KR19990023209A - Scrolling Images on Set-Top Boxes - Google Patents

Abstract

Systems and methods are provided for visualizing Internet pages or any other type of image of variable size on a TV screen using a conventional set top box in a digital TV service.

The image is stored in the set-top box memory in its compressed format, and only the portion that fits the display size is extracted and sent to the decoder for decompression and display. If scrolling of the image is requested by the user, another portion is extracted and delivered to the decoder to be decompressed and displayed on the TV screen.

Description

Scrolling Images on Set-Top Boxes

The present invention relates to the display of digitally compressed images on decoding output devices, and more particularly to a method and system for displaying digitally compressed images having a larger size than the display.

As the prevalence of digital TV services has increased, typical TV sets have become a set-top box that elaborates digital information received over communication channels (e.g. satellites, cables) to display images on TV screens. Called devices are accompanied more and more often. This set-top box is a kind of small PC with limited power and memory capacity. Limited memory in this kind of device is usually not a problem because the processing power required by digital TV services is very limited. If set-top boxes are becoming very popular in the future, many digital service providers will want to develop the processing power of such devices.

Many providers of digital TV services will seek to give their customers the possibility to access content taken from other sources, such as the Internet. They can be entertainment as well as business information.

US patent application US-A-825326 discloses a structure called Data Carousel for transmitting a set of frames on a broadcast channel. The data carousel consists of a set of image frames that are periodically sent to the user. It also includes an application running on a set-top box and allows navigation across frames. The search is accomplished by linking information about the location of the hot-spots to the graphics page and linking each hot-spot criterion to the page. Each frame has two parts: a compressed image and a search information table. An application running on a set-top box stores a particular frame (which may be a root frame or a user-selected frame, depending on the context) in the set-top box memory. The search information table is then separated from the compressed image, which is displayed with the hot-spots located as a result of the search information table. Each frame may correspond to, for example, an Internet page and may be logically associated with another. The data carousel structure allows the user to search across a set of graphics pages broadcast by a wideband channel. The user may select one of the pages of the set, while illuminating the conversation of interactivity.

In a structure such as the data carousel described above, display of a page having a variable size on a TV screen may be desirable. The original image (eg in HTML format) must be preprocessed in order to be converted and compressed into a format compatible with the set-top box decoding device to which the image is addressed. The image in this compressed digital format is then sent to a set top box that decodes the image and displays it on a TV screen. In general, the size of the original uncompressed digital bit-map may be larger than the size of the TV screen, in which case the image must be cut into slices before being compressed and transmitted.

A simple and rough solution is to crop the final image at the border. In this way the image is partially corrupted, which in some cases may be unacceptable.

If the original image does not fit the vertical size of the target screen, another known method for dividing the original image is to divide the uncompressed color bit-map into multiples of the screen border size. Some graphical representations of the divisions should be added to the adjusted sub-page. This is necessary to inform the viewer about the presence of additional and logically linked sub-pages. The big problem with this approach is that properly and logically connected graphics elements located close to the screen borders can be cropped and displayed on other pages, negatively impacting the validity of the visualized results.

The problem becomes even worse if the original image exceeds both the vertical and horizontal size of the screen.

It is an object of the present invention to provide a technique for reducing the above deficiencies of the prior art.

According to the present invention, there is provided a method of displaying a digital image on a receiving device, the receiving device comprising: receiving means for receiving a data segment via a communication channel; Storage means for storing the digital image; And processing means, and connectable to display means for displaying a digital image whose size is larger than the size of the display means, wherein the method for displaying the digital image comprises compressing the image at the receiving device. Receiving in a format and storing the compressed image in the memory means; Selecting a first portion of the compressed image; Decompressing a first portion of the image; Displaying the decompressed first portion on the display means; In response to user control, selecting a second portion of the compressed image; Decompressing a second portion of the image; And displaying the decompressed second portion on the display means.

Moreover, according to the present invention, there is provided a receiving device connectable to display means for displaying a digital image whose size is larger than that of the display means, the receiving device compressing the digital image in a compressed format via a communication channel. Receiving means for receiving by means of; Storage means for storing the compressed digital image; First processing means for selecting a first portion of the compressed image; Second processing means for decompressing a first portion of the image and transmitting the first portion of the decompressed image to the display means; Third processing means for responding to user control and for selecting a second portion of the compressed image; And fourth processing means for decompressing a second portion of the image and sending the second portion of the decompressed image to the display means.

1 is a schematic diagram of a transmission system embodying the present invention.

2 is a schematic diagram of a Set Top Box.

3 is a schematic diagram of an image compression process according to a preferred embodiment of the present invention.

