Patent Publication Number: US-2011074820-A1

Title: Information displaying device and information displaying method

Description:
TECHNICAL FIELD 
     The present invention relates to an information display apparatus and information display method that display various kinds of information, such as a message, gadget, or the like, superimposed on content. 
     BACKGROUND ART 
     In recent years, systems that distribute content comprising digital copyrighted works such as music, images, games and the like by digital broadcasting, the Internet, and so forth, have been developed, and are reaching the stage of commercialization. At the same time, methods have been studied for displaying various kinds of information, including mail, memos, or suchlike messages, or gadgets displaying weather information, news, and the like, superimposed on such distributed content while that content is being viewed. 
     With conventional technology, while content is being viewed, various kinds of information, such as messages or gadgets, are displayed so as not to interfere with viewing within a range in which content can be viewed. For example, Patent Literature 1 discloses an information display apparatus that, on receiving an instant message displayed superimposed on content, displays the received instant message in an area away from the center of the main screen. 
     Citation List 
     Patent Literature 
     [PTL 1] 
     Japanese Translation of a PCT Application Laid-Open No. 2008-510222 
     SUMMARY OF INVENTION 
     Technical Problem 
     However, a problem with a conventional information display apparatus is as follows. Namely, with conventional technology, when an information display apparatus performs information display when information arrives or based on a user operation, superimposition information is displayed in a fixed manner in an area away from the center of the main screen irrespective of the detail of content displayed in the main screen (hereinafter referred to as “main screen content”) or the detail of information displayed superimposed on main screen content (hereinafter referred to as “superimposition information”). 
     Therefore, in a case such as when text information is displayed in other than the center of the screen, as in a news program, there is a problem of superimposition information interfering with content viewing. A further problem is that, when superimposition information is a message announcing an emergency situation, the message is displayed in an area that does not catch the eye. 
     It is an object of the present invention to provide an information display apparatus and information display method that enable superimposition information to be displayed in such a way that the superimposition information does not interfere with viewing of main screen content. 
     Solution to Problem 
     An information display apparatus of the present invention is an information display apparatus that displays content and superimposition information superimposed on the content in a main screen of a display section, and employs a configuration having: a decision section that decides a first display method of the superimposition information based on a main screen classification of main screen content displayed in the main screen, a characteristic of the superimposition information, and an information amount of the superimposition information; and a control section that displays the superimposition information in a display area corresponding to the main screen classification using the first display method. 
     An information display method of the present invention is an information display method of an information display apparatus that displays content and superimposition information superimposed on the content in a main screen of a display section, and includes: a decision step of deciding a first display method of the superimposition information based on a main screen classification of main screen content displayed in the main screen, a characteristic of the superimposition information, and an information amount of the superimposition information; and a control step of displaying the superimposition information in a display area corresponding to the main screen classification using the first display method. 
     ADVANTAGEOUS EFFECTS OF INVENTION 
     The present invention enables superimposition information to be displayed in such a way that the superimposition information does not interfere with viewing of main screen content. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a drawing showing the overall schematic configuration of an information display system according to an embodiment of the present invention; 
         FIG. 2  is a block diagram showing the configuration of a content distribution server according to the above embodiment; 
         FIG. 3  is a block diagram showing the configuration of a terminal apparatus according to the above embodiment; 
         FIG. 4  is a block diagram showing the configuration of a display information control section according to the above embodiment; 
         FIG. 5  is a drawing showing the table configuration of a content storage section according to the above embodiment; 
         FIG. 6  is a drawing showing the table configuration of a content information storage section according to the above embodiment; 
         FIG. 7  is a drawing showing the table configuration of a superimposition information storage section according to the above embodiment; 
         FIG. 8  is a drawing showing the table configuration of a display control rule storage section according to the above embodiment; 
         FIG. 9  is a drawing showing the table configuration of a main screen switching-time display control rule storage section according to the above embodiment; 
         FIG. 10  is a flowchart showing processing that displays superimposition information; 
         FIG. 11  is a flowchart showing a superimposition information display format decision process; 
         FIG. 12  is a drawing showing a main screen at the time of superimposition information display; 
         FIG. 13  is a flowchart showing a superimposition information update process; 
         FIG. 14  is a flowchart showing processing that performs a display change at the time of main screen switching; and 
         FIG. 15  is a drawing showing a main screen after main screen switching. 
     
    
    
     DESCRIPTION OF EMBODIMENT 
     Now, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. 
     Embodiment 
       FIG. 1  is a drawing showing the overall schematic configuration of an information display system according to an embodiment of the present invention. 
     The information display system in  FIG. 1  is a system in which content is played back and various kinds of information are displayed by terminal apparatus  200 , and includes content distribution server  100  that performs holding and distribution of content, terminal apparatus  200  that acquires and plays back content and displays various kinds of information superimposed on that content, and communication path  300  mutually connecting content distribution server  100  and terminal apparatus  200 . 
     Content distribution server  100  is a server apparatus or broadcasting station facility that has a function for connecting to communication path  300 , holds content and content information, and transmits content and content information to terminal apparatus  200 . Content distribution server  100  is implemented by a workstation or the like. 
