Patent Publication Number: US-2019200088-A1

Title: Systems and methods for presenting content

Description:
FIELD OF THE INVENTION 
     The present technology relates to the field of content provision. More particularly, the present technology relates to techniques for presenting content through computing devices. 
     BACKGROUND 
     Today, people often utilize computing devices (or systems) for a wide variety of purposes. Users can operate their computing devices to, for example, interact with one another, create content, share content, and access information. Under conventional approaches, content items (e.g., images, videos, audio files, etc.) can be made available through a content sharing platform. Users can operate their computing devices to access the content items through the platform. Typically, the content items can be provided, or uploaded, by various entities including, for example, content publishers and also users of the content sharing platform. In some instances, the content items can be categorized and/or curated. 
     SUMMARY 
     Various embodiments of the present disclosure can include systems, methods, and non-transitory computer readable media configured to determine a request for a content item, wherein the content item is to be presented through a display screen of a computing device. A view direction of a user operating the computing device is determined. One or more frames of the content item are quantized based at least in part on the view direction. 
     In some embodiments, the quantization is performed so that a region corresponding to the view direction is presented at a higher video quality than regions outside of the view direction. 
     In some embodiments, the quantization is performed in real-time as the frames are being streamed to the computing device. 
     In some embodiments, changes to the view direction are determined at periodic time intervals during playback of the content item, and wherein subsequent frames of the content item are quantized based on the changes to the view direction. 
     In some embodiments, the quantized frames of the content item are cached and served in response to subsequent requests for the content item. 
     In some embodiments, the systems, methods, and non-transitory computer readable media are configured to obtain quantized residual data by decompressing the content item and re-quantize the quantized residual data based on the view direction. 
     In some embodiments, the re-quantizing comprises assigning specified parameter values to frame blocks corresponding to regions of frames that are outside of the view direction, the specified parameter values being higher than parameter values assigned to a region corresponding to the view direction. 
     In some embodiments, the content item is a virtual reality content item created using a single stream that captures a given scene, wherein frames corresponding to all directions from which the scene was captured are encoded at a specified quality level. 
     In some embodiments, the systems, methods, and non-transitory computer readable media are configured to receive a set of coordinates that describe the view direction from the computing device. 
     In some embodiments, the systems, methods, and non-transitory computer readable media are configured to provide the quantized frames of the content item to the computing device for presentation. 
     Various embodiments of the present disclosure can include systems, methods, and non-transitory computer readable media configured to determine a request for a content item from a computing device. One or more view directions of a user operating the computing device can be predicted during playback of the content item. One or more frames of the content item are quantized based at least in part on the predicted view directions. 
     In some embodiments, the view directions are predicted from heat map data corresponding to the content item, the heat map data describing historical view patterns of users that previously accessed the content item. 
     In some embodiments, the historical view patterns identify one or more regions in the frames that received a threshold amount of view activity. 
     In some embodiments, the view directions are determined based at least in part on saliency information corresponding to the content item, the saliency information identifying one or more salient points of interest that appear in frames of the content item. 
     In some embodiments, the frames are quantized so that regions in the frames that correspond to the salient points of interest appear at a higher video quality than the remaining regions of the frames. 
     In some embodiments, frame blocks corresponding to the predicted view directions are quantized so that content represented by the frame blocks appears at a higher video quality than content outside of the predicted view directions. 
     In some embodiments, frame blocks outside of the predicted view directions are quantized so that content represented by the frame blocks appears at a lower video quality than content corresponding to the predicted view directions. 
     In some embodiments, the content item is one of a two-dimensional content item, a content item composed using a single stream, or a content item composed using multiple streams. 
     In some embodiments, the systems, methods, and non-transitory computer readable media are configured to provide the quantized frames of the content item to the computing device for presentation. 
     In some embodiments, the quantized frames of the content item are cached and served in response to subsequent requests for the content item. 
     It should be appreciated that many other features, applications, embodiments, and/or variations of the disclosed technology will be apparent from the accompanying drawings and from the following detailed description. Additional and/or alternative implementations of the structures, systems, non-transitory computer readable media, and methods described herein can be employed without departing from the principles of the disclosed technology. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates an example system including an example content provider module, according to an embodiment of the present disclosure. 
         FIG. 2  illustrates an example of a content features module, according to an embodiment of the present disclosure. 
         FIGS. 3A-C  illustrate examples of streaming a virtual reality content item, according to an embodiment of the present disclosure. 
         FIGS. 4A-B  illustrate examples of enhancing a virtual reality content item, according to an embodiment of the present disclosure. 
         FIG. 5  illustrates an example method, according to an embodiment of the present disclosure. 
         FIG. 6  illustrates another example method, according to an embodiment of the present disclosure. 
         FIG. 7  illustrates a network diagram of an example system including an example social networking system that can be utilized in various scenarios, according to an embodiment of the present disclosure. 
         FIG. 8  illustrates an example of a computer system or computing device that can be utilized in various scenarios, according to an embodiment of the present disclosure. 
     
    
    
     The figures depict various embodiments of the disclosed technology for purposes of illustration only, wherein the figures use like reference numerals to identify like elements. One skilled in the art will readily recognize from the following discussion that alternative embodiments of the structures and methods illustrated in the figures can be employed without departing from the principles of the disclosed technology described herein. 
     DETAILED DESCRIPTION 
     Approaches for Presenting Content 
     People use computing devices (or systems) for a wide variety of purposes. As mentioned, under conventional approaches, a user can utilize a computing device to share content items (e.g., documents, images, videos, audio, etc.) with other users. Such content items can be made available through a content sharing platform. Users can operate their computing devices to access the content items through the platform. Typically, the content items can be provided, or uploaded, by various entities including, for example, content publishers and also users of the content sharing platform. 
     In some instances, a user can access virtual reality content through a content provider. Such virtual reality content can be presented, for example, in a viewport that is accessible through a computing device (e.g., a virtual reality device, headset, or any computing device capable of presenting virtual reality content). In general, a virtual reality content item (or immersive video) corresponds to any virtual reality media that encompasses (or surrounds) a viewer (or user). Some examples of virtual reality content items include spherical videos, half sphere videos (e.g., 180 degree videos), arbitrary partial spheres, 225 degree videos, and 3D 360 videos. Such virtual reality content items need not be limited to videos that are formatted using a spherical shape but may also be applied to immersive videos formatted using other shapes including, for example, cubes, pyramids, and other shape representations of a video recorded three-dimensional world. 
     In some embodiments, a virtual reality content item can be created by stitching together various video streams (or feeds) that were captured by cameras that are placed at particular locations and/or positions to capture a view of the scene (e.g., 180 degree view, 225 degree view, 360 degree view, etc.). Once stitched together, a user can access, or present (e.g., playback), the virtual reality content item. Generally, while accessing the virtual reality content item, the user can zoom and change the direction (e.g., pitch, yaw, roll) of the viewport to access different portions of the scene in the virtual reality content item. The direction of the viewport can be used to determine which stream of the virtual reality content item is presented. 
     In some instances, a virtual reality content item may be composed of a single video stream that captures a complete view of a scene (e.g., 180 degree view, 225 degree view, 360 degree view) in which all directions are encoded at the same quality level (e.g., high quality). Since all directions of the virtual reality content item are encoded at the same quality level, a computing device accessing the virtual reality content item may require additional resources (e.g., network bandwidth) to adequately present the virtual reality content item. In such instances, the overall user experience can be degraded when these additional resources are not available. Accordingly, such conventional approaches may not be effective in addressing these and other problems arising in computer technology. 