4 illustrates a data packet used for image transmission according to a preferred embodiment of the present invention.

5 is a schematic diagram of a scrolling process according to a preferred embodiment of the present invention.

Explanation of symbols for the main parts of the drawings

101: provider 103: transmitter

105: TV receiver 107: set top box

109: remote control

DETAILED DESCRIPTION Various embodiments of the invention are now described in detail by way of example with reference to the accompanying drawings.

1 is a diagram showing a schematic structure of a digital video presentation system that can embody the present invention. The system 100 includes a provider 101 which is an image source to be displayed and a transmitting device 103 for transmitting a compressed digital image to a plurality of receivers via a communication channel. According to a preferred embodiment of the present invention, the image is transmitted to the satellite communication system, but any other means (eg antenna or cable) for transmitting data packets to the plurality of receiving devices can be used. Each receiver has a TV set 105 and a set-top box 107 that processes the image received via the communication channel and converts the image into a format compatible with the TV receiver 105. Both the TV receiver 105 and the set top box 107 are controlled by the user. Such control can be realized, for example, by a single remote control 109.

Full digital bit-map images are very difficult to process in terms of storage occupation and transfer time. This reduces the bit-map size by compressing the image before transmission. According to a preferred embodiment, the international standard MPEG-II has been used as the compression format, but other standards (eg JPEG or GIF) can also be used.

2 schematically illustrates the structure of a set top box that may be used to implement a preferred embodiment of the present invention. The demultiplexer 201 receives as a input a transport stream comprising application data and a video / audio stream. The transport stream is a means for transmitting information to a plurality of receivers via a communication channel by the transmitter 103. Demultiplexer 201 extracts application data and video / audio streams from the transport stream. A video / audio stream, eg film, is then sent directly to the MPEG decoder 203, which decompresses the image and displays it on the TV screen.

On the other hand, the application data stream is stored on the memory 205. The application data stream may comprise still images, such as I-frames of instructions and Data Carousel architecture. The instructions are interpreted and executed by the set top box CPU 207 in accordance with an operating system stored on the memory 205.

In a preferred embodiment of the invention, operating system open TVs have been used.

As mentioned above, one of the possible sources of images that may be of interest to set-top box users is the Internet. The data carousel structure can be used to provide a limited conversation to the user by making a set of pages linked to each other available. The size of these pages can be larger than the TV screen.

The problem of displaying images larger than the screen size is a well known problem in computer science. According to the state of the technology approach, images received over a communication channel must be decompressed and stored as a bit-map in main memory. A scrollable view of the next image can be displayed in the graphics window. Unfortunately, as mentioned above, devices of this kind typically have only limited memory for economic reasons and storing as a bit-map takes up a lot of memory space. Moreover, the graphic elabolation capability, which is required to process an image in its bitmap form, is typically not very large in a set top box.

According to a preferred embodiment of the present invention, the received image is stored in the set top box memory in its compressed format (MPEG-II format). Sub-rectangles of the entire image are extracted from the memory, decompressed and displayed. If image scrolling is required by the user via remote control 109, another sub-rectangle is extracted from the memory, decompressed and displayed. In this way, the occupancy of the memory is substantially reduced because the compressed image is much smaller than the image that is not fully compressed. This is only possible if from the compressed memory image the location of a well defined and relatively small rectangular area of the original uncompressed image can be determined so that the exact sub-rectangle to be decompressed and displayed on the compressed image can be identified. . The MPEG-II standard format satisfies this requirement, ie the image must be editable without having to be decompressed.

Referring to FIG. 3, the preprocessing of the image prior to transmission is shown. Head-end 101 is the source of the image to be displayed. The image may for example be taken by an internet page and processed by the head-end 101. However, any digital image of any size can be transmitted. According to a preferred embodiment, the input data representing the digital image is a bitmap of pixels having color information associated with each pixel. The color of each pixel can be expressed, for example, via intensity values for each of the three RGB components (or YUV components).

According to a preferred embodiment, before being transmitted, the compressed image is processed by the head-end 101. In terms of offset values from certain reference points, a table is created according to the position on the compressed image of any syntactical elements, such as a slice of an image or macro-block. This information is very helpful in increasing the processing speed when scrolling is required by the user. Otherwise, processing must find such syntax elements, and this behavior can have a big impact on the end result due to limited hardware power. As mentioned above, according to a preferred embodiment of the present invention, the MPEG-II compression standard is used. This format allows you to edit the image without decompressing it. Editing should allow reconstruction from sub-rectangle encoded data of the original image, which is still in compressed format.

In the embodiments detailed herein, only vertical scrolling of the image has been considered for reasons of more common scrolling. However, using similar preprocessing described for vertical scrolling, a table for horizontal scrolling can be made. In this case the different levels of the coding structure have to be analyzed because, in the case of the MPEG-II standard, picture macro-block components have to be accessed.

The head-end server 101 packetizes an image or a set of images, which are then wrapped into a MPEG-II transport stream. This is done by wrapping the required MPEG-II header data and transport stream header structure around the data packet. The MPEG-II transport stream is then multiplexed by the transmitter 103 and transmitted over a communication channel as a digital video broadcast. Except for the size and content, the digital video broadcast data stream is the same as the transport stream carrying the video content and is treated as such. The compressed image is then sent over a channel (e.g. satellite or cable) to a plurality of set-top boxes whose services are addressed.

Along with the image or set of images, the application is sent. This application will be performed by the set top box processor 207 and will allow the user to interact with the displayed image or set of images. For example, in the data carousel described in US-A-825326, the application contains all the information for selecting a given frame and searching across the relevant page. Data packets require an image data packet with two types: a compressed image and associated information (e.g. the above mentioned location table and data carousel's search data table) and a set-top box to display and process the image. It can be an application data packet containing all the information. According to a preferred embodiment, the application broadcasts as an image or set of images, but this is not the only way to make an application useful to a set-top box CPU. For example, the application may be stored permanently in the memory 205 of the set top box. Sending an application to an image or a set of images has the obvious advantage that no modification is required to the existing structure and each receiving set top box.

4 is a diagram schematically illustrating a data packet including an image in the case where the present invention is implemented in data kerosene transmission.

Reference is now made to FIG. 5. When the stream is received by the set top box 107, the demultiplexer 201 stores the video / audio stream and all other data in the memory 205. CPU 207 then executes the application program. If the image to be displayed is larger than the size of the TV screen, the default base portion of the image is initially extracted for viewing on the screen. It is natural to select the upper left portion of the image, but any sub-rectangle is equally possible. The extracted portion, which is still in compressed format, is then passed to the MPEG decoder 203, which merely decompresses the image and visualizes the image on the TV screen. The image may be provided to a viewer accompanied by one or more hot spots that provide information about the operations that may be performed with the remote control 109.

As an example, in the case of a data carousel, the hot spots visually indicate which link can be selected by the user. The scrolling of the image may be associated with one of these hot spots and may be visually selected on the screen or simply controlled by appropriate commands upon remote control. If scrolling is requested, the application finds the right sub-rectangle from the compressed image stored in memory 205 and passes it to decoder 203, which repeats the decompression operation and displays the image on the TV. Send to the screen.

The present invention has the effect of using a digital TV service to visualize an Internet page or any other kind of image of variable size on a TV screen using it without any modification of a conventional set top box. They only perform their usual operations. For example, from the decoder's point of view, the decoder does not make any difference whether the compressed image is a still image (eg MPEG I-frame) or a single picture of a movie. The decoder continues to play the image on the TV screen until a new image is received. This is exactly what is usually done when transferring a movie on a TV screen.

Claims (8)

In the method of displaying a digital image, Receiving means for receiving a data segment via a communication channel, Memory means for storing digital images, and Processing means Including, Connectable to display means for displaying the digital image, wherein the size of the image is larger than the size of the display means; Receiving the image in a compressed format and storing the compressed image in the memory means, Selecting a first portion of the compressed image, Decompressing a first portion of the compressed image, Displaying the decompressed first portion on the display means; In response to user control, selecting a second portion of the compressed image, Decompressing a second portion of the image, and Displaying the decompressed second portion on the display means. Method of displaying a digital image comprising a. The method of claim 1, wherein the compressed image is compressed according to the MPEG-II standard. A method as claimed in claim 1, wherein the receiving device is also capable of receiving a TV video / audio stream. 4. A method according to claim 1, wherein the display means is a TV receiver. In a receiving device connectable to display means for displaying a digital image, the size of the image being larger than the size of the display means. Receiving means for receiving a digital image in a compressed format over a communication channel, Memory means for storing the compressed digital image, First processing means for selecting a first portion of the compressed image, Second processing means for decompressing a first portion of the image and transmitting the first portion of the decompressed image to the display means; Third processing means for responding to user control and for selecting a second portion of the compressed image, and Fourth processing means for decompressing a second portion of the image and transmitting the second portion of the decompressed image to the display means Receiving device comprising a. 5. The receiving device of claim 4, wherein the receiving device is a set top box capable of receiving a TV video / audio stream. A set top box according to claim 6, wherein said display means is a TV receiver. 8. A set-top box according to claim 6 or 7, which is compatible with the MPEG-II standard.