     Terminal apparatus  200  is an apparatus that has a function for connecting to communication path  300 , acquires and holds various kinds of information, such as messages or gadgets, outputs content and various kinds of information to a display or suchlike display section (screen), and performs content playback and information display. 
     Specifically, terminal apparatus  200  is a data playback apparatus, data recording apparatus, or a device combining these, such as an STB (Set Top Box), digital TV (television), DVD (Digital Versatile Disc) recorder, HDD (Hard Disk Drive) recorder, PC (Personal Computer), PDA (Personal Digital Assistant), mobile phone, or the like, for receiving digital broadcasting. 
     Communication path  300  is a network that connects content distribution server  100  and terminal apparatus  200  unidirectionally or bidirectionally. Specifically, communication path  300  comprises a broadcast signal from a broadcasting station, a wired network such as Ethernet (registered trademark), a radio network such as a radio LAN (Local Area Network), or a network combining these. 
     Using  FIG. 2  through  FIG. 15 , this embodiment will specifically describe processing whereby terminal apparatus  200  displays various kinds of information superimposed on main screen content during content display and changes the display method for various kinds of information when main screen content is switched in this kind of information display system. 
     Definitions of identifiers in this embodiment will now be given. 
     A content identifier is information for uniquely identifying content in the information display system. 
     A superimposition information identifier is information for uniquely identifying superimposition information displayed on a display section (screen) of terminal apparatus  200 . 
     A provider identifier is information for uniquely identifying a provider that provides content in the information display system. 
     Next, the configurations of content distribution server  100  and terminal apparatus  200  will be described in detail. 
     First, the configuration of content distribution server  100  will be described in detail.  FIG. 2  is a block diagram showing the detailed configuration of content distribution server  100 . 
     Content storage section  111  stores content. 
     Content information storage section  112  stores content information that is information relating to content. 
     Communication section  101  connects to communication path  300 , and performs communication with terminal apparatus  200 . 
     Content acquisition and transmission section  102  acquires content from content storage section  111 , acquires content information from content information storage section  112 , and transmits the acquired content and content information to terminal apparatus  200 . 
     Next, the configuration of terminal apparatus  200  will be described in detail.  FIG. 3  is a block diagram showing the detailed configuration of terminal apparatus  200 . 
     Superimposition information storage section  211  stores superimposition information that is displayed superimposed on the main screen of display section  205 . Superimposition information is a message, memo, gadget, mail, or the like. 
     Display control rule storage section  212  stores superimposition information display control rules. 
     Main screen switching-time display control rule storage section  213  stores superimposition information display control rules in the event of main screen content switching transition of display section  205 . 
     Communication section  201  connects to communication path  300 , and performs communication with content distribution server  100  and other terminal apparatuses. 
     Content reception and playback section  202  receives or acquires and plays back content transmitted from content distribution server  100 . 
     Display information receiving section  203  stores a message input to terminal apparatus  200  via user command receiving section  206 , in superimposition information storage section  211 . Also, display information receiving section  203  acquires a message sent from an external terminal apparatus via communication section  201 , or receives weather or suchlike information. Display information receiving section  203  stores an acquired message or received weather or suchlike information in superimposition information storage section  211 . 
     Display information control section  204  controls the display position and display format of superimposition information, and displays superimposition information superimposed on main screen content.  FIG. 4  is a block diagram showing the internal configuration of display information control section  204 . 
     Superimposition information acquisition section  2041  acquires superimposition information from superimposition information storage section  211 . 
     Display object determination section  2042  determines the presence or absence of superimposition information to be displayed superimposed on main screen content, based on a superimposition information display condition. In other words, display object determination section  2042  determines superimposition information that is a display object. The determination method used by display object determination section  2042  will be described later herein. 
     Decision section  2043  acquires a display control rule from display control rule storage section  212  or main screen switching-time display control rule storage section  213 , and decides the superimposition information display position and display format based on the acquired display control rule. A method of deciding the display method (display position and display format) in decision section  2043  will be described later herein. 
     Display control section  2044  displays superimposition information on display section  205  in accordance with the decided display method. 
     Update determination section  2045  determines whether or not the superimposition information display method is to be updated based on the display condition of the superimposition information determined as the display object. The determination method used by update determination section  2045  will be described later herein. 
     Returning to  FIG. 3  again, display section  205  is a display device such as a plasma display panel or LCD panel (not shown), and displays content and superimposition information. 
     User command receiving section  206  receives input from a user by a remote controller, direct operation of terminal apparatus  200 , or the like. For example, user command receiving section  206  receives input such as a content identifier identifying content, a content acquisition command, superimposition information, a superimposition information display command, and so forth. 
     This concludes a detailed description of the configurations of content distribution server  100  and terminal apparatus  200 . 
     Of the storage sections and processing sections composing content distribution server  100  and terminal apparatus  200 , the storage sections are implemented by storage media such as an HDD or RAM (Random Access Memory), and the processing sections are implemented by programs or the like executed using LSI (Large Scale Integration) or suchlike hardware or a CPU (Central Processing Unit), RAM, ROM (Read Only Memory), or the like. It is desirable for the storage sections and processing sections in terminal apparatus  200  to be made tamper-resistant by hardware or software. 
     Next, data and data structures handled in this embodiment will be described. 
