13 (YES in S117), the arithmetic circuit 11 terminates the process.

[0085] If no operation to terminate the series of processes is entered (NO in S117), and an operation to change the playlist is entered (YES in S118), the arithmetic circuit 11 returns to the process in S109.

[0086] Furthermore, if no operation to change the playlist is input (NO in S118), the arithmetic circuit 11 returns to the process of S110.

[0087] The order of the steps described above is not limited, and the order of processing can be changed as long as the content can be played back by multiple playback devices 20. Also, some processing can be executed in parallel. Furthermore, although the content reception processing is not shown in the flowchart in Figure 6A, it is assumed that the content reception processing has been performed in advance by the control device 10A and the content data 121 is stored in the storage device 12.

[0088] In this way, even if there is a discrepancy in the internal clocks 16 and 25 of each device 10A, 20A, and 20B, the control device 10A can correct the discrepancy and control the playback device 20 in synchronization.

[0089] <Processing in the Playback Device> The processing performed in the playback device 20 according to the first embodiment will be explained using the flowchart shown in Figure 7.

[0090] The arithmetic circuit 21 receives the content and playlist transmitted from the control device 10A (S201). The arithmetic circuit 21 stores the received content as content data 221 in the storage device 22. The arithmetic circuit 21 also stores the received playlist as playlist data 222 in the storage device 22.

[0091] Furthermore, the arithmetic circuit 21 receives a request to transmit the time (S202).

[0092] When the request is output in step S202, the arithmetic circuit 21 obtains the time of the internal clock 25 (S203).

[0093] Furthermore, the calculation circuit 21 transmits the time obtained in step S203 to the control device 10A (S204).

[0094] Upon receiving a playback control signal transmitted from the control device 10A (YES in S205), the arithmetic circuit 21 starts playback of the content (S206). Specifically, the arithmetic circuit 21 extracts the playlist of identifiers included in the playback control signal from the playlist data 222. Then, according to the extracted playlist, it starts playback of the content included in the content data 221 at the playback start time included in the playback control signal.

[0095] When the control unit 10A sends a stop control signal (YES in S207), the arithmetic circuit 21 stops playing the content (S208).

[0096] Subsequently, the arithmetic circuit 21 returns to the processing of step S205 and plays the content (S209) until it receives a signal from the control device 10A to terminate the series of operations.

[0097] Thus, the playback device 20 starts playing the content at the playback start time included in the playback control signal transmitted from the control device 10A. Furthermore, the playback start time included in the playback control signal is determined by correcting for the discrepancies in the internal clocks 16 and 25 of each device 10A, 20A, and 20B. Therefore, the playback device 20 can achieve content playback synchronized with other playback devices 20.

[0098] [Second Embodiment] <Playback System> As shown in Figure 8, the playback system 1B according to the second embodiment includes a control device 10B, a playback device 20, a display device 30, and a network 40. The configurations of the control device 10B, the playback device 20, and the display device 30 are the same as those of the control device 10A, playback device 20A, and display device 30A described above using Figures 1 to 4, so a detailed explanation using the figures will be omitted. The control device 10B according to the second embodiment can control the playback of the first and second content by a single playback device 20.

[0099] In the playback system 1B according to the second embodiment, the control device 10B can switch and display two or more contents on the playback device 20 so that the user can compare them. In this case, the two or more contents may be related contents. For example, the two or more contents may contain the same content but have different effects. If the first content is played and then stopped midway, and then the second content is played from the same point as when the first content was stopped, the user can easily compare the contents.

[0100] <<Various processes executed by the control device's arithmetic circuit>> The arithmetic circuit 11 of the control device 10B executes processes such as content reception processing, playlist generation processing, time management processing, playlist selection processing, playback start position storage processing, control signal generation processing, communication processing, and playlist switching processing. Processes other than playlist switching processing are the same as those described above in the control device 10A of the first embodiment.

[0101] The playlist switching process is the process of switching from playing the first playlist to playing the second playlist in response to user input during the playlist selection process. Specifically, during the playlist switching process, the identifier of the second playlist is selected.

[0102] <Processing in the Playback System> Referring to Figure 9, the processing in the playback system 1B according to the second embodiment will be described. Here, in the playback system 1B, an example will be described in which the content is played sequentially in order to compare the display of the first content and the display of the second content.

[0103] First, the control device 10B generates a playlist according to the user's operation (playlist generation process) (S301). Here, the playlist generated by the control device 10B includes two or more related playlists.

[0104] The control device 10B transmits the content and playlist to the playback device 20 (playlist generation process) (S302). The playback device 20 stores the received content and playlist in the storage device 22.

