Patent Publication Number: US-2017371518-A1

Title: Virtual reality content control

Description:
TECHNOLOGICAL FIELD 
     Embodiments of the present invention relate to controlling advancement of virtual reality content. Such virtual reality content may be viewed, for example, using a head-mounted viewing device. 
     BACKGROUND 
     Virtual reality provides a computer-simulated environment that simulates a viewer&#39;s presence in that environment. A viewer may, for example, experience a virtual reality environment using a head-mounted viewing device that comprises a stereoscopic display. 
     BRIEF SUMMARY 
     According to various, but not necessarily all, embodiments of the invention there is provided a method, comprising: determining at least one region of interest in visual virtual reality content; monitoring whether at least a defined proportion of a viewer&#39;s field of view coincides with the determined at least one region of interest in the visual virtual reality content; and controlling advancement of the visual virtual reality content based on whether the at least a defined proportion of the viewer&#39;s field of view coincides with the determined at least one region of interest in the visual virtual reality content. 
     According to various, but not necessarily all, embodiments of the invention there is provided computer program code that, when performed by at least one processor, causes at least the following to be performed: determining at least one region of interest in visual virtual reality content; monitoring whether at least a defined proportion of a viewer&#39;s field of view coincides with the determined at least one region of interest in the visual virtual reality content; and controlling advancement of the visual virtual reality content based on whether the at least a defined proportion of the viewer&#39;s field of view coincides with the determined at least one region of interest in the visual virtual reality content. 
     The computer program code may be provided by a computer program. The computer program may be stored on a non-transitory computer-readable medium. 
     According to various, but not necessarily all, embodiments of the invention there is provided an apparatus, comprising: means for determining at least one region of interest in visual virtual reality content; means for monitoring whether at least a defined proportion of a viewer&#39;s field of view coincides with the determined at least one region of interest in the visual virtual reality content; and means for controlling advancement of the visual virtual reality content based on whether the at least a defined proportion of the viewer&#39;s field of view coincides with the determined at least one region of interest in the visual virtual reality content. 
     According to various, but not necessarily all, embodiments of the invention there is provided an apparatus, comprising: at least one processor; and at least one memory storing computer program code that is configured, working with the at least one processor, to cause the apparatus at least to perform: determining at least one region of interest in visual virtual reality content; monitoring whether at least a defined proportion of a viewer&#39;s field of view coincides with the determined at least one region of interest in the visual virtual reality content; and controlling advancement of the visual virtual reality content based on whether the at least a defined proportion of the viewer&#39;s field of view coincides with the determined at least one region of interest in the visual virtual reality content. 
     According to various, but not necessarily all, embodiments of the invention there is provided a method, comprising: storing at least one identifier identifying at least one region of interest in visual virtual reality content, wherein the at least one identifier is for controlling advancement of the visual virtual reality content based on whether a defined proportion of a viewer&#39;s field of view coincides with the at least one region of interest identified by the at least one identifier. 
     According to various, but not necessarily all, embodiments of the invention there is provided computer program code that, when performed by at least one processor, causes at least the following to be performed: storing at least one identifier identifying at least one region of interest in visual virtual reality content, wherein the at least one identifier is for controlling advancement of the visual virtual reality content based on whether a defined proportion of a viewer&#39;s field of view coincides with the at least one region of interest identified by the at least one identifier. 
     According to various, but not necessarily all, embodiments of the invention there is provided an apparatus, comprising: means for storing at least one identifier identifying at least one region of interest in visual virtual reality content, wherein the at least one identifier is for controlling advancement of the visual virtual reality content based on whether a defined proportion of a viewer&#39;s field of view coincides with the at least one region of interest identified by the at least one identifier. 
     According to various, but not necessarily all, embodiments of the invention there is provided an apparatus, comprising: at least one processor; and at least one memory storing computer program code that is configured, working with the at least one processor, to cause the apparatus to perform at least: storing at least one identifier identifying at least one region of interest in visual virtual reality content, wherein the at least one identifier is for controlling advancement of visual virtual reality content based on whether a defined proportion of a viewer&#39;s field of view coincides with the at least one region of interest identified by the at least one identifier. 
     According to various, but not necessarily all, embodiments of the invention there is provided examples as claimed in the appended claims. 