     First, details of the storage sections of content distribution server  100 , and data held by these storage sections, will be described with reference to the accompanying drawings. 
     Content storage section  111  is a database that manages content, and is used to acquire content corresponding to a content identifier included in a content distribution schedule or a content acquisition request from terminal apparatus  200 . Specifically, as shown in  FIG. 5 , content storage section  111  has content management table D 400  comprising content identifier D 401  and content D 402  corresponding to content identifier D 401 . 
     For example,  FIG. 5  shows that content D 402  corresponding to “CONTENT-ID-0001” of content identifier D 401  is “CONTENT-DATA-0001”. Registration of content and content identifiers in content storage section  111  is performed by a content provider or the like. 
     Content information storage section  112  is a database that manages content information that is information relating to content, and is used to acquire content corresponding to a content identifier included in a content distribution schedule or a content acquisition request from terminal apparatus  200 . 
     Specifically, as shown in  FIG. 6 , content information storage section  112  has content information management table D 500  in which content identifier D 501  and content genre D 502  are mutually associated. For example,  FIG. 6  shows that when content identifier D 501  is “CONTENT-ID-0001”, content genre D 502  is “News”. Registration of content information in content information storage section  112  is performed by a content provider or the like. 
     Content and content information acquired from content storage section  111  and content information storage section  112  are transmitted to terminal apparatus  200 . 
     Next, data held by the storage sections of terminal apparatus  200  will be described with reference to the accompanying drawings. 
     Superimposition information storage section  211  is a database that manages superimposition information, and is used to acquire superimposition information that is displayed superimposed on main screen content displayed on display section  205  of terminal apparatus  200 . 
     Specifically, as shown in  FIG. 7 , superimposition information storage section  211  has superimposition information management table D 600  in which superimposition information identifier D 601 , information classification D 602  indicating the classification of superimposition information, information detail D 603  indicating the detail of superimposition information, basic information amount D 604  indicating the initial value of the size of an area in which superimposition information is displayed on the screen, importance D 605  indicating the importance of superimposition information, and display condition D 606  indicating a superimposition information display condition, are mutually associated. 
     For example,  FIG. 7  shows that when superimposition information identifier D 601  is “INFO-ID-0001”, information classification D 602  of the superimposition information is “Memo”, information detail D 603  are “Heat up curry in fridge”, basic information amount D 604  is “5 points”, importance D 605  is “High”, and display condition D 606  is “Until 12:00 January 5”. 
     Of the data included in superimposition information management table D 600 , information classification D 602  indicating the classification of superimposition information and importance D 605  indicating the importance of superimposition information indicate characteristics of superimposition information. Also, basic information amount D 604  indicating the initial value of the size of an area in which superimposition information is displayed indicates the information amount of superimposition information. 
     A point used as a unit of basic information amount in superimposition information management table D 600  indicates an area for which the superimposition information display area size is 1 when the entire screen area of display section  205  is taken to be 100. Therefore, the basic information amount indicates an area occupied by the display of superimposition information. The basic information amount unit is not limited to a point, and any unit may be used as long as it is uniquely decided upon in the information display system. 
     Data registration in superimposition information storage section  211  is performed by display information receiving section  203  (1) when a message is input to terminal apparatus  200  via user command receiving section  206 , (2) when a message, or weather or suchlike information, reported from another terminal via communication section  201  is acquired or received, or (3) when data, or a gadget or suchlike information, acquired from the Internet via a browser or the like is acquired. 
     Display control rule storage section  212  is a database that manages display control rules, and is used to acquire display control rules that control the display of superimposition information. 
     Specifically, as shown in  FIG. 8 , display control rule storage section  212  has display control rule management table D 700  in which provider identifier D 701  indicating a provider, main screen genre D 702  indicating the genre of main screen content, displayable area D 703  indicating an area in which superimposition information can be displayed, and display control condition D 704  indicating a display control condition for superimposition information corresponding to main screen genre D 702 , are mutually associated. 
     For example,  FIG. 8  shows that when provider identifier D 701  is “CP-ID-0001” and main screen genre D 702  is “News”, displayable area D 703  is “Right upper-half”, and display control condition D 704  is “News information display NG”. 
       FIG. 8  also shows that even if main screen genre D 702  is “News”, when provider identifier D 701  is “CP-ID-0004”, unlike the case in which provider identifier D 701  is “CP-ID-0001”, displayable area D 703  is “Upper-half”, and display control condition D 704  is “Display up to 15 points”. Thus, a displayable area or display control condition for displaying superimposition information is decided by a provider identifier or main screen genre. That is to say, a provider identifier or main screen genre can be said to indicate the classification of content displayed in the main screen. 
     Thus, display control rule storage section  212  manages display control rules according to a main screen content classification. Data registration or updating in display control rule storage section  212  is performed by pre-registration upon shipping terminal apparatus  200 , or reception via communication section  201  from a provider device, another terminal, or the like. Since display control rule registration or updating can be performed via communication section  201 , flexible display control by a provider, terminal manufacturer, or the like, is possible. 
     In this embodiment, display control rules have been described as being set by a provider for each content genre, but display control rules common to all providers may also be set, or display control rules may be set for each classification other than content genre, for instance. 
