CZ331199A3 - Retrieving computer file from a transmitter via a receiver(decoder into a computer - Google Patents

Abstract

The file, or part thereof, is divided into a series of R data groups and each of these groups is divided into a series of C blocks of data. Yippee a group of redundant blocks is created, each of which is a the redundant block is related to one of the data blocks blocks in R groups by being a XOR bit function (non-equivalence) or XNOR of these data blocks. Each from data block groups and a group of redundant blocks are repeatedly transmitted from the transmitter (2008). In the receiver / decoder (2020) at least some of the broadcast blocks are received and transmitted to a computer (18). The computer (18) is used for determining for at least one of the received redundant blocks, whether this redundant block and all up to one from the relevant data blocks, if yes, then regenerates the one data block. Lost data blocks they can thus be regenerated without waiting for recurrence broadcasting.

Description

Downloading a computer file from a transmitter via a receiver / decoder to a computer

Technical field

The present invention relates to: a method of downloading a computer file from a transmitter (such as a satellite uplink) via a receiver / decoder (such as a digital satellite television setup control box) to a computer (such as a PC or workstation);

Computers for use in performing part of such a method;

A recording medium (such as a diskette or CD-ROM) carrying a computer program for programming the processing means of such a computer;

An MPEG broadcasting system; and a receiver / decoder, which is arranged to receive MPEG video and / or audio data tables and computer file data blocks.

BACKGROUND OF THE INVENTION

The advent of digital broadcasting systems designed primarily for broadcasting television signals, in particular, but not exclusively, satellite television systems has opened the possibility of using these systems for other purposes. One of these other purposes or options is to make computer files or software available for download to the end user.

Data errors occur relatively frequently in such transmission systems. While .but these errors can often be corrected in case of errors in video or audio data with • · · ·

• · ·

Using interpolation techniques and the like, an error in only a single bit of a computer file can make the file unusable.

Thus, a first aspect of the present invention relates more specifically to a method of downloading a computer file from a transmitter via a receiver / decoder to a computer, comprising the steps of: splitting the file into blocks of data; transmitting blocks from a transmitter; receiving transmitted blocks at the receiver / decoder; and feeding the received blocks from the receiver / decoder to the computer. The blocks typically include CRC codes so that they can be tested for validity, and the transmission of the blocks can usually be repeated, so that if the block is not received correctly or not at all, for the first time when it is transmitted, it can be received at the second or subsequent subsequent transmissions. The problem with such a scheme is the additional time needed to receive a file if one or more blocks are not validly received. In the extreme case, if only the last block is not validly received, then the total download time will be approximately double. Another problem associated with this scheme is that if the blocks are not downloaded in the order in which they are transmitted, for example, because the download speed from the receiver / decoder to the computer is less than the download speed from the transmitter to the receiver / decoder, then several blocks can be relatively large. In an extreme case, the latency for the last block may be nearly as large as the time required to transmit a complete set of blocks, although all of the blocks are validly received.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provided a method of downloading a computer file from a transmitter via

• · · ·

A computer receiver / decoder, the method comprising the steps of: splitting a file, or a portion thereof, into a series of R groups of data, and further splitting each of the groups into a series of C blocks of data; forming groups C of redundant blocks, wherein each redundant block is related to a corresponding one of the data blocks in the R groups by being bit non-equivalence or equivalence of those data blocks; transmitting each of the data block groups and the redundant block group from the transmitter; receiving at least some of the transmitted blocks in the receiver / decoder; feeding the received blocks from the receiver / decoder to the computer; and determining with the computer for at least one of the received redundant blocks whether the redundant block and all but one of its respective data blocks have been received, and if so regenerating said one data block by performing a non-equivalence or equivalency bit operation on the redundant block and the corresponding received data blocks.

For the avoidance of doubt, reference to the bitwise operation of the non-equivalence to a plurality of data blocks means that each bit of the first block is executed with an XOR (non-equivalence) function with the corresponding bit of the second block. then to the last of the blocks. For simplicity, it is the first bit of the first block with which the XOR function is performed with the first bit of the second block, with the result of this operation being performed with the XOR function with the first bit of the third block and so on to determine the first result bit and the like , third bits, and so on. However, it is of course possible to use different predetermined block bit permutations in XOR operations. A similar comment applies to cases in which equivalence operations (XNOR) are used instead of non-equivalence operations.

The first aspect of the present invention provides the advantage, especially towards the end of the file download operation, that if the data block has not yet been received, it may be possible to regenerate the block from the respective redundant block and the corresponding data blocks already received without having to wait until the remaining data block is transmitted and validly received. If there was a problem in transmitting or receiving a particular block, then there is a relatively high probability that there will also be a problem in transmitting or receiving a subsequent block in the same series of C blocks. However, by appropriately selecting a C value, the probability that there will also be a problem of sending or receiving a corresponding block in subsequent series of C blocks will be relatively small. It should be understood that the addition of such redundant blocks will increase the time required to transmit all of the blocks by 100 / R%. However, by appropriately selecting the value of R, it can be achieved that the advantages provided by this aspect of the present invention outweigh this disadvantage. Typically, the values of C and R may be selected as 50 and 10, respectively.

The determination and regeneration steps may be performed for only some of the received redundant blocks, particularly those approaching the end of the file download operation. However, these determination and regeneration steps are preferably performed for each of the received redundant blocks for which all but one of the respective data blocks have been received. In the latter case, the method of the invention may further comprise the step of determining when sufficient of the blocks have already been received to allow regeneration of any remaining blocks and then interruption of receiving further blocks for the file or a portion thereof. hence, the regeneration steps may take place after all the required blocks have been received.

R and C values can be fixed for all file download operations. However, to provide flexibility, the method further comprises the steps of transmitting from the data transmitter indicating the values of the numbers R and C, receiving the R and C data at the receiver, and transmitting the data R and C to the computer; wherein the computer is able to use the supplied R and C data to determine to which of the data blocks each redundant block relates.

The blocks are preferably arranged such that the i-th (for i = 1 to C) one of the redundant blocks in the group C of the redundant blocks is thus related to the i-th data block in each of the R groups of C data blocks. Of course, other relationships are also possible.

According to a second aspect of the present invention, there is provided a computer for use in performing part of the method of the first aspect of the invention, the computer comprising: means for receiving blocks from a receiver / decoder; means for processing received blocks, the processing means being programmed to determine for at least one of the received redundant blocks whether the redundant block and all but one of its respective data blocks have been received, and if so to regenerate said one data block by executing a bit operations of non-equivalence or equivalence on the redundant block and respective received data blocks; and a memory means for storing the received data blocks and any regenerated data block.

Preferably, the processing means is programmed to perform this determination and regeneration for each of the received redundant blocks for which all but one of the respective data blocks have been received. In this case, the processing means is preferably programmed to determine when sufficient blocks have already been received to allow regeneration of any remaining data blocks, and to force the receiving means to interrupt receiving other blocks of the file or a portion thereof.

Preferably, the receiving means is able to receive data indicating the values of the numbers R and C, and the processing means is programmed to use the R and C data to determine to which of the data blocks each redundant block relates.

Preferably, the processing means is programmed to join together the received data blocks and any such regenerated data blocks to reconstruct the computer file or part thereof, and the memory means is able to store the reconstructed file or part thereof.

According to a third aspect of the present invention, a recording medium is provided carrying a computer program for programming the computer processing means of the second aspect of the invention to operate as described above.

According to a fourth aspect of the present invention, an MPEG broadcast system is provided comprising: means for splitting a file, or a portion thereof, for downloading to a receiver / decoder into a series of R groups of data and further splitting;

these groups into a series of C blocks of data; means for regenerating a group C of redundant blocks, each of which is related to a respective one of the data blocks in the R groups, being bit non-equivalence or equivalence of those data blocks; and means for transmitting each of the data block groups and the redundant block group.

A fifth aspect of the present invention also relates more specifically to a method of downloading a computer file from a transmitter via a receiver / decoder to a computer, the method comprising the steps of: splitting the file into blocks of data; retransmitting these blocks from the transmitter; receiving transmitted blocks in a receiver / decoder; and feeding the received blocks from the receiver / decoder to the computer.

The data blocks are transmitted from the transmitter to a 15 receiver / decoder at a fixed data rate, which can usually be 700 kbit / s. To allow the receiver / decoder to be used with computers having different capabilities, and to use those capabilities, the receiver / decoder must be able to download blocks to the computer in different modes having different data rates, such as the IEEE 1284 ECP mode having a typical data rate of 1. Mbit / s, IEEE 1284 mode and parallel bytes having a typical data rate of 400 kbit / s, IEEE 1284 mode with parallel four-bit words having a typical data rate of 150 to 200 kbit / s, and RS-232 serial mode having 25 maximum a data rate of perhaps 115 kbit / s and a conventional data rate rather substantially lower than this maximum rate.

When the data rate to the receiver / decoder 3Q is faster than the data rate from the receiver / decoder, certain steps must be taken to ensure that all of the data from the receiver / decoder is quicker. The data blocks were received and downloaded to the computer. The data blocks were received and downloaded to the computer. . This could be achieved by creating a buffer in the receiver / decoder that is large enough to hold the entire computer file. But that would be expensive, of course. Alternatively, the minimum data rate from the receiver / decoder to the computer could be estimated by dividing the expected data rate into the receiver / decoder to detect a rounded integer X, and then one in each X of the received blocks could be downloaded to the computer so / X blocks would be received in one phase and this phase could then be repeated X times to download all N blocks. However, in terms of efficiency, this procedure is dependent on the fact that the data rate to the computer is accurately estimated, but this is not possible because this data rate may vary. Serious problems with this procedure would also arise if a particular data block were lost. A fifth aspect of the present invention is concerned with finding solutions to these problems.

According to a fifth aspect of the present invention, there is provided a method of downloading a computer file from a transmitter via a receiver / decoder to a computer, the method comprising the steps of: splitting a file into a number of (N) blocks; retransmitting these blocks of the file from the transmitter, each with the identity of the block; and in the receiver / decoder, generating N flags that are initially reset, one for each block; and cyclically performing the steps of: receiving one of the blocks being transmitted and determining whether a flag for the block is set and, if not, passing the block from the receiver to the computer and setting the flag for the block; until all of the flags are set.

·· ♦ * <·

It should therefore be understood that now it does not matter in which order the blocks are received by the receiver / decoder. The receiver / decoder is able to determine whether a block is needed and, if so, download the block to the computer. If the receiver / decoder can download blocks to the computer as quickly as the blocks can be downloaded to the receiver / decoder, then most, if not all, of the blocks will be downloaded sequentially. However, if the receiver / decoder cannot download blocks to the computer as quickly as the blocks can be downloaded to the receiver / decoder, for example at only half the speed, then generally speaking, alternating blocks will be downloaded during one phase and then the remaining blocks. If the ratio between download / decoder download speed and receiver / decoder download speed changes, then the arrangement described above will automatically adjust the interleaving of the blocks.

Preferably, after each handover step, the computer is arranged to send a acknowledgment of the handover

Of a Q block to a receiver / decoder, and wherein, in response to receiving this acknowledgment for that block, an adjustment step is performed for each block. Accordingly, if the block is not properly acknowledged by the computer, then the receiver / decoder downloads the block again at the next possible opportunity.

The method of the invention may further comprise the step of repeating the method, but without the step of resetting the flags. Thus, if there is an interruption in receiving the blocks, the download method may be resumed without retrying the download of blocks that have already been received.

• · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · ····

According to a sixth aspect of the present invention there is provided a receiver / decoder that is arranged to receive MPEG video and / or audio data tables and computer file blocks, the computer file being received as a plurality of N such blocks that are cyclically received, each of which includes identifying the block, the receiver / decoder comprising: means for storing a plurality of N flags that are initially reset, one for each block of the computer file; means for temporarily storing the currently received block of the computer file; means for passing the block stored in the block storing means to the computer; and control means, which is arranged to determine whether a flag for the currently received block is set in the flag storing means; and, if not, to force the block handler to forward the block from the block storage means to the computer and to set a flag for the block in the flag storage means.

The receiver / decoder of the invention further preferably comprises means for receiving a confirmation from the computer that such block o has been received from the block handover means, and wherein the control means is able to set a flag for that block in response to receiving the acknowledgment for that block.

Advantageously, the control means may be controlled to create a recovery of receiving computer file blocks after a lost connection without resetting the flags.

The block handler means may be one of a plurality of such block handler means that exist in different types, for example comprising at least two of: a parallel IEEE port with ECP mode; IEEE parallel port with EE · · · · · · * * * EE EE EE port EE EE port port EE port port port • byte mode; IEEE parallel port with 4-bit word mode; and RS-232 serial port.

It should be understood that features of the first and fifth aspects of the present invention can be used together in a 5 method of downloading a computer file from a transmitter via a receiver / decoder to a computer.

Preferred features of the present invention will be described in the following description purely by way of example with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows the overall architecture of a digital television system;

Fig. 2 shows the architecture of the interactive lo system of the digital television system of Fig. 1;

Giant. 3 is a schematic representation of a receiver / decoder interface forming part of the system of FIGS. 1 and 2;

Giant. 4 is a schematic representation of a remote control unit (remote control) used in a digital television system;

Giant. 5 illustrates an arrangement of blocks forming a collection 25 to be downloaded;

Giant. 6 illustrates the order of blocks while a file is downloaded;

Fig. 7 is a functional diagram of a receiver / decoder during a file download operation;

· .. · ·........ · · ·.

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Figures 8 to 12 are individual flowcharts illustrating processes that take place in a receiver / decoder during a file download operation;

Fig. 13 is an alternative illustration of an arrangement of blocks forming a file to be downloaded;

Figure 14 is an illustration in greater detail of the first matrix of the blocks shown in Figure 13;

Fig. 15 is an illustration of the generalized matrix of blocks shown in Fig. 13;

Fig. 16 is a flowchart illustrating a process that takes place in an application and data service channel in a television system to prepare a download file; and

17 is a flowchart illustrating a process that takes place on a computer during a file download operation.

DETAILED DESCRIPTION OF THE INVENTION

An overview of the digital television system 1000 of the present invention is shown in Fig. 1. The invention includes a mostly conventional digital television system 2000 that uses the known MPEG-2 compression system to transmit compressed digital signals. More specifically, the MPEG-2 compressor 2002 at the broadcast center receives a digital signal stream (usually a video signal stream). The compressor 2002 is coupled to the multiplexer and encoder 2004 via a link 2006. The multiplexer 2004 receives a plurality of additional input signals, assembles one or more transmit streams, and transmits

9 9 9 9

9

9 9 999999 •

999 9999 99 99 compressed digital signals to the transmitter 2008 of the broadcast center via the 2010 connection, which of course can be represented by a number of different forms including telecommunications lines. Transmitter 2008 transmits electromagnetic signals via uplink 2012 to satellite transponder 2014, where these signals are electronically processed and transmitted via theoretical downlink 2016 to terrestrial receiver 2018, typically in the form of a parabolic antenna owned or rented by the end user. The signals received by receiver 2018 are transmitted to an integrated receiver / decoder 2020 owned or rented by the end user and associated with the end user television equipment 2022. The receiver / decoder 2020 decodes the compressed MPEG-2 signal into a television signal for the television device 2022.

The conditional access system 3000 is coupled to the multiplexer 2004 and receiver / decoder 2020 and is located partly in the broadcast center and partly in the decoder. This system allows the end user to access digital 2 Ω television broadcasts (transmissions) from one or more broadcasters. A smart card capable of decoding commercial bidding messages (i.e., one or more television programs that are sold by the broadcaster) can be inserted into a 25 receiver / decoder 2020. Using a decoder 2020 and a smart card, the end user can purchase commercial offers either in prepay mode or pay-per-view mode.

The multiplexer 2004 and receiver / decoder 2020 are also connected with the interactive system 4000, which is again located ·· ····

99 »· * 1»

AND

9 9 9 partly in the broadcast center and partly in the decoder, which allows the end user to interact with various applications via modem return channel 4002.

Giant. 2 illustrates the general architecture of the interactive television system 4000 of the digital television system 1000 of the present invention.

For example, this interactive system 4000 allows end users to purchase items from on-screen catalogs, consult local news and weather maps on demand, and play games through their television devices.

In summary, the interactive system 4000 includes four main elements • a creative tool 4004 in the broadcast center or elsewhere to allow the broadcaster to create, develop, debug and test applications;

Application and data service channel 4006 in the broadcast center, coupled to the creative tool 4004 to enable the broadcaster to prepare, validate and format applications and data for delivery to multiplexers and an encoder 2004 for inclusion in an MPEG-2 transport stream (typically its private portions) to be sent to the end user;

A virtual machine including an execution means (RTE) 4008, which, in executable code, is installed in a receiver / decoder 2020 owned or rented by the end user to allow the end user to receive, verify, decompress and download (download) applications to the work memory of the decoder 2020 for execution.

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99

This execution means 4008 also implements resident general purpose applications. The execution means 4008 is hardware and operating system independent;

a modem return channel 4002 between the receiver / decoder 2020 and the application and data server 4006 to enable signals instructing the application and data server 4006 to load data and applications into the MPEG-2 transport stream at the request of the end user.

The interactive television system operates using applications that control the functions of the receiver / decoder and the various devices contained therein. Applications are represented in executing means 4008 as source files. A module is a collection of source files and data. The receiver / decoder memory volume is the memory space for the modules. The modules may be downloaded to the receiver / decoder 2020 from the MPEG-2 transport stream.

The physical interfaces of receiver / decoder 2020 are used to download data. Referring to Fig. 3, it will be seen that the decoder 2020 comprises, for example, six inserter devices; MPEG stream tuner 4028, serial interface 4030, parallel interface 4032, modem 4034, and two smart card readers 4036.

For purposes of this description, the application is a machine code section for controlling the high-level functions of the receiver / decoder 2020. For example, when the end user directs the focus of the remote controller 2026 (as shown in more detail in FIG. 4) at the button object seen in • fe ···· Feef feef feef feef feef feef feef feef feef feef feef feef feef feef feefefef feefefef feefefefefefe fefe fefe fefe fefe screen 2022 and press the enter key to start the sequence of instructions, associated with this button.

The interactive application offers menus and executes commands at the request of the end user and provides data related to the purpose of the application. The applications may be either resident applications, that is, they are stored in ROM (or FLASH or other non-volatile memory) of the receiver / decoder 2020, or they may be transmitted and downloaded to the RAM (or FLASH) of this decoder 2020.

Examples of applications are: • Initialization applications. The receiver / decoder 2020 is equipped with a resident initialization application, which is an adaptable set of modules (this term is defined in more detail below), allowing the receiver / decoder 2020 to operate immediately in an MPEG-2 environment.

This application provides essential features that can be modified by the broadcaster if desired. This app also provides an interface between resident apps and downloaded apps.

• Startup application. The startup application allows any application, whether downloaded or resident, to work in the receiver / decoder 2020. This application acts as a bootloader executed when entering the service to run the application. The startup application is downloaded to RAM and can therefore be easily updated. It can be arranged so that the interactive applications available on each channel can be selected and launched either immediately after downloading or after downloading in advance. In the case of a download in advance, the application is downloaded to «« 4 4 · · * • · · 4 • 4 ·

4 4

44 44 • 4 ·. 4 »4

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4444 44 «4 memory 2024 and is activated by the on-demand startup application.

• Program guide. Program Guide is an interactive application that provides comprehensive information about programs. For example, it can provide information, say, about one week TV programs that will be featured on each channel of a digital TV file. Press the key on the remote

......... to the controller 2026, the end user enters an additional screen overlaying the event (s) shown on the television screen 2022 This added screen is a browser providing information about current and subsequent events (s) on each digital TV file channel. By pressing another key on the remote control 2026, the end user enters another application that displays a list of event information within a week. The end user can also search and sort events according to simple and customized criteria.

The end user can also directly access the selected channel.

• Pay per view application. The pay-per-view application is an interactive service available on each PPV channel of a digital television file in conjunction with a conditional access system 3000. _R The end user can enter into the application using the program guide and search channels. In addition, the application will start automatically as soon as the PPV event is detected on the PPV channel. The end-user can then purchase an ongoing event either through his / her subsidiary. 9 9 9 9 · · ······ · · · ······· · · · · Smart cards 3020 or via communication server 3022 (using a modem, telephone and DTMF codes, MINITEL system or the like). This application can be either resident in ROM receiver / decoder 2020 or downloadable to RAM receiver / decoder 2020.

• PC download applications. Upon request, the end user may download computer software using this PC download application.

• ....... Application magazine. This magazine search application includes cyclic video broadcasting of images with end user navigation through the buttons shown on the screen.

• Quiz application. The quiz application is preferably synchronized with the transmission of the quiz program. For example, multiple answer questions are displayed on the TV screen 2022 and the end user can select an answer using the remote control 2026. The quiz application can inform the user whether the answer is correct or not and can calculate the user score.

· Application teíeshopping. In one example, this teleshopping application. the offers of goods for sale are transmitted to the receiver / decoder 2020 and displayed on the television 2022. Using the remote control 202 6, the user can select a particular item to buy.

An order for this item is sent via the modem return channel 4 002 to the application and data service channel

4006 or a standalone retail system whose telephone number has been downloaded to the receiver / decoder 2020, optionally with a credit card account loading command, which has been inserted into one smart card reader 4036 in the receiver / decoder 2020.

• Telebanking application. In one example of this telebanking application, a user inserts a bank card into one of the smart card reader 4036 at the receiver / decoder 2020. The receiver / decoder 2020 calls the user's bank using a phone number stored in the bank card or stored in the receiver / decoder 2020, and then this application provides a number of options that can be selected using the remote control 2026, such as downloading via an account balance telephone line, transferring items between accounts, requesting a checkbook, and the like.

• Internet search engine application. In one example of this web browser application, user instructions, such as a web page tracking request having a certain URL, are entered using remote control 2026 and these instructions are transmitted via modem reverse channel 4002 to application and data service channel 4006.

The respective website is then integrated into the broadcast from the broadcast center, received by the receiver / decoder 2020 via the uplink 2012, the transponder 2014 and the downlink 2016, and displayed on the television device.

2022.

The individual characters of the PC download application will now be described. A certain technical problem to be solved is that the computer to which the software is currently requested to download will have a different data input speed ·· 4 4 44

compared to the speed at which the data is transmitted. This difference can be, for example, from 9 kbit / s to 1000 kbit / s, the software being transmitted over the MPEG-2 data stream at a rate of, say, 500 kbit / s.

To solve this problem, in the broadcast center, the software is generally divided into N blocks (see Fig. 5) and then re-fed into the private section of the MPEG data stream (see Fig. 6). The receiver / decoder 2020 includes a bitmap that describes all of these software blocks. When the download is initiated, each bit in this bitmap is set to zero. The steps in the download procedure are: reading the block number; if bit = 0, sending a block to the receiving computer; and the receiving computer checks the block and sends an acknowledgment if appropriate. The receiving computer needs its own software, usually provided on a diskette (flexible disk), to connect different blocks of broadcast software. Automatic interleaving provides flow control measures. Since the data transmission rate cannot be changed, the blocks are automatically interleaved in successive cycles. According to the bit rate of the receiving computer, in successive carousel cycles, say, every third or fourth block is transmitted to the decoder 2020 until all the blocks are received.

Problems can occur if the block is lost. In general, the solution to this problem is to use the redundancy concept using the XOR (non-equivalence) function. Additional redundant blocks are added to the data stream from which the values of the lost blocks can be derived if necessary.

The PC download application will now be described in more detail. During a PC download, data is typically downloaded from the transponder 2014 to the receiver / decoder 2020 via

a 4028 MPEG stream tuner typically at a data rate of typically 700 kbit / s and from the receiver / decoder 2020 to a computer via a parallel interface 4032 or a serial interface 4030.

The receiver / decoder 2020 supports downloading to a computer via the 4032 parallel interface in IEEE 1284 ECP mode having a typical data rate of 1 Mbit / s, in a byte mode having a typical speed of 400 kbit / s and a four-bit word mode having a typical speed of 150 to 200 kbit / s.

The receiver / decoder 2020 also supports downloading to computer 10 via a serial interface 4030 in RS-232 mode, which has a maximum data rate of possibly up to 115 kbit / s and a typical data rate rather substantially less than this maximum rate. The receiver / decoder 2020 provides all these download modes to the computer for flexibility, with the user normally selecting the fastest download mode available.

When the data rate to the receiver / decoder 2020 is faster than the data rate from the receiver / decoder 2020, certain steps must be taken to ensure that all

O Γ) Data blocks were received and downloaded to the computer. This could be achieved by providing a buffer in the receiver / decoder 2020 that is large enough to hold the entire computer file. But that would be expensive, of course. Alternatively, the minimum could be estimated

O c data rate from receiver / decoder 2020 to the computer that divides the expected data rate into receiver / decoder 2020 to determine the rounded integer X, and then one in each X of the received blocks could be downloaded to the computer so N / X the blocks would be received in one phase and this phase could then be repeated X times so that all N blocks are downloaded. However, in terms of efficiency, this procedure is dependent on the fact that the data rate to the computer is accurately estimated, but this is not possible because this data rate may vary. Serious problems with this procedure would also arise if a particular data block were lost.

To solve these problems, the receiver / decoder 2020 is operatively arranged during a PC download operation as shown in FIG. 7. The incoming bit stream from the receiver 2018 goes through the block detection function 10 and can then be passed by the selector 12 to the buffer 14A or buffer 14B. The contents of the selected one of the buffers 14a, 14B can then be passed through the selector 16 and the selected one of the parallel port 4032 and the serial port 4030 to the corresponding port of the PC 18. The buffers 14A, 14B are formed through the RAM portions of the receiver / decoder 2020 is also a bit map 20. Block detection functions 10, selectors 12, 16, buffers 14A, 14B, parallel port 4032, serial port 4030, and bit map 20 are controlled by a processor 22 performing a download PC application.

The operation of the receiver / decoder 2020 during the PC download operation will now be described with reference to the flowcharts shown in FIGS. 8-12. During the initialization process, as shown in FIG. 8, in step 25 the received block is detected through the block detection function 10, and the number of N blocks from the header of each block is determined, which includes the block number i and the total number of N blocks. In step 26, bit map 20 is set with a number of bits equal to N and each bit is reset to 0. V

3 ° steps 28, 30 are the buffer flag A and the ·· ·· flag

9 9 9 9 99 9 Buffer B both set to empty. In the example described, the possible states of these flags are empty, filling, full, emptying. In step 32, the output mode to the computer is set. Then, at step 34, the initialization process proceeds to the processing of the six processes shown in the flowcharts of Fig. 9, Fig. 10A, Fig. 10B, Fig. 11A, Fig. 11B and Fig. 12, which are performed substantially in parallel.

Giant. 9 illustrates a routine that controls the start of θ download to buffers 14A, 14B. In step 36, the process waits until a new block is detected by the block detection function 10. Once the new block is detected, in step 38, the new block number i is again determined by the block detection function 10. In step 40, bit map 20 checks whether the bit (s) is set to 1, and if so, the block is ignored and the process returns to its beginning. If not, then at step 42 the buffer flag A is tested to see if it is empty, and if so, at step 44 the buffer flag A is set to fill, and then at step 46 the block download to buffer 14A begins. through the selector 12 and the process then returns to its start. If at step 42, the buffer flag A is not set to empty, then at step 48 the buffer flag B is tested to see if it is empty. If so, then in step 50, c is the buffer flag B set to fill, and then in step 52 the download of the block to buffer 14B is initiated via the selector 12 and the process then returns to its start. If none of the buffer flags is set to empty in steps 42 and 48, then the process returns to its beginning.

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Giant. 10A illustrates a routine that is performed at the end of block download to buffer 14A. In step 54, the process waits until the end of the block is detected by the block detection function 10. Then, in steps 56, 58, the block is checked using

CRC contained in the block. If the block is OK, then at step 60, the buffer flag A is set to full, while if the block is defective, the buffer flag A is set to empty in step 62, thereby ignoring the block. The complementary routine is performed at the end of the block download to buffer 14B, as shown in FIG. 10B.

Giant. 11A illustrates a routine that controls the download of a block from buffer A to PC 18. At step 64, the process waits until the buffer flag A is set to 15 full. Then, in step 66, a check is made whether the buffer flag B is set to flush, and if so, then the process waits until the buffer 14B is completely emptied. Then, in step 68, the buffer flag A is set to flush. Then, at step 70, the download of the block i in the buffer 14A is started via the selector 16 to the PC 18 using the set output mode. In step 72, the process waits until the download is complete. Then, at step 74, the acknowledgment check is performed from PC 18. If the acknowledgment is received, then at step 76. bit b (i) for block i is in c.

bit map 20 is set to 1, and then at step 78, the buffer flag B is set to blank. Then the process returns to its beginning. If the acknowledgment is not received in step 74, then step 76 is omitted, and thus downloading this block will not be considered. A complementary routine is performed to control block download from buffer 14B to PC 18, as shown in FIG. 11B.

Giant. 12 illustrates a routine that checks that the download of a computer file is complete. In step 80, it is checked that all bits b (1) to b (N) in bit map 20 are set to 1 and, if so, the file download operation is terminated with respect to receiver / decoder 2020.

Thus, it should be clear from the above description that it does not matter now in which order the blocks are received by the receiver / decoder 2020. The receiver / decoder 2020 is able to determine whether a block is needed and if so places the block in one from the buffers 14A, 14B and waits until the PC 18 is ready to receive this block. If a block fails a CRC check or if the block is not correctly acknowledged by the PC 18, then the receiver / decoder 2020 downloads the block again at the next available opportunity. Thus, if the receiver / decoder 2020 can download blocks to the PC 18 as quickly as the blocks can be downloaded to the receiver / decoder 2020, then most, if not all, of the blocks will be downloaded sequentially. However, if the receiver / decoder 2020 cannot download blocks to the PC 18.

as fast as the blocks can be downloaded to the receiver / decoder 2020, for example at only half the speed, then generally the alternating blocks will be downloaded during one phase and then the remaining blocks will be downloaded during the subsequent phase. If the ratio between download speed to receiver / decoder 2020 and download speed to receiver / decoder 2020 changes, then the arrangement

The above described will automatically set the blocking (interleaving) of the blocks.

The memory requirements of the arrangement described above, apart from the operating software requirements, are two buffers 14A, 14B and a bitmap 20. Typically, the block size will be 2 bytes (although up to 4 bytes can be included in one MPEG-2 table) and the maximum number of blocks in file will be 2 ¹⁶ blocks.

Thus, the memory requirements would be 4 kbyte cache 14A, 14B, and 2 ^16/8 = 8 kbytes bitmap for the 20th, which together account for 12 kbyte to allow downloading large files x2 2 ¹⁶ kbytes = 128 Mbytes.

In the arrangement described above, the PC 18 is programmed such that once each block has been received, the block is written to the PC 18 hard disk with a file name that includes the block number as well. Then, once all the blocks have been received, the data in the N files is combined to regenerate the original computer file.

In the following description, a modification of the arrangement described above will be described with reference to Figures 5 to 12 to solve a case in which a connection is lost between the transmitting center and the receiver / decoder 2020. In this case, the loss of connection is detected by the receiver / decoder 2020 and the user may be asked whether or not he wishes to restart the download operation. If so, then a file download is requested in the manner described above except that step 26 in Fig. 8 is omitted, so that bits 1 (b) to b (N) of the existing bitmap 20 are not reset to zero. Thus, it can be ensured that the download operation is resumed without requiring blocks that have already been downloaded to be downloaded again.

»· · · · ·

The concept of redundancy using the XOR function will now be described in more detail. In the arrangement described above with reference to Figs. 5 and 6, the data blocks were considered as mere sequences of blocks 1 to Ν. In the arrangement that will now be described, the blocks can be considered as a series of matrices, each containing (R + 1) rows and C columns of the block, as shown in Figures 13 to 15. particularly shown in Fig. 14, in the first matrix (matrix 1), the top row comprises blocks numbered i = 1 to C, the next row contains blocks numbered i = C + 1 to 2C and so on up to the bottom row which contains blocks numbered i = RC + 1 to (R + 1) C. In a more general case, the matrix numbered j, as shown in Figure 15, the top row contains blocks numbered i = (j-1) (E + 1) C + 1 to ((j-1) (R + 1) +1) C and the bottom row contains blocks numbered i = (j (R + 1) -1) C + 1 to j (R + 1) C. In the general position in row r and column c in matrix j, block number i = ((j-1) (R + 1) + (r-1)) C + c. In these matrices, the blocks in each of the rows, except for the lower row (r = 1 to R), are the data blocks into which the downloadable computer file is divided. However, the blocks in the bottom row (r = R + 1) are redundant blocks that have been calculated and added to the MPEG bitstream through the application and data service channel 4006. More specifically, as shown in FIG. download divided into data blocks, each of 2 bytes in size. In step 102, the R and C values are set. In step 104, the matrix number counter j is set to 1. In step 106, the first RC data blocks that are considered to be the matrix C of the columns and R of the data block series are read. In step 108, a redundant block is calculated for each column c = 1 to C. More specifically, the redundant block is calculated as a bitwise XOR operation on the data blocks in

·· ·· ♦ 9 9 9

999 999

9

99 column. In step 110, the redundant blocks are incorporated as an additional bottom row (r = R + 1) of the matrix. In step 112, block numbers i = (j-1) (R + 1) C + 1 to (j (R + 1) -1) C are added as headers to the data blocks, block numbers i = are added as headers of redundant blocks (j (R + 1) -1) C + 1 to j (R + 1) C, and the blocks are stored. In step 114, a test is made to determine if the end of the file has been reached, and if not, in step 116 the matrix number counter j is increased. Steps 102 to 108 are then repeated for the following RC data blocks. This continues until the end of the computer file is reached. File entry is then added to the directory or index of the MPEG-2 table, including file name, size and date, and R and C values. The processed data blocks and redundant data blocks are then ready for transmission.

Ί 5

When a user wishes to download such a file using the receiver / decoder 2020, selects the file entry from a directory or index, and the receiver / decoder 2020 then passes the file information including R and C values to the PC 18. Then, during the PC download of this file, the receiver / decoder 2020 may not function differently from the methods described above with reference to Figs. 7-12. However, the PC 18 is programmed (via a program loaded into the PC 18 from a diskette or CD- ROM or downloaded to PC 18 from receiver / decoder 2020) to work with redundant

Q '-Ί ° blocks as described below. Generally, each time the PC 18 detects that a redundant block has just been downloaded, it checks whether all but one data block in the same column of the same matrix as the received redundant block has been received. If so, the PC 18 regenerates the missing data block of the execution bit by η_ χ,. from XOR operation on received data blocks and receipt

99

4 9

9 9

999 999 • · · ·

999 9999 • ·· · redundant block and stores this regenerated data block as if it was received from the receiver / decoder 2020.

More specifically, as seen with reference to FIG.

17, in the initial step 120, the PC 18 receives the values R, C and then in step 122 receives the block. In step 124, PC 18 retrieves its block number i from the head of the received block. At step 126, PC 18 stores the block as block i. In step 128, PC 18 sends an acknowledgment to receiver / decoder 2020. on one (R1) of the blocks was received in each of the C columns. This can be done by checking the hard disk directory of the PC 18 where the blocks are stored, or preferably for speed reasons, by using a bitmap in the memory of the PC 18 that is marked when each block is stored. If at least all but one of the blocks have been stored for each column, then enough blocks have been received and the process continues to step 132, but if not, the process returns to step 122 to receive the next block. Step 132 controls the FOR-NEXT loop. For each column, the PC 18 determines in step 134 whether all of the data blocks for that column (i.e., the R-1 data blocks) have been received. If so, the FOR-NEXT loop continues to the next column. However, if not, in step 136, the PC 18 regenerates the missing data block by performing an XOR bit operation on the data blocks that have been received and on the redundant block. Then, in step 138, PC 18 stores the regenerated data block and proceeds to the next column in the FOR-NEXT loop. At the end of this FOR-NEXT loop, it proceeds to step 140, in which the computer file is regenerated from the received data blocks, and at step 142, the computer file is stored on the PC 18 hard disk. is a data block or redundant block ·· ·· »9 9 9 • 9 9 9

999 999

9

99 ·· ···· »» ·

I 9 9 through verifying the truth of the relationship 0 <i - jRC <C, where the matrix number j is determined from z = int ((i-1) / (R + 1) C) +1, where int () denotes the whole part () . If the statement is true, the block is a redundant block, but if it is false, the block is a data block.

The arrangement described above solves two major problems. The first problem is associated with short interruptions in the bit stream from transponder 2014 to ground receiver 2018. It is clear that if a particular block i was affected by such an interruption, there is a relatively high probability that the next block i + 1 in the same row will also be affected . The value of C is selected such that there is a relatively low probability that the next block i + C in the same column will also be affected. By ensuring that the R of the (R + 1) blocks in each column is correctly received, the remaining block can then be regenerated using the redundant block and the XOR bit operation properties. The second problem is related to the effective speed at which the blocks are received towards the end of the file download operation. It should be understood that if only one block is expected, the waiting period may be nearly as long as the time required to transmit all blocks in the file. With the arrangement described above, there is a high probability that if only a few data blocks would otherwise be expected, these data blocks can be regenerated from redundant blocks and data blocks that have already been received. It should be noted, however, that the transmission of additional redundant blocks adds some time to the total time needed to transmit the entire file, and therefore the benefits of interrupting transmission and reducing the waiting time for the last few blocks must be balanced due to the disadvantage of increasing the overall transmission time.

0 · »0 · · 0 0 ·

000 999 • suitable choice of C and R values. This choice of C and R values may be subjected to statistical studies or to the trial and error method. However, typically these values could be C = 50 and R = 10. Preferably both C and R values are greater than five.

In the example described above, the C and R values are determined when the file is ready for broadcast-ready blocks, and these C and R values are included in the table directory or index for the files to be downloaded.

Alternatively, the C and R values may be predetermined without their values being included in the table directory or index, and the PC 18 may be pre-programmed with these C and R values.

In the example described above, blocks are downloaded until enough blocks have been downloaded to allow file regeneration. Then the missing blocks are regenerated and the entire file is also regenerated. In an alternative example, if a redundant block for a particular column has already been downloaded and all but one of the data blocks of that column have been downloaded, the missing data block can be regenerated and marked as received at this stage without waiting for the blocks to download enough file.

In the above-described device, the receiver / decoder 2020 has been illustrated as being separate from the PC 18. However, it should be understood that the receiver / decoder 2020 may form part of the PC 18, for example in the form of an added card.

It should be understood that the present invention has been described above purely by way of example, and that modifications of particular details may be made within the scope of the invention.

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4.

Each feature described in the description and (where appropriate) in the claims and drawings may be formed independently or in any suitable combination.

In the aforementioned preferred embodiments, certain features of the present invention have been implemented using computer software. However, it will be obvious to those skilled in the art that any of these features can be realized using hardware. Moreover, it should be understood that functions performed by hardware, computer software and the like are performed on or using electrical and similar signals.

At this point reference is made to parallel patent applications of the same applicant having the same filing date and the following titles: generation and transmission of signals (representative mark: 73142 / PT), smart card for use with a coded broadcast receiver and representative (representative mark: 73143 / PT), Transmitting and receiving system and conditional access system (representative mark: 73145 / PT), Downloading a computer file from a transmitter via a receiver / decoder to a computer (representative mark: 73146 / PT), Broadcasting and receiving television programs and other data (shortcut tag:

73147 / PT), Method of uploading data to MPEG receiver / decoder and MPEG broadcasting system for its implementation (representative mark: 73148 / PT), Organization of computer memory (representative mark: 73149 / PT), Method of development and testing of the control program (representative mark : 73150 / PT), Selecting slots from the transmitted data stream (representative mark: 73151 / PT), Access control system (representative mark: 73152 / PT), Data processing system (representative mark: 73153 / PT), Transmitting and receiving system, receiver / decoder and remote control unit • fe fefe ··

• fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe feef feef feef feefefe (representative mark: 73154 / PT). Descriptions of these documents are incorporated herein by reference. The list of applications contains the present application.

Represents fe.

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Claims (10)

PATENT CLAIMS A method of downloading a computer file from a transmitter via a receiver / decoder to a computer, comprising the steps of: dividing the file into a number of (N) blocks; retransmitting these blocks of the file from the transmitter, each with the identity of the block; and at the receiver / decoder: generating N flags that are initially reset, one for each block; and cyclically performing the steps of: receiving one of the blocks being transmitted, and determining whether a flag for that block is set; and if not, passing this block from the receiver to the computer and setting a flag for that block; until all of the flags are set. The method of claim 1, wherein after each handover step, the computer is arranged to send a acknowledgment of receipt of the handover block to the receiver / decoder, wherein the set-up step for each block is performed in response to receiving acknowledgment for that block. 3. The method according to claim 1 or 2, further comprising the step of repeating the method according to claim 1. of claim 1 or 2 before setting all flags, but without the step of resetting the flags. 4. A method of downloading a computer file from a transmitter in front of a receiver / decoder to a computer substantially as described herein with reference to the accompanying drawings. ·· 999 · 9 9 9 999 999 9 • 9 99 9 99 A receiver / decoder that is arranged to receive MPEG video and / or audio data tables and blocks of computer file data, the computer file being received as a plurality of N blocks that are cyclically received, each of which includes identifying the block, indicating comprising: means for storing a plurality of N flags that are initially reset, one for each block of the computer file; means for temporarily storing the currently received block of the computer file; means for passing the block stored in the block storing means to the computer; and control means, which is arranged to determine whether a flag for the currently received block is set in the flag storing means; and if not, to control the block handover means to pass the block from the block storage means to the computer, and to set a flag for the block in the flag storage means. 6. The receiver / decoder of claim 5, further comprising means for receiving a confirmation from the computer that such a block has been received from the block handler, and wherein the control means is able to set a flag for that block in response. to receive this acknowledgment for this block. A receiver / decoder according to claim 5 or 6, wherein the control means is operable to create a recovery of receiving computer file blocks after a lost connection without resetting the flags. • · • φ φ φ · ··· φφφ φ A receiver / decoder according to any one of claims 5 to 7, characterized in that the block transfer means is one of a plurality of such block transfer means of different types. The receiver / decoder of claim 8, wherein the plurality of block handover means comprises at least two of the group consisting of: an IEEE parallel port with an ECP mode; IEEE parallel byte mode port; IEEE parallel port with 4-bit word mode; and RS-232 serial port. A receiver / decoder substantially as described herein with reference to the accompanying drawings.