    
    
     
       BRIEF DESCRIPTION 
       For a better understanding of various examples described in the detailed description, reference will now be made by way of example only to the accompanying drawings in which: 
         FIG. 1  illustrates a first apparatus in the form of a chip or a chip-set; 
         FIG. 2  illustrates a second apparatus in the form of an electronic device which comprises the first apparatus illustrated in  FIG. 1 ; 
         FIG. 3  illustrates a third apparatus in the form of a chip/chip-set; 
         FIG. 4  illustrates a fourth apparatus in the form of an electronic device that comprises the apparatus illustrated in  FIG. 3 ; 
         FIG. 5  illustrates a flow chart of a first method performed by the first and/or second apparatus; 
         FIG. 6  illustrates a flow chart of a second method performed by the third and/or fourth apparatus; 
         FIGS. 7 and 8  illustrate schematics in which virtual reality content is being created; 
         FIG. 9  illustrates a region of interest at a first time in visual virtual reality content; 
         FIG. 10  illustrates multiple regions of interest at a second time in the visual virtual reality content; 
         FIG. 11  illustrates a region of interest at a third time in the visual virtual reality content; 
         FIGS. 12A and 12B  illustrate two different examples of a defined proportion of a field of view of a viewer; 
         FIG. 13  illustrates a schematic of a viewer viewing the visual virtual reality content at the first time in the visual virtual reality content, as schematically illustrated in  FIG. 9 ; 
         FIG. 14  illustrates a viewer viewing the visual virtual reality content at the third time in the visual virtual reality content, as schematically illustrated in  FIG. 11 ; and 
         FIG. 15  schematically illustrates the viewer viewing the visual virtual reality content at the third time in the visual virtual reality content, as schematically illustrated in  FIG. 11 , where the user has moved his field of view relative to  FIG. 14 . 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the invention relate to controlling advancement of visual virtual reality content based on whether at least a defined proportion of a user&#39;s field of view coincides with at least one pre-defined region of interest in the visual virtual reality content. 
       FIG. 1  illustrates an apparatus  10  that may be a chip or a chip-set. The apparatus  10  may form part of a computing device such as that illustrated in  FIG. 2 . 
     The apparatus  10  comprises at least one processor  12  and at least one memory  14 . A single processor  12  and a single memory  14  are shown in  FIG. 1  and discussed below merely for illustrative purposes. 
     The processor  12  is configured to read from and write to the memory  14 . The processor  12  may comprise an output interface via which data and/or commands are output by the processor  12  and an input interface via which data and/or commands are input to the processor  12 . 
     The memory  14  is illustrated as storing a computer program  17  which comprises computer program instructions/code  18  that control the operation of the apparatus  10  when loaded into the processor  12 . The processor  12 , by reading the memory  14 , is able to load and execute the computer program code  18 . The computer program code  18  provides the logic and routines that enable the apparatus  10  to perform the methods illustrated in  FIG. 5  and described below. In this regard, the processor  12 , the memory  14  and the computer program code  18  provide means for performing the methods illustrated in  FIG. 5  and described below. 
     Although the memory  14  is illustrated as a single component in  FIG. 1 , it may be implemented as one or more separate components, some or all of which may be integrated and/or removable and/or may provide permanent/semi-permanent dynamic/cached storage. 
     The computer program code  18  may arrive at the apparatus  10  by any suitable delivery mechanism  30 . The delivery mechanism  30  may be, for example, a non-transitory computer-readable storage medium such as an optical disc or a memory card. The delivery mechanism  30  may be a signal configured to reliably transfer the computer program code  18 . The apparatus  10  may cause propagation or transmission of the computer program code  18  as a computer data signal. 
       FIG. 2  illustrates a second apparatus  20  in the form of a computing device which comprises the first apparatus  10 . The second apparatus  20  may, for example, be a personal computer. 
     In the example illustrated in  FIG. 2 , the processor  12  and the memory  14  are co-located in a housing/body  27 . The second apparatus  20  may further comprise a display and one or more user input devices (such as a computer mouse), for example. 
     The elements  12  and  14  are operationally coupled and any number or combination of intervening elements can exist between them (including no intervening elements). 
