MXPA97005810A - System to receive variable coding formats and number of transmis channels - Google Patents

Abstract

A receiver system (12) selects adaptively and automatically to transmit signals that are variable in the number of channels that are transmitted, their type of signal coding and their modulation format. A system receives (15) a digital bit stream representing video information encoded in one of a plurality of different formats, and transmitted in one of a plurality of transmission channels. In the system, a method for acquiring data transmitted on a transmission channel involves selecting (17) a transmission channel from a plurality of channels and selecting (17) a modulation format (25). The method also involves selecting to receive the modulation format and determining (50) whether valid data is being received on the selected transmission channel. The steps of the method are repeated until the valid data is received. The method may involve selecting (17) a type of coding (30, 40) and selecting to receive the type of coding. In addition, the data acquisition method may involve capturing program guide information and re-selecting a transmission channel in response to program guide information.

Description

SYSTEM FOR RECEIVING VARIABLE ENCODING FORMATS AND NUMBER OF TRANSMISSION CHANNELS This invention relates to the field of digital signal processing and, more particularly to the acquisition, processing and storage of video data and Program Guide Information derived from the input data encoded in variable transmission coding formats. In video processing and storage applications, digital video data is typically encoded to conform to the requirements of a known standard. One such widely adopted standard is the MPEG2 image coding standard (Expert Group of Moving Images), hereinafter referred to as the "MPEG standard". The MPEG standard is comprised of a system coding section (ISO / IEC 13818-1, June 10, 1994) and a video coding section (ISO / IEC 13818-2, January 20, 1995). successively referred to as the "MPEG system standard" and the "MPEG video standard" respectively. The video data encoded to the MPEG standard is in the form of a packet data stream that typically includes the data content of many program channels (for example the content corresponding to cable television channels 1-125). For a decoder to decode the packet data stream and retrieve the content of the video data from the program channels selected for display, for example, the individual packets comprising the selected program channels must be identified and assembled. To retrieve the content of the selected program channels, the information in a Program Guide is used in the identification and assembly of individual data packages that constitute the selected programs. For this purpose the Program Guide data is acquired from the program data stream which is the input for a video decoder. The Program Guide data is formed within a sufficient Master Program Guide (MPG) to decode the selected programs. Once they are formed, the MPG can be used to decode the selected programs for another application device. However, in some video transmission systems it is necessary to acquire and form the MPG from the Program Guide data encoded in variable transmission coding formats. The variable transmission coding formats are used in wireless terrestrial video transmission systems to selectively provide improved levels of transmission signal noise immunity. However, a transmission coding format that provides improved noise immunity requires increased transmission bandwidth. An example of a system that uses variable transmission coding formats owns a Multi-Point Microwave Distribution System (MMDS) that uses a "line of sight" transmission system. In such a system, a coding format that provides a transmission signal with a higher degree of noise immunity also incurs a higher error correction code and consequently requires larger transmission bandwidth. Similarly, for a fixed transmission bandwidth, providing a bandwidth signal with a higher degree of noise immunity reduces the output of information that can be obtained. In addition, the coding format used may vary on a temporary or geographic basis to accommodate variations in reception conditions associated with atmospheric or panning characteristics. The variation in the transmission modulation and the error correction coding format and the associated required transmission bandwidth present problems for a video receiver in both the decoding of formats of variable co and in the acquisition of a compatible MPG. These problems are solved with a system in accordance with the present invention. The use of variable enco formats may result in a variation in the transmission bandwidth available for the program data content. The inventors have recognized herein that the number of program channels_ that are transmitted using variable transmission co formats can be changed together with the co format. further, the number of program channels can be varied over time and with the geographical transmission area. The inventors have further recognized that it is desirable for a receiver system to be able to adaptively receive variable transmission coding formats and a variable number of program channels. This allows the signal noise immunity of the transmission system to be adjusted to the requirements of a particular transmission area, the receiver can be configured to provide greater immunity to the transmission signal noise in a particular transmission area where the conditions of reception deteriorate due to, for example, steep terrain. A described receiver system selectably and automatically selects the transmission signals that are variable in: a) the number and frequency location of the channels that are transmitted, b) the type of signal coding for example encoded "interlaced" or " not interlaced "and c) the modulation format for example the formats that use the symbol constellations of 64 or 256 elements. In accordance with the principles of the present invention, a system receives a digital bitstream representing the encoded video information in one of a plurality of different formats and transmitted in one of a plurality of transmission channels. In the system, a method for acquiring the data transmitted on a transmission channel involves * selecting a transmission channel from a plurality of channels and selecting a modulation format. The method also involves selecting to receive the modulation format and determining whether valid data is being received on the selected transmission channel 5. The steps of the method are repeated. In a feature of the invention, the method of acquiring data transmitted on the transmission channel involves selecting a type of coding and selecting to receive the type of coding. In another feature of the invention, the method for acquiring data involves repeating the method steps until the valid data is received, capturing the program guide information on the selected transmission channel and re-selecting to receive a transmission channel. in response to the guidance information of program.

Brief Description of the Drawings Figure 1 is an apparatus block diagram, in accordance with the principles of the invention, for demodulating and decoding transmission coding format signals for display. Figure 2 shows a flow diagram for a system selection process. Direct Error Correction decoder for a variable transmission coding format signal. Figure 3 shows a diagram for a process of acquiring a Master Program Guide (MPG) from an input signal that contains multiple Physical Transmission Channels (PTCs). Figure 4 shows a flow chart of a process for providing the selected video channel or program guide information for display from an input signal containing multiple Physical Transmission Channels (PTCs). Figure 5 shows a flow chart for a process for forming program guide information and incorporating the program guide information into a video program data stream for transmission in variable transmission coding formats. Figure 1 is a block diagram of a receiver system, in accordance with the principles of the invention, for demodulating and decoding variable transmission coding format signals for display. The receiver system selectably and automatically selects transmission signals that are variable in: a) the number and frequency location of the channels that are transmitted, b) the type of signal coding for example encoded "interlaced" or "non-interlaced" "and c) the modulation format for example the formats that use the symbol constellations of 64 or 256 elements. The parameters indicative of the type of coding and of the modulation format are advantageously incorporated into the Program Guide information within the transmitted signals to facilitate the reception and decoding of the variable transmission coding formats. The ability of the receiver system of Figure 1 to adaptively receive the variable transmission coding formats allows the signal noise immunity of the transmission system to be adjusted to the requirements of a particular transmission area. For example, the receiver may be configured to provide greater immunity to transmit signal noise in a particular transmission area where the reception conditions deteriorate due to rugged terrain thereby, the receiver may be configured for a less modulation format. noise sensitive using for example 64 elements (preferably up to 256 elements) and encoded data "interlaced", for example. However, the enhanced noise immunity coding requires more signal bandwidth which results in less bandwidth being available for the program data content and therefore less program channels can be transmitted. Consequently, the receiver of Fig. 1 also adapts to the variation in the number and frequency location of the channels that are transmitted. Although the system is described in the context of a system for receiving variable transmission coding format signals that are compatible with MPEG, it is only illustrative.

The principles of the invention can be applied to systems in which the transmission channels can vary in number or frequency location, or to systems in which the type of coding or the modulation format can be varied. Such systems may include, for example, non-MPEG compatible systems, which involve other types of coded data streams and other methods of transporting the Program Guide information. Furthermore, although the described system is described as transmission program processing, it is only illustrative. The term "program" is used to represent any form of packet data such as telephone messages, computer programs, internet data or other communications, for example. In summary, in the video receiver system 12 of FIG. 1, a carrier modulated with video data is received by the antenna 15 and processed by the unit 20. The resulting digital output signal is demodulated by the demodulator 25. demodulated output from the unit 25, optionally differentially decoded by the decoder 30, is provided to the unit 50 by means of multiplexers ("multiplex") 35 and 45 after the optional interlaced decoding of the interleaver decoder 40. The output optionally interleaved decoder from the multiplex 45 is mapped in byte length data segments, deinterleaved and the Reed-Solomon error is corrected in the unit 50. The output data corrected from the unit 50 is processed by the transport processor compatible with the MPEG that separates the data according to the type based on an analysis of header information and provides synchronization and information indication n error used in subsequent video data decompression. The compressed video and audio output data from the processor 55 are decompressed by the MPEG decoder 60 to provide audio and video output data to the audio processor 70 and the video processor 65. The processors 65 and 70 format the audio and video signals to be suitable for reproduction by the unit 75. A user of the video receiver selects for the display either a video channel or an on-screen menu, such as the program guide, by means of the use of a remote control (not shown to simplify the drawing). The system controller 17 uses the selection information, provided from the remote control unit, to appropriately configure the elements of Figure 1 to receive, demodulate and decode the type of input signal coding, including differential and non-differential codes , interlaced or non-interlaced codes and, the input signal modulation format, which includes 64 or 256 element symbol constellations. The elements 20, 25, 30, 40, 50 and 55 of Fig. 1 are individually configured for the type of input signal by fixing the control register values within those elements and by selecting signal paths by means of the multiplexes 35 and 45 using bidirectional data and the control data collector C. It will be noted that the functions of the demodulator and the decoder works by implementing units 20, 25, 30, 40 and 50 that are known and described generally , for example, in the text reference Digital Communication, Lee and Messerschmidt (Kluwer Academic Press), Boston MA, USA, 1988). Considering Figure 1 in detail, a carrier modulated with video data received by antenna 15, is converted to digital form and processed by input processor 20. Input processor 20 includes radio frequency (RF) selector and mixer of intermediate frequency and amplification stages for down-conversion of the input video signal to a lower frequency band suitable for further processing. In this illustrative system, the input signal received by the antenna contains 33 Physical Transmission Channels (PTCs 0-32). Each Physical Transmission Channel (PTC) is located in a bandwidth of 6 MHz and contains up to 6 video channels for example that correspond to cable TV channels 2-7. It is assumed for exemplification purposes that a video receiver user selects a video (SC) channel for viewing using a remote control unit (not shown to simplify the drawing). The system controller 17 uses the information provided from the remote control unit to properly configure the elements of the system 12 to receive the PTC corresponding to the selected video channel SC. After the descending conversion, the output signal from unit 20 for the selected PTC has a bandwidth of 6 MHz and a center frequency in the range of 119-405 MHz. The controller 17 configures the radio frequency (RF) selector and the radio mixer. intermediate frequency (IF) and the amplification stages of the unit 20 to receive the selected PTC. The frequency output with downconversion for the selected PTC is demodulated by unit 25. The primary functions of the demodulator 25 are the recovery and tracking of the carrier frequency, the recovery of the clock frequency of transmitted data and the recovery of the data. of video themselves. A carrier recovery cycle in unit 25 processes the output of unit 20 to retrieve the baseband video information. The data of the unit 20 is a stream of binary data representing a symbol sequence in which each symbol is represented by assigned digital values. A set of symbols can be represented in a complex plane as a set of points called a symbol constellation, as is known. The variable transmission signal formats that are the input to the system 12 use the Quadrature Amplitude Modulated Symbol