Systems and Methods for Virtual Set-Top Support of an HTML Client
1. A method, comprising, at a server remote from a client device:
- executing an HTML-based virtual client application;
using the HTML-based virtual client application to;
traverse a Document Object Model (DOM) tree to identify differences between a set of sequential images in sequential video frames of a sequence of video frames to render a rendered image corresponding to a video frame, the rendered image associated with HTML commands; and
generate an HTML wrapper for the rendered image that includes data encoded in accordance with the differences identified by traversing the DOM tree; and
sending the HTML wrapper to the client device to be processed by an HTML-based application on the client device to enable the image to be displayed at a display coupled to the client device.
A server remote from a client device executes an HTML-based virtual client application. The server uses the HTML-based virtual client application to traverse a Document Object Model (DOM) tree to identify differences between a set of sequential images in sequential video frames of a sequence of video frames to render a rendered image corresponding to a video frame, the rendered image associated with HTML commands. The server uses the HTML-based virtual client application to generate an HTML wrapper for the rendered image that includes data encoded in accordance with the differences identified by traversing the DOM tree. The server sends the HTML wrapper to the client device to be processed by an HTML-based application on the client device to enable the image to be displayed at a display coupled to the client device.
- 1. A method, comprising, at a server remote from a client device:
executing an HTML-based virtual client application; using the HTML-based virtual client application to; traverse a Document Object Model (DOM) tree to identify differences between a set of sequential images in sequential video frames of a sequence of video frames to render a rendered image corresponding to a video frame, the rendered image associated with HTML commands; and generate an HTML wrapper for the rendered image that includes data encoded in accordance with the differences identified by traversing the DOM tree; and sending the HTML wrapper to the client device to be processed by an HTML-based application on the client device to enable the image to be displayed at a display coupled to the client device.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
- 13. A server system, comprising:
one or more processors; and memory storing one or more programs for execution by the one or more processors, the one or more programs including instructions for; executing an HTML-based virtual client application; sending the HTML wrapper to a client device to be processed by an HTML-based application on the client device to enable the image to be displayed at a display coupled to the client device.
- 14. A non-transitory computer-readable storage medium, storing one or more programs configured for execution by one or more processors of a server system, the one or more programs including instructions for:
executing an HTML-based virtual client application;
This application is a continuation of U.S. application Ser. No. 15/851,589, filed Dec. 21, 2017, entitled “Systems and Methods for Virtual Set-top Support of an HTML Client,” which claims priority and benefit to U.S. Provisional Application No. 62/438,946, filed Dec. 23, 2016, entitled “Systems and Methods for Virtual Set-top Support of an HTML Client.” These applications are hereby incorporated by reference in their entirety.
The present disclosure relates to the creation of an encoded video sequence, and more particularly to using scene information for encoding the video sequence and decomposing and sending the video sequence in a simplified HTML-encapsulated format that can be rendered by multiple generations of (e.g., any generation of) an HTML-language-based software application.
It is known to encode and transmit multimedia content for distribution within a network. For example, video content may be encoded as MPEG or H.264/5 video wherein pixel-domain data is converted into a frequency-domain representation, quantized, entropy encoded, and placed into an appropriate transport format (e.g., MPEG transport stream). The video stream can then be transmitted to a client device, decoded, and returned to the spatial/pixel domain for display on a display device.
The encoding of the video may be spatial, temporal, or a combination of both. Spatial encoding generally refers to the process of intra-frame encoding wherein spatial redundancy (information) is exploited to reduce the number of bits that represent a spatial location. Spatial data is converted into a frequency domain over a small region. In general, for small regions it is expected that the data will not drastically change and therefore in the region much of the information will be stored in low-frequency components with the higher-frequency components being at or near zero. Thus, the lack of high-frequency information in a small area is used to reduce the representative data size. Data may also be compressed using temporal redundancy. One method for exploiting temporal redundancy is through the calculation of motion vectors. Motion vectors establish how objects or pixels move between frames of video. Thus, a ball may move between a first frame and a second frame by several pixels in a specific direction. Thus, once a motion vector is calculated, the information about the spatial relocation of the ball information from the first frame to the second frame can be used to reduce the amount of information that is used to represent the motion in an encoded video sequence. In practical applications the motion vector is rarely a perfect match and an additional residual pixel representation is used to compensate for the imperfect temporal reference.