     In  FIG. 2 , the memory  14  is illustrated as storing virtual reality content data  21 . The virtual reality content data  21  may, for example, comprise audiovisual content in the form of a video (such as a movie) or a video game. The virtual reality content data  21  provides virtual reality content that may, for example, be experienced by a viewer using a head-mounted viewing device. The virtual reality content data  21  comprises visual virtual reality content data  22 , a plurality of identifiers  24  and multiple audio tracks  26 . 
     The visual virtual reality content data  22  provides visual virtual reality content. The visual virtual reality content might be stereoscopic content and/or panoramic content which extends beyond a viewer&#39;s field of view when it is viewed. In some examples, the visual virtual reality content is 360° visual virtual reality content in which a viewer can experience a computer-simulated virtual environment in 360°. In some other examples, the visual virtual reality content might cover less than the full 360° around the viewer, such as 270° or some other amount. In some implementations, the visual virtual reality content is viewable using a head-mounted viewing device and a viewer can experience the computer-simulated virtual environment by, for example, moving his head while he is wearing the head-mounted viewing device. In other implementations, the visual virtual reality content is viewable without using a head-mounted viewing device. 
     In some implementations, the visual virtual reality content data  22  might include different parts which form the visual virtual reality content data  22 . Different parts of the data  22  might have been encoded separately and relate to different types of content. The different types of content might be rendered separately. For instance, one or more parts of the data  22  might have been encoded to provide visual background/scenery content, whereas one or more other parts of the data  22  might have been encoded to provide foreground/moving object content. The background/scenery content might be rendered separately from the foreground/moving object content. 
     The identifiers  24  identify pre-defined regions of interest in the visual virtual reality content data. The identifiers  24  are for use in controlling advancement of the visual virtual reality content. This will be described in further detail later. 
     The multiple audio tracks  26  provide audio which accompanies the visual virtual reality content. Different audio tracks may provide the audio for different virtual regions of the (360°) environment simulated in the visual virtual reality content. Additionally, some audio tracks may, for example, provide background/ambient audio whereas other audio tracks may provide foreground audio that might, for example, include dialogue. 
       FIG. 3  illustrates a third apparatus  110  that may be a chip or a chip-set. The third apparatus  110  may form part of a computing device such as that illustrated in  FIG. 4 . 
     The apparatus  110  comprises at least one processor  112  and at least one memory  114 . A single processor  112  and a single memory  114  are shown in  FIG. 3  and discussed below merely for illustrative purposes. 
     The processor  112  is configured to read from and write to the memory  114 . The processor  112  may comprise an output interface via which data and/or commands are output by the processor  112  and an input interface via which data and/or commands are input to the processor  112 . 
     The memory  114  is illustrated as storing a computer program  117  which comprises the computer program instructions/code  118  that control the operation of the apparatus  110  when loaded into the processor  112 . The processor  112 , by reading the memory  114 , is able to load and execute the computer program code  118 . The computer program code  118  provides the logic and routines that enable the apparatus  110  to perform the methods illustrated in  FIG. 6  and described below. In this regard, the processor  112 , the memory  114  and the computer program code  118  provide means for performing the methods illustrated in  FIG. 6  and described below. 
     Although the memory  114  is illustrated as a single component in  FIG. 3 , it may be implemented as one or more separate components, some or all of which may be integrated/removable and/or may provide permanent/semi-permanent dynamic/cached storage. 
     The computer program code  118  may arrive at the apparatus  110  via any suitable delivery mechanism  130 . The delivery mechanism  130  may be, for example, a non-transitory computer-readable storage medium such as an optical disc or a memory card. The delivery mechanism  130  may be a signal configured to reliably transfer the computer program code  118 . The apparatus  110  may cause the propagation or transmission of the computer program code  118  as a computer data signal. 
       FIG. 4  illustrates a fourth apparatus  120  in the form of a computing device which comprises the third apparatus  110 . In some implementations, the apparatus  120  is configured to connect to a head-mounted viewing device. In those implementations, the apparatus  120  may, for example, be a games console or a personal computer. In other implementations, the apparatus  120  may be a head-mounted viewing device or a combination of a games console/personal computer and a head-mounted viewing device. 
     In the example illustrated in  FIG. 4 , the memory  114  is illustrated as storing the virtual reality content data  20  explained above. The processor  112  and the memory  114  are co-located in a housing/body  127 . 
     The elements  12  and  14  are operationally coupled and any number or combination of intervening elements can exist between them (including no intervening elements). 