     An improved approach overcomes the foregoing and other disadvantages associated with conventional approaches. In some embodiments, a request for a content item can be determined. The content item can be presented through a display screen of a computing device. A view direction of a user operating the computing device is determined. One or more frames of the content item are quantized based at least in part on the view direction. In some embodiments, a request for a content item can be received from a computing device. One or more view directions of a user operating the computing device can be predicted during playback of the content item. One or more frames of the content item are quantized based at least in part on the predicted view directions. Many variations are possible. 
       FIG. 1  illustrates an example system  100  including an example content provider module  102 , according to an embodiment of the present disclosure. As shown in the example of  FIG. 1 , the content provider module  102  can include a content module  104 , a streaming module  106 , and a content features module  108 . In some instances, the example system  100  can include at least one data store  112 . A client module  114  can interact with the content provider module  102  over one or more networks  150  (e.g., the Internet, a local area network, etc.). The client module  114  can be implemented in a software application running on a computing device (e.g., a virtual reality device, headset, or any computing device capable of presenting virtual reality content). In various embodiments, the network  150  can be any wired or wireless computer network through which devices can exchange data. For example, the network  150  can be a personal area network, a local area network, or a wide area network, to name some examples. The components (e.g., modules, elements, etc.) shown in this figure and all figures herein are exemplary only, and other implementations may include additional, fewer, integrated, or different components. Some components may not be shown so as not to obscure relevant details. 
     In some embodiments, the content provider module  102  can be implemented, in part or in whole, as software, hardware, or any combination thereof. In general, a module, as discussed herein, can be associated with software, hardware, or any combination thereof. In some implementations, one or more functions, tasks, and/or operations of modules can be carried out or performed by software routines, software processes, hardware, and/or any combination thereof. In some cases, the content provider module  102  can be implemented, in part or in whole, as software running on one or more computing devices or systems, such as on a user computing device or client computing system. For example, the content provider module  102 , or at least a portion thereof, can be implemented as or within an application (e.g., app), a program, or an applet, etc., running on a user computing device or a client computing system, such as the user device  710  of  FIG. 7 . Further, the content provider module  102 , or at least a portion thereof, can be implemented using one or more computing devices or systems that include one or more servers, such as network servers or cloud servers. In some instances, the content provider module  102  can, in part or in whole, be implemented within or configured to operate in conjunction with a social networking system (or service), such as the social networking system  730  of  FIG. 7 . It should be understood that there can be many variations or other possibilities. 
     In some embodiments, the content provider module  102  can be configured to communicate and/or operate with the at least one data store  112  in the example system  100 . In various embodiments, the at least one data store  112  can store data relevant to the function and operation of the content provider module  102 . One example of such data can be content items (e.g., virtual reality content items) that are available for access (e.g., streaming, viewing, etc.). In some implementations, the at least one data store  112  can store information associated with the social networking system (e.g., the social networking system  730  of  FIG. 7 ). The information associated with the social networking system can include data about users, social connections, social interactions, locations, geo-fenced areas, maps, places, events, pages, groups, posts, communications, content, feeds, account settings, privacy settings, a social graph, and various other types of data. In some implementations, the at least one data store  112  can store information associated with users, such as user identifiers, user information, profile information, user specified settings, content produced or posted by users, and various other types of user data. It should be appreciated that there can be many variations or other possibilities. 
     In various embodiments, the content module  104  can provide access to various types of content items (e.g., virtual reality content items) to be presented through a viewport. This viewport may be provided through a display of a computing device (e.g., a virtual reality computing device) in which the client module  114  is implemented, for example. In some instances, the computing device may be running a software application (e.g., social networking application) that is configured to present content items. Some examples of virtual reality content can include videos composed using monoscopic 360 degree views or videos composed using stereoscopic 180 degree views, to name some examples. In various embodiments, virtual reality content items can capture views (e.g., 180 degree views, 225 degree views, 360 degree views, etc.) of one or more scenes over some duration of time. Such scenes may be captured from the real world and/or be computer generated. 
     In some embodiments, a virtual reality content item can be created by stitching together various video streams (or feeds) that were captured by cameras that are placed at particular locations and/or positions to capture a view of the scene. Such streams may be pre-determined for various directions, e.g., angles (e.g., 0 degree, 30 degrees, 60 degrees, etc.), accessible in a virtual reality content item. Once stitched together, a user can access, or present, the virtual reality content item to view a portion of the virtual reality content item along some direction (or angle). Generally, the portion of the virtual reality content item (e.g., stream) shown to the user can be determined based on the location and direction of the user&#39;s viewport in three-dimensional space. In one example, the computing device in which the client module  114  is implemented can request presentation of a virtual reality content item (e.g., spherical video). In this example, the streaming module  106  can provide one or more streams of the virtual reality content item to be presented through the computing device. The stream(s) provided will typically correspond to a direction of the viewport in the virtual reality content item being accessed. As presentation of the virtual reality content item progresses, the client module  114  can continually provide the content provider module  102  with information describing the direction at which the viewport is facing. The streaming module  106  can use this information to determine which stream to provide the client module  114 . For example, while accessing the virtual reality content item, the client module  114  can notify the content provider module  102  that the viewport is facing a first direction. Based on this information, the streaming module  106  can provide the client module  114  with a first stream of the virtual reality content item that corresponds to the first direction. 
     In some embodiments, a virtual reality content item may be created as a single video stream (e.g., a non-switching single-stream) that captures a scene using one or more cameras. For example, all directions from which the scene was captured can be encoded at the same quality level. In such embodiments, the single video stream can be provided for presentation through a display screen of a computing device in which the client module  114  is implemented. 
     In some embodiments, the content features module  108  provides a number of different features for enhancing the presentation of content items. More details describing the content features module  108  will be provided below in reference to  FIG. 2 . 
       FIG. 2  illustrates an example of a content features module  202 , according to an embodiment of the present disclosure. In some embodiments, the content features module  108  of  FIG. 1  can be implemented with the content features module  202 . As shown in the example of  FIG. 2 , the content features module  202  can include a training content module  204 , a view tracking data module  206 , a heat map data module  208 , a saliency module  210 , a head orientation prediction module  212 , and a frame compression module  214 . 
     In various embodiments, the training content module  204  can be configured to obtain content items to be used for training one or more models (e.g., saliency prediction models). Such content items may include videos (e.g., virtual reality content items, immersive videos, etc.). In general, a virtual reality content item (or immersive video) corresponds to any virtual reality media that encompasses (or surrounds) a viewer (or user). Some examples of virtual reality content items include spherical videos, half sphere videos (e.g., 180 degree videos), arbitrary partial spheres, 225 degree videos, and 3D 360 videos. Such virtual reality content items need not be limited to videos that are formatted using a spherical shape but may also be applied to immersive videos formatted using other shapes including, for example, cubes, pyramids, and other shape representations of a video recorded three-dimensional world. 