     In the above description, display control rules have been described as being set from a provider&#39;s viewpoint, but provision may also be made for settings to be made from a user&#39;s viewpoint so as to provide good visibility for the user himself. In this case, a provider may provide a user with items for which setting is permitted and items for which setting is not permitted. For example, a displayable area may be designated as a user-settable item, while a display control condition is designated as a non-user-settable item. 
     Main screen switching-time display control rule storage section  213  is a database that manages display control rules in the event of main screen switching, and is used to acquire display control rules that control a superimposition information display method when main screen content is switched at the time of superimposition information display. 
     Specifically, as shown in  FIG. 9 , main screen switching-time display control rule storage section  213  has main screen switching-time display control rule management table D 800  comprising provider identifier D 801  indicating a provider that provides main screen content, display change timing D 802  indicating a predetermined time until which a superimposition information display method is to be changed after a transition of main screen content to switched-to content, and main screen switching-time condition D 803  indicating a control condition when a superimposition information display method is changed. 
     For example,  FIG. 9  shows that when provider identifier D 801  is “CP-ID-0001”, display change timing D 802  is “5 seconds”, and main screen switching-time condition D 803  is “Slow shift”. 
     Registration or updating of display control rules in main screen switching-time display control rule storage section  213  is performed by pre-registration upon shipping terminal apparatus  200 , or reception via communication section  201  from a provider device, another terminal, or the like. Display control rule registration and updating via communication section  201  makes flexible display control possible by a provider, terminal manufacturer, or the like. 
     In this embodiment, a case has been described by way of example in which display control rules are set on a provider-by-provider basis, but display control rules common to all providers may also be set, or display control rules may be set on a classification-by-classification basis, such as for each content genre. Also, in the above description, a case has been described in which display control rules have been described as being set from a provider&#39;s viewpoint, but provision may also be made for display control rules to be set from a user&#39;s viewpoint so as to provide good visibility for the user himself. 
     This concludes a description of data and data structures handled in this embodiment. 
     Next, processing will be described that is necessary for terminal apparatus  200 , on receiving content in the information display system, to [1] play back content in the main screen while displaying superimposition information superimposed on the main screen content, and [2] change a superimposition information display method when main screen content switching is performed at the time of superimposition information display. 
     In order to implement processing [1] and [2] above, terminal apparatus  200  requires (1) superimposition information acquisition and storage processing, (2) content reception and display processing, (3) superimposition information display processing, and (4) superimposition information display change processing at the time of main screen content switching. Processing (1) through (4) above will now be described with reference to  FIG. 10  through  FIG. 15 . 
     (1) Superimposition Information Acquisition and Storage Processing 
     First, a description will be given of processing by various sections when display information receiving section  203  of terminal apparatus  200  acquires superimposition information, and stores this information in superimposition information storage section  211 . 
     In response to input of a message or suchlike information and a data acquisition command from a user, display information receiving section  203  starts superimposition information acquisition and storage processing. The user inputs information specifying a message to be displayed superimposed on main screen content as superimposition information, or data to be acquired, to a terminal apparatus  200  application via user command receiving section  206 . 
     User command receiving section  206  receives input from the user, and display information receiving section  203  acquires an input message or suchlike information as superimposition information. Alternatively, display information receiving section  203  acquires superimposition information based on information specifying input data. Display information receiving section  203  assigns a superimposition information identifier to the acquired superimposition information, and stores this information in superimposition information storage section  211  together with a corresponding information classification, importance, display condition, and so forth. 
     For example, if a mother leaving the house on the morning of a holiday leaves the memo “Heat up curry in fridge” for her child who is still sleeping, user command receiving section  206  inputs “Memo” as the information classification, “High” as importance, “Display until 12:00 January 5” as a display condition, and so forth. Also, display information receiving section  203  automatically calculates the basic information amount of these items of superimposition information. 
     In this way, display information receiving section  203  of terminal apparatus  200  stores superimposition information, superimposition information characteristics such as information classification and importance, a basic information amount, and a display condition in superimposition information storage section  211  in a mutually associated form. 
     Provision may also be made for user command receiving section  206  to simplify information input by a template or multiple-choice format, or to present a superimposition information display image to the user, and for the user to be able to change the information amount, display condition, or the like of superimposition information. 
     Also, when the user specifies a gadget to be acquired as superimposition information by user command receiving section  206 , as in the case of a weather gadget, provision may be made for display information receiving section  203  to acquire a weather gadget and store it in superimposition information storage section  211  automatically. When display information receiving section  203  acquires gadget information, it does not acquire a gadget itself, but data automatically acquired by the gadget, and stores this in superimposition information storage section  211 . 
     In the above description, a case has been described in which a user directly inputs a message or information specifying data to user command receiving section  206 , but display information receiving section  203  can also store superimposition information in superimposition information storage section  211  using the same kind of method when receiving mail or suchlike superimposition information sent from another terminal. 
     In this case, display information receiving section  203  sets superimposition information characteristics such as information classification and importance by estimating them from the detail of mail as well as through specification by the sender of the mail, or by assigning them automatically based on existing information such as sender information, for instance. There are various conceivable superimposition information acquisition and superimposition information characteristic setting methods, but these are not essential to the present invention, and therefore a detailed description of other methods is omitted here. 