Motion-vector calculation is a time-consuming and processor-intensive step in compressing video content. Typically, a motion-search algorithm is employed to attempt to match elements within the video frames and to define motion vectors that point to the new location to which objects or portions of objects have moved. This motion search algorithm tries to find for each macroblock the optimal representation of that macroblock in past and/or future reference frames, and determines the vector to represent that temporal relation. The motion vector is subsequently used to minimize the residual pixel information that is compressed in the compression process. It would be beneficial if a mechanism existed that assists in the determination of these motion vectors.
Another time-consuming and processor-intensive component of the encoding process for more advanced codecs is the process to find the optimal macroblock type, partitioning of the macroblock, and the weighing properties of the slice. H.264, for example, has four of 16×16, nine of 8×8 and nine of 4×4 luma intra-prediction modes and four 8×8 chroma intra-prediction modes, and inter-macroblocks can be partitioned from as coarse as 16×16 to as fine grained as 4×4. In addition, it is possible to assign a weight and offset to the temporal references. A mechanism that defines or assists in finding these parameters directly would improve scalability.
Many of these complex video encoding/decoding concerns are, for the purposes of ordinary video program encoding and playback, addressed in hardware (e.g., by silicon chips). However, to utilize advanced capabilities of video encoding/decoding to aid a remote application in effectively serving a client device, these functions need to be executed outside of a hardware solution. Hence, the difficulty is substantial to exploit powerful image processing subsystems in an application software environment outside of hardware support. When considering the minimal computing power of many client-side consumer electronics devices, it would not be possible to execute an application that depends on such capabilities in the client.
A solution to the problems identified above is to run the client in the cloud, with output of the application being encoded and streamed as video along with certain software commands to assist in reconstructing various image components and properly rendering the result. The user interacting with the client of such systems will perceive the application that they are interacting with to be executing in the client whereas the actual execution is taking place on a remote server. The premise is that the client device would only need a minimal subset of support functions (e.g., the implementation of a return channel for user input) and that the complex function of displaying the user-interface (UI) elements was done by the device'"'"'s common capability to display a low-delay video stream. In practice, however, more and more functionality has been added to the client device to make this work for a variety of use cases (such as to work around the device'"'"'s latency, handle interactivity versus buffering (which adds delay to interactions of the user), achieve a user interface that is blended with video overlays, implement digital rights management (DRM) functions, etc.), so the promise of just requiring an ultra-thin client that essentially only decodes video to support such a system is increasingly less desirable.
However, by leveraging existing software on a client device (e.g., a set-top box), such as a simple browser, and providing simplified commands from a cloud-based application server, a true ‘run anywhere’ paradigm can be realized that can be executed on typical client devices. Complex HTML logic and commands are translated to simplified HTML commands that can be execute by multiple generations (e.g., essentially any generation) of an HTML-based program in an efficient manner such that the server-side execution of a complex HTML application can be tracked and decomposed into more primitive HTML elements that can be interpreted and results rendered on most devices (e.g., virtually any device) with an HTML browser system. This so-called simplified HTML can be defined as the subset of HTML commands that in common can be executed by a plurality of HTML browsers that run multiple generations (e.g., almost any generation) of the HTML language in current use on media playback devices (e.g., from different manufacturers) such as set-top boxes, smart TVs, mobile phones, tablets, and personal computers, among other devices capable of executing HTML commands.
In some embodiments, a fully standard-compliant HTML browser is run in the cloud and its rendered output is converted to a subset of HTML primitives and associated images so the target client device'"'"'s browser need only handle these primitives and draw respective images. For example, the output in the virtual display is encoded to several non-overlapping dirty rectangles, which are sent to the client device and decoded on an HTML canvas in the device'"'"'s memory.
Another approach is to traverse the Document Object Model (DOM) and group-related DOM nodes and convert them into images that can be transferred to the client and reused in a temporal manner. Rendering engines (e.g., Apple'"'"'s Webkit or Google'"'"'s Blink) already do this to facilitate GPU-assisted compositing of webpages, the idea being that for most screen updates (such as animations and scrolling) the pixel representations of these grouped DOM nodes do not change and once texture material is passed to the GPU it can be composited much more efficiently than when all rendering is done by the CPU without the additional support of the GPU. This also advantageously offloads the CPU for other tasks. This concept, with similar benefits, is also applicable to the model described above. The standard-compliant HTML browser running server-side (i.e., running in the cloud) uses the client device'"'"'s HTML browser as just a graphics engine with similar properties as a GPU. In some embodiments, because texture updates are expensive in terms of network bandwidth and delay, DOM nodes are grouped into textures, transferred to the device'"'"'s browser, and used in a temporal fashion by reusing the images, stored in a cache, to render multiple frames.