[0105] The control device 10B generates a playback control signal to start playback of the playlist according to the user's operation. The control device 10B also transmits the generated playback control signal to the playback device 20 (control signal generation process, communication process) (S303). The playback control signal includes the identifier of the playlist used for content playback and the playback start position. The playback start position included in the playback control signal in step S304 is the beginning of the playlist.

[0106] The playback device 20 starts playing content according to the first playlist in accordance with the playback control signal received in step S303 (S304). In this specification, playback of content according to the first playlist may also be described as playback of the first playlist. Also in this specification, playback of content according to the second playlist may also be described as playback of the second playlist.

[0107] Subsequently, the control device 10B transmits a stop control signal to the playback device 20 according to the user's operation (control signal generation process, communication process). At this time, the control device 10 also stores the stop position, which indicates the time from the start to the stop of the first playlist, in the storage device 12 (S305).

[0108] The playback device 20 stops playback of the first playlist in accordance with the stop control signal received in step S305 (S306).

[0109] Next, the control device 10B generates a switching control signal to switch playlists according to the user's operation. The control device 10B also transmits the generated switching control signal to the playback device 20 (playlist switching process, control signal generation process, communication process) (S307). The switching control signal includes an identifier for the second playlist.

[0110] Subsequently, the control device 10B generates a playback control signal according to the user's operation. The playback device 20 then starts playback of the second playlist according to the switching control signal (S309). The playback control signal includes information indicating the playback start position of the second playlist. As shown in Figure 10, the playback start position of the second playlist is the point where the time length from the beginning of the second playlist to the playback start point is the same as the time length from the beginning of the first playlist stored in the storage device 12 in step S305 to the playback stop point.

[0111] As described above, when the control device 10B switches from playback of the first playlist to playback of the second playlist, it sets the position on the second playlist corresponding to the stop position of playback of the first playlist as the playback start position. Therefore, the user can easily compare the corresponding frames of the first playlist and the second playlist.

[0112] <Processing in the control device> The processing performed by the control device 10B according to the second embodiment will be explained using the flowcharts shown in Figures 11A and 11B.

[0113] The arithmetic circuit 11 generates a playlist (playlist generation process) (S401) according to the user's operation via the input device 13. The arithmetic circuit 11 generates, for example, two or more playlists containing content with different effects.

[0114] The arithmetic circuit 11 transmits the content and playlist to the playback device 20 (playlist generation process) (S402).

[0115] The arithmetic circuit 11 sets (initializes) the playback start position to the beginning of the playlist (playback start position storage processing) (S403).

[0116] The arithmetic circuit 11 accepts a playlist selection according to the user's operation input via the input device 13. The arithmetic circuit 11 also transmits the identifier of the selected playlist to the playback device 20 (playlist selection process, communication process) (S404). Here, the arithmetic circuit 11 can accept the selection of two playlists: a first playlist and a second playlist. The first playlist is the playlist to be played before switching. The second playlist is the playlist to be played after switching.

[0117] When the arithmetic circuit 11 receives a playback operation in accordance with the user's input via the input device 13 (YES in step S405), it generates a playback control signal (control signal generation process) (S406). The playback control signal includes the playback start position of the first playlist to be played back by the playback device 20.

[0118] The arithmetic circuit 11 transmits the playback control signal generated in step S406 to the playback device 20 (communication processing) (S407). As a result, the playback device 20 starts playback of the content from the playback start position.

[0119] When the arithmetic circuit 11 receives a playback stop operation in accordance with the user's operation input via the input device 13 (YES in step S408), it generates a stop control signal (control signal generation process) (S409).

[0120] Furthermore, the arithmetic circuit 11 updates the playback start position stored in the storage device 12, using the position where playback stops in the content as the new playback start position (playback start position storage processing) (S410).

[0121] The arithmetic circuit 11 transmits the stop control signal generated in step S409 to the regeneration device 20. (Communication processing) (S411).

[0122] When the user inputs an operation to terminate the series of processes via the input device 13 (YES in S412), the arithmetic circuit 11 terminates the process.

[0123] If no operation to terminate the series of processes is entered (NO in S412), and an operation to change the playlist is entered (YES in S413), the arithmetic circuit 11 specifies the playback start position in the first playlist (playback start position management process) (S414).

[0124] Furthermore, the arithmetic circuit 11 stores the specified playback start position in the memory device 12 (playback start position management process) (S415).

[0125] Subsequently, the playback start position specified in step S416 is designated as the playback start position of the second playlist (playback start position management process), and the process returns to step S404 (S416).

