Overlay rendering of user interface onto source video

A method of combining an interactive user interface for generating a blended output that includes the interactive user interface and one or more supplemental images. At a client device remote from a server, a video stream that contains an interactive user interface is received from the server using a first data communications channel configured to communicate video content, and a command that relates to an interactive user interface is transmitted to the server. In response to the transmitting, an updated user interface is received from the server using the first data communications channel, and one or more supplemental images for supplementing the interactive user interface are received using a second data communications channel different from the first data communications channel. The updated user interface and the one or more supplemental images are blended to generate a blended output, which is transmitted toward the display device for display thereon.

TECHNICAL FIELD

The present invention relates to interactive video distribution systems, and more particularly to blending a source video with an interactive user interface to generate a single image, where the source video and interactive user interface are separately provided.

BACKGROUND ART

It is known in the prior art to provide interactive user interfaces for television programs. Such interactive user interfaces include, for example, electronic program guides (EPG) that may be manipulated to search for broadcast programs or schedule recordings. Interactive user interfaces also include simple video games, menuing systems to access video on demand, and other similar such mechanisms.

Interactive user interfaces may be combined with source video, such as video on a broadcast or cable channel. There are two broad ways to combine such interfaces with source video: scale down the source video and fill the rest of the screen with the interactive user interface, or keep the source video full-screen but overlay the user interface onto the screen. As an example of the first combination, modern EPGs often show dynamically-generated channel information with a small preview window that shows video for a current channel. As an example of the second combination, television sets often provide volume controls as elements that overlay an area of the screen, typically near the bottom or along one side, while continuing to display the underlying source video content full-screen.

The latter method to combine user interfaces with source video can itself be broken into two different categories: opaque user interfaces and translucent, or partially transparent, user interfaces. Different techniques can be used for these different categories. For example, if it is known in advance that a user interface will be opaque, then the pixels of the underlying source video content may be discarded at the beginning of the overlay process. This ability to discard pixels simplifies processing of the overlays and permits compositing of the user interface directly into the source image. For certain block-based encoding schemes, compositing can be accomplished at a block level. However, for partially transparent user interfaces, the underlying pixels must be retained and blended with the user interface.

It is also known in the art to overlay images using blending. For purposes of the present disclosure, “blending” refers to a process of alpha compositing; that is, the process of combining two colors using a transparency coefficient, a. Using this technique, each pixel of each image may be viewed as being associated with four values: three color values and one alpha value, each between 0.0 and 1.0, either by storing these values per pixel or in a lookup table such as for example a palette. If the color values are red-green-blue, for example, then these four values are denoted RGBA. Alpha blending takes as input the RGBA values of a foreground pixel and a background pixel, and produces as output a pixel having RGBA values color(output)=α(f)*color(f)+(1−α(f))*color(b) and α(output)=α(f)+α(b)*(1−α(f)), where α(f) and α(b) are the transparency coefficients of the foreground and background pixels, respectively. In other words, the colors and transparency coefficients of the output are a weighted average of the foreground and background pixel, using “α” as the weight. Thus, if α=0.0 in the foreground pixel, then the colors in the output pixel are the same as that of the background (that is, the foreground pixel is not visible). If α is increased from 0.0 toward 1.0, more of the foreground pixel becomes visible, until when α=1.0 the color of the output pixel is the same as that of the foreground pixel (that is, the background pixel is completely overlaid by the foreground pixel).

However, it is generally disadvantageous to blend user interfaces at the server (e.g., at a cable headend), for a number of reasons. First, a typical television provider will have hundreds of thousands or millions of subscribers, a significant portion of whom will, at any given time, require interactive user interfaces. Each subscriber may be watching a different source video, and blending all of these source videos with any number of user interfaces is a problem that does not scale well. Second, blending a user interface with a source video requires access to the pixels of the source video, but the source video that is broadcast is typically ingested from a content provider, encoded according to a transmission encoding that exceeds available computational power. Third, a significant latency may be caused by the blending process, creating an unacceptable ‘sluggishness’ in the response of the user interface.