In accordance with some embodiments, a method is provided for creating a composited video-frame sequence for an application wherein the video-frame sequence is encoded per a predetermined specification, such as MPEG-2, H.264 or other block-based encoding protocol or variant thereof. A current scene state for the application is compared to a previous scene state wherein each scene state includes a plurality of objects. A video construction module determines if properties of one or more objects have changed (e.g., the object'"'"'s position, transformation matrix, texture, translucency, etc.) based upon a comparison of the scene states. If properties of one or more objects have changed, the delta between the object'"'"'s states is determined and used by a fragment-encoding module in the case in which the corresponding fragment has not already been generated and stored in a fragment-caching module. The information is used to define, for example, the motion vectors used by the fragment-encoding module in the construction of the fragments for the stitching module, which assembles the fragments, from which to build the composited video frame sequence.
In some embodiments, the information about the changes in the scene'"'"'s state is also used to decide whether a macroblock is to be encoded spatially, using an intra-encoded macroblock, or temporally, using an inter-encoded macroblock, and, given a certain encoding, what the optimal partitioning of the macroblock is. In some embodiments, the information about the changes in the scene'"'"'s state may also assist in finding the optimal weight and offset of the temporal reference to minimize the residual. The benefits of using scene state information in the encoding process include a gain in efficiency with respect to the resources used to encode the fragments, as well as improvements in the visual quality of the encoded fragments or to minimize the size of the encoded fragments because spatial relations in the current scene state or temporal relations between the previous scene state and current scene state can be more accurately determined.
Objects may be maintained in a two-dimensional coordinate system. Alternatively, two-dimensional (flat) objects may be maintained in a three-dimensional coordinate system, or a full three-dimensional object model may be maintained in a three-dimensional coordinate system. The objects may be kept in a hierarchical structure, such as a scene graph. Additional three-dimensional object or scene properties known to the trade may be used (e.g., perspective, lighting effects, reflection, refraction, fog, etc.).
The scene states (previous and current) may result from the output of an application engine such as an application execution engine. This cloud-based application execution engine may be a web browser, a script interpreter, operating system, or other computer-based environment that is accessed during operation of the application. The application execution engine may interface with the described system using a standardized API (application programming interface), such as, for example, OpenGL. The system may translate the scene representation as expressed through the API to a convenient internal representation or directly derive state changes from the API'"'"'s primitives.
The above-described method may be embodied as a computer program product where the computer program product includes a non-transitory computer readable medium having computer code thereon for performing the method and thus for creating an encoded video sequence. The method may be performed by a system that includes one or more processors that perform specified functions in the creation of the encoded video sequence. For example, the system includes the one or more processors and also includes memory storing instructions that, when executed by the one or more processors, cause the system to perform the method.
In some embodiments, a process translates certain scene-graph changes to pixel representations that are encoded in data structures. The data structures may be encoded in HTML wrappers and transmitted to a client application on a client device to be decoded and rendered by the client for display. The data structures can be any graphical representation that can be encoded using any common HTML command to convey the representation to a standard HTML-based client application such as a web browser. In this context, and by way of example, a common HTML command means a simplified HTML language command set which utilizes only the basic functions of HTML4 common to HTML interpreters found in the majority of (e.g., most) consumer electronics devices that employ HTML interpreters.
Information layers prepared by the server for transmission toward and subsequent use by a client application can be any information representation that is decodable by the client application. For example, the client application could be any standard web browser such as Microsoft'"'"'s Internet Explorer, Google'"'"'s Chrome, and Mozilla'"'"'s Firefox, among others. The client application could also be a custom-written software application that utilizes an HTML interpreter as an imbedded element.
The foregoing features of embodiments will be more readily understood by reference to the following detailed description, taken with reference to the accompanying drawings, in which:
As used in this description and the accompanying claims, the following terms shall have the meanings indicated, unless the context otherwise requires:
“Video Construction Module” compares scene states and derives which areas on the display device are to be changed. The video construction module determines how to map the changed areas to encoded fragments that can be stitched together and maintains a cache of already encoded fragments. If fragments are not available in an encoded form, the video construction module interacts with a fragment encoding module to encode the fragment.