     A head-mounted viewing device may comprise a stereoscopic display and one or more motion sensors. The stereoscopic display comprises optics and one or more display panels, and is configured to enable a viewer to view the visual virtual reality content stored as the visual virtual reality content data  22 . The one or more motion sensors may be configured to sense the orientation of the head-mounted display device in three dimensions and to sense motion of the head-mounted display device in three dimensions. The one or more motion sensors may, for example, comprise one or more accelerometers, one or more magnetometers and/or one or more gyroscopes. 
     A head-mounted viewing device may also comprise headphones or earphones for conveying the audio in the audio tracks  26  to a user/viewer. Alternatively, the audio in the audio tracks  26  may be conveyed to a user/viewer by separate loudspeakers. 
     A first example of a first method according to embodiments of the invention will now be described in relation to  FIG. 5 . 
     In the first example of the first method, at block  501  in  FIG. 5 , virtual reality content is created and stored as virtual reality content data  21 . The visual aspect is stored as visual virtual reality content data  22  and the audible aspect is stored as multiple audio tracks  26 . 
     At block  502  in  FIG. 5 , a user provides user input at the second apparatus  20  identifying various regions of interest in the visual virtual reality content data  22  in the memory  14  of the second apparatus  20 . The user input causes the processor  12  of the second apparatus  20  to store identifiers  24  in the virtual reality content data  21  which identify those regions of interest in the visual virtual reality content data  22 . 
     The stored identifiers  24  identify different regions of interest in the visual virtual reality content at different times in the visual virtual reality content. The identification of regions of interest in the visual virtual reality content enables advancement of the visual virtual reality content to be controlled when it is consumed. This is described below in relation to  FIG. 6 . 
     A first example of a second method according to embodiments of the invention will now be described in relation to  FIG. 6 . 
     In this first example of the second method, the virtual reality content data  21  stored in the memory  14  of the second apparatus  20  is provided to the fourth apparatus  120  illustrated in  FIG. 4 . In some implementations of the invention, the virtual reality content data  21  may be stored on a server and downloaded or streamed to the fourth apparatus  120 . In other implementations, the virtual reality content data  21  may be provided to the fourth apparatus  120  by an optical disc or a memory card, for example. 
     At block  601  in  FIG. 6 , a viewer is consuming the virtual reality content provided by the virtual reality content data  21 . For instance, he may be consuming the virtual reality content via a head-mounted viewing device. The processor  112  of the fourth apparatus  120  causes and enables the viewer to consume the virtual reality content. As explained above, the fourth apparatus  120  may be the head-mounted viewing device or a computing device that is connected to the head-mounted viewing device, such as a games console or a personal computer, or it may be a combination of the two. 
     At block  601  in  FIG. 6 , the processor  112  of the apparatus  120  analyses the visual virtual reality content data  22  and determines that there is at least one region of interest in the visual virtual reality content (provided by the visual virtual reality content data  22 ) that forms part of the virtual reality content being consumed by the user. The at least one region of interest has been pre-defined (in the manner described above in relation to  FIG. 5 ) and is identified by at least one of the identifiers  24  which forms part of the virtual reality content data  21 . 
     At block  602  in  FIG. 6 , the processor  112  of the fourth apparatus  120  monitors whether at least a defined proportion of a viewer&#39;s field of view coincides with the determined at least one region of interest in the visual virtual reality content. In some implementations, the processor  112  begins to monitor the position and orientation of the defined proportion of the viewer&#39;s field of view before a region of interest has been determined. In other implementations, this monitoring only commences after a region of interest has been identified by the processor  112 . 
     The viewer&#39;s total field of view when viewing visual virtual reality content may depend upon the head-mounted viewing device that is being used to view the visual virtual reality content and, in particular, the optics of the visual virtual reality content. 
     In some implementations, the “defined proportion” of the viewer&#39;s field of view may be the viewer&#39;s total field of view when viewing the visual virtual reality content. 
     For instance, if the viewer&#39;s total field of view when viewing the visual virtual reality content is 100° in a transverse plane, then in such implementations the defined proportion of the viewer&#39;s field of view encompasses the whole 100°. 