SUMMARY OF THE EMBODIMENTS

Various embodiments of the invention overcome the disadvantages of blending, at the server, interactive user interfaces with underlying source video in two distinct ways. First, many client devices, such as set top boxes or smart televisions, have the ability to perform alpha blending. Thus, it is possible to transmit the user interface from a remote server, such as one found at a cable headend, to the client device, on demand and out-of-band using a separate protocol, such as a modified RFB or XRT protocol. Second, even if a client device does not have the ability to perform alpha blending locally, such blending can be accelerated at the remote server through a combination of image caching and reconstruction of the client device decoder state to the point where blending becomes a scalable operation.

Some implementations include a method of providing, at a client device, an interactive user interface for generating an output, for a display, that includes a source video and an interactive user interface. The method includes receiving, at a client device remote from a server, the source video from the server using a first data communications channel configured to communicate video content, wherein the first data communications channel comprises a quadrature amplitude modulation (QAM) protocol. Furthermore, the method includes transmitting to the server a command related to an interactive user interface, and receiving, in response to the transmitting, one or more images of the interactive user interface using a second data communications channel different from the first data communications channel, wherein the second data communications channel comprises a transmission control protocol over internet protocol (TCP/IP) protocol. The source video is blended with the received one or more images to generate an output, and the output is transmitted toward a display device for display thereon.

In some embodiments, the interactive user interface comprises a menu.

In some embodiments, the received video content is encoded using an MPEG specification, an AVS specification, or a VC-1 specification. Furthermore, in some embodiments, the one or more images of the interactive user interface are encoded using a bitmap (BMP) file format, a portable network graphics (PNG) file format, a joint photographic experts group (JPEG) file format, or a graphics interchange format (GIF) file format.

In some embodiments, each image of the one or more images is associated with a corresponding transparency coefficient, and wherein blending the source video with the received one or more images comprises blending according to the transparency coefficient.

In some embodiments, wherein the blending comprises blending in a spatial domain.

In another aspect, a method includes providing, at a server, an interactive user interface for generating a output, for a display, that includes the interactive user interface and a source video. The method includes transmitting frames of a source video toward a client device, remote from the server, using a data communications channel configured to communicate video content, while simultaneously buffering in a memory of the server a plurality of encoded frames from the source video for subsequent transmission to the client device. The buffered frames include a first frame that is intra-encoded and one or more additional frames that are inter-encoded based on the first frame. Responsive to receiving from the client device a command that relates to the interactive user interface, the method includes determining a buffered frame in the plurality of buffered frames that corresponds to a time associated with the command, and blending the determined frame with one or more images of the interactive user interface to generate an output. Using the data communications channel, the output is transmitted toward the client device for display on the display device.

In some embodiments, transmitting the frames of the source video and transmitting the output frame each comprise transmitting according to a screen resolution or a screen dimension of the display device.

In some embodiments, the interactive user interface comprises a menu.

In some embodiments, the encoding specification is an MPEG specification, an AVS specification, or a VC-1 specification. Furthermore, in some embodiments, the one or more images of the interactive user interface are encoded using a bitmap (BMP) file format, a portable network graphics (PNG) file format, a joint photographic experts group (JPEG) file format, or a graphics interchange format (GIF) file format.

In some embodiments, the data communications channel comprises at least one of: quadrature amplitude modulation (QAM) using a cable network infrastructure, user datagram protocol over internet protocol (UDP/IP) using an internet protocol television (IPTV) infrastructure, or hypertext transfer protocol (HTTP) using a public or private internet infrastructure.

In some embodiments, each image of the one or more images is associated with a corresponding transparency coefficient, and wherein blending the determined frame with the one or more images comprises blending according to the transparency coefficient.

In some embodiments, blending the determined frame with one or more images includes (i) decoding the determined frame according to the encoding specification to generate a decoded frame; (ii) blending the decoded frame with the one or more images in a spatial domain to generate a blended frame; and (iii) encoding the blended frame according to the encoding specification to generate the output frame. Furthermore, in some implementations, encoding the blended frame comprises searching for motion vectors.

In some embodiments, the output frame is encoded according to the encoding specification.

In yet another aspect, a method includes combining, at a client device, an interactive user interface for generating a blended output, for a display, that includes the interactive user interface and one or more supplemental images. The method includes receiving, at a client device remote from a server, an interactive user interface from the server using a first data communications channel configured to communicate video content. Furthermore, the method includes transmitting to the server a command that relates to an interactive user interface, and receiving, in response to the transmitting, an updated user interface from the server using the first data communications channel, and the one or more supplemental images for supplementing the interactive user interface using a second data communications channel different from the first data communications channel. The updated user interface and the one or more supplemental images are blended to generate a blended output, and the blended output is transmitted toward the display device for display thereon.

In some embodiments, the interactive user interface comprises a source video stitched with user interface content.

In some embodiments, the encoding specification is an MPEG specification, an AVS specification, or a VC-1 specification.

In some embodiments, the first data communications channel comprises at least one of: quadrature amplitude modulation (QAM) using a cable network infrastructure, user datagram protocol over internet protocol (UDP/IP) using an internet protocol television (IPTV) infrastructure, or hypertext transfer protocol (HTTP) using a public or private internet infrastructure.

In some embodiments, the one or more supplemental images are encoded using a bitmap (BMP) file format, a portable network graphics (PNG) file format, a joint photographic experts group (JPEG) file format, or a graphics interchange format (GIF) file format.

In some embodiments, the second data communications channel comprises at least one of transmission control protocol over internet protocol (TCP/IP), remote frame buffer (RFB) protocol, and extended remoting technology (XRT) protocol.

In some embodiments, each supplemental image of the one or more supplemental images is associated with a corresponding transparency coefficient, and wherein blending the updated user interface with the one or more supplemental images comprises blending according to the transparency coefficient.

In some embodiments, blending comprises blending in a spatial domain.

In some embodiments, the command is a request for secure content, wherein the one or more supplemental images are received from a third party server, and the second data communications channel uses a secure transport protocol.

In yet another aspect, the method includes providing, at a server, an interactive user interface for generating a blended output, for a display, that includes the interactive user interface and one or more supplemental images. The method includes transmitting, at a server remote from a client device, the interactive user interface from a server using a first data communications channel configured to communicate video content, and receiving a command that relates to the interactive user interface. Furthermore, the method includes generating an updated interactive user interface, blending the updated user interface and the one or more supplemental images to generate a blended output frame, and transmitting the blended output frame toward a client device for display on a display device thereon.

In some embodiments, the method further includes transmitting the updated interactive user interface toward the client device for display on the display device thereon, and switching between transmitting the blended output frame and transmitting the updated interactive user interface.

In some embodiments, the encoding specification is an MPEG specification, an AVS specification, or a VC-1 specification.

In some embodiments, the first data communications channel comprises at least one of: quadrature amplitude modulation (QAM) using a cable network infrastructure, user datagram protocol over internet protocol (UDP/IP) using an internet protocol television (IPTV) infrastructure, or hypertext transfer protocol (HTTP) using a public or private internet infrastructure.

In some embodiments, the image format of the one or more supplemental images is a bitmap (BMP) file format, a portable network graphics (PNG) file format, a joint photographic experts group (JPEG) file format, or a graphics interchange format (GIF) file format.

In some embodiments, the method includes first determining that the client device is not capable of overlaying.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

Definitions

“Video” means both silent moving images and moving images accompanied by sound, except where otherwise indicated.

An “encoding specification” is a specification according to which video data are encoded by a transmitting electronic device and decoded by a receiving electronic device. Examples of encoding specifications are MPEG-2, MPEG-4, AVS, and VC-1.

A “client device” is an electronic device capable of receiving and decoding data according to an encoding specification for display on a display device. Examples of client devices include cable and satellite set top boxes, some video game consoles, and some televisions.

FIG. 1schematically shows a system in accordance with one embodiment of the invention. This embodiment includes a client device10that provides an output display signal to a display device11. The client device10generally receives signals, such as linear broadcast television signals, from one or more servers12, by way of a first data communications network131. The client device10also receives images that form an interactive user interface, such as electronic program guide signals, by way of a second data communications network132. The client device10then combines these signals to generate the output display signal. The aforementioned elements are now described in more detail.

The client device10may be implemented as a set top box, a video game console, a television, or other electronic device known in the art. The client device10includes an overlay module101that is capable of overlaying an image on an input video signal to generate an output video signal as a sequence of composite images. The operation of the overlay module101is described in more detail in connection withFIG. 2. The client device10also includes a video decoder102, which is capable of decoding audiovisual data that was encoded according to an encoding specification. Such video decoders are well known in the art, and may be implemented as an integrated circuit. Audiovisual data typically are encoded to reduce size for transmission through the data communications network131.

The client device10also has several input/output (I/O) ports103. One I/O port103is used to receive audiovisual data from the data communications network131, while another is used to receive images from the data communications network132. Another I/O port may be used in some embodiments to receive images that comprise an interactive user interface. In other embodiments, the same I/O port is used to receive both the audiovisual data and the interactive user interface images. Another I/O port is used to accept user input in the form of commands. Some commands may instruct the client device10to tune to a different channel (i.e., to receive different audiovisual data from the data communications network131or from another data network such as the Internet). Other commands may instruct the client device to record audiovisual data, either as it arrives at the client device10or at a future time and on a specified channel. Some commands will cause the display of an interactive user interface, while other commands will not. Various embodiments of the present invention are directed toward processing of commands that cause the display of such a user interface. The I/O ports103may be implemented using hardware known in the art, such as an IR receiver to interface with a remote control, a coaxial jack to interface with a cable television distribution network, a wired or wireless Ethernet port to interface with an Ethernet network, a video jack to provide the output display signal to the display device11, and so on. The display device11itself may be implemented as a standard CRT, LCD, LED, or plasma monitor as is known in the art, or other similar device.

The one or more servers12may be implemented using computer equipment known in the art; however their functions are novel when operated in accordance with various embodiments of the present invention. In accordance with some embodiments of the invention, a large number of servers12may be present, and cooperate to provide the functions described below. However, for convenience and clarity, the remainder of the detailed description will assume that only one server12is present.

The server12includes a number of audio, video, and/or audiovisual data sources121, an application execution environment122, and an encoder123. Note that other components may be used in an implementation of the server12, although these have been omitted for clarity. These components are now described in more detail.

The audio/video data sources121may be, for example, non-linear multimedia data stored on a non-volatile storage device in the form of a movie, television program, television commercial, game graphics and sounds, user interface sounds, or other such form. The data sources121also may include linear multimedia data sources, such as a television broadcast stream received live by antenna or private network.

An application execution environment122executes an interactive application on behalf of a user. The application may be, for example, a menuing system, a video game system, or other interactive application. The environment122responds to input interactive commands by providing images to the client device10using data communications network132. The environment122includes at least application logic1221, a source of images1222, and an image cache1223. Application logic1221may be implemented as an executable file or a script that provides a state machine for operating an interactive user interface. Any format of application file may be used as application logic1221; for example, a hypertext markup language (HTML) file that includes JavaScript may be used, or a compiled binary file may be used.

The application logic1221may dynamically generate one or more images1222that comprise the interactive user interface. The images1222often persist in a volatile memory of the server12for speed of access, for example in an image cache1223. The images1222may be generated by the application execution environment logic1221according to a screen resolution or a screen dimension of the display device11, which may be statically configured or may be determined dynamically when the client device10first establishes a communications session with the server12. Typically, for efficiency purposes, the application logic1221will transmit images from the image cache1223if possible, and dynamically create images1222for transmission only if they are not already in the image cache1223. The use of a cache1223advantageously permits interactive user interface images to be reused by the server12(or by other servers) between different requests for the user interface, even if those requests come from different end users or at different times. Images in the image cache1223typically are indexed using a hashing function defined by the environment122. The use of the hashing function permits many images to be quickly retrieved from the image cache1223, advantageously providing increased scalability. Additionally and/or alternatively, in some embodiments, server(s)12will transmit references to the images (such as Uniform Resource Locators or URLs), as opposed to the images themselves, so that the client can retrieve them on demand (e.g., by means of HTTP). Such embodiments would be advantageous, as an intermediate network cache (not shown), accessible through second data communications channel132, may be used to store reusable images closer to the client device.

The encoder123encodes the source audiovisual data according to an encoding specification, such as MPEG, AVS, or VC-1. The encoder123and the decoder102use the same encoding specification, so that the encoded audiovisual data may be decoded once it passes through the data communications network131. In the case that the source audiovisual data are already encoded, the encoder acts as a simple pass-through. However, in the case that the source audiovisual data are not in a format decodable by the decoder102, the encoder123transcodes the data into a decodable format.

As can be seen fromFIG. 1, the encoded audiovisual data (from the encoder123) and the user interface images (either from images1222or the cache1223) travel to the client device along two different data channels. The first data channel through the first data communications network131is designed specifically to communicate video content. Thus, for example, the network131may include a cable network infrastructure that deploys quadrature amplitude modulation (QAM), as is known in the art. Alternately, the network131may have an internet protocol television (IPTV) infrastructure that uses user datagram protocol over internet protocol (UDP/IP) to communicate encoded video. In yet another implementation, the network131may be part of a public or private internet infrastructure, and use hypertext transfer protocol (HTTP) tunneling to communicate the encoded video.

By contrast, the second data communications network132may be designed to communicate images, rather than video. In particular, this means that the second network132may operate on a much lower bandwidth or a higher reliability than the first network131. Thus, for example, the second network132may support data channels using the transmission control protocol over internet protocol (TCP/IP), the remote frame buffer (RFB) protocol, or the extended remoting technology (XRT) protocol. Images that are transmitted on the second network132may be encoded, for example, using a bitmap (BMP) file format, a portable network graphics (PNG) file format, a joint photographic experts group (JPEG) file format, or a graphics interchange format (GIF) file format. The use of PNG is particularly advantageous, as each pixel is stored with a corresponding transparency coefficient (a value).

FIG. 2is a flowchart showing operation of a client device10in the system ofFIG. 1in accordance with an embodiment of the invention. In particular,FIG. 2illustrates a method of providing, in the client device10, an interactive user interface for simultaneous display with a source video on a display device11. The method begins with a process21in which the client device10receives source video using a first data communications channel131. In a typical embodiment, the client device10will display this source video as it arrives on the display device11, as is known in the art. Next, in process22the client device10transmits a command related to an interactive user interface to a server12. This command may be transmitted, for example, in response to the client device10receiving on an I/O port103a signal that a button or buttons on a remote control has been pressed. The button or buttons may be provided on the remote control to call up an interactive program guide, a video game, or other interactive application.

In process23, the client device10responsively receives one or more images of the interactive user interface, using a second data communications channel132. For example, the images might include a number of buttons, switches, or dials for collective simultaneous display as a user interface. Alternately, the images might be designed to be displayed sequentially, as in the case of a “trick play” interface that includes a video timeline and a mark indicating a current time stamp. Seeking through the video may be performed by pressing a fast-forward or rewind button on the remote control, and movement of the timing mark along the timeline typically may be sped up by repeated button presses. The images may come from the images1222or the image cache1223of the application execution environment122.

Next, in a process24, the client device10, and in particular the overlay module101, alpha blends the source video with the received images to generate an output frame of pixels. In accordance with various embodiments of the invention, the received interactive user interface images are considered to be partially transparent foreground images (0.0<α<1.0), and frames of the source video are considered to be opaque background images (α=1.0). The choice of a for the user interface images advantageously may be made to be approximately 0.5, so that the interactive user interface appears evenly blended with the background source video. Or, the value of a may be varied on a per-pixel basis (i.e., per pixel alpha blending) within each image; for example, providing a downward a-gradient at the edges of a user interface image will produce an effect of the image ‘fading into the background’ at its edges. Global alpha blending and per pixel alpha blending may be combined by multiplying each per pixel alpha blending value with the global alpha blending value before the blending process is applied. The blending process24is performed using an appropriate received user interface image or images with respect to each frame of the source video for as long as the interactive user interface should be displayed on the screen, thereby providing a continuously-displayed interactive user interface.

Finally, in process25, the client device10transmits each output frame toward the display device11for display. An I/O port103may be used in processes21,22,23,25to receive or transmit data. A computing processor may be used in process24to perform the required blending.

The above embodiments are preferred because the image cache1223may be used to increase scalability of the content delivery platform provided by the server12(or a server cloud). This is true because it is feasible to cache individual user interface images separately from their underlying source videos, while it is generally infeasible to cache a vast number of pre-blended images due to limited storage space. The separate caching of user interface images, in turn, is a result of the ability of the client device10to receive these images using an I/O port103and perform blending in the overlay module101.

In some situations, it may be impossible to use these embodiments, because a client device10may not have the necessary I/O ports103or an overlay module101. In these situations, it is instead necessary to perform blending at the server12, rather than the client10, and such blending has its own challenges.

One such challenge is that the user interface images must be blended by the server12, but can be sent to the client device10only as encoded audiovisual data. Therefore, it is necessary to decode the source video into a spatial domain (i.e., as a frame of pixels), blend the user interface images with the source video in the spatial domain, then re-encode the blended image according to the encoding specification. These processes require server computational capacity, and do not scale well.

Another challenge is that there is noticeable latency between the time at which the interface command occurs and when the user interface can be displayed. This challenge is illustrated by consideration ofFIG. 3, which schematically shows a time sequence31of frames of video in relation to an interactivity command32. In this figure, a sequence31of frames includes a number of individual video frames311-317. The frames are labeled by a frame type, which may be either intra-encoded or inter-encoded. An intra-encoded frame encodes video data according to data found only in the frame, while an inter-encoded frame encodes video data according to data found in the given frame and in surrounding frames. For purposes of clarity, MPEG frame types are used in the figures and detailed description to provide an example implementation, but any encoding specification may be used in accordance with an embodiment of the invention.

The sequence31of frames includes two types of frames: I-frames that are intra-encoded and P-frames that are inter-encoded. I-frames are encoded using image information found only in themselves. Thus, I-frames encode a full-screen image, which is useful to indicate a ‘scene change’ or to eliminate display artifacts. Two frames311,317are I-frames. P-frames are encoded using information found in the previous image by estimating movement of pixels using two-dimensional “motion vectors”. Thus, P-frames are useful for predicting movement fixed or slow-moving ‘camera pan’ images where most of the image content of the previous frame is present in the next frame. This relationship between P-frames and their predecessor frames is indicated by the backwards-facing arrows inFIG. 3. Frames312-316are P-frames. MPEG also defines a B-frame, not shown inFIG. 3, which interpolates both forward and backward between other frames.

Suppose an interface command32arrives at the server12when a P-frame316is being displayed on the display device11. Because it is inter-encoded, the information in this P-frame is insufficient by itself to reconstruct the complete image being displayed (i.e., to reconstruct the decoder state). In fact, the information necessary is found in a combination of the frames311-316. One could introduce a latency33between the time of the command32and the next I-frame317, at which time the overlay image is blended34. However, if the group of pictures31contains two seconds worth of source video, the average wait time from the command32to the next I-frame317(and the appearance of the user interface) is one second, which is unacceptably unresponsive. Therefore, in various embodiments of the invention, all of the data in each group of pictures31(that is, from one intra-encoded frame until the next one) are buffered in the server12before being transmitted to permit blending of the interactive user interface images with the currently-displayed image from the source video.

The server12uses buffered frames to simulate, for blending, the state of the decoder102in the client device10. This process is illustrated by the sequence35, in which an encoder in the server12constructs the state of the decoder102. The server12retrieves the first frame311of the buffered frames, and uses it as an initial simulated state351. The server12then retrieves the second frame312of the buffered frames, and applies its data to the initial simulated state351to obtain a second simulated state352. The server12retrieves the third frame313of the buffered frames, and applies its data to the second simulated state352to obtain a third simulated state353. This process continues until the simulation reaches a state356that corresponds to a frame316corresponding to a time associated with the command32. Once the server12has recovered the state of the decoder102, it may perform blending as described above in connection with element24ofFIG. 2.

FIG. 4schematically shows a system in accordance with an embodiment of the invention in which the server12performs blending. The disclosure ofFIG. 4overlaps to large extent with that ofFIG. 1, so only the changes will be remarked upon here. As noted above, in the scenario under consideration, the client device10inFIG. 4lacks an overlay module101found inFIG. 1. Therefore, the server12includes, in addition to the encoder123ofFIG. 1, a decoder/blender124for decoding and blending source video with an interactive user interface. Note that while the functions of decoding and blending are combined in decoder/blender124for purposes of this disclosure, these functions may be implemented in separate hardware or software. Also as described above, the server12further includes a buffer memory125for buffering frames of source video data. During ordinary operation of the system ofFIG. 4, most frames of source video data buffered in the buffer memory125are discarded without being blended, and the decoder/blender124acts as a simple pass-through. However, when a user provides an interactive command to the application execution environment122, the environment122provides images to the blender124(either preferably statically from its cache1223, or dynamically from the image generator1222) for blending with the buffered video. The decoder/blender124decodes the source video data and simulates the state of the decoder102as described with respect to element35ofFIG. 3. The decoder/blender124then blends the interactive user interface images into the source video, one frame at a time. The decoder/blender124provides an output to the encoder123, which encodes the data according to the appropriate encoding specification for transmission to the client device10.

FIG. 5is a flowchart showing operation of a server in the system ofFIG. 4. In particular,FIG. 5shows a method of providing, in a server12, an interactive user interface for simultaneous display with a source video on a display device11. In a first process51, the server12transmits frames of the source video toward the client device10for display. Simultaneously, in a second process52, the server12buffers frames from the source video for subsequent transmission. In process53, the server12receives from the client device10a command32that relates to the interactive user interface. In process54, the decoder/blender124determines a buffered frame316in the buffer memory125that corresponds to a time associated with the command32. In process55, the decoder/blender124blends the determined frame with one or more images of the interactive user interface received from the application execution environment122to generate an output frame that is subsequently encoded by the encoder123. Then, in process56, the server12transmits the output frame toward the client device10for display on the display device11.

Note that the encoder123may be required to do a motion vector search after blending. There are several optimizations that can be performed to speed up this process. In a first optimization, the encoder123could make use of motion information found in the original video frame when it was decoded by the decoder/blender124. However, the encoder123must verify whether the same motion is still present in the blended image due to the presence of the interactive user interface. In a second optimization, the source video images could be divided into rectangular areas, and motion vectors for each area are encoded separately. In this case, motion vectors for rectangles that do not intersect the user interface are unaffected by the blending, and no additional motion vector search is required for these rectangles.

FIG. 6Aschematically shows a system in accordance with an embodiment of the invention in which overlay images are used to supplement a streamed interactive user interface. In U.S. application Ser. No. 12/443,571 (“Method for Streaming Parallel User Sessions, System and Computer Software”), the contents of which are hereby incorporated by reference in its entirety, a system is disclosed where an interactive user interface is streamed to a client device over a first data communications channel. The streamed interactive user interface is realized by stitching a plurality of fragments and streams into a single compliant audiovisual stream. It has been identified that for a number of reasons it is beneficial to overlay images over an encoded stream instead of encoding them in the stream, which also holds for cases in which the audiovisual stream is an interactive user interface. For example, it is beneficial to overlay images in cases involving a sprite-like user interface element (e.g., a cursor). Such a user interface element is generally arbitrarily placed on the screen and it may be more efficient to decouple the element from the interactive user interface by overlaying images. In particular, if the user interface element was instead encoded (e.g., by the fragment encoder) and subsequently stored in cache, the cache would quickly reach capacity because a sprite-like user interface element, unlike some other user interface elements (e.g., a menu), does not have a predefined position. Another example may be that the interactive user interface has a partial screen video element over which another user interface element is supposed to be rendered. In this case it is more efficient from a scalability point of view to render only the new interface element as overlay image(s).

The system disclosed inFIG. 6Ais fundamentally the same as that shown inFIG. 1. Here, the client device60receives an interactive user interface via a first data communications channel63from a server62. In some embodiments, server62runs an application in the application execution engine621that generates fragments by means of a fragment encoder630; caches these fragments in a cache632; and combines these (cached) fragments by means of a stitcher622(otherwise known as an assembler) to generate, and subsequently stream, an interactive user interface via the first data communications channel63to the client device60(as described in, U.S. application Ser. No. 12/443,571 (“Method for Streaming Parallel User Sessions, System and Computer Software”)). Optionally, in some embodiments, the interactive user interface is directly encoded by an encoder of server62(not shown inFIG. 6A) from pixel data. The interactive user interface may be supplemented by the generation of images634that are to be overlain by the client device60. These images may also be stored in a cache632for reuse across sessions in the same way as fragments are reused across sessions. For example, in some implementations, the interactive user interface includes a source video with images from cache632overlaid. The images may be sent via a second data communications channel64to the I/O ports601of client device60. Additionally and/or alternatively, in some embodiments, server(s)62will transmit references to the images (such as Uniform Resource Locators or URLs), as opposed to the images themselves, so that the client can retrieve them on demand (e.g., by means of HTTP). Such embodiments are advantageous, as an intermediate network cache641, accessible through second data communications channel64, can be used to store reusable images closer to the client device. The stream received from server62is decoded in the decoder602and combined with the images received or retrieved from server62in the overlay module603for display on61as described in the embodiment described in relation toFIG. 1. In some implementations, client device60switches between 1) receiving the interactive user interface from the stitcher, and 2) blending the interactive user interface from the stitcher with overlay images.

FIG. 6Bis a flowchart showing operations of a client device in the system ofFIG. 6A. The flow chart is very similar to the operations described in the flow chart inFIG. 2. However, instead of receiving a source video using the first data communications channel, the client device receives (6000) the interactive user interface via the first data communications channel. In some embodiments, the interactive user interface is a video stream, such as an MPEG video stream. Next, a command related to that interactive user interface is transmitted (6010) to the server. The client may subsequently receive (6020) updates to the interactive user interface via the first data communications channel and/or supplemental images from the same server to supplement the interactive user interface. The remaining processes24and25are the same as those described with respect toFIG. 1.

In some embodiments, since the first data communications channel and the second data communications channel are completely independent channels, the graphical information transmitted over both data channels is likely to be related. Therefore, special care must be taken when the images are combined with the video stream representing the interactive user interface. A loosely coupled synchronization mechanism, such as for example a presentation timestamp and timeout for each image, may be used to synchronize the display of images with the streamed interactive user interface.

FIG. 7Aschematically shows an alternative embodiment of the system described inFIG. 6A. The system disclosed inFIG. 7Ais similar to the systems depicted byFIGS. 4 and 6A. Here, the server (specifically, overlay module724of server72), and not the client device, overlays images over the encoded stream. In other words, the blending occurs at the server, as described in relation toFIG. 4.

As illustrated, in some implementations, client device703does not include an overlay module. Moreover, as shown, the system ofFIG. 7Adoes not utilize a second data communications channel.

As in the system ofFIG. 6A, stitcher722generates an interactive user interface by combining fragments, generated by fragment encoder730, and stored in cache732. Overlay module724overlays images734over the resulting interactive user interface received from stitcher722. As illustrated, client device70then receives the encoded stream, which includes interactive user interface and overlay images734, via a first data communications channel73from server72. In optional implementations, server72(or, alternatively, overlay module724) is configured to switch between transmitting (i) the encoded stream including the interactive user interface and overlay images734, and (ii) only the interactive user interface. Alternatively, in some implementations, overlay module724and stitcher722exist and operate as a single component of server72.

FIG. 7Bis a flowchart showing operations of a client device in the system ofFIG. 7A. The flow chart is very similar to the operations described in the flow chart inFIG. 6B, but written with respect to a server (e.g., server72) that is configured (e.g., overlay module724) to overlay images. In process7000, the server transmits the interactive user interface via a first data communications channel. Next, in process7010, the server receives a command related to the interactive user interface. In process7020, the server generates an updated interactive user interface. Further, in process7030, the server blends the updated interactive user interface with supplemental images to generate a blended output frame which, in process7040, is transmitted towards the client device. As described above, in optional implementations, the server switches between transmitting (i) the blended output frame including the interactive user interface and overlay images, and (i) the interactive user interface.

FIG. 8Aschematically shows an alternative embodiment, similar to the system described inFIG. 6A, in which the supplemental overlay images are sourced from a third party server. The embodiment provides a strict separation between an interactive user interface and information from a third party, by conveying the interactive user interface and information from a third party over separate data communications channels. An example of a system requiring such a separation is a banking application where the interactive user interface is the same for every user, except for account related information that is sent directly to the end user as supplemental images (e.g., supplemental images sent by third party server85) over a secure data communications channel (e.g., second data communications channel84).

The system disclosed inFIG. 8Ais very similar to the system depicted byFIG. 6A. The main difference being that one or more images originate from a third party server85, and are sent as supplemental images to client device80over second data communications channel84. In some embodiments, second data communications channel84is a secure channel (e.g., a secure transport protocol is used for the images, such as HTTPS). The application may use application logic834to liaise with application logic840of an application844on a third party server85via a communication channel87to generate one or more images842that supplement the interactive user interface with third party information.

FIG. 8Bis a flowchart showing operations of a client device in the system ofFIG. 8A. The flow chart is similar to the flow chart inFIG. 6B. Here, the device transmits (8020) a request for secure content, and supplemental images are received (8030) from a third party server over a second data communications channel, where, in some embodiments, the second data communications channel uses a secure transport protocol.

The embodiments of the invention described above are intended to be merely exemplary; numerous variations and modifications will be apparent to those skilled in the art. All such variations and modifications are intended to be within the scope of the present invention as defined in any appended claims. For those skilled in the art it will also be evident that it may be beneficial for systems to switch between the embodiments of the invention on demand.

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