[0126] On the other hand, if no operation to change the playlist is input (NO in S413), the arithmetic circuit 11 returns to the process in S404.

[0127] The order of the steps described above is not limited; the order of processing can be changed as long as it allows for playlist switching in the playback device 20. Furthermore, some processes may be executed in parallel.

[0128] In this way, the control device 10B can play the second playlist from a position corresponding to the stop position of the first playlist. Therefore, with the control device 10B, when comparing multiple playlists, corresponding frames can be easily compared.

[0129] <Processing in the Playback Device> The processing performed in the playback device 20 according to the second embodiment will be explained using the flowchart shown in Figure 12.

[0130] The arithmetic circuit 21 receives the content and playlist transmitted from the control device 10B (S501). The arithmetic circuit 21 stores the received content as content data 221 in the storage device 22. The arithmetic circuit 21 also stores the received playlist as playlist data 222 in the storage device 22.

[0131] When the arithmetic circuit 21 receives a playback control signal transmitted from the control device 10B (YES in S502), it starts playing the playlist (S503).

[0132] When the control unit 10B sends a stop control signal (YES in S504), the calculation circuit 21 stops playback of the playlist (S505).

[0133] Subsequently, the arithmetic circuit 21 returns to the processing in step S502 and plays the content until it receives a signal from the control device 10B to terminate the series of operations (S506).

[0134] Thus, when the playback device 20 switches from playing the first playlist to playing the second playlist, it can start playing the second playlist from a position corresponding to the stop position of the first playlist. This allows the playback device 20 to easily compare corresponding frames when comparing multiple playlists.

[0135] [Switching Example] Figure 13A shows an example of a screen 500 including a display unit 501 that displays the first playlist. The screen 500 includes a scale 502 in the lower part of the display unit 501 that indicates the current position in the entire playlist. In Figure 13A, it shows the position at 00:15:01 from the start of the first playlist. Figure 13B shows an example of the screen when the user switches from the state in Figure 13A to the second playlist. As shown in Figure 13B, even after switching, the second playlist starts playing from the point at 00:15:01 when the playback of the first playlist ended. Therefore, the user can easily compare the playlists by referring to the corresponding frames.

[0136] In the second embodiment of the playback system 1B, the display of the playlist is not limited to a display using the display device 30 of the playback device 20. For example, during playlist generation, a screen 500 may be displayed on the monitor 14 of the control device 10B for comparison.

[0137] [Variations of Switching] In the above description, for example, as shown in the sequence diagram of Figure 9, the control device 10B transmits the stop control signal (S305), the switching control signal (S307), and the play control signal (S308) individually. In contrast, as shown in Figure 14, playback stop, playlist switching, and playback start may be controlled by transmitting only the switching control signal (S310). In the example shown in Figure 14, the switching control signal transmitted in step S310 may be a combination of the stop control signal, the switching control signal, and the play control signal of the sequence in Figure 9.

[0138] 《Outline of Embodiments》 (1) The control method of the present disclosure is a control method for controlling the playback of content by first and second playback devices using a control device, wherein the first playback device is equipped with a first internal clock for timing time, the second playback device is equipped with a second internal clock for timing time, the control device is equipped with an arithmetic circuit and a third internal clock for timing time, the control device is equipped with an arithmetic circuit and a third internal clock for timing time, the control device is equipped with an arithmetic circuit that transmits a request to each of the first and second playback devices to transmit the timing being measured, the control device is equipped with an arithmetic circuit that transmits a request to each of the first and second playback devices to transmit the timing of the timing being measured, the control device is equipped with an arithmetic circuit that transmits a request to each of the first and second playback devices to transmit the timing of the first internal clock, and the control device is equipped with a first internal clock for timing time a first internal clock for timing time, The following are performed: transmit a first control signal to the first playback device to play the first content at a first playback start time, wherein the first playback start time is determined using the first difference with respect to the playback start time; and transmit a second control signal to the second playback device to play the second content at a second playback start time, wherein the second playback start time is determined using the second difference with respect to the playback start time.

[0139] This allows for the correction of time differences between different devices, enabling synchronized playback of multiple content items.

[0140] (2) In the control method of (1), the control device may be instructed to perform the following actions: determine the first playback start time by adding a predetermined time required by the first playback device from the reception of the first control signal to the playback of the first content; and determine the second playback start time by adding a predetermined time required by the second playback device from the reception of the second control signal to the playback of the second content.

[0141] This allows for playback that takes into account the discrepancies that occur when each device starts up.