     In other implementations, the defined proportion of the viewer&#39;s field of view might be less than the viewer&#39;s total field of view when viewing the visual virtual reality content. For example, the defined proportion could be much less than the viewer&#39;s total field of view, such as the central 20° of the viewer&#39;s field of view in a transverse plane, when the viewer&#39;s total field of view is 100° in the transverse plane. Alternatively, the defined proportion could now be a single viewing line within the viewer&#39;s field of view, such as a line situated at the center of the viewer&#39;s field of view. 
     At block  603  in  FIG. 6 , the processor  112  of the fourth apparatus  120  controls advancement of the visual virtual reality content based on whether the at least a defined proportion of the viewer&#39;s field of view coincides with the determined at least one region of interest in the visual virtual reality content. In some implementations, if the processor  112  determines that the defined proportion of the viewer&#39;s field of view coincides with the at least one region of interest in the visual virtual reality content, it enables the advancement of the visual virtual reality content. For instance, if the visual virtual reality content is a video (such as a movie), it enables playback of the video to continue. If the visual virtual reality content is a video game, it enables the video game to advance. 
     Alternatively, if the defined proportion of the viewer&#39;s field of view does not coincide with the determined at least one region of interest in the visual virtual reality content, the processor  112  may cease advancement of at least a portion of the visual virtual reality content. For instance, if the visual virtual reality content is a video (such as a movie), the processor  112  may pause the whole or a region of the visual virtual reality content (such as a region containing the determined at least one region of interest) until the defined proportion of the viewer&#39;s field of view and the determined at least one region of interest begin to coincide. Similarly, if the visual virtual reality content is a video game, the processor  112  may cease advancement of at least a portion of the video game (such as a region containing the determined at least one region of interest) until a defined proportion of the viewer&#39;s field of view begins to coincide with the determined at least one region of interest. 
     In implementations where different parts (such as the foreground/moving objects and the background/scenery) are rendered separately, the portion that is ceased might be the foreground/moving objects and the background/scenery might continue to move/be animated. For instance, leaves might move and water might ripple. The movement/animation might be looped. 
     In addition to the above, the processor  112  may control advancement of audio based upon whether the defined proportion of the viewer&#39;s field of view coincides with at least one determined region of interest. For instance, it may pause one or more audio tracks if the defined proportion of the viewer&#39;s field of view does not coincide with the determined at least one region of interest. It may recommence playback of that/those audio track(s) if and when the defined proportion of the viewer&#39;s field of view begins to coincide with the determined at least one region of interest. The paused/recommended audio track(s) may include audio that is intended to be synchronized with events in a portion of the visual virtual reality content where advancement has been ceased. The paused/recommenced audio track(s) could be directional audio from the determined at least one region of interest. The paused/recommenced audio track(s) could, for example, include dialog from one or more actors in the determined region of interest or music or sound effects. 
     In some implementations, the processor  112  may enable playback of one or more audio tracks to continue or commence while playback of one or more other audio tracks has been paused. The other audio track(s) could include ambient music or sounds of the environment, for example. The other audio track(s) could be looped in some implementations. 
     Controlling advancement of visual virtual reality content based on whether a defined proportion of a viewer&#39;s field of view coincides with one or more predefined regions of interest is advantageous because it provides a mechanism for preventing a viewer from missing important parts of visual virtual reality content. For example, it may prevent a viewer from missing salient plot points in visual virtual reality content by pausing at least part of the visual virtual reality content until the viewer&#39;s field of view is in an appropriate position. The viewer is therefore able to explore a virtual environment fully without concern that he may miss important plot points. 
     A second example of the first method according to embodiments of the invention will now be described in relation to  FIGS. 5, 7 and 8 . 
       FIG. 7  illustrates a schematic in which (visual and audible) virtual reality content is being recorded by one or more virtual reality content recording devices  703 . The virtual reality content may be professionally recorded content, or content recorded by an amateur. The virtual reality content recording device(s)  703  are recording both visual and audible content. In the scene being recorded, a first actor  701  and a second actor  702  are positioned on a beach  704 . The first actor  701  throws a ball  705  to the second actor  702 . 
       FIG. 7  illustrates the scene at a first time where the first actor  701  has not yet thrown the ball  705  to the second actor  702 .  FIG. 8  illustrates the scene at a point in time where the ball  705  has been caught by the second actor  702 . The dotted line designated by the reference numeral  706  represents the motion of the ball  705 . 