     In the above-described way, display information receiving section  203  acquires superimposition information, and stores it in superimposition information storage section  211  associated with characteristics and a display condition for that superimposition information. 
     (2) Content Reception and Display Processing 
     Next, a description will be given of processing by various sections when content reception and playback section  202  of terminal apparatus  200  receives content from content distribution server  100  and displays this information on display section  205 . 
     In response to information input and a content acquisition command from a user, content reception and playback section  202  starts content acquisition processing. The user inputs a content identifier or information based on a content identifier to an application of terminal apparatus  200  via user command receiving section  206 . A case is described below by way of example in which the user inputs content identifier “CONTENT-ID-0001”, and content reception and playback section  202  starts content acquisition processing. 
     When user command receiving section  206  receives input from the user, content reception and playback section  202  generates a content acquisition request message that includes a content identifier, and transmits the generated content acquisition request message to content distribution server  100  via communication section  201 . 
     Content distribution server  100  receives the content acquisition request message via communication section  101 . Next, content acquisition and transmission section  102  extracts content identifier “CONTENT-ID-0001” from the content acquisition request message, and acquires corresponding content “CONTENT-DATA-0001” and content genre “News” from content storage section  111  and content information storage section  112 . 
     Then content acquisition and transmission section  102  generates a content transmission message that includes the acquired content, content genre, and provider identifier “CP-ID-0001”, and transmits the generated content transmission message to terminal apparatus  200  via communication section  101 . 
     On receiving the content transmission message via communication section  201 , content reception and playback section  202  of terminal apparatus  200  displays the received content in the main screen of display section  205 . Also, content reception and playback section  202  stores the content genre and provider identifier as information relating to the content being displayed. 
     As an example of content acquisition and playback, a case has here been described in which content distribution server  100  performs on-demand distribution via the Internet, but if content distribution server  100  is a broadcasting station, content distribution server  100  may extract a content identifier from a distribution schedule or the like, multiplex the corresponding content, content genre, and provider identifier, and distribute these as a broadcast wave. There are various conceivable content, content genre, and provider identifier distribution methods and operations, but these are not essential to the present invention, and therefore a detailed description thereof is omitted here. 
     When a user switches viewed content, the above processing is performed for each content after switching. 
     In the above-described way, content reception and playback section  202  acquires content from content distribution server  100  in response to a content acquisition request from a user, and displays the acquired content in the main screen of display section  205 . 
     (3) Superimposition Information Display Processing 
     Next, a description will be given, with reference to  FIG. 10 , of processing by various sections until display information control section  204  of terminal apparatus  200  displays superimposition information stored in superimposition information storage section  211  superimposed on main screen content. 
     Display information control section  204  starts superimposition information display processing in response to a superimposition information display command from a user (step S 901 ). The user inputs a superimposition information display command via user command receiving section  206  by a user remote operation or the like. 
     First, display object determination section  2042  of display information control section  204  confirms the presence or absence of superimposition information that is a display object from superimposition information storage section  211 , and determines whether or not display processing is necessary (step S 902 ). As shown in  FIG. 7 , display conditions such as a period indicating superimposition information are included in superimposition information management table D 600  stored in superimposition information storage section  211 . 
     For example, when superimposition information identifier D 601  is “INFO-ID-0001”, display condition D 606  is “Until 12:00 January 5”. In this case, display object determination section  2042  acquires the current time, and determines that there is superimposition information that is a display object if the current time is included in the display condition period, or determines that there is no superimposition information that is a display object if the current time is not included in the display condition period. 
     Display object determination section  2042  performs the above determination for all superimposition information stored in superimposition information management table D 600  of superimposition information storage section  211 . Next, if there is even one item complying with the display condition, display object determination section  2042  determines that there is superimposition information that is a display object, and that display processing is necessary (step S 902 : YES). On the other hand, if there is no item complying with the display condition, display object determination section  2042  determines that there is no superimposition information that is a display object, and that display processing is unnecessary (step S 902 : NO). 
     There are assumed to be various other display conditions, such as “Until message detail can be confirmed”, “If it is raining”, “If user who gave display command is father”, “Information for daughter”, and so forth. Display object determination section  2042  acquires information required for determining respective display conditions from inside and outside the terminal apparatus, and determines the presence or absence of superimposition information that is a display object. Display condition items are not limited to these. 
     In the event of determining that display processing is unnecessary (step S 902 : NO), display object determination section  2042  notifies the user that there is no superimposition information that is a display object, and terminates the processing (step S 911 ). Provision may also be made for display object determination section  2042  to include a reason for the absence of superimposition information that is a display object in the notification—for example, information such as “There are no messages for father”, or “There is no information for display today”. 
     If display object determination section  2042  determines that display processing is necessary (step S 902 : YES), decision section  2043  acquires content information corresponding to main screen content from content reception and playback section  202  (step S 903 ). Specifically, if content having content identifier “CONTENT-ID-0002” is being viewed, decision section  2043  acquires provider identifier “CP-ID-0002” and content genre “Baseball” corresponding to content identifier “CONTENT-ID-0002”. Below, a case is described by way of example in which display information control section  204  receives a superimposition information display command while the user is viewing content having content identifier “CONTENT-ID-0002”. 