[0142] (3) In the control method of (1) or (2), the calculation circuit is connected to a monitor, and the calculation circuit may be instructed to display a preview screen on the monitor, which includes content to be displayed on the first playback device by a first control signal and content to be displayed on the second playback device by a second control signal, with a predetermined time delay from the acceptance of the playback operation.

[0143] This allows for a clearer understanding of the content playback status.

[0144] (4) In any of the control methods of (1) to (3), the control device further includes causing the arithmetic circuit of the control device to perform the following: determine a first time interval from the time the request is sent to the first playback device until the time of the first internal clock is received; and determine a second time interval from the time the request is sent to the second playback device until the time of the second internal clock is received, wherein the first difference is determined using the first time interval, and the second difference is determined using the second time interval.

[0145] This allows for a more accurate determination of delays in content playback.

[0146] (5) In the control methods of (1) to (4), the content may include at least one of video or audio.

[0147] This allows for synchronization and correction of timing discrepancies when playing multiple video and / or audio content in sync.

[0148] (6) In any of the control methods described in (1) to (5), the first content and the second content may be the same content or different content that is played in sync.

[0149] This allows for the correction of time differences between different devices, enabling synchronized playback of multiple content items.

[0150] (7) In any of the control methods of (1) to (6), the first content and the second content are a group of content including a plurality of content to be played in a plurality of order, and the arithmetic circuit may generate a playlist indicating the identifier of the plurality of content, the playback order of each content, the time required to play each content, and the start time of playback of each content out of the total time when playing according to the playback order, and transmit it to the playback device.

[0151] This allows for synchronization and correction of timing discrepancies when playing pre-generated content playlists.

[0152] (8) A playback method performed on a playback device connected to a control device that performs any of the control methods of (1) to (7), wherein the first content and the second content are a group of content including a plurality of content to be played in a plurality of order, and the calculation circuit generates a playlist indicating the identifier of the plurality of content, the playback order of each content, the time required to play each content, and the start time of playback of each content out of the total time when playing according to the playback order, and transmits it to the playback device.

[0153] This allows for the correction of time differences between different devices, enabling synchronized playback of multiple content items.

[0154] (9) Another control method of the present disclosure is a control method for controlling the playback of first and second content by a playback device using a control device, wherein the control device comprises an arithmetic circuit accessible to a monitor, and the arithmetic circuit of the control device is caused to: transmit the first and second content to the playback device; display on the monitor any point on the time axis in which the first content is played back; when the display receives the arbitrary point, determine the elapsed time from the start of the first content to the arbitrary point; stop the playback of the first content at the arbitrary point; and transmit a control signal to the playback device to start the second content from the point in time after the elapsed time has elapsed from the start.

[0155] This makes it easier to compare and play multiple pieces of content.

[0156] The control method in (10)(9) may involve causing the arithmetic circuit of the control device to, when any point in time on the time axis is selected during playback of the first content, to transmit a control signal to the playback device to stop playback of the first content and to start playback of the second content.

[0157] This makes it easier to understand and compare multiple pieces of content.

[0158] In the control methods of (11), (9), or (10), the content may include at least one of video or audio.

[0159] This makes it easier to compare multiple video and / or audio content.

[0160] In any of the control methods described in (12)(9) to (11), the first and second contents may be related contents with different effects.

[0161] This makes it easier to compare content with different effects.

[0162] (13) In any of the control methods of (9) to (12), the content is video content formed by multiple frames, and the time point on the time axis may be one of the multiple frames.

[0163] This makes it easier to compare content consisting of multiple frames by comparing the corresponding frames.

[0164] (14) A playback method performed on a playback device connected to a control device that performs any of the control methods of (9) to (13), wherein the playback device's arithmetic circuit is instructed to start or stop playback of the content in accordance with a control signal received from the control device.

[0165] This makes it easier to compare and play multiple pieces of content.

[0166] (15) The computer program of this disclosure causes a control device to execute the control method described in any one of (1) to (7) or (9) to (13).

[0167] This allows for the correction of time differences between different devices, enabling synchronized playback of multiple content items.

[0168] (16) Other computer programs of the present disclosure cause a playback device to perform the playback method of (8) or (14).

[0169] This makes it easier to compare and play multiple pieces of content.

[0170] The adjustment methods, adjustment devices, and computer programs described in all claims of this disclosure are implemented by hardware resources, such as a processor, memory, and cooperation with computer programs.

[0171] The control method, playback device, and computer program disclosed herein are useful for adjusting content before playback.