       FIG. 9  illustrates the visual virtual reality content provided by visual virtual reality content data  22  which is created by the virtual reality content creation device(s)  703  when the scene is captured in  FIGS. 7 and 8 . A director of the movie chooses to identify the first actor  701  and the ball  705  as a region of interest  901 . He provides appropriate user input to the second apparatus  120  and, in response, the processor  12  of the second apparatus  20  creates and stores an identifier which identifies the region of interest  901  in the virtual reality content data  21 , at the first time in the playback of the visual virtual reality content which is depicted in  FIG. 9 . 
       FIG. 10  illustrates a second time in the visual virtual reality content, which is subsequent to the first time. At the second time, the first actor  701  has thrown the ball  705  to the second actor  702 , but the ball  705  has not yet reached the second actor  702 . The director of the movie decides to identify the first actor  701  as a first region of interest  1001 , the ball  705  as a second region of interest  1002  and the second actor  702  as a third region of interest  1003  for the second time in the visual virtual reality content. The director provides appropriate user input to the second apparatus  120  and, in response, the processor  112  creates and stores identifiers  24  in the memory  14  which identify the regions of interest  1001 ,  1002  and  1003  in the visual virtual reality content data  22  at the second time in the playback of the visual virtual reality content. 
       FIG. 11  illustrates the visual virtual reality content at a third time, subsequent to the first and second times. At the third time, the second actor  702  has caught the ball  705 . The director of the movie decides that he wishes to identify the second actor  702  and the ball  705  as a region of interest  1101  and provides appropriate user input to the second apparatus  120 . In response, the processor  112  of the second apparatus  120  creates and stores an identifier identifying the region of interest  1101  in the visual virtual reality content at the third time in the playback of the visual virtual reality content. 
     In some implementations, the regions of interest may not be identified by a user manually providing user input. Alternatively, the regions of interest may be identified automatically by image analysis performed by the processor  12 , and the corresponding identifiers may be created and stored automatically too. 
     A second example of the second method according to embodiments of the invention will now be described in relation to  FIGS. 6 and 12A to 15 . 
       FIG. 12A  illustrates a first example of a defined proportion of a field of view of a viewer in a transverse plane. In the example illustrated in  FIG. 12A , the viewing position of the viewer is designated by the point labeled with reference number  1203 . A first dotted line  1201  illustrates a first extremity of a viewer&#39;s field of view in the transverse plane and a second dotted line  1202  designates a second extremity of a viewer&#39;s field of view in the transverse plane. The curved arrow labeled with the reference number  1204  designates a third extremity of the viewer&#39;s field of view in the transverse plane. The area bound by the lines  1201 ,  1302  and  1204  represents the area that is viewable by the viewer in the transverse plane, when viewing visual virtual reality content (for instance, via a head-mounted viewing device). 
     In the first example, the cross-hatching in  FIG. 12A  indicates that the whole of the viewer&#39;s field of view, when viewing the visual virtual reality content (for instance, via a head-mounted viewing device), is considered to be the “defined proportion” of that field of view. 
     A human&#39;s real-life field of view may be almost 180° in a transverse plane. The total field of view of a viewer while viewing the visual virtual reality content may be the same or less than a human&#39;s real-life field of view. 
       FIG. 12B  illustrates a second example of a defined proportion of a field of view of a viewer. In this example, the area between the first dotted line labeled with reference number  1201 , the dotted lined labeled with the reference number  1202  and the curved arrow labeled with the reference numeral  1204  represents the area that is viewable by a viewer in a transverse plane, when viewing visual virtual reality content, as described above. However, the example illustrated in  FIG. 12B  differs from the example illustrated in  FIG. 12A  in that the “defined proportion” of the field of view of the viewer is less than the total field of view of the viewer when viewing visual virtual reality content. In this example, the defined proportion of the field of view of the viewer is the angular region between the third and fourth dotted lines labeled with the reference numerals  1205  and  1206  and is indicated by cross-hatching. It encompasses a central portion of the field of view of the viewer. In this example, the defined proportion of the field of view could be any amount which is less than the total field of view of the viewer when viewing visual virtual reality content. 
     It will be appreciated that  FIGS. 12A and 12B  provide examples of a defined proportion of a field of view of a viewer in a transverse plane for illustrative purposes. In practice, the processor  112  may also monitor whether a defined proportion of the viewer&#39;s field of view in a vertical plane coincides with a region of interest. The processor  112  may, for example, determine a solid angle in order to determine whether a defined proportion of a viewer&#39;s field of view coincides with a region of interest in visual virtual reality content. 