     Decision section  2043  identifies and acquires a display control rule corresponding to main screen content from display control rule storage section  212  using a provider identifier and content genre acquired from content reception and playback section  202  as keys (step S 904 ). Specifically, decision section  2043  identifies a display control rule using provider identifier “CP-ID-0002” and content genre “Baseball” corresponding to main screen content (content identifier “CONTENT-ID-0002”) as keys, and acquires displayable area “Lower ¾” and display control condition “Display information amount up to 10 points”. 
     Superimposition information acquisition section  2041  acquires superimposition information for which display processing was determined to be necessary in step S 902  from superimposition information storage section  211  (step S 905 ). 
     Decision section  2043  executes a superimposition information display format decision process (step S 906 ). The superimposition information display format decision process will be described later herein. 
     Display control section  2044  executes a superimposition information update process (step S 907 ) and terminates superimposition information display processing. The superimposition information update process will be described later herein. 
     The superimposition information display format decision process in step S 906  in  FIG. 10  will now be described with reference to the flowchart in  FIG. 11 . 
     Decision section  2043  extracts a display control condition corresponding to the main screen classification from the display control rule acquired in step S 904  (step S 1001 ), and acquires a parameter relating to the extracted display control condition or related information (step S 1002 ). 
     Specifically, decision section  2043  acquires the information “Display information amount up to 10 points” that is a display control condition corresponding to provider identifier “CP-ID-0002” and content genre “Baseball”. Next, decision section  2043  acquires a display information amount of each item of superimposition information necessary for confirmation of satisfaction of the display control condition. For example, if it was determined by display object determination section  2042  in step S 902  that 3 lines of superimposition information from the top of  FIG. 7  need to be display objects, decision section  2043  acquires “5 points”, “10 points”, and “2 points”. 
     Then, based on a parameter or related information acquired in step S 1002 , decision section  2043  determines whether or not the information detail and basic information amount of superimposition information satisfy the display control condition (step S 1003 ). 
     If the information detail and basic information amount of superimposition information satisfy the display control condition (step S 1003 : YES), decision section  2043  does not perform step S 1004 , but proceeds to the processing in step S 1005  described later herein. 
     On the other hand, if the information detail and basic information amount of superimposition information do not satisfy the display control condition (step S 1003 : NO), decision section  2043  changes the basic information amount of superimposition information that does not satisfy the display control condition, or excludes superimposition information that does not satisfy the display control condition from display objects, and deletes it from the display layout (step S 1004 ). 
     Specifically, when the display control condition is “Display information amount up to 10 points”, and the total of basic information amounts “5 points”, “10 points”, and “2 points” of superimposition information determined to be display objects is 17 points, the display control condition is not satisfied. In this case, based on the importance of each item of superimposition information, decision section  2043  performs display format modification or processing for exclusion from the display objects, starting from superimposition information of low importance (step S 1004 ). 
     When laying out 3 lines of superimposition information from the top of  FIG. 7 , decision section  2043  decides, for example, that low-importance superimposition information having superimposition information identifier “INFO-ID-0002” is to be displayed as an icon. Making superimposition information having superimposition information identifier “INFO-ID-0002” an icon enables the basic information amount to be changed from “10 points” to “3 points”, as a result of which the total of the three basic information amounts becomes 10 points, and the display control condition can be satisfied. 
     Thus, decision section  2043  changes the superimposition information display format, or selects superimposition information to be excluded from the display objects and decides the display format of the selected superimposition information to be “non-display”, based on superimposition information characteristics and basic information amounts, so as to satisfy a display control condition corresponding to a main screen classification. 
     Provision may also be made for decision section  2043  to include a display information amount reduction method such as “Iconize information detail of low importance” or “Delete information detail of low importance” in display control conditions beforehand. Also, if there is a plurality of mail from the same sender in the case of the display control condition “Do not display information duplicating other information, or information for which there is an update”, provision may be made for decision section  2043  to decide to exclude mail other than the latest mail from display objects, and to display only the latest mail. Furthermore, in the case of the display control condition “News information display NG”, provision may be made for display object determination section  2042  to determine whether or not superimposition information is to be made a display object in step S 902  based on the information classification and information detail of superimposition information. 
     Display control section  2044  creates and displays a superimposition information layout for which the display format and display objects have been changed as necessary by decision section  2043  in a displayable area in accordance with a main screen content provider identifier and main screen genre—that is, main screen classification (step S 1005 ). 
       FIG. 12  is a drawing showing a sample layout of 3 lines of superimposition information from the top of  FIG. 7 .  FIG. 12  shows an example of a case in which the main screen content provider identifier is “CP-ID-0002”, and the main screen genre is “Baseball”. In order for baseball score G 101  to be constantly displayed during viewing of this main screen content, the displayable area for superimposition information has been set as “Lower ¾” as a display control condition (see  FIG. 8 ). In the example shown in  FIG. 12 , information detail having superimposition information identifiers “INFO-ID-0001” and “INFO-ID-0003” are displayed as memo display G 111  and gadget display G 113  with the basic information amount unchanged, superimposition information identifier “INFO-ID-0002” has been iconized, and is displayed as icon G 112  with the basic information amount changed. 