“Fragment Caching Module” stores fragments in volatile memory (e.g., the system'"'"'s RAM) or persistent memory (e.g., a disc-based file system).
“Fragment Encoding Module” transforms graphical data and associated information about spatial and/or temporal relations into one or more encoded fragments.
“Stitching Module” receives as input one or more fragments (e.g., MPEG encoded elements) along with layout information and then constructs complete video frames for a video sequence (e.g., MPEG video frames for an MPEG elementary stream).
“Scene” is a model of an image generated by an application execution engine consisting of objects and their properties;
“Scene state” is the combined state of all objects and their properties at a moment in time.
“DOM” (document object model) is a convention for representing and interacting with objects in markup languages such as HTML and XML documents.
“DOM tree” is a representation of a DOM (document object model) for a document (e.g., an HTML file) having nodes wherein the topmost node is the document object.
“CSS” (cascading style sheets) provide the graphical layout information for a document (e.g., an HTML document) and how each object or class of objects should be represented graphically. The combination of a DOM object and the corresponding CSS files (i.e. layout) is referred to as a rendering object.
“Render layer” is a graphical representation of one or more objects of a scene graph state. For example, a group of objects that have a geographical relationship such as an absolute or a relative position to each other may form a render layer. An object may be a separate render layer if, for example, the object is transparent, has an alpha mask, or has a reflection. A render layer may be defined by a screen area, such as a screen area that can be scrolled. A render layer may be designated for an area that may have an overlay (e.g., a pop up). A render layer may be defined for a portion of a screen area if that area is to have an applied graphical filter (e.g., a blur, color manipulation, or shadowing). A layer may be defined by a screen area that has associated video content. Thus, a render layer may be a layer within a scene graph state or a modification of a scene graph state layer in which objects are grouped according to a common characteristic.
“Fragment” is one or more MPEG-encoded macroblocks, as disclosed in U.S. patent application Ser. No. 12/443,571, filed Oct. 1, 2007, the contents of which are incorporated by reference in their entirety. A fragment may be intra-encoded (spatially-encoded), inter-encoded (temporally-encoded), or a combination thereof.
As shown, the application execution environment 110 may produce an output for graphical processing. Examples of application execution environments 110 include both computer software and hardware and combinations thereof for executing the application. Applications can be written for certain application execution environments including WebKit, JAVA compilers, script interpreters (e.g., Perl etc.) and various operating systems including, for example, iOS and Android OS.
The video construction engine 170 takes advantage of the data that it receives from the application execution environment 110 to exploit redundancies in requests for the presentation of information within user sessions and between user sessions as well as determining motion changes of objects from a previous video frame or scene graph state to a current frame or scene graph state. The system of
The video construction engine 170 may receive OpenGL data and can construct a scene graph from the OpenGL data. The video construction engine 170 compares the current scene graph state to one or more previous scene graph states to determine if motion occurs between objects within the scene. If motion occurs between the objects, this motion can be translated into a motion vector and this motion vector information can be passed to an encoding module 150. Thus, the encoding module 150 need not perform a motion vector search and can add the motion vectors into the video frame format (e.g., MPEG video frame format). MPEG elements can be constructed that are encoded MPEG macroblocks that are inter-frame encoded. These macroblocks are passed to the stitching module 160, which receives stitching information about the video frame layout and stitches together encoded MPEG elements to form complete MPEG encoded video frames in accordance with the scene graph. Either simultaneously or in sequence, the video construction engine 170 may hash the parameters for objects within the scene graph according to a known algorithm. The video construction engine 170 compares the hash value to hash values of objects from previous scene graphs and if there is a match within the table of hashes, the construction engine 170 locates MPEG-encoded macroblocks (i.e., MPEG elements) that are stored in memory and are related to the hash. These MPEG elements can be passed directly to the stitching engine 160, which stitches the MPEG elements together to form complete MPEG-encoded video frames. Thus, the output of the stitching module 160 is a sequence of encoded video frames that contain both intra-frame encoded macroblocks and inter-frame encoded macroblocks. Additionally, the video construction engine 170 outputs pixel-based information to the encoding engine 150. This pixel-based information may be encoded using spatial based encoding algorithms including the standard MPEG DCT processes. This pixel-based information results from changes in the scene (visual display) in which objects represented by rectangles are altered. The encoded macroblocks can then be passed to the stitching engine 160.