     In monitoring whether a defined proportion of a viewer&#39;s field of view coincides with a region of interest in visual virtual reality content, the processor  112  might be configured to determine a viewer&#39;s viewpoint (for instance, by tracking a viewer&#39;s head) and configured to determine whether a (theoretical) line, area or volume emanating from the viewer&#39;s viewpoint intersects the region of interest. 
     In some implementations, the processor  112  may be configured to monitor whether a defined proportion of a viewer&#39;s field of view coincides with a region of interest in visual virtual reality content by using one or more cameras to track a viewer&#39;s gaze. This might be the case in implementations in which the virtual reality content is viewed using a head-mounted viewing device and in implementations where it is not. If a head-mounted viewing device is not used, the visual virtual reality content could, for instance, be displayed on one or more displays surrounding the viewer. 
     In implementations where a viewer&#39;s gaze is tracked, if the visual virtual reality content is stereoscopic, the processor  112  may be configured to determine the depth of the region(s) of interest and determine the depth of a viewer&#39;s gaze. The processor  112  may be further configured to monitor whether at least a defined proportion of a viewer&#39;s field of view coincides with the determined region(s) of interest by comparing the depth of the viewer&#39;s gaze with the depth of the region(s) of interest. 
       FIGS. 13 to 15  illustrate a schematic of a viewer viewing the visual virtual reality content that was shown being recorded in  FIGS. 7 and 8  and which includes the identifiers which were created and stored as described above and illustrated in  FIGS. 9 to 11 . 
     In this second example of the second method, the processor  112  may be continuously cycling through the method illustrated in  FIG. 6 . This is described in detail below. 
     Playback of the visual virtual reality content commences and reaches the first time in the playback of the visual virtual reality content, as illustrated in  FIG. 9 .  FIG. 13  schematically illustrates a viewer  1301  viewing the visual virtual reality content at the first time in the playback of the visual virtual reality content. When the viewer reaches the first time in the playback of the visual virtual reality content, the processor  112 , which is continuously cycling through the method illustrated in  FIG. 6 , determines that there is an identifier stored in the virtual reality content data  21  which identifies a region of interest  901  at the first time in the playback of the visual virtual reality content (as shown in  FIG. 9 ). At block  602  in  FIG. 6 , the processor  112  determines that the defined proportion of the viewer&#39;s field of view coincides with the region of interest  901  at the first time in the playback of the visual virtual reality content. Consequently, at block  603  in  FIG. 6 , the processor  112  controls advancement of the visual virtual reality content by enabling playback of the visual virtual reality content and any audio synchronized with events in the region of interest  901  to continue. 
     Advancement/playback of the visual virtual reality content continues and, in this example, the viewer&#39;s field of view remains directed towards the first actor  701 .  FIG. 14  illustrates a viewer viewing the visual virtual reality content at the third time in the playback of the visual virtual reality content (as shown in  FIG. 11 ) where the ball  705  has been thrown from the first actor  701  to the second actor  702 . 
     While the ball  705  was in midair, the first actor  701  was indicated to be a region of interest, as depicted by the dotted box  1001  in  FIG. 10 . Thus, the processor  112  of the fourth apparatus  120  continued to allow the visual virtual reality content to advance while it was cycling through the method of  FIG. 6 . However, at the third time (as illustrated in  FIG. 11 ), the first actor  701  is no longer a region of interest, and the only region of interest in the visual virtual reality content is the second actor  702  holding the ball  705  as indicated by the dotted box  1101  in  FIG. 11 . The processor  112  determines that the (new) region of interest  1101  is the only region of interest at the third time in the playback of the visual virtual reality content, and monitors whether at least a defined proportion of the viewer&#39;s field of view coincides with the determined (new) region of interest  1101 . However, initially, as depicted in  FIG. 14 , the defined proportion of the viewer&#39;s field of view no longer coincides with any regions of interest at the third time in the playback of the visual virtual reality content. Consequently, in this example, at block  603  in  FIG. 6 , the processor  112  controls advancement of the visual virtual reality content by causing advancement/playback of at least a portion of the visual virtual reality content to cease. For example, the whole of the visual virtual reality content may be paused, or merely a portion which comprises the at least one region of interest. 