     The content items obtained by the training content module  204  can vary depending on the type of model being trained. For example, in some embodiments, a general saliency prediction model may be trained using various unrelated content items that were created by various publishers and corresponding heat map data for those content items. This general saliency prediction model can be used to determine salient points of interest in various types of content items. In some embodiments, a publisher-specific saliency prediction model may be trained using content items that were posted by a given publisher (e.g., content creator) and corresponding heat map data for those content items. This publisher-specific saliency prediction model can be used to determine salient points of interest in content that is subsequently posted by that publisher. In some embodiments, a category-specific saliency prediction model may be trained using content items that all correspond to a given category (e.g., genre, topic, interest, etc.) and corresponding heat map data for those content items. This category-specific saliency prediction model can be used to determine salient points of interest in new content items that correspond to the given category. 
     In some embodiments, the view tracking data module  206  can be configured to obtain respective view tracking data for each of the content items being used to train the models. For example, view tracking data for a given content item may be collected for each user (or viewer) that has accessed the content item. The view tracking data for a user may identify regions that were accessed through the user&#39;s viewport during presentation of the content item. Such view tracking data may be collected for each frame corresponding to the content item. In some embodiments, a user&#39;s view tracking data for a content item can be determined based on changes to the user&#39;s viewport during presentation of the content item. Such changes to the viewport may be measured using various approaches that can be used either alone or in combination. For example, changes to the viewport may be measured using sensor data (e.g., gyroscope data, inertial measurement unit data, etc.) that describes movement of the computing device being used to present the content item. In another example, changes to the viewport can be measured using gesture data describing the types of gestures (e.g., panning, zooming, etc.) that were performed during presentation of the content item. Some other examples for measuring changes to the viewport include using input device data that describes input operations (e.g., mouse movement, dragging, etc.) performed during presentation of the content item, headset movement data that describes changes in the viewport direction during presentation of the content item, and eye tracking data collected during presentation of the content item, to name some examples. 
     In some embodiments, the heat map data module  208  can be configured to generate (or obtain) heat maps for each of the content items being used to train the models. In some embodiments, heat maps for a given content item may be generated based on view tracking data for the content item. As mentioned, the view tracking data module  206  can obtain respective view tracking data for users that viewed a content item. Each user&#39;s view tracking data can indicate which regions of a given frame (or set of frames) were accessed using a user&#39;s viewport during presentation of a content item. That is, for any given frame in the content item, the heat map data module  208  can generate (or obtain) user-specific heat maps that graphically represent regions in the frame that were of interest to a given user. In some embodiments, heat maps can be generated for a set of frames that correspond to some interval of time. For example, a respective heat map can be generated for every second of the content item. In some embodiments, user-specific heat maps for a given content item can be combined to generate aggregated heat maps that represent aggregated regions of interest in frames corresponding to the content item. Thus, for example, the respective user-specific heat maps can be aggregated on a frame-by-frame basis so that each frame of the content item is associated with its own aggregated heat map that graphically identifies the regions of interest in the frame. These regions of interest can correspond to various points of interest that appear in frames and were determined to be of interest to some, or all, of the users that viewed the content item. In some embodiments, these regions of interest can correspond to various points of interest that appear in frames and were determined to be of interest to users sharing one or more common characteristics with the user who is to view the content item. 
     In some embodiments, the saliency module  210  can be configured to train a saliency prediction model. In such embodiments, the saliency prediction model can be used to identify content (e.g., points of interest) that is likely to be of interest to a given user accessing a content item in which the identified content appears. For example, the saliency prediction model can determine that a first point of interest which appears in a given frame of a content item is likely to be of interest to a user over a second point of interest that also appears in the frame. In some embodiments, the saliency prediction model is trained using the content items that were obtained by the training content module  204  and their respective aggregated heat maps. For example, in some embodiments, each frame of a content item and its corresponding aggregated heat map can be provided as a training example to the saliency prediction model. In some embodiments, the saliency prediction model is trained using aggregated heat map data that has been labeled to identify points of interest. The aggregated heat map can be used to identify regions of the frame that were viewed more than others. Such view activity can be represented in the aggregated heat map using various shapes that describe the size of the view region and/or colors that indicate concentrations of view activity in any given region of the frame. Based on this information, the saliency prediction model can learn which pixels in the frame were interesting (or relevant) to users in the aggregate. In some embodiments, pixels in the frame that fall within the shapes and/or colors represented in the aggregated heat map can be identified as being interesting (or relevant) to users in the aggregate. In some embodiments, these pixels correlate to points of interest that appear in frames. As a result, the saliency prediction model can learn which points of interest appearing in a frame were of interest to users in the aggregate with respect to other points of interest that also appear in the frame. Once trained, the saliency prediction model can be used to identify content (e.g., points of interest) that is likely to be of interest in new content items. In some embodiments, the saliency prediction model can be used to predict salient points of interest for stored content items (e.g., video on-demand). In some embodiments, the saliency prediction model can be used to predict salient points of interest (e.g., points of interest that are likely to be of interest) for live content items (e.g., live video broadcasts). 
     In various embodiments, heat map data, aggregated or otherwise, need not be actual heat maps that are represented graphically but may instead be some representation of view tracking data. For example, in some embodiments, the heat map data may identify clusters of view activity within individual frames of content items. In some embodiments, the clusters of view activity that are identified from heat map data can be used independently to identify salient points of interest in various content items. For example, in some embodiments, heat map data identifying clusters of view activity in frames during a live video broadcast (e.g., over the past n seconds of the broadcast) can be used to identify salient points of interest that appear in subsequent frames. 
     The ability to predict salient content (e.g., points of interest) in new content items provides a number of advantages. For example, in some embodiments, the head orientation prediction module  212  can be configured to determine changes to a user&#39;s head orientation during presentation of a given content item. In such embodiments, the content item (or frames of the content item) being viewed can be provided as input to the saliency prediction model that was trained by the saliency module  210 . The saliency prediction model can output information indicating which content in the frames is likely to be of interest to the user viewing the content item. In general, the user&#39;s head orientation (e.g., viewport) is expected to align with regions in the frames that include content that is likely to be of interest. In some embodiments, predicted changes to the user&#39;s head orientation can be used to improve streaming of the content item, as described below. 
     The frame compression module  214  can be configured to apply various techniques to compress frames of content items (e.g., virtual reality content items). In some embodiments, the frame compression module  214  can apply frame quantization techniques to single-stream content items. Unlike content items that are composed of multiple streams which are served based on a user&#39;s view direction, a single-stream content item can be streamed using one stream that captures a complete view of a scene (e.g., 180 degree view, 225 degree view, etc.). In some embodiments, a single-stream content item represents a 360 degree view of a scene in which all directions are encoded at a high quality. In some embodiments, the frame compression module  214  adjusts the quantization of frames of single-stream content items during playback. In some embodiments, the frame compression module  214  can selectively quantize portions of frames based on which portions of the frames are being accessed (or viewed) during playback. As a result, portions of frames being viewed can be presented at a higher quality while the remaining portions of the frames are presented at a lower quality. In some embodiments, such quantization is performed server-side in real-time as frames are being streamed (e.g., on-the-fly at delivery time). 
     For example, a user operating a computing device can access a single-stream content item to be presented through a viewport. The viewport may be provided through a display of the computing device (e.g., a virtual reality computing device). In this example, the single-stream content item may represent a view of a scene in which all directions have been encoded at a high quality. In various embodiments, the frame compression module  214  can determine the user&#39;s view direction during playback of the content item. Once determined, the frame compression module  214  can correlate the view direction to a region (e.g., a bounding shape) in the viewport. The frame compression module  214  can then obtain quantized residual data by decompressing the content item. This quantized residual data may be obtained on a per-frame basis, for example. In this example, the frame compression module  214  can re-quantize frames of the content item so that content appearing within the bounding shape appears at a higher quality than content appearing outside of the bounding shape. Such enhancement may be achieved in a number of ways. For example, in some embodiments, the frame compression module  214  may reduce the quality of content appearing outside of the bounding shape by assigning higher quantization parameter values to frame blocks (e.g., blocks of pixels) located outside of the bounding shape. In some embodiments, the frame compression module  214  may enhance the quality of content appearing within the bounding shape by assigning lower quantization parameter values to frame blocks located within the bounding shape. In some embodiments, the frame compression module  214  may both assign lower quantization parameter values to frame blocks located within the bounding shape while assigning higher quantization parameter values to frame blocks located outside of the bounding shape. This re-quantized content can then be provided to the user&#39;s computing device for presentation. 
     In various embodiments, the frame compression module  214  can continually determine changes in view direction during playback of a content item so that frames can be quantized based on view direction. In general, the frame compression module  214  may determine changes to the view direction upon presentation of every frame or some specified number of frames. In another example, changes to the view direction may be determined periodically based on a specified time interval (e.g., every second). In some embodiments, view direction information is provided by a user computing device during playback of a content item. For example, when accessing a single-stream content item, a user&#39;s computing device can continually determine changes in view direction during playback of the content item. These changes can then be provided to a computing system of a content provider in which the frame compression module  214  is implemented. For example, the computing device can provide the content provider with a set of coordinates describing a view direction (e.g., an x-axis coordinate, a y-axis coordinate, a z-axis coordinate, and a value indicating playback time). In general, changes in view direction may be measured using various approaches that can be used either alone or in combination. For example, changes to the view direction may be measured using sensor data (e.g., gyroscope data, inertial measurement unit data, etc.) that describes movement of a computing device being used to present the content item. In another example, changes to the view direction can be measured using gesture data describing the types of gestures (e.g., panning, zooming, etc.) that were performed during presentation of the content item. Some other examples for measuring changes to the view direction include using input device data that describes input operations (e.g., mouse movement, dragging, etc.) performed during presentation of the content item, headset movement data that describes changes in the view direction during presentation of the content item, and eye tracking data collected during presentation of the content item, to name some examples. 
     In some embodiments, re-quantized frame data is stored (e.g., cached) at a computing system of a content provider in which the frame compression module  214  is implemented. In such embodiments, when a content item is accessed by a given user, the content provider can provide previously cached re-quantized frame data corresponding to the content item. In some embodiments, a given content item may be associated with multiple versions of re-quantized frame data. That is, each version of the re-quantized frame data may correspond to a particular viewing pattern. For example, one version of the re-quantized frame data may enhance various regions that were viewed by a first category of users while another version of the re-quantized frame data may enhance different regions that were viewed by a second category of users. In such embodiments, the version provided to a given user can be determined by classifying the user into a given category of users and providing the version that corresponds to that category of users. 
     As mentioned, the frame compression module  214  can be configured to apply various techniques to compress frames of content items. In some embodiments, the frame compression module  214  can apply frame quantization techniques to various types of content items (e.g., flat two-dimensional videos, virtual reality content items, single-stream content items, multi-stream content items, etc.) based on user view directions that are predicted. 
     For example, in some embodiments, view directions may be determined based on heat map data that identifies regions in frames that were viewed by one or more users during playback. Such heat map data may be generated using view tracking data, as described above in reference to the heat map data module  208 . In some embodiments, this heat map data is generated from historical view patterns of users that accessed a given content item. For example, a user operating a computing device can access a content item to be presented through a viewport. In this example, the frame compression module  214  can identify one or more regions in frames of the content item that received a threshold amount of view activity based on heat map data. The frame compression module  214  can then quantize the frames so that content appearing within the identified regions appears at a higher quality than content appearing outside of the identified regions. This quantization can be performed using any of the approaches described above. For example, regions of a given frame that did not receive a threshold amount of view activity can be compressed more aggressively than regions of the frame that did receive the threshold amount of view activity. The quantized content can then be provided to the user&#39;s computing device for presentation. In some embodiments, content items that were quantized based on heat map data are stored and provided when subsequent requests for those content items are received. 
     In some embodiments, view directions may be determined based on saliency information that identifies salient points of interest in frames. In some embodiments, this saliency information may be determined by a saliency prediction model, as described above in reference to the saliency module  210 . For example, a user operating a computing device can access a content item to be presented through a viewport. In this example, the frame compression module  214  can identify one or more salient points of interest in frames of the content item. The frame compression module  214  can then quantize the frames so that content corresponding to the salient points of interest appears at a higher quality than the remaining content in the frames. This quantization can be performed using any of the approaches described above. The quantized content can then be provided to the user&#39;s computing device for presentation. In some embodiments, content items that were quantized based on saliency information are stored and provided when subsequent requests for those content items are received. 
       FIGS. 3A-C  illustrate examples of streaming a virtual reality content item, according to an embodiment of the present disclosure.  FIG. 3A  illustrates an example  300  of a viewport  304  displaying a portion of a video stream  306  of a virtual reality content item (e.g., a spherical video). The viewport  304  is shown in the diagram of  FIG. 3A  as being positioned within a representation  302  of a virtual reality content item to facilitate understanding of the various embodiments described herein. In some embodiments, a virtual reality content item captures a 360-degree view of a scene (e.g., a three-dimensional scene). The virtual reality content item can be created by stitching together various video streams, or feeds, that were captured by cameras positioned at particular locations and/or positions to capture a 360 degree view of the scene. As mentioned, in some embodiments, the virtual reality content item can be created as a single-stream content item that represents a view of a scene using one video stream in which all directions of the scene are encoded in high quality. 
     A user can access, or present, the virtual reality content item through a viewport  304  to view a portion of the virtual reality content item at some angle. The viewport  304  may be accessed through a software application (e.g., video player software) running on a computing device. The virtual reality content item can be projected as a sphere, as illustrated by the representation  302 . Generally, while accessing the virtual reality content item, the user can change the direction (e.g., pitch, yaw, roll) of the viewport  304  to access another portion of the scene captured by the virtual reality content item.  FIG. 3B  illustrates an example  350  in which the direction of the viewport  354  has changed in an upward direction (as compared to viewport  304 ). As a result, the video stream  356  of the virtual reality content item being accessed through the viewport  354  has been updated (e.g., as compared to video stream  306 ) to show the portion of the virtual reality content item that corresponds to the updated viewport direction. 
     The direction of the viewport  304  may be changed in various ways depending on the implementation. For example, while accessing the virtual reality content item, the user may change the direction of the viewport  304  using a mouse or similar device or through a gesture recognized by the computing device. As the direction changes, the viewport  304  can be provided a stream corresponding to that direction, for example, from a content provider system. In another example, while accessing the virtual reality content item through a display screen of a mobile device, the user may change the direction of the viewport  304  by changing the direction (e.g., pitch, yaw, roll) of the mobile device as determined, for example, using gyroscopes, accelerometers, touch sensors, and/or inertial measurement units in the mobile device. Further, if accessing the virtual reality content item through a virtual reality head mounted display, the user may change the direction of the viewport  304  by changing the direction of the user&#39;s head (e.g., pitch, yaw, roll). Naturally, other approaches may be utilized for navigating presentation of a virtual reality content item including, for example, touch screen or other suitable gestures. 
     In some embodiments, the stream(s) are provided in real-time based on the determined direction of the viewport  304 . For example, when the direction of the viewport  304  changes to a new position, the computing device through which the viewport  304  is being accessed and/or the content provider system can determine the new position of the viewport  304  and the content provider system can send, to the computing device, stream data corresponding to the new position. Thus, in such embodiments, each change in the viewport  304  position is monitored, in real-time (e.g., constantly or at specified time intervals) and information associated with the change is provided to the content provider system such that the content provider system may send the appropriate stream that corresponds to the change in direction. In various embodiments, changes in the direction of the viewport  304  during presentation of the content item are captured and stored. In some embodiments, such viewport tracking data is used to generate one or more user-specific heat maps and/or aggregated heat maps for the content item. For example,  FIG. 3C  illustrates an example user-specific heat map  360  that was generated based on changes to the user&#39;s viewport direction (e.g., view activity) during presentation of the video. In the example of  FIG. 3C , the user-specific heat map  360  indicates that the user&#39;s attention was focused on a first point of interest  362  and a second point of interest  364  during presentation of the virtual reality content item. This heat map data can be used for myriad applications as described above. 
       FIGS. 4A-B  illustrate examples of enhancing a virtual reality content item, according to an embodiment of the present disclosure.  FIG. 4A  illustrates an example frame  402  of a content item which includes a first point of interest  404  and a second point of interest  406 . In some embodiments, the frame  402  can be provided to a saliency prediction model to determine salient points of interest. In this example, the saliency prediction model may determine that the second point of interest  406  is a salient point of interest that is likely to be of interest to users viewing the content item. In some embodiments, the first point of interest  404  and the second point of interest  406  can be determined from heat map data corresponding to the virtual reality content item. In some embodiments, the second point of interest  406  (or a region  408  corresponding to the second point of interest  406 ) can be enhanced visually during presentation of the content item, as described above. For example, in some embodiments, the second point of interest  406  can be presented at a higher video quality than the remaining parts of the frame  402 . Such enhancements may be achieved by re-quantizing various portions of the frame  402 , as described above. In another example,  FIG. 4B  illustrates an example frame  412  of a content item which includes a first point of interest  414  and a second point of interest  416 . In this example, a view direction  418  of a user viewing the content item can be determined and used to re-quantize the frame  412 . For example, content appearing outside of the view direction  418  can be quantized more aggressively than content appearing within the view direction  418 , as described above. 
       FIG. 5  illustrates an example method  500 , according to an embodiment of the present disclosure. It should be appreciated that there can be additional, fewer, or alternative steps performed in similar or alternative orders, or in parallel, within the scope of the various embodiments discussed herein unless otherwise stated. 
     At block  502 , a request for a content item is determined. The content item is to be presented through a display screen of a computing device. At block  504 , a view direction of a user operating the computing device is determined. At block  506 , one or more frames of the content item are quantized based at least in part on the view direction. 
       FIG. 6  illustrates an example method  600 , according to an embodiment of the present disclosure. It should be appreciated that there can be additional, fewer, or alternative steps performed in similar or alternative orders, or in parallel, within the scope of the various embodiments discussed herein unless otherwise stated. 
     At block  602 , a request for a content item can be received from a computing device. At block  604 , one or more view directions of a user operating the computing device can be predicted during playback of the content item. At block  606 , one or more frames of the content item are quantized based at least in part on the predicted view directions. 
     It is contemplated that there can be many other uses, applications, and/or variations associated with the various embodiments of the present disclosure. For example, in some cases, user can choose whether or not to opt-in to utilize the disclosed technology. The disclosed technology can also ensure that various privacy settings and preferences are maintained and can prevent private information from being divulged. In another example, various embodiments of the present disclosure can learn, improve, and/or be refined over time. 
     Social Networking System—Example Implementation 
       FIG. 7  illustrates a network diagram of an example system  700  that can be utilized in various scenarios, in accordance with an embodiment of the present disclosure. The system  700  includes one or more user devices  710 , one or more external systems  720 , a social networking system (or service)  730 , and a network  750 . In an embodiment, the social networking service, provider, and/or system discussed in connection with the embodiments described above may be implemented as the social networking system  730 . For purposes of illustration, the embodiment of the system  700 , shown by  FIG. 7 , includes a single external system  720  and a single user device  710 . However, in other embodiments, the system  700  may include more user devices  710  and/or more external systems  720 . In certain embodiments, the social networking system  730  is operated by a social network provider, whereas the external systems  720  are separate from the social networking system  730  in that they may be operated by different entities. In various embodiments, however, the social networking system  730  and the external systems  720  operate in conjunction to provide social networking services to users (or members) of the social networking system  730 . In this sense, the social networking system  730  provides a platform or backbone, which other systems, such as external systems  720 , may use to provide social networking services and functionalities to users across the Internet. 
     The user device  710  comprises one or more computing devices (or systems) that can receive input from a user and transmit and receive data via the network  750 . In one embodiment, the user device  710  is a conventional computer system executing, for example, a Microsoft Windows compatible operating system (OS), Apple OS X, and/or a Linux distribution. In another embodiment, the user device  710  can be a computing device or a device having computer functionality, such as a smart-phone, a tablet, a personal digital assistant (PDA), a mobile telephone, a laptop computer, a wearable device (e.g., a pair of glasses, a watch, a bracelet, etc.), a camera, an appliance, etc. The user device  710  is configured to communicate via the network  750 . The user device  710  can execute an application, for example, a browser application that allows a user of the user device  710  to interact with the social networking system  730 . In another embodiment, the user device  710  interacts with the social networking system  730  through an application programming interface (API) provided by the native operating system of the user device  710 , such as iOS and ANDROID. The user device  710  is configured to communicate with the external system  720  and the social networking system  730  via the network  750 , which may comprise any combination of local area and/or wide area networks, using wired and/or wireless communication systems. 
     In one embodiment, the network  750  uses standard communications technologies and protocols. Thus, the network  750  can include links using technologies such as Ethernet, 802.11, worldwide interoperability for microwave access (WiMAX), 3G, 4G, CDMA, GSM, LTE, digital subscriber line (DSL), etc. Similarly, the networking protocols used on the network  750  can include multiprotocol label switching (MPLS), transmission control protocol/Internet protocol (TCP/IP), User Datagram Protocol (UDP), hypertext transport protocol (HTTP), simple mail transfer protocol (SMTP), file transfer protocol (FTP), and the like. The data exchanged over the network  750  can be represented using technologies and/or formats including hypertext markup language (HTML) and extensible markup language (XML). In addition, all or some links can be encrypted using conventional encryption technologies such as secure sockets layer (SSL), transport layer security (TLS), and Internet Protocol security (IPsec). 
     In one embodiment, the user device  710  may display content from the external system  720  and/or from the social networking system  730  by processing a markup language document  714  received from the external system  720  and from the social networking system  730  using a browser application  712 . The markup language document  714  identifies content and one or more instructions describing formatting or presentation of the content. By executing the instructions included in the markup language document  714 , the browser application  712  displays the identified content using the format or presentation described by the markup language document  714 . For example, the markup language document  714  includes instructions for generating and displaying a web page having multiple frames that include text and/or image data retrieved from the external system  720  and the social networking system  730 . In various embodiments, the markup language document  714  comprises a data file including extensible markup language (XML) data, extensible hypertext markup language (XHTML) data, or other markup language data. Additionally, the markup language document  714  may include JavaScript Object Notation (JSON) data, JSON with padding (JSONP), and JavaScript data to facilitate data-interchange between the external system  720  and the user device  710 . The browser application  712  on the user device  710  may use a JavaScript compiler to decode the markup language document  714 . 
     The markup language document  714  may also include, or link to, applications or application frameworks such as FLASH™ or Unity™ applications, the Silverlight™ application framework, etc. 
     In one embodiment, the user device  710  also includes one or more cookies  716  including data indicating whether a user of the user device  710  is logged into the social networking system  730 , which may enable modification of the data communicated from the social networking system  730  to the user device  710 . 
     The external system  720  includes one or more web servers that include one or more web pages  722   a ,  722   b , which are communicated to the user device  710  using the network  750 . The external system  720  is separate from the social networking system  730 . For example, the external system  720  is associated with a first domain, while the social networking system  730  is associated with a separate social networking domain. Web pages  722   a ,  722   b , included in the external system  720 , comprise markup language documents  714  identifying content and including instructions specifying formatting or presentation of the identified content. As discussed previously, it should be appreciated that there can be many variations or other possibilities. 
     The social networking system  730  includes one or more computing devices for a social network, including a plurality of users, and providing users of the social network with the ability to communicate and interact with other users of the social network. In some instances, the social network can be represented by a graph, i.e., a data structure including edges and nodes. Other data structures can also be used to represent the social network, including but not limited to databases, objects, classes, meta elements, files, or any other data structure. The social networking system  730  may be administered, managed, or controlled by an operator. The operator of the social networking system  730  may be a human being, an automated application, or a series of applications for managing content, regulating policies, and collecting usage metrics within the social networking system  730 . Any type of operator may be used. 
     Users may join the social networking system  730  and then add connections to any number of other users of the social networking system  730  to whom they desire to be connected. As used herein, the term “friend” refers to any other user of the social networking system  730  to whom a user has formed a connection, association, or relationship via the social networking system  730 . For example, in an embodiment, if users in the social networking system  730  are represented as nodes in the social graph, the term “friend” can refer to an edge formed between and directly connecting two user nodes. 
     Connections may be added explicitly by a user or may be automatically created by the social networking system  730  based on common characteristics of the users (e.g., users who are alumni of the same educational institution). For example, a first user specifically selects a particular other user to be a friend. Connections in the social networking system  730  are usually in both directions, but need not be, so the terms “user” and “friend” depend on the frame of reference. Connections between users of the social networking system  730  are usually bilateral (“two-way”), or “mutual,” but connections may also be unilateral, or “one-way.” For example, if Bob and Joe are both users of the social networking system  730  and connected to each other, Bob and Joe are each other&#39;s connections. If, on the other hand, Bob wishes to connect to Joe to view data communicated to the social networking system  730  by Joe, but Joe does not wish to form a mutual connection, a unilateral connection may be established. The connection between users may be a direct connection; however, some embodiments of the social networking system  730  allow the connection to be indirect via one or more levels of connections or degrees of separation. 
     In addition to establishing and maintaining connections between users and allowing interactions between users, the social networking system  730  provides users with the ability to take actions on various types of items supported by the social networking system  730 . These items may include groups or networks (i.e., social networks of people, entities, and concepts) to which users of the social networking system  730  may belong, events or calendar entries in which a user might be interested, computer-based applications that a user may use via the social networking system  730 , transactions that allow users to buy or sell items via services provided by or through the social networking system  730 , and interactions with advertisements that a user may perform on or off the social networking system  730 . These are just a few examples of the items upon which a user may act on the social networking system  730 , and many others are possible. A user may interact with anything that is capable of being represented in the social networking system  730  or in the external system  720 , separate from the social networking system  730 , or coupled to the social networking system  730  via the network  750 . 
     The social networking system  730  is also capable of linking a variety of entities. For example, the social networking system  730  enables users to interact with each other as well as external systems  720  or other entities through an API, a web service, or other communication channels. The social networking system  730  generates and maintains the “social graph” comprising a plurality of nodes interconnected by a plurality of edges. Each node in the social graph may represent an entity that can act on another node and/or that can be acted on by another node. The social graph may include various types of nodes. Examples of types of nodes include users, non-person entities, content items, web pages, groups, activities, messages, concepts, and any other things that can be represented by an object in the social networking system  730 . An edge between two nodes in the social graph may represent a particular kind of connection, or association, between the two nodes, which may result from node relationships or from an action that was performed by one of the nodes on the other node. In some cases, the edges between nodes can be weighted. The weight of an edge can represent an attribute associated with the edge, such as a strength of the connection or association between nodes. Different types of edges can be provided with different weights. For example, an edge created when one user “likes” another user may be given one weight, while an edge created when a user befriends another user may be given a different weight. 
     As an example, when a first user identifies a second user as a friend, an edge in the social graph is generated connecting a node representing the first user and a second node representing the second user. As various nodes relate or interact with each other, the social networking system  730  modifies edges connecting the various nodes to reflect the relationships and interactions. 
     The social networking system  730  also includes user-generated content, which enhances a user&#39;s interactions with the social networking system  730 . User-generated content may include anything a user can add, upload, send, or “post” to the social networking system  730 . For example, a user communicates posts to the social networking system  730  from a user device  710 . Posts may include data such as status updates or other textual data, location information, images such as photos, videos, links, music or other similar data and/or media. Content may also be added to the social networking system  730  by a third party. Content “items” are represented as objects in the social networking system  730 . In this way, users of the social networking system  730  are encouraged to communicate with each other by posting text and content items of various types of media through various communication channels. Such communication increases the interaction of users with each other and increases the frequency with which users interact with the social networking system  730 . 
     The social networking system  730  includes a web server  732 , an API request server  734 , a user profile store  736 , a connection store  738 , an action logger  740 , an activity log  742 , and an authorization server  744 . In an embodiment of the invention, the social networking system  730  may include additional, fewer, or different components for various applications. Other components, such as network interfaces, security mechanisms, load balancers, failover servers, management and network operations consoles, and the like are not shown so as to not obscure the details of the system. 
     The user profile store  736  maintains information about user accounts, including biographic, demographic, and other types of descriptive information, such as work experience, educational history, hobbies or preferences, location, and the like that has been declared by users or inferred by the social networking system  730 . This information is stored in the user profile store  736  such that each user is uniquely identified. The social networking system  730  also stores data describing one or more connections between different users in the connection store  738 . The connection information may indicate users who have similar or common work experience, group memberships, hobbies, or educational history. Additionally, the social networking system  730  includes user-defined connections between different users, allowing users to specify their relationships with other users. For example, user-defined connections allow users to generate relationships with other users that parallel the users&#39; real-life relationships, such as friends, co-workers, partners, and so forth. Users may select from predefined types of connections, or define their own connection types as needed. Connections with other nodes in the social networking system  730 , such as non-person entities, buckets, cluster centers, images, interests, pages, external systems, concepts, and the like are also stored in the connection store  738 . 
     The social networking system  730  maintains data about objects with which a user may interact. To maintain this data, the user profile store  736  and the connection store  738  store instances of the corresponding type of objects maintained by the social networking system  730 . Each object type has information fields that are suitable for storing information appropriate to the type of object. For example, the user profile store  736  contains data structures with fields suitable for describing a user&#39;s account and information related to a user&#39;s account. When a new object of a particular type is created, the social networking system  730  initializes a new data structure of the corresponding type, assigns a unique object identifier to it, and begins to add data to the object as needed. This might occur, for example, when a user becomes a user of the social networking system  730 , the social networking system  730  generates a new instance of a user profile in the user profile store  736 , assigns a unique identifier to the user account, and begins to populate the fields of the user account with information provided by the user. 
     The connection store  738  includes data structures suitable for describing a user&#39;s connections to other users, connections to external systems  720  or connections to other entities. The connection store  738  may also associate a connection type with a user&#39;s connections, which may be used in conjunction with the user&#39;s privacy setting to regulate access to information about the user. In an embodiment of the invention, the user profile store  736  and the connection store  738  may be implemented as a federated database. 
     Data stored in the connection store  738 , the user profile store  736 , and the activity log  742  enables the social networking system  730  to generate the social graph that uses nodes to identify various objects and edges connecting nodes to identify relationships between different objects. For example, if a first user establishes a connection with a second user in the social networking system  730 , user accounts of the first user and the second user from the user profile store  736  may act as nodes in the social graph. The connection between the first user and the second user stored by the connection store  738  is an edge between the nodes associated with the first user and the second user. Continuing this example, the second user may then send the first user a message within the social networking system  730 . The action of sending the message, which may be stored, is another edge between the two nodes in the social graph representing the first user and the second user. Additionally, the message itself may be identified and included in the social graph as another node connected to the nodes representing the first user and the second user. 
     In another example, a first user may tag a second user in an image that is maintained by the social networking system  730  (or, alternatively, in an image maintained by another system outside of the social networking system  730 ). The image may itself be represented as a node in the social networking system  730 . This tagging action may create edges between the first user and the second user as well as create an edge between each of the users and the image, which is also a node in the social graph. In yet another example, if a user confirms attending an event, the user and the event are nodes obtained from the user profile store  736 , where the attendance of the event is an edge between the nodes that may be retrieved from the activity log  742 . By generating and maintaining the social graph, the social networking system  730  includes data describing many different types of objects and the interactions and connections among those objects, providing a rich source of socially relevant information. 
     The web server  732  links the social networking system  730  to one or more user devices  710  and/or one or more external systems  720  via the network  750 . The web server  732  serves web pages, as well as other web-related content, such as Java, JavaScript, Flash, XML, and so forth. The web server  732  may include a mail server or other messaging functionality for receiving and routing messages between the social networking system  730  and one or more user devices  710 . The messages can be instant messages, queued messages (e.g., email), text and SMS messages, or any other suitable messaging format. 
     The API request server  734  allows one or more external systems  720  and user devices  710  to call access information from the social networking system  730  by calling one or more API functions. The API request server  734  may also allow external systems  720  to send information to the social networking system  730  by calling APIs. The external system  720 , in one embodiment, sends an API request to the social networking system  730  via the network  750 , and the API request server  734  receives the API request. The API request server  734  processes the request by calling an API associated with the API request to generate an appropriate response, which the API request server  734  communicates to the external system  720  via the network  750 . For example, responsive to an API request, the API request server  734  collects data associated with a user, such as the user&#39;s connections that have logged into the external system  720 , and communicates the collected data to the external system  720 . In another embodiment, the user device  710  communicates with the social networking system  730  via APIs in the same manner as external systems  720 . 
     The action logger  740  is capable of receiving communications from the web server  732  about user actions on and/or off the social networking system  730 . The action logger  740  populates the activity log  742  with information about user actions, enabling the social networking system  730  to discover various actions taken by its users within the social networking system  730  and outside of the social networking system  730 . Any action that a particular user takes with respect to another node on the social networking system  730  may be associated with each user&#39;s account, through information maintained in the activity log  742  or in a similar database or other data repository. Examples of actions taken by a user within the social networking system  730  that are identified and stored may include, for example, adding a connection to another user, sending a message to another user, reading a message from another user, viewing content associated with another user, attending an event posted by another user, posting an image, attempting to post an image, or other actions interacting with another user or another object. When a user takes an action within the social networking system  730 , the action is recorded in the activity log  742 . In one embodiment, the social networking system  730  maintains the activity log  742  as a database of entries. When an action is taken within the social networking system  730 , an entry for the action is added to the activity log  742 . The activity log  742  may be referred to as an action log. 
     Additionally, user actions may be associated with concepts and actions that occur within an entity outside of the social networking system  730 , such as an external system  720  that is separate from the social networking system  730 . For example, the action logger  740  may receive data describing a user&#39;s interaction with an external system  720  from the web server  732 . In this example, the external system  720  reports a user&#39;s interaction according to structured actions and objects in the social graph. 
     Other examples of actions where a user interacts with an external system  720  include a user expressing an interest in an external system  720  or another entity, a user posting a comment to the social networking system  730  that discusses an external system  720  or a web page  722   a  within the external system  720 , a user posting to the social networking system  730  a Uniform Resource Locator (URL) or other identifier associated with an external system  720 , a user attending an event associated with an external system  720 , or any other action by a user that is related to an external system  720 . Thus, the activity log  742  may include actions describing interactions between a user of the social networking system  730  and an external system  720  that is separate from the social networking system  730 . 
     The authorization server  744  enforces one or more privacy settings of the users of the social networking system  730 . A privacy setting of a user determines how particular information associated with a user can be shared. The privacy setting comprises the specification of particular information associated with a user and the specification of the entity or entities with whom the information can be shared. Examples of entities with which information can be shared may include other users, applications, external systems  720 , or any entity that can potentially access the information. The information that can be shared by a user comprises user account information, such as profile photos, phone numbers associated with the user, user&#39;s connections, actions taken by the user such as adding a connection, changing user profile information, and the like. 
     The privacy setting specification may be provided at different levels of granularity. For example, the privacy setting may identify specific information to be shared with other users; the privacy setting identifies a work phone number or a specific set of related information, such as, personal information including profile photo, home phone number, and status. Alternatively, the privacy setting may apply to all the information associated with the user. The specification of the set of entities that can access particular information can also be specified at various levels of granularity. Various sets of entities with which information can be shared may include, for example, all friends of the user, all friends of friends, all applications, or all external systems  720 . One embodiment allows the specification of the set of entities to comprise an enumeration of entities. For example, the user may provide a list of external systems  720  that are allowed to access certain information. Another embodiment allows the specification to comprise a set of entities along with exceptions that are not allowed to access the information. For example, a user may allow all external systems  720  to access the user&#39;s work information, but specify a list of external systems  720  that are not allowed to access the work information. Certain embodiments call the list of exceptions that are not allowed to access certain information a “block list”. External systems  720  belonging to a block list specified by a user are blocked from accessing the information specified in the privacy setting. Various combinations of granularity of specification of information, and granularity of specification of entities, with which information is shared are possible. For example, all personal information may be shared with friends whereas all work information may be shared with friends of friends. 
     The authorization server  744  contains logic to determine if certain information associated with a user can be accessed by a user&#39;s friends, external systems  720 , and/or other applications and entities. The external system  720  may need authorization from the authorization server  744  to access the user&#39;s more private and sensitive information, such as the user&#39;s work phone number. Based on the user&#39;s privacy settings, the authorization server  744  determines if another user, the external system  720 , an application, or another entity is allowed to access information associated with the user, including information about actions taken by the user. 
     In some embodiments, the social networking system  730  can include a content provider module  746 . The content provider module  746  can, for example, be implemented as the content provider module  102  of  FIG. 1 . In some embodiments, the content provider module  746 , or some of its features, can be implemented in a computing device, e.g., the user device  710 . The network  750  can, for example, be implemented as the network  150  of  FIG. 1 . As discussed previously, it should be appreciated that there can be many variations or other possibilities. 
     Hardware Implementation 
     The foregoing processes and features can be implemented by a wide variety of machine and computer system architectures and in a wide variety of network and computing environments.  FIG. 8  illustrates an example of a computer system  800  that may be used to implement one or more of the embodiments described herein in accordance with an embodiment of the invention. The computer system  800  includes sets of instructions for causing the computer system  800  to perform the processes and features discussed herein. The computer system  800  may be connected (e.g., networked) to other machines. In a networked deployment, the computer system  800  may operate in the capacity of a server machine or a client machine in a client-server network environment, or as a peer machine in a peer-to-peer (or distributed) network environment. In an embodiment of the invention, the computer system  800  may be the social networking system  730 , the user device  710 , and the external system  820 , or a component thereof. In an embodiment of the invention, the computer system  800  may be one server among many that constitutes all or part of the social networking system  730 . 
     The computer system  800  includes a processor  802 , a cache  804 , and one or more executable modules and drivers, stored on a computer-readable medium, directed to the processes and features described herein. Additionally, the computer system  800  includes a high performance input/output (I/O) bus  806  and a standard I/O bus  808 . A host bridge  810  couples processor  802  to high performance I/O bus  806 , whereas I/O bus bridge  812  couples the two buses  806  and  808  to each other. A system memory  814  and one or more network interfaces  816  couple to high performance I/O bus  806 . The computer system  800  may further include video memory and a display device coupled to the video memory (not shown). Mass storage  818  and I/O ports  820  couple to the standard I/O bus  808 . The computer system  800  may optionally include a keyboard and pointing device, a display device, or other input/output devices (not shown) coupled to the standard I/O bus  808 . Collectively, these elements are intended to represent a broad category of computer hardware systems, including but not limited to computer systems based on the ×86-compatible processors manufactured by Intel Corporation of Santa Clara, Calif., and the ×86-compatible processors manufactured by Advanced Micro Devices (AMD), Inc., of Sunnyvale, Calif., as well as any other suitable processor. 
     An operating system manages and controls the operation of the computer system  800 , including the input and output of data to and from software applications (not shown). The operating system provides an interface between the software applications being executed on the system and the hardware components of the system. Any suitable operating system may be used, such as the LINUX Operating System, the Apple Macintosh Operating System, available from Apple Computer Inc. of Cupertino, Calif., UNIX operating systems, Microsoft® Windows® operating systems, BSD operating systems, and the like. Other implementations are possible. 
     The elements of the computer system  800  are described in greater detail below. In particular, the network interface  816  provides communication between the computer system  800  and any of a wide range of networks, such as an Ethernet (e.g., IEEE 802.3) network, a backplane, etc. The mass storage  818  provides permanent storage for the data and programming instructions to perform the above-described processes and features implemented by the respective computing systems identified above, whereas the system memory  814  (e.g., DRAM) provides temporary storage for the data and programming instructions when executed by the processor  802 . The I/O ports  820  may be one or more serial and/or parallel communication ports that provide communication between additional peripheral devices, which may be coupled to the computer system  800 . 
     The computer system  800  may include a variety of system architectures, and various components of the computer system  800  may be rearranged. For example, the cache  804  may be on-chip with processor  802 . Alternatively, the cache  804  and the processor  802  may be packed together as a “processor module”, with processor  802  being referred to as the “processor core”. Furthermore, certain embodiments of the invention may neither require nor include all of the above components. For example, peripheral devices coupled to the standard I/O bus  808  may couple to the high performance I/O bus  806 . In addition, in some embodiments, only a single bus may exist, with the components of the computer system  800  being coupled to the single bus. Moreover, the computer system  800  may include additional components, such as additional processors, storage devices, or memories. 
     In general, the processes and features described herein may be implemented as part of an operating system or a specific application, component, program, object, module, or series of instructions referred to as “programs”. For example, one or more programs may be used to execute specific processes described herein. The programs typically comprise one or more instructions in various memory and storage devices in the computer system  800  that, when read and executed by one or more processors, cause the computer system  800  to perform operations to execute the processes and features described herein. The processes and features described herein may be implemented in software, firmware, hardware (e.g., an application specific integrated circuit), or any combination thereof. 
     In one implementation, the processes and features described herein are implemented as a series of executable modules run by the computer system  800 , individually or collectively in a distributed computing environment. The foregoing modules may be realized by hardware, executable modules stored on a computer-readable medium (or machine-readable medium), or a combination of both. For example, the modules may comprise a plurality or series of instructions to be executed by a processor in a hardware system, such as the processor  802 . Initially, the series of instructions may be stored on a storage device, such as the mass storage  818 . However, the series of instructions can be stored on any suitable computer readable storage medium. Furthermore, the series of instructions need not be stored locally, and could be received from a remote storage device, such as a server on a network, via the network interface  816 . The instructions are copied from the storage device, such as the mass storage  818 , into the system memory  814  and then accessed and executed by the processor  802 . In various implementations, a module or modules can be executed by a processor or multiple processors in one or multiple locations, such as multiple servers in a parallel processing environment. 
     Examples of computer-readable media include, but are not limited to, recordable type media such as volatile and non-volatile memory devices; solid state memories; floppy and other removable disks; hard disk drives; magnetic media; optical disks (e.g., Compact Disk Read-Only Memory (CD ROMS), Digital Versatile Disks (DVDs)); other similar non-transitory (or transitory), tangible (or non-tangible) storage medium; or any type of medium suitable for storing, encoding, or carrying a series of instructions for execution by the computer system  800  to perform any one or more of the processes and features described herein. 
     For purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the description. It will be apparent, however, to one skilled in the art that embodiments of the disclosure can be practiced without these specific details. In some instances, modules, structures, processes, features, and devices are shown in block diagram form in order to avoid obscuring the description. In other instances, functional block diagrams and flow diagrams are shown to represent data and logic flows. The components of block diagrams and flow diagrams (e.g., modules, blocks, structures, devices, features, etc.) may be variously combined, separated, removed, reordered, and replaced in a manner other than as expressly described and depicted herein. 
     Reference in this specification to “one embodiment”, “an embodiment”, “other embodiments”, “one series of embodiments”, “some embodiments”, “various embodiments”, or the like means that a particular feature, design, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. The appearances of, for example, the phrase “in one embodiment” or “in an embodiment” in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Moreover, whether or not there is express reference to an “embodiment” or the like, various features are described, which may be variously combined and included in some embodiments, but also variously omitted in other embodiments. Similarly, various features are described that may be preferences or requirements for some embodiments, but not other embodiments. 
     The language used herein has been principally selected for readability and instructional purposes, and it may not have been selected to delineate or circumscribe the inventive subject matter. It is therefore intended that the scope of the invention be limited not by this detailed description, but rather by any claims that issue on an application based hereon. Accordingly, the disclosure of the embodiments of the invention is intended to be illustrative, but not limiting, of the scope of the invention, which is set forth in the following claims.