The application execution engine may be proximate to the client device, operational on the client device, or may be remote from the client device, such as in a networked client/server environment. The control signal for the dirty rectangle causes the application execution engine to generate a scene graph having a scene graph state that reflects the changes to the screen (e.g., dirty rectangles of the screen display). For example, the application execution environment 110 may include a web browser operating within an operating system. The web browser represents a page of content in a structured hierarchical format such as a DOM and corresponding DOM tree. Associated with the DOM tree is a CSS that specifies where and how each object is to be graphically rendered on a display device. The web browser creates an output that can be used by a graphics engine. The output that is produced is the scene graph state, which may have one or more nodes and objects associated with the nodes forming a layer (i.e. a render layer). As requests occur from a client device for updates or updates are automatically generated (e.g., in a script), a new or current scene graph state is generated. Thus, the current scene graph state represents a change in the anticipated output video that will be rendered on a display device.
Once the current scene graph state is obtained 200 by the video construction engine 170, the scene graph state can be compared 210 with a previous scene graph state. The comparison of scene graph states can be performed hierarchically by layer and by object. For each object associated with a node, differences in the positions of objects from the scene graph states can be identified as well as differences in characteristics, such as translucence and lighting.
For example, in a simple embodiment, a circle may be translated by a definable distance between the current scene graph state and a previous scene graph state. The system queries whether one or more objects within the scene graph state have moved. If one or more objects have been identified as moving between scene graph states, information about the motion translation is determined 220. This information may require the transformation of position data from a three-dimensional world coordinate view to a two-dimensional screen view so that pixel-level motion (two-dimensional motion vectors) can be determined. This motion information can then be passed on to an encoder (e.g., encoding engine 150) in the form of a motion vector 230. Thus, the motion vector information can be used by the encoder to create inter-frame encoded video frames. For example, the video frames may be P- or B-frame MPEG-encoded frames.
In addition to objects moving, scene elements may also change. Thus, a two-dimensional representation of information to be displayed on a screen can be ascertained from the three-dimensional scene graph state data. Rectangles can be defined 240 as dirty rectangles, which identify data on the screen that has changed. These rectangles can by hashed 250 according to a known formula that will take into account properties of the rectangles. The hash value can then be compared 260 to a listing of hash values associated with rectangles that were updated from previous scene graph states. The list of hash values may be for the current user session or for other user sessions. Thus, if a request for a change in the content being displayed in an application is received from multiple parties, the redundancy in information being requested can be exploited and processing resources conserved. For example, if the hash matches a hash within the searchable memory (260—Yes), encoded graphical data (e.g., either a portion of an entire video frame of encoded data or an entire frame of encoded data) that is linked to the hash value in the searchable memory is retrieved 270 and the data can be combined with other encoded video frames.
Additionally, if a rectangle is identified as being dirty and a hash is not identified (260—No), the spatial information for that rectangle can be passed to the encoder, which will spatially encode the data for the rectangle. As used herein, the term content may refer to a dirty rectangle or an object from a scene graph state.
The application execution environment 300 creates a current scene graph 320. The current scene graph may be translated using a library of functions, such as the OpenGL library 330. The resulting OpenGL scene graph state 340 is passed to the video construction engine 310. The OpenGL scene graph state 340 for the current scene graph is compared to a previous scene graph state 350 in a comparison module 360. This may require the calculation and analysis of two-dimensional projections of three-dimension information that are present within the scene graph state. Such transformations are known by one of ordinary skill in the art. It should be recognized that OpenGL is used herein for convenience and that a scene graph state may be created in other ways. Thus, the scene graph state need not be converted into OpenGL before a scene graph state comparison is performed.
Differences between the scene graphs are noted and dirty rectangles can be identified 370. A dirty rectangle 370 represents a change to an identifiable portion of the display (e.g., a button changing from an on-state to an off-state). There may be more than one dirty rectangle that is identified in the comparison of the scene graph states. Multiple objects within a scene may change simultaneously, causing the identification of more than one dirty rectangle.