     In some implementations, the processor  112  might not cease advancement of the visual virtual reality content instantaneously when it determines that the defined proportion of the viewer&#39;s field of view does not coincide with a region of interest. There may, for example, be a short delay before it does so and, if the defined proportion of the viewer&#39;s field of view begins to coincide with a region of interest during the delay period, advancement of visual virtual reality content is not ceased. This may help to prevent frequent pausing and recommencement of content. 
     The processor  112  might not cease advancement/playback of the visual virtual reality content in some implementations. Instead, it might slow down advancement/playback of the whole of the visual virtual reality content or a portion of it (such as a portion which comprises the at least one region of interest). 
     The viewer then moves his field of view such that the defined proportion of his field of view coincides with the region of interest  1101  at the third time in the playback of the visual virtual reality content, as depicted in  FIG. 15 . The processor  112  determines that the defined proportion of the viewer&#39;s field of view now coincides with the region of interest  1101  at the third time in the playback of the visual virtual reality content and controls advancement of the visual virtual reality content by re-enabling advancement/playback of the visual virtual reality content. 
     In some implementations, it may not be necessary for the defined proportion of the viewer&#39;s field of view to coincide with a determined region of interest in order for the processor  112  to re-enable advancement of the visual virtual reality content. For instance, the processor  112  might be configured to monitor a trajectory of movement of the defined proportion of the viewer&#39;s field of view and to control advancement of the visual virtual reality content based on whether the defined proportion of the viewer&#39;s field of view is expected to coincide with a determined region of interest. This may be done, for instance, by interpolating the movement trajectory of the defined proportion of the viewer&#39;s field of view and determining whether the interpolated trajectory coincides with the determined region of interest. 
     References to ‘computer-readable storage medium’, ‘computer’, ‘processor’ etc. should be understood to encompass not only computers having different architectures such as single/multi-processor architectures and sequential (Von Neumann)/parallel architectures but also specialized circuits such as field-programmable gate arrays (FPGA), application specific circuits (ASIC), signal processing devices and other processing circuitry. References to computer program, instructions, code etc. should be understood to encompass software for a programmable processor or firmware such as, for example, the programmable content of a hardware device whether instructions for a processor, or configuration settings for a fixed-function device, gate array or programmable logic device etc. 
     As used in this application, the term ‘circuitry’ refers to all of the following: 
     (a) hardware-only circuit implementations (such as implementations in only analog and/or digital circuitry) and
 
(b) to combinations of circuits and software (and/or firmware), such as (as applicable): (i) to a combination of processor(s) or (ii) to portions of processor(s)/software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and
 
(c) to circuits, such as a microprocessor(s) or a portion of a microprocessor(s), that require software or firmware for operation, even if the software or firmware is not physically present.
 
     This definition of ‘circuitry’ applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term “circuitry” would also cover an implementation of merely a processor (or multiple processors) or portion of a processor and its (or their) accompanying software and/or firmware. The term “circuitry” would also cover, for example and if applicable to the particular claim element, a baseband integrated circuit or applications processor integrated circuit for a mobile phone or a similar integrated circuit in a server, a cellular network device, or other network device. 
     The blocks illustrated in  FIGS. 5 and 6  may represent steps in a method and/or sections of code in the computer programs  17  and  18 . The illustration of a particular order to the blocks does not necessarily imply that there is a required or preferred order for the blocks and the order and arrangement of the block may be varied. Furthermore, it may be possible for some blocks to be omitted. 
     Although embodiments of the present invention have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the invention as claimed. For example, in some implementations, the processor  112  may be configured to cause display of one or more indicators (such as one or more arrows) which indicate to a viewer where the region(s) of interest is/are at a particular time in visual virtual reality content. The processor  112  may cause the indicator(s) to appear, for instance, if advancement of the visual virtual reality content has been ceased/paused, or if it has been ceased/paused for more than a threshold period of time. 
     The form of the visual virtual reality content might be different from that described above. For instance, it may comprise dynamically updating information content such as one or more dynamically updating web page feeds. 
     Features described in the preceding description may be used in combinations other than the combinations explicitly described. 
     Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not. 
     Although features have been described with reference to certain embodiments, those features may also be present in other embodiments whether described or not. 
     Whilst endeavoring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon. 
     I/we claim: