MXPA00010628A - Receiver/decoder and method of processing video data - Google Patents

Abstract

A method of processing video data in a receiver/decoder comprising at least one port (31) for receiving data and memory means (40) comprising a data buffer area (45A0, 45A1) for storing incoming data for display, and a graphics buffer area (45Ai) for storing graphics data, said method comprising passing graphics data stored in the graphics buffer area to the data buffer area for combination with display data stored therein.

Description

RECEIVER / PESCODER AND METHOD FOR PROCESSING VIDEO DATA The present invention relates to a receiver / decoder and a method for processing video data. The term "receiver / decoder" used herein may connote a receiver to receive either encoded or uncoded signals, for example, television and / or radio signals, which may be broadcast or transmitted by some other means. The term may also connote a decoder to decode the received signals. The embodiments of these receivers / decoders may include an integral decoder with the receiver for decoding the received signals, for example, in a "top box", this decoder operating in combination with a typically separate receiver, or a decoder including additional functions. , such as a network browser, a video recorder, or a television. In a digital television transmission system, the received signals pass through a receiver / decoder and then into a television set. As used herein, the term "digital television system" includes, for example, any satellite, terrestrial, cable or other system. The receiver / decoder decodes a compressed MPEG type signal into a television signal for the television set. This is controlled by a manual remote controller, through an interface in the receiver / decoder. The receiver / decoder is used to process the incoming bit stream, and includes a variety of application modules that cause the receiver / decoder to perform a variety of control and other functions. This receiver / decoder can have a variety of devices coupled to it, such as a card reader for the user to pass an authorization card through to confirm which services the user is authorized to use, a control rod of television receiver portable, a television display unit, and a second card reader for use with credit cards to allow the user to perform bank functions from the house. You can also have a variety of ports attached to it, for example, a modem for accessing the Internet and for conducting banking transactions from home. The receiver / decoder typically includes a buffer arrangement to handle the incoming data. The basic principle of the buffer in a receiver / decoder is that a section of the memory in a memory is designed as a buffer. The incoming data from a port is fed into the buffer. The size of the buffer can be chosen to be large enough to accommodate most or all incoming messages, or the buffer can be operated with two pointers, one for the point where new input data is being written into the buffer and the other for the point where stored data is being read from the buffer. The receiver / decoder typically includes a 4-layer structure for generating the image to be displayed on the television set, the four layers being a fixed image layer, a moving image layer, a graphics layer, and a cursor layer. The graphics layer is preferably used for both icons (typically geometric shapes) and titles (usually but not always subtitles). The use of a common layer, the graphics layer, for both icons and titles causes difficulties to maintain an update of both icons and titles satisfactorily, particularly since a title can appear in any position on the screen. The main object of the present invention is to provide an improved buffer arrangement in a receiver / decoder to solve this and other problems. The present invention provides a method for processing video data in a receiver / decoder comprising at least one port for receiving data and memory elements comprising a data buffer area for storing incoming data for display, and a graphics buffer area for storing graphic data, said method comprising passing graphics data stored in the graphics buffer area to the data buffer area for combination with the display data stored therein. In a preferred embodiment, the incoming data comprises video text data, such as one or more subtitles, and the graphic data comprises icon data. When a subtitle screen has been completely received in the area of the data buffer, a central processing unit in the receiver / decoder, under the control of a device, passes the icon data to the data buffer area , preferably just before the data stored in the data buffer area is combined with other data to provide video data. Therefore, the invention faces the advantage that in the case of an overlap between the icon and part of the subtitle, the icon will be placed over the part of the subtitle, but the non-overlapping portions can be displayed at the same time with the icon. In a preferred embodiment, the data buffer area comprises two sub-areas of data buffer, the incoming display data being directed to one of the sub-areas at a time. The two sub-areas can be interchanged so that additional incoming display data is stored in the other sub-area and the graphics data stored in the graphics buffer area is transferred to the other sub-area. This may allow a subtitle screen to be stored in a sub-area while a previously received subtitle screen is being taken out of another subarea, thereby avoiding overwriting the previously received subtitle screen with new data. Preferably, the two sub-areas are exchanged immediately after the graphic data stored in the graphics buffer area passes into one of the sub-areas of the data buffer. The area of the graphics data memory may comprise a plurality of graphics buffer sub-areas in which the graphics data may be stored, the graphics data being passed to the data buffer area from a selected one of the sub-areas of graphics buffer. This may allow, for example, that several different icons are generated and stored before the reception of any video text data, so that there is no need for the icon generating elements to continuously generate icon data. Preferably, the combined graphics and the displayed data are further combined with other received data to provide video data. In this way, although other incoming display data is stored in a sub-area of data buffer and the graphics data stored in the graphics buffer area is being passed to that sub-area of data buffer, the combined data of the other sub-area of data buffer can be further combined with the other received data, again avoiding by overwriting the previously received subtitle screen with new data. Preferably, the graphic data stored in the graphics buffer area is passed to the data buffer area for combination with display data stored therein immediately before the graphics combined in this way and the display data are combined with said other received data. The video data may comprise four data layers, these combined graphics and display data comprise one of said layers. If so, the four data layers can comprise the combined graphs and the display data layer, a data layer of still images, a data layer of moving images, and a cursor data layer.

The moving image data layer and the display data may comprise at least part of an MPEG data stream. The present invention also provides a receiver / decoder comprising at least one port for receiving data, memory elements comprising a data buffer area for storing incoming data for display, and a graphics buffer area for storing data from graphics, and elements for passing the graphics data stored in the graphics buffer area to the data buffer area for combination with the display data stored therein. A preferred mode of the receiver / decoder comprises at least one port for receiving data, a crue memory comprises a data buffer area for storing incoming data for display and a graphics data memory area for storing graphics data, and a processor for passing graphics data stored in the graphics buffer area to the data buffer area for combination with display data stored therein. The data buffer area may comprise two sub-areas of data buffer, and the receiver / decoder may further comprise means, eg, a microprocessor, for directing the incoming data to one of the sub-areas. The receiver / decoder may further comprise control means, such as, for example, a device, the address means being arranged to direct the incoming display data to one of the data buffering sub-areas as specified by the control means. . The receiver / decoder may further comprise means, e.g., a device, for swapping the two sub-areas so that additional incoming display data may be stored in the other sub-area and the graphics data stored in the graphics buffer area can be passed to the other subarea. The exchange means may be adapted to exchange the two sub-areas of data buffer immediately after the graphic data stored in the graphics buffer area passes to one of the sub-areas of the data buffer. The graphics buffer area may comprise a plurality of graphics buffer sub-areas in which the graphics data is storable, the graphics data being passable to the data buffer area from a selected one of the memory sub-areas. intermediate graphics.

The receiver / decoder may further comprise means for combining the combined graphics and displaying data with other received data to provide video data. In a preferred embodiment, the combining means is a mixing circuit. The passage means can be accommodated to pass the graphic data stored in the graphics buffer area to the data buffer area for combination with display data stored therein immediately before the combining means combine the combined graphs and display data with the other data received. The receiver / decoder may further comprise a buffer memory control element, such as, for example, a device, the sub-areas of the data buffer being received by a buffer memory control element. The present invention also extends to a transmission and reception system that includes a receiver / decoder as mentioned above, and means for transmitting this data. In a preferred embodiment, the system is a digital television system. Various receiver / decoder functions can be implemented in hardware, for example, in a dedicated integrated circuit; this can provide increased speed of operation. Preferably, however, at least some of the functions are implemented in software, preferably implemented by processing means running the applications; this can allow greater flexibility, require fewer components, and allow the receiver / decoder to be updated more easily. The receivers / decoders that make up the invention will now be described, by way of example, with reference to the drawings, in which: Figure 1 is a schematic diagram of a digital television system; Figure 2 is a schematic diagram of the structure of a receiver / decoder of the system of Figure 1; Figure 3 is a block diagram of the layered architecture of the receiver / decoder; Figure 4 is a schematic diagram of the arrangement of a graphic processor of a receiver / decoder; Figure 5 is a schematic diagram of a graphics processor direct access memory (RAM); and Figure 6 is a schematic diagram illustrating the combination of layers of a video display. An overview of the digital television system 1 is shown in Figure 1. The invention includes a mostly conventional digital television system 2 which uses the known MPEG-2 compression system to transmit compressed digital signals. In greater detail, the MPEG-2 compressor, 3, in a transmission center receives a digital signal stream (typically a stream of video signals). The compressor 3 is connected to a multiplexer and to a mixer 4 via the link 5. The multiplexer 4 receives a plurality of other input signals, assembles the transport current and transmits compressed digital signals to a transmitter 6 of the transmission center via the link 7, which of course can take a wide variety of forms including telecommunications links. The transmitter 6 transmits electromagnetic signals via the uplink 8 to a satellite transponder 9, where they are processed electronically and transmitted via the downward notional link 10 to the terrestrial receiver 12, conventionally in the form of a proprietary or rented satellite dish. by the end user. The signals received by the receiver 12 are transmitted to an integrated receiver / decoder 13 owned or rented by the end user and connected to the television set of the end user 14. The receiver / decoder 13 decodes the compressed MPEG-2 signal into a signal of television for the television set 1. Other transport channels for the transmission of data are possible, such as terrestrial transmission, cable transmission, combined satellite / cable links, telephone networks, and so on. In a multichannel system, the multiplexer 4 handles audio and video information received from several parallel sources and interacts with the transmitter 6 to transmit the information along with a corresponding number of channels. In addition to audiovisual information, messages or applications or any other kind of digital data can be entered into any or all of the interlaced channels with the digital audio and video information transmitted. A conditional access system 15 is connected to the multiplexer 4 and to the receiver / decoder 13, and is located partially in the transmission center and partially in the decoder. It allows the end user to have access to digital television transmissions from one or more transmission providers. A smart card, capable of decoding messages related to commercial offers (that is, one or more television programs sold by the transmission provider), can be inserted into the receiver / decoder 13. Using the decoder 13 and the smart card, the end user can buy commercial offers either in a subscription mode or in a pay per view mode. As mentioned above, the programs transmitted by the system are mixed by the multiplexer 4, the conditions and the encoding keys in cryptic key applied to a given transmission are determined by the access control system 15. The transmission of mixed data of This way is well known in the field of paid television systems. Typically, the mixed data is transmitted together with a control word to demix the data, the same control word being cryptically encoded by the operation key call and transmitted in cryptically encoded form. The mixed data and the cryptically encoded control word are then received by the decoder 13 having access to an equivalent to the operating key stored in the smart card inserted in the decoder to cryptically decode the control word encoded cryptically and thereafter demix the transmitted data. A paid subscriber will receive, for example, in a rights control message (ECM) monthly transmitted the exploitation key necessary to decode the control word encoded cryptically to enable it to see the transmission. An interactive system 16, also connected to the multiplexer 4 and the receiver / decoder 13 and again partially located in the transmission center and partially in the decoder, allows the end user to interact with several applications via a modem rear channel 17. The rear modem channel it can also be used for communications used in the conditional access system 15. An interactive system can be used, for example, to allow the viewer to immediately communicate with the transmission center to request authorization to view a particular event, copy an application , etc. Referring to Figure 2, the elements of the receiver / decoder 13 or the top box will now be described. The elements shown in this Figure will be described in terms of functional blocks. The decoder 13 comprises a central processor 20 that includes associated memory elements and adapted to receive input data from a serial interface 21, a parallel interface 22, a modem 23 (connected in the rear modem channel 17 of FIG. 1), and connection contacts 24 on the front panel of the decoder. The decoder is additionally adapted to receive inputs from an infrared remote control 25 via a control unit 26 and also has two smart card readers 27, 28 adapted to view the bank or subscription smart cards 29, 30 respectively. The subscription smart card reader 28 is fitted with an inserted subscription card 30 and with a conditional access unit 29 to supply the necessary control word to a demultiplexer / demixer 30 to allow the cryptically encoded transmitted signal to be demixed. The decoder also includes a conventional tuner 31 and a demodulator 32 for receiving and demodulating the satellite transmission before being filtered and demultiplexed by the unit 30. The data processing within the decoder is generally handled by the central processor 20. Figure 3 illustrates the software architecture of the central processor 20 of the receiver / decoder. Referring to Figure 3, the software architecture comprises an Execution Time Machine 4008, a Device Manager 4068 and a plurality of devices 4062 and device units 4066 for executing one or more applications 4056. As used in this description , an application is a piece of computer code for controlling high-level functions or preferably the receiver / decoder 13. For example, when the end user places the focus of the remote control 25 on a lower object seen on the screen of the television set 14 and press a validation key, the instruction sequence that is associated with the button is executed. An interactive application proposes menus and executes commands at the request of the end user and provides related data for the purpose of the application. The applications can be either resident applications, that is, stored in the ROM read-only memory (or immediate memory FLASH or other non-volatile memory) of the receiver / decoder 13, or transmitted and copied into the RAM or memory direct access memory. Immediate receiver / decoder 13. The applications are stored in memory locations in the receiver / decoder 13 and are represented as resource files. The resource files comprise files of graphical object description units, variable block unit files, instruction sequence files, application files and data files, as described in greater detail in the patent specifications mentioned above. The receiver / decoder contains memory divided into a direct access memory volume, an immediate memory volume and a read-only memory volume, but this physical organization is distinct from the logical organization. The memory can also be divided into memory volumes associated with the different interfaces. From a point of view, the memory can be considered as part of the hardware; from another point of view, the memory can be considered as supporting or containing the total system shown apart from the hardware. The central processor 20 can be considered as centered on a runtime machine 4008 that is part of a virtual machine 4007. This is coupled to the applications on one side (the "high level" side), and on the other hand (the "low level" side), via several intermediate logical units discussed below, to the hardware of the receiver / decoder 4061, which comprises the various ports as discussed above (ie, for example, the serial interface 21, the parallel interface 22, modem 23, and control unit 26). With specific reference to Figure 3, several applications 4057 are coupled to the virtual machine 4007; some of the most commonly used applications may be more or less permanently resident in the system, as indicated in 4057, while others will be copied into the system, for example from the MPEG data stream or from other ports as required . The virtual machine 4007 includes, in addition to the runtime machine 4008, some resident library functions 4006 which include a toolbox 4058. The library contains miscellaneous functions in C language used by the machine 4008. These include data manipulation. such as compression, expansion or comparison of data structures, online drawing, and so on. The library 4006 also includes information about non-modifiable programming in the receiver / decoder 13, such as hardware and software version numbers and available shortcut memory space, and a usable function when copying a 4062 device. The functions can be copied to the library, being stored in the immediate memory or in the direct access memory. The runtime machine 4008 is coupled with a device manager 4068 that is coupled with a set of devices 4062 which are coupled with the device drivers 4060 which in turn are coupled with the ports or interfaces. In general terms, a device driver can be considered as defining a logical interface, so that two different device drivers can be coupled to a common physical port. A device will typically be attached to more than one device driver; and a device is coupled to a single device driver, the device will typically be designed to incorporate full functionality required for communication, so that the need for a separate device driver is avoided. Certain devices can communicate with each other. As will be described later, there are three ways of communicating 4064 devices to the runtime machine: by means of variables, buffers, and events that are passed to a set of event queues.

Each receiver / decoder function 13 is represented as a device 4062 in the software architecture of the receiver / decoder 13. The devices can be either local or remote. Local 4064 devices include smart cards, SCART connector signals, modems, serial and parallel interfaces, an MPEG audio and video player, and a section and table extractor in MPEG. Remote 4066 devices, executed at a remote location, differ from local devices because a port and procedure must be defined by the system authority or the designer, rather than by a device and proportional device controller designed by the receiver manufacturer / decoder. The runtime machine 4008 runs under the control of a processor and a common application programming interface. These are installed in every receiver / decoder 13 so that all the receivers / decoders 13 are identical from the point of view of the application. The machine 4008 executes applications 4056 in the receiver / decoder 13. It executes interactive applications 4056 and receives events from outside the receiver / decoder 13, displays text graphics, calls devices for services and uses functions of the library 4006 connected to the machine 4008 for specific calculations.

The runtime machine 4008 is an executable code installed in each receiver / decoder 13, and includes an interpreter for interpreting and executing applications. The machine 4008 is adaptable to any operating system, including a single task operation system (such as MS-DOS). The machine 4008 is based on process sequence units (which take several events such as key presses, to carry out several actions), and contains its own programmer to handle event queues from different hardware interfaces. It also handles the display of graphics and text. A process sequencing unit comprises a set of action groups. Each event causes the process sequencer unit to move from its current action group to another action group depending on the character of the event, and execute the actions of the new action group. The machine 4008 comprises a code loader for loading and unloading applications 4056 in the memory of the receiver / decoder. Only the necessary code is loaded into direct access memory or immediate memory, in order to ensure optimal use. The downloaded data is verified by an authentication mechanism to avoid any modification of a 4056 application or the execution of any unauthorized application. The machine 4008 further comprises a decompressor. As the application code (a form of intermediate code) is compressed to save space and to quickly download the MPEG stream or via an integrated receiver / decoder mode, the code must be decompressed before loading it into direct access memory. The machine 4008 also comprises an interpreter to interpret the application code to update various variable values and determine status changes, and an error verifier. Before using the services of any 4062 device, a program (such as a sequence of application instructions) must be declared as a "client", that is, a logical access to device 4062 of a 4068 device manager. The administrator gives the client a customer number to which it refers in all accesses to the device. A device 4062 can have several clients, the number of clients for each device 4062 is specified depending on the type of device 4062. A client is introduced to the device 4062 by a procedure of "Device: Open Channel". This procedure assigns a customer number to the customer. The client can be removed from the 4068 device manager from the client list using a "Device: Close Channel" procedure. Access to the devices 4062 provided by the device manager 4068 can be synchronous or asynchronous. For synchronous access, a "Device: Call" procedure is used. This is a means of accessing data that is immediately available or functionality that does not involve waiting for the desired response. For asynchronous access, a "Device: I / O" procedure is used. This is a means of access data that involves waiting for a response, for example scanning tuner frequencies to find a multiplex or returning to a table from the MPEG stream. When the requested result is available, an event is placed in the queue of the machine to signal its arrival. Another procedure "Device: Event" provides a means to handle unexpected events. As noted above, the main cycle of the runtime machine is coupled with a variety of process sequencer units, and when the main cycle encounters a suitable event, the control is temporarily transferred to one of the sequencer units of processes. In this way, you can see that the central processor provides a platform that has considerable flexibility to allow an application to communicate with a variety of devices. In the case of received audio and video signals, the MPEG packets containing these signals are demultiplexed and filtered so that they pass real-time audio and video data in the form of an elementary packet (PES) data stream. audio and visuals to dedicated audio and video processors or decoders 33, 34. The converted output of the audio processor 33 passes to a preamplifier 35 and thereafter via the audio output of the receiver / decoder. The converted output of the video processor 34 passes via a graphics processor 36 and a PAL / SECAM encoder 37 to the video output of the receiver / decoder. Referring to Figure 2, the graphics processor 36 is preferably designed to generate a display screen that combines moving images together with superimposed text or other images. More specifically, you can combine four layers: a still image layer, a moving image layer, a graphics layer, and a cursor layer. As described in more detail below, the graphics processor 36 additionally receives graphics data for display (such as generated images, etc.) from the central processor 20 and combines this information with information received from the video processor 34 to generate the screen display. As shown in greater detail in Figure 4, the graphics processor 36 includes dedicated direct access memory area 40, the dedicated microprocessor 41, and the graphics library 42. Referring to Figure 5, the direct access memory area. 40 of the graphics processor 36 is divided into several buffer areas; a fixed image layer buffer area 43, a moving image layer buffer 44 area and a graphics layer 45 buffer area. The fixed image layer is used for background images of a nature Widely static The circuitry and software associated with the stationary image layer buffer area 43 can preferably generate an image thereon by any desired combination of the following processes: generate and fill rectangles with specific colors (defined by up to 24 bits); - copy images received from the MPEG data stream; - repeat an image that occupies less of the area of the full screen, to produce a wallpaper effect. The moving image layer is used for the incoming video signals obtained from the MPEG data stream. The circuitry and software associated with the moving image layer buffer area 44 can preferably be adapted to the size and scale of the incoming images, and combine images of a plurality of sources in different areas of the buffer area. The graphics layer is used to produce titles and icons (graphics). Titles are often subtitles, which appear centered near the bottom edge of the image, but may also appear in other positions on the image. The icons are usually geometric shapes such as rectangles, circles, backgrounds, and dialog boxes (you will notice that the term "icon" here is used in a broad sense). The graphics layer is defined by one or more rectangular regions, each rectangular region being defined by the coordinates of the upper left corner of the region and the size of the region. In accordance with the foregoing, the buffer area of the graphics layer 45 is subdivided into a plurality of buffer regions 45A, 45B, ... 45N, a buffer region for each of the rectangular regions of the memory. graphics layer. Each buffer region 45A ... comprises a plurality of sub-areas 45A, 45A ... 45An. Each buffer region is created by a "subtitle" device 4062, under the control of an application 4056, in the central processor 20 using a command procedure stored in the graphics library 42. Referring to FIG. 6, the content of the buffer area of the still image layer 43 and the moving image layer buffer area 44, as read, are mixed together by a mixer circuit 50 which can be set to combine (alpha combine) , that is, in a translucent way) these departures; and the output of the mixing circuit 50 is combined with the content of the buffer area of the graphics layer 45, as the content is read, by a similar mixing circuit 51. The output of that mixing circuit is combined with the output of a hardware cursor generator 52 combining the circuit 53 which superimposes a cursor signal on the combination of the first layers. The cursor layer is preferably superimposed opaquely, that is, without the blending option, on the combination of the first three layers, so that the combination of the first three layers darkens completely within the area of the cursor. However, one of the available bit values of the cursor pixels is preferably "transparent", so that the cursor effectively has "holes" in it through which the underlying combined image of the first three layers can be viewed. . This four-layer structure produces potential problems with respect to the third layer, that is, the graphics layer. These problems arise due to two separate types of display elements, titles and icons, being generated in the same layer. Therefore there is the possibility of conflict between these two types of display elements.

For example, it will often be desirable to change titles and icons at different times (and it will often be desirable for icons to remain in place longer than titles). As noted above, the fact that titles can appear in any position on the screen, instead of only in the standard closed caption position, means that this possibility of conflict is substantial. To overcome this problem, each buffer region 45A, 45B ... includes two buffer subareas 45A ° and 45A1 which are reserved for use by the subtitle device 4062 for constructing and displaying subtitles. The subtitle device 4062 in the central processor 20 selects which of the two buffer subareas 45 and 45A will be used to receive incoming data for display and produces a suitable command for the graphics processor 36. In turn, the microprocessor 45 of the graphics processor 36 directs the incoming data to the selected buffer sub-areas. For this purpose, the two buffer subareas 45A ° and 45A1 are treated as a "working buffer" and a "display buffer". The sub-area in which the input data is currently being fed is the working buffer, so that its content will be changing. The received data (subtitles) are directed to the two buffer subareas 45A ° and 45A alternately. In other words, the 4062 subtitling device inverts the roles of the two sub-areas each time the working buffer has a new full subtitle page to display, since the contents of that sub-area will not change anymore, giving a stable image the which is acceptable to the viewer so that the sub-area can be used as the display buffer. The content of the display buffer is read as the graphics layer for combination with the still image layer and the combined moving image layer. The interval between the exchange of papers of the two subareas 45A ° and 45A, that is, between the exchange of the display working buffer, is typically from 5 to 10 seconds. At this point, the subtitle device 4062 in the central processor 20 produces a suitable command to the graphics processor 36 to exchange the roles of the two subareas 45A ° and 45A, and, in turn, the microprocessor 41 of the graphics processor 36 clarifies the content of the other subarea and directs the incoming data to that subarea. Each buffer region 45A, 45B ... includes another additional buffer area, namely an icon buffer area 45A1, 45B1 ..., as shown in Figure 5. Each icon buffer area 45A1 comprises one or more sub-areas of icons buffer, 45A2, 45A3 ... up to 45A15. Each subarea of icon buffer contains respectively icon image data. The icon image can be generated by software stored in the central processor 20, stored in the direct access memory area 20A (or the buffer area) or the central processor 20 and copied by the central processor 20 in a sub-area of designated icon buffer of the direct access memory area 41 of the graphics processor 36. As soon as an icon image has been stored in the graphics processor 36, it remains in its buffer sub-area and can be copied repeatedly to either of the two. buffer subareas 45A ^ and 45A whenever required. In this way, a complete series of icon images can be constructed, which can be used in any sequence and at any time that is required. The combination of the two images, the subtitle image in one or another of the sub-areas of buffer 45A? and 45 and the icon image in the buffer area of icon 45A1, is achieved by copying the icon image in the working buffer, that is, in either of the two sub-areas 45A ° and 45A1 is not currently in the display buffer. As specified by the control application, the subtitle device 4062 produces an appropriate command to the graphics processor 36 to copy the contents of a specified icon buffer subarea to the working buffer just before the working buffer the display buffer becomes, that is, when a complete subtitle page has been stored in the working buffer. With the above arrangement, the currently displayed icon image is stored in the display buffer, the next icon image to be displayed may already be stored in the working buffer, and a new icon image may be under construction by the icon generator while the job buffer is receiving subtitle data. This arrangement requires synchronization between the exchange of working and adjacent reproduction buffers and the construction of new icon images. At any time, the application controlling the 4062 subtitling device may require that the currently displayed icon image be changed without altering the subtitle displayed, for example, after the entry of a command from remote control 25. In this case , the subtitle device 4062 outputs a command to the graphics processor 36 to copy an icon image stored in the buffer area of the icon immediately to the display buffer on the image of the icon already stored therein. In summary, when a subtitle screen has been fully received in the data buffer area, a central processing unit in the receiver / decoder, under the control of a device, passes data from icons to the data buffer area , preferably just before the data stored in the data buffer area is combined with other data to provide video data. Therefore, in the case of an overlap between the icon and part of the subtitle, the icon can be placed over that part of the subtitle, but the non-overlapping parts can be displayed at the same time as the icon. The precise details of the implementation of several functions described above, and their distribution between hardware and software, are a matter of choice for the implementer and will not be described in detail. However, it will be noted that the integrated circuits capable of performing the operations required in the receiver / decoder are commercially available or can be easily designed, and these can be used as the basis for a hardware accelerator or more preferably modified to produce an accelerator. dedicated hardware, to implement several of the required operations, thereby reducing the processing power required to run the software. However, the required operations can be implemented in software if there is sufficient processing power. Modules and other components have been described in terms of the features and functions provided by each component, along with optional and preferable features. With the information given and with the specifications provided, the actual implementation of these characteristics and the precise details are left to the implementer. As an example, certain modules could be implemented in software, preferably written in the programming language C and preferably compiled to run with the processor used to run the application; however, some components can be run on a separate processor, and some or all of the components can be implemented using dedicated hardware. The above modules and components are illustrative only, and the invention can be implemented in a variety of ways, and, in particular, some components can be combined with others that perform similar functions, or some can be omitted in simplified implementations. The hardware and software implementations of each of the functions can be mixed freely, both between components and within a single component. It will be readily understood that functions performed by hardware, computer software, and the like are performed on or using electrical signals and the like. Software implementations can be stored in a read-only memory, or they can be patched in immediate memory. It will be understood that the present invention has been described above and only by way of example, and modifications of details can be made within the scope of the invention. Each feature described in the description, and (where appropriate) the claims and drawings may be provided independently or in any suitable combination.

Claims (22)

1. A method for processing video data in a receiver / decoder comprising at least one port for receiving data and memory elements comprising a data buffer area for storing incoming data for display, and a graphics buffer area to store graphics data, said method comprises passing graphics data stored in the graphics buffer area to the data buffer area for combination with the display data stored therein. A method according to claim 1, wherein the data buffer area comprises two sub-areas of data buffer, the incoming display data being directed to one of the sub-areas at a time. 3. A method according to claim 2, wherein the two sub-areas are exchanged so that other incoming display data is stored in the other sub-area and the graphic data stored in the graphics buffer area is passed to the other sub-area. subarea. A method according to claim 3, wherein the two sub-areas are exchanged immediately after the graphics data stored in the graphics buffer area is passed to one of the data buffer sub-areas. A method according to any preceding claim, wherein the graphics buffer area comprises a plurality of graphics buffer sub-areas in which the graphics data is stored, the graphics data being passed to the buffer area data from a selected one of the graphics buffer sub-area. 6. A method according to any preceding claim, wherein the combined graphics data and display data are combined with other received data to provide video data. 7. A method according to claim 6, wherein the graphic data stored in the graphics buffer area is passed to the data buffer area for combination with display data stored therein immediately before the data storage area. Charts thus combined and the exhibition data are combined with the other data received. A method according to any preceding claim, wherein the video data comprises four data layers, the combined graphics and the display data comprise one of said layers. A method according to claim 8, wherein the four data layers comprise the combined graphics and the display data layer, a fixed image data layer, a moving image data layer, and a layer of cursor data. 10. A method according to claim 9, wherein the moving image data layer and the display data comprise at least part of an MPEG data stream. 11. A receiver / decoder comprising at least one port for receiving data, memory elements comprising a data buffer area for storing incoming data for deployment, and a graphics buffer area for storing graphics data, and elements for passing the graphic data stored in the graphic data memory area to a data buffer area for its combination with display data stored therein. A receiver / decoder according to claim 11, wherein the data buffer area comprises two or more data buffer, and the receiver / decoder further comprises elements for dividing incoming data in one of said sub-areas. A receiver / decoder according to claim 12, further comprising control elements, the address elements being arranged to direct S7 input display data to one of the data buffer sub-areas as specified by the means of control. 14. A receiver / decoder according to claim 12 or 13, which further comprises means for exchanging the two sub-areas so that other additional display data are storable in the other sub-area and the graphic data stored in the graphics buffer area is passable to the other sub-area. A receiver / decoder according to claim 14, wherein the exchange element is adapted to exchange the two sub-areas of data buffer immediately after the graphics data stored in the graphics buffer area is passed to one of the sub-areas of data buffer. 16. A receiver / decoder according to any of claims 11 to 15, wherein the graphics buffer area comprises a plurality of graphics buffer sub-areas in which the graphic data is storable, being passable the graphic data to the data buffer area from a selected one of the graphics buffer sub-areas. 17. A receiver / decoder according to any of claims 11 to 16, further comprising elements for combining the combined graphics and the displayed data with other received data to provide video data. A receiver / decoder according to claim 17, wherein the passage element is arranged to pass graphics data stored in the graphics buffer area to the data buffer area for combination with the display data stored therein immediately before the combining elements combine the combined graphs and display data with the other received data. 19. A transmission and reception system including a receiver / decoder according to any of claims 11 to 18, and means for transmitting said data. 20. A method for processing video data in a receiver / decoder substantially as described herein with reference to the accompanying drawings. 21. A receiver / decoder substantially as described herein with reference to the accompanying drawings. 2

2. A transmission and reception system substantially as described herein with reference to the accompanying drawings.