From the list of dirty rectangles 370, a list of MPEG fragment rectangles 380 (i.e. spatially defined fragments, such as a plurality of macroblocks on macroblock boundaries) can be determined for the dirty rectangle (or for each dirty rectangle). The term MPEG fragment rectangle as used in the present context refers to spatial data and not frequency-transformed data and is referred to as an MPEG fragment rectangle because MPEG uses a block-based formatting schema (i.e. macroblocks that are generally 16×16 pixels in shape). Defining dirty rectangles as MPEG fragment rectangles can be achieved by defining an MPEG fragment rectangle for a dirty rectangle wherein the dirty rectangle is fully encompassed within a selection of macroblocks. Thus, the dirty rectangle fits within a rectangle composed of spatially defined macroblocks. In some embodiments, the dirty rectangles are combined or split to limit the number of MPEG fragment rectangles that are present or to avoid small changes in large rectangles.
For each MPEG fragment rectangle, a listing of nodes according to z-order (depth) in the scene graph that contributed to the rectangle contents is determined. This can be achieved by omitting nodes that are invisible, have a low opacity, or have a transparent texture.
For each MPEG fragment rectangle, a hash value 382 is created based upon relevant properties of all nodes that have contributed to the rectangle contents (e.g., absolute position, width, height, transformation matrix, hash of texture bitmap, opacity). If the cache contains an encoded MPEG fragment associated with that hash value, then the encoded MPEG fragment is retrieved from the cache. In the present context, the term encoded MPEG fragment refers to a portion of a full frame of video that has been encoded according to an MPEG standard. The encoding may be DCT encoding for blocks of data or may also include MPEG-specific header information for the encoded material. If the calculated hash value does not match an MPEG fragment in the cache, then the dirty rectangle contents (using the scene graph state) are rendered from a three-dimensional world view to a two-dimensional screen view and the rendered pixel data (i.e. spatial data) are encoded in an encoder, such as an MPEG encoder 385. The encoded MPEG data (e.g., encoded MPEG fragment(s) 390) for the scene are stored into the cache.
As part of the encoding process, the fragment is analyzed to determine whether the encoding can best be performed as ‘inter’ encoding (an encoding relative to the previous screen state) or as ‘intra’ encoding (an independent encoding). Inter-encoding is preferred in general because it results in less bandwidth and may result in higher quality streams. All changes in nodes between scene graphs are determined including movement, changes of opacity, and changes in texture for example. The system then evaluates whether these changes contribute to a fragment, and whether it is possible to express these changes efficiently in the video codec'"'"'s primitives. If the evaluation indicates that changes to dominant nodes can be expressed well in the video codec'"'"'s primitives, then the fragment is inter-encoded. These steps are repeated for every screen update. Since the ‘new scene graph’ will become the ‘previous scene graph’ in the next screen update, intermediate results can be reused from previous frames.
Since objects may be maintained in a two-dimensional coordinate system, as two-dimensional (flat) objects in a three-dimensional coordinate system, or as full three-dimensional object models in a three-dimensional coordinate system, a mapping is made for each object from the scene'"'"'s coordinate system to the current and previous field of view. The field of view is the extent of the observable scene at a given moment. For each object on the list of changed, added, or removed objects, it is determined in step 1202 whether the object'"'"'s change, addition or removal was visible in the field of view of the scene'"'"'s current state or the field of view of the previous state and what bounding rectangle represented that change in states.
Bounding rectangles pertaining to the objects'"'"' previous and current states may overlap in various constellations. Fragments, however, do not overlap. Before fragments are identified, overlapping conditions are resolved. This is done in step 1203 by applying a tessellation (i.e., tiling) process as depicted in
Suppose that overlapping rectangles 1301 for object A and 1302 for object B as depicted by
Returning to step 1203, the tessellation process is first applied to the rectangles pertaining to the objects'"'"' previous states. When an object changes position or its transformation matrix changes, graphical data may be revealed that was obscured in the previous state. The object'"'"'s new bounding rectangle typically only partially overlaps with the object'"'"'s previous bounding rectangle. A fragment is made that encodes this exposure. Therefore, step 1203 first applies the tessellation process to all bounding rectangles of the objects'"'"' previous states. Subsequently, the bounding rectangles of the objects'"'"' current states are added to the tessellation process. The resulting rectangles represent the fragments that constitute the update from the previous scene state to the current scene state. Steps 1204 to 1208 are performed for each fragment.
Step 1204 determines the “fragment tessellation” process. The resulting rectangles represent the fragments that constitute the update, which objects contribute to the fragment'"'"'s pixel representation, and which contributing object is the dominant object. If an object dominates the fragment'"'"'s pixel representation, the object'"'"'s rectangle pertaining to the previous state is used as a reference window for temporal reference and the fragment may be inter-encoded. If multiple objects dominate the fragment'"'"'s representation, a union of multiple previous state rectangles may be used as a reference window. Alternatively, the fragment'"'"'s current bounding rectangle may be used as a reference window.
The fragment objects contribute to the fragment'"'"'s pixel representation and to which contributing object is the dominant object. If an object dominates the fragment'"'"'s pixel representation, the object'"'"'s rectangle pertaining to the previous state objects and encoding attributes (e.g., such as profile, level or other codec specific settings, differences in quantization, use of the loop filter, etc.) may be used to distinguish encoder-specific variants of otherwise equivalent fragments. If the fragment has a reference window, the hash is extended with the coordinates of the reference window in pixel units, the properties of the objects contributing to the reference window, and the transformation matrix of the dominant object. Hence, the hash as determined in step 1205 uniquely describes the fragment that encodes the scene'"'"'s current state for the fragment'"'"'s rectangle and, if a temporal relation can be established, a transition from the scene'"'"'s previous state to the current.
In step 1206 the hash uniquely identifying the fragment is checked against a hash table. If the hash cannot be found in the hash table, the fragment description is forwarded to the fragment encoding module and encoded in step 1207. If the hash is found in the hash table, the associated encoded fragment is retrieved from the fragment caching module and transferred to the stitching module (i.e., stitcher) in step 1208.
In step 1207, fragments are encoded from pixel data pertaining to the current scene state and, if available, pixel data pertaining to the previous scene state and metadata obtained from the scene'"'"'s state change (e.g., the type of fragment, transformation matrices of the objects contributing to the fragment, changes in translucency of the objects) into a stitchable fragment. Many efficiency and quality improvements may be achieved in step 1207. Many steps in the encoding process, such as the intra/inter decision, selection of partitions, motion estimation, and weighted prediction parameters benefit from the metadata because it allows for derivation of the spatial or temporal relations relevant for the encoding process. Once a fragment has been encoded, the fragment is stored in the fragment caching module and transferred to the stitching module in step 1208.
Step 1208 forwards stitchable fragments to the stitching module. Objects are generally handled as atomic entities, except for the background object. The background object is a fixed object at infinite distance that spans the entire field of view. A consequence of treating the background as an atomic entity would mean that small changes to the background would potentially permeate in the hash values of all fragments in which the background is visible. Therefore, in some embodiments the background texture is treated as described in U.S. Pat. No. 9,123,084, which is incorporated by reference in its entirety. Changes to the background thus only have consequences for fragments overlapping the dirty rectangles of the background.
The following examples relate to embodiments using a DOM-based application execution engine 1101, scene graph module 1104, and video construction engine 1107 (
The tree-like structure provides a hierarchical representation wherein attributes of parent objects can be attributed to the child objects. The root object represents the entire scene 610, while child nodes of a certain node may contain a decomposition of the parent node into smaller objects. The nodes may contain a texture (bitmap object), a 3D transformation matrix that specifies how the texture is positioned in a 3D space, and graphical attributes such as visibility and transparency. A child node inherits all attributes, transformations, and filters from the parent node.
For example, movement between scene graphs for an object such as the “cover list” 620 would indicate that each of the child objects (cover1, cover2, cover3, and cover4) 621, 622, 623, 624 would also move by an equal amount. As shown, the screen shot of
The scene graph comparison between the previous scene graph and the current scene graph may be performed in the following manner wherein the scene graph is transformed from a 3D to a 2D space. A node in a scene graph corresponds to an object having a texture (2D bitmap) and a transformation indicating how that object is floating in space. It also contains the z-order (i.e., the absolute order to render things). In OpenGL the transformation consists of a matrix:
- m m m m
- m m m m
- m m m m
- m m m m
This transformation is applied to an element ‘a’ in a 3D space by matrix multiplication. The element ‘a’ is identified by four points: the origin and the three top positions of the object in x, y and z direction. The bottom row elements m, m and m specify translation in 3D space. Elements m, m, m, m, m, m, m, m, and m specify the three top positions of an object (i.e., the furthest point out in x, y, and z directions) where that particular point will end up by using matrix multiplication. This allows for object or frame rotation, slanting, shearing, shrinking, zooming, and translation etc. and repositioning of the object in world space at any time.
When two transformations have been applied to an object per matrix ‘m’ (from the previous scene graph) and ‘n’ (from the current scene graph), the “difference” between the two is m−n, as determined through matrix subtraction. The result of the matrix subtraction gives the amount of rotation, slanting, shearing, shrinking, zooming, translation etc. that has been performed to the object between the previous frame and the current frame.