     Provision may also be made for the layout, including superimposition information display position, color depth, coloration, and so forth, to be user-settable. 
     Display control section  2044  displays superimposition information using a layout in accordance with a displayable area and information amount (step S 1006 ). 
     In the above-described way, decision section  2043  executes a superimposition information display format decision process. 
     In the above description, a case has been described by way of example in which decision section  2043  applies restrictions to a superimposition information display format based on a display control condition corresponding to a main screen classification. Here, if superimposition information requires urgency, provision may be made for a display control condition to be ignored, and for display control section  2044  to display superimposition information in a suitable format. For example, display control section  2044  may exceptionally display the message “Grandfather urgently hospitalized” requiring urgency in large format in the center of the screen, ignoring the display control condition. 
     The superimposition information update process in step S 907  in  FIG. 10  will now be described with reference to the flowchart in  FIG. 13 . 
     Update determination section  2045  extracts a display condition of each item of superimposition information determined to be a display object in step S 906  (step S 1101 ), and determines whether or not the superimposition information display method is to be updated based on changing circumstances (step S 1102 ). Specifically, when “Smaller until 22:00 January 5” or “Always display” is extracted, update determination section  2045  determines that display updating/deletion is necessary in the former case because it is necessary to perform a smaller display with time, but determines that display updating/deletion is unnecessary in the latter case. 
     In the event of determining that superimposition information display updating is unnecessary (step S 1102 : NO), update determination section  2045  terminates the superimposition information update process (step S 907 ). 
     On the other hand, in the event of determining that superimposition information display updating is necessary (step S 1102 : YES), update determination section  2045  acquires a parameter relating to a display condition or related information (step S 1103 ). An actual example of related parameter or related information acquisition is omitted here since the process is similar to that in step S 1102 . 
     Based on a parameter or related information acquired in step S 1103  and a display condition, update determination section  2045  determines whether or not processing for superimposition information display updating or deletion is necessary under the present circumstances (step S 1104 ). If update/deletion processing is necessary, update determination section  2045  performs superimposition information display update/deletion processing (step S 1105 ). 
     Specifically, when the display condition is “Until 12:00 January 5”, if the current time is 11:00, update determination section  2045  determines that update/deletion processing is unnecessary, and display control section  2044  does not perform update/deletion processing. On the other hand, if the current time is 12:00, update determination section  2045  determines that update/deletion processing is necessary, and display control section  2044  performs update/deletion processing. 
     Thus, when detection of a predetermined time or update trigger “until user confirmation” is necessary, a predetermined time or user operation is set as a detection condition in an update trigger detection section (not shown), and corresponding display updating is performed at the time of trigger detection. 
     Also, when it is necessary to change the display continually with the passage of time, as in the case of the display condition “Smaller until 22:00 January 5”, display control section  2044  can implement this by performing predetermined display update processing at intervals of several tens of seconds, or by performing polling to confirm processing detail. When the superimposition information display size is reduced or increased according to time or according to a user operation or the like, in order to reduce shifting of the user&#39;s viewpoint, display control section  2044  may perform enlargement or reduction with a fixed superimposition information center point, center line, and frame edge, for instance. 
     Updating of displayed superimposition information such as described above is particularly effective for displaying information whose importance decreases with the passage of time, or displaying information whose importance increases with the passage of time. For example, message mail such as “Will be home at 22:00” becomes of less importance as the time for returning home, 22:00, approaches, and can therefore be displayed in a smaller size as 22:00 approaches. Conversely, a weather gadget such as “Today&#39;s forecast: Rain” increases in importance as a departure time approaches, and can therefore be displayed in a larger size as the departure time approaches. 
     In the above-described way, update determination section  2045  and display control section  2044  execute a superimposition information update process. 
     In the above-described way, after receiving a superimposition information display command, display information control section  204  displays superimposition information stored in superimposition information storage section  211  superimposed on main screen content. 
     (4) Superimposition Information Display Change Processing at the Time of Main Screen Content Switching 
     Lastly, a description will be given, with reference to  FIG. 14 , of processing by various sections from reception by display information control section  204  of terminal apparatus  200  of a main screen switching command at the time of superimposition information display, until display information control section  204  changes the superimposition information display position and display format to a display method suitable for main screen content that is switched to. 
     Display information control section  204  starts superimposition information display change processing at the time of main screen content switching in response to a main screen switching command from a user at the time of superimposition information display (step S 1201 ). The user inputs a main screen switching command via user command receiving section  206  by a user remote operation or the like. 
     Decision section  2043  acquires a provider identifier corresponding to switched-to content from content reception and playback section  202 , and identifies and acquires display change timing and a main screen display switching condition from main screen switching-time display control rule storage section  213  using the provider identifier as a key (step S 1202 ). 
     Decision section  2043  counts the time from transition of the main screen content to the switched-to content by a timer, and when the count value reaches the display change timing, performs the following display change processing (step S 1203 ). For example, if the display change timing is “5 seconds”, the superimposition information display method is not changed until superimposition information has been displayed for 5 seconds using the same display method as before the switch. 
     By this means, even if the user is performing zapping viewing, the superimposition information display method does not change with dizzying rapidity, but is switched after the user has reached a state in which he is viewing the main screen content placidly. 
     Display object determination section  2042  and decision section  2043  apply the previously described superimposition information display format decision process to main screen content for which the display change timing has been reached, determine a display object, and decide a display format (step S 1204 ). 
     Display control section  2044  displays superimposition information in a display area corresponding to the classification of the switched-to content based on a main screen switching-time condition (step S 1205 ). 
     Specifically, when the main screen switching-time condition is “Slow shift”, during zapping, display control section  2044  continues to display superimposition information using the same display method as before zapping. Then, when zapping ends and a predetermined time indicated by the display change timing has elapsed, display control section  2044  slowly slides the superimposition information from the pre-zapping display method to a new display method suitable for the switched-to main screen content. 
     Provision may also be made for display control section  2044  not to display superimposition information during zapping, but to display superimposition information using a new method suitable for the switched-to main screen content after a predetermined time has elapsed. Provision may also be made for display control section  2044  to make the color of superimposition information lighter, or make the display size smaller, during zapping. 
     As an example, a description will be given of updating of displayed superimposition information when main screen content is switched from a state in which the superimposition information shown in  FIG. 12  is being displayed to provider identifier “CP-ID-0002” content genre “News”. 
     As shown in  FIG. 7 , the basic information amounts of superimposition information being displayed superimposed on main screen content in  FIG. 12  are “5 points”, “10 points”, and “2 points”, and the total basic information amount is “17 points”. Here, a display control condition corresponding to provider identifier “CP-ID-0002” and main screen genre “News” of switched-to content is “17 points”. 
     Therefore, the total basic information amount of superimposition information satisfies the display control condition. That is to say, the display control condition is satisfied in confirmation of display control condition satisfaction (step S 1003 ) in the superimposition information display format decision process (step S 1204 ) of the flow of superimposition information display change processing at the time of main screen content switching. 
     Consequently, after main screen content switching, display of the basic information amount of superimposition information is possible without change.  FIG. 15  is a drawing showing an example of a superimposition information layout after main screen content switching. As shown in  FIG. 15 , message mail “Will be home around 22:00” being displayed by icon G 112  before the switch, has been changed to message display G 212 . 
     Also, since the displayable area for main screen content after switching is “Upper half”, information detail “Heat up curry in fridge” have their display position changed from memo display G 111  to memo display G 211 , and information detail “Weather gadget” have their display position changed from gadget display G 113  to gadget display G 213 . 
     By such display position changes, display control section  2044  can perform display in such a way that superimposition information is not superimposed on news program telop G 201 , enabling superimposition information to be displayed without interfering with the viewing of main screen content. 
     When changing the display size of superimposition information, display control section  2044  may perform enlargement with a fixed superimposition information center point, center line, and frame edge, as explained in the previously described superimposition information update process. Also, for a similar reason, when changing the display position of superimposition information, display control section  2044  may move the display position with a fixed superimposition information center point, center line, and frame edge. 
     In the above-described way, in the event of receiving a main screen switching command at the time of superimposition information display, display information control section  204  displays superimposition information after changing to a display method suitable for switched-to main screen content. 
     As described above, by performing (1) superimposition information acquisition and storage processing, (2) content reception and display processing, and (3) superimposition information display processing, terminal apparatus  200  can better avoid interference with main screen content viewing while displaying superimposition information using a suitable information amount, display position, and display format according to a main screen classification, superimposition information characteristics, and basic information amount of superimposition information, without the need for a user operation each time main screen content switching is performed. 
     Also, by performing (4) superimposition information display change processing as described above at the time of main screen switching, terminal apparatus  200  can perform a suitable display change without a dizzyingly rapid change of superimposition information display, even when a user is performing channel zapping or the like. 
     In the above description, a case has been described in which some kind of content is being played back in the main screen, but the present invention can also be applied when content is not being played back in the main screen, or when something other than content is being played back in the main screen, such as when browsing by a Web browser in a digital TV is being displayed in the main screen. 
     For example, when nothing is being played back in the main screen, display information control section  204  can display superimposition information arbitrarily in the main screen area without restrictions, with the displayable area as “Entire area”, and a display control condition as “Nothing in particular”. 
     The disclosure of Japanese Patent Application No. 2009-080098, filed on Mar. 27, 2009, including the specification, drawings and abstract, is incorporated herein by reference in its entirety. 
     INDUSTRIAL APPLICABILITY 
     The present invention is suitable for use as a content distribution service receiving terminal using package media such as DVDs, a content display terminal using digital broadcasting, CATV, the Internet, or the like, and so forth. 
     REFERENCE SIGNS LIST 
       100  Content distribution server 
       101 ,  201  Communication section 
       102  Content acquisition and transmission section 
       111  Content storage section 
       112  Content information storage section 
       200  Terminal apparatus 
       202  Content reception and playback section 
       203  Display information receiving section 
       204  Display information control section 
       2041  Superimposition information acquisition section 
       2042  Display object determination section 
       2043  Decision section 
       2044  Display control section 
       2045  Update determination section 
       205  Display section 
       206  User command receiving section 
       211  Superimposition information storage section 
       212  Display control rule storage section 
       213  Main screen switching-time display control rule storage section 
       300  Communication path