Claims

1. A control method for controlling the playback of content by first and second playback devices using a control device, wherein the first playback device is equipped with a first internal clock for timing time, the second playback device is equipped with a second internal clock for timing time, the control device is equipped with an arithmetic circuit and a third internal clock for timing time, the control device is equipped with an arithmetic circuit and a third internal clock for timing time, the control device is equipped with an arithmetic circuit that transmits a request to each of the first and second playback devices to transmit the timing being measured, the control device is equipped with an arithmetic circuit that transmits a request to each of the first and second playback devices to transmit the timing of the timing being measured, the control device is equipped with an arithmetic circuit that transmits a request to each of the first and second playback devices, the control device is equipped with a first internal clock for timing time second internal clock for timing time, the control device is equipped with an arithmetic circuit and a third internal clock for timing time, the control device is equipped with an arithmetic circuit and a third internal clock for timing time, the control device is equipped with an arithmetic circuit that transmits a request to each of the first and second playback devices to transmit the timing of the timing being measured, the control device is equipped with a first internal clock for timing time, the control device is equipped with a second internal clock for timing time, the control device is equipped with an arithmetic circuit and a third internal clock for timing time, the control device is equipped with an arithmetic circuit and a third internal clock for timing time, the control device is equipped with an A control method that performs the following: transmitting a first control signal to the first playback device to play a first content at a first playback start time, wherein the first playback start time is determined using the first difference with respect to the playback start time; and transmitting a second control signal to the second playback device to play a second content at a second playback start time, wherein the second playback start time is determined using the second difference with respect to the playback start time.

2. The control method according to claim 1, wherein the control device is made to perform the following actions: determine the first playback start time by adding a predetermined time required by the first playback device from the reception of the first control signal to the playback of the first content; and determine the second playback start time by adding a predetermined time required by the second playback device from the reception of the second control signal to the playback of the second content.

3. The control method according to claim 1, wherein the calculation circuit is connected to a monitor, and the calculation circuit is instructed to display a preview screen on the monitor, which includes content to be displayed on the first playback device by a first control signal and content to be displayed on the second playback device by a second control signal, with a predetermined time delay from the acceptance of the playback operation.

4. The control method according to claim 1, further comprising causing the arithmetic circuit of the control device to perform the following: determine a first time interval from the time the request is sent to the first playback device until the time of the first internal clock is received; and determine a second time interval from the time the request is sent to the second playback device until the time of the second internal clock is received, wherein the first difference is determined using the first time interval, and the second difference is determined using the second time interval.

5. The control method according to claim 1, wherein the content includes at least one of video or audio.

6. The control method according to claim 1, wherein the first content and the second content are the same content or different content that are played in sync.

7. The control method according to claim 1, wherein the first content and the second content are a group of content including a plurality of content to be played in a plurality of order, and the arithmetic circuit generates a playlist indicating the identifier of the plurality of content, the playback order of each content, the time required to play each content, and the start time of playback of each content out of the total time when playing according to the playback order, and transmits it to the playback device.

8. A playback method performed on a playback device connected to the control device described in claim 1, wherein the first content and the second content are a group of content including a plurality of content to be played in a plurality of order, and the arithmetic circuit generates a playlist indicating identifiers for the plurality of content, the playback order of each content, the time required to play each content, and the start time of playback for each content out of the total time when playing according to the playback order, and transmits it to the playback device.

9. A control method for controlling the playback of first and second content by a playback device using a control device, wherein the control device comprises an arithmetic circuit accessible to a monitor, and the control device is configured to: transmit the first and second content to the playback device; display on the monitor any point on the time axis in which the first content is played back; when the display receives the arbitrary point, calculate the elapsed time from the start of the first content to the arbitrary point; stop the playback of the first content at the arbitrary point; and transmit a control signal to the playback device to start the second content from the point where the elapsed time has elapsed from the start.

10. The control method according to claim 9, wherein the control device causes the arithmetic circuit to transmit a control signal to the playback device to stop playback of the first content and to start playback of the second content when any point in time on the time axis is selected during playback of the first content.

11. The control method according to claim 9, wherein the content includes at least one of video or audio.

12. The control method according to claim 9, wherein the first and second contents are related contents with different effects.

13. The control method according to claim 9, wherein the content is video content formed by a plurality of frames, and the time point on the time axis is specified as one of the plurality of frames.

14. A playback method performed on a playback device connected to a control device according to claim 9, wherein the playback method causes the arithmetic circuit of the playback device to start or stop playback of the content in accordance with a control signal received from the control device.

15. A computer program that causes the arithmetic circuit of the control device to execute the control method described in any one of claims 1 to 7, 9 to 13.

16. A computer program that causes the calculation circuit of the playback device to execute the playback method described in either claim 8 or 14.

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