Projecting a 3D image onto a 2D surface is well known in the art. In one embodiment, the system first calculates projections of the 3D scene graphs onto a 2D plane, where the transformation matrices also become 2D. The motion vector (obtained by subtracting the transformation matrices) is then 2D and can be directly applied by the MPEG encoder. One motion vector per (destination) macroblock is passed, if motion was detected. The motion vector has a defined (x, y) direction, having a certain length that indicates direction and distance covered between the current frame and the previous frame. The encoder then assumes that the reference information for a macroblock is in the reverse direction of the motion vector.
In some embodiments, hashing and caching of dirty rectangles is performed on individual layers of a scene graph state instead of on 2D projections of these layers. Hashing and caching of dirty rectangles on individual layers of a scene graph state is more efficient compared to hashing and caching of 2D projections of these layers, because the layers represent independent changes.
It can be seen from these figures and the description above that the invention presents a significant improvement in providing a practical means of conveying a complex user-interactive application often rendered in complex and advanced HTML language, such as HTML5, to a simplified (e.g., HTML4-compatible, or compatible with HTML5 without one or more extensions) HTML browser environment found on a wide variety of consumer devices such as smart TVs, mobile phones, tablets, and low-cost (e.g., thin-client) Internet set-top boxes.
The present invention may be embodied in many different forms, including, but in no way limited to, computer program logic for use with a processor (e.g., a microprocessor, microcontroller, digital signal processor, or general purpose computer), programmable logic for use with a programmable logic device (e.g., a Field Programmable Gate Array (FPGA) or other PLD), discrete components, integrated circuitry (e.g., an Application Specific Integrated Circuit (ASIC)), or any other means including any combination thereof. In an embodiment of the present invention, predominantly all of the reordering logic may be implemented as a set of computer program instructions that is converted into a computer executable form, stored as such in a computer-readable medium (e.g., a non-transitory computer-readable storage medium), and executed by a microprocessor within the array under the control of an operating system.
Computer program logic implementing all or part of the functionality previously described herein may be embodied in various forms, including, but in no way limited to, a source code form, a computer executable form, and various intermediate forms (e.g., forms generated by an assembler, compiler, networker, or locator). Source code may include a series of computer program instructions implemented in any of various programming languages (e.g., an object code, an assembly language, or a high-level language such as Fortran, C, C++, JAVA, or HTML) for use with various operating systems or operating environments. The source code may define and use various data structures and communication messages. The source code may be in a computer executable form (e.g., via an interpreter), or the source code may be converted (e.g., via a translator, assembler, or compiler) into a computer executable form.
The computer program may be fixed in any form (e.g., source code form, computer executable form, or an intermediate form) either permanently or transitorily in a tangible storage medium, such as a semiconductor memory device (e.g., a RAM, ROM, PROM, EEPROM, or Flash-Programmable RAM), a magnetic memory device (e.g., a diskette or fixed disk), an optical memory device (e.g., a CD-ROM), a PC card (e.g., PCMCIA card), or other memory device. The computer program may be fixed in any form in a signal that is transmittable to a computer using any of various communication technologies, including, but in no way limited to, analog technologies, digital technologies, optical technologies, wireless technologies, networking technologies, and inter-networking technologies. The computer program may be distributed in any form as a removable storage medium with accompanying printed or electronic documentation (e.g., shrink wrapped software or a magnetic tape), preloaded with a computer system (e.g., on system ROM or fixed disk), or distributed from a server or electronic bulletin board over the communication system (e.g., the Internet or World Wide Web.)
Hardware logic (including programmable logic for use with a programmable logic device) implementing all or part of the functionality previously described herein may be designed using traditional manual methods, or may be designed, captured, simulated, or documented electronically using various tools, such as Computer Aided Design (CAD), a hardware description language (e.g., VHDL or AHDL), or a PLD programming language (e.g., PALASM, ABEL, or CUPL.)
While the invention has been described with reference to specific embodiments, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended clauses.
Embodiments of the present invention may be described, without limitation, by the following clauses. While these embodiments have been described in the clauses by process steps, an apparatus comprising a computer with associated display capable of executing the process steps in the clauses below is also included in the present invention. Likewise, a computer program product including computer executable instructions for executing the process steps in the clauses below and stored on a computer readable medium is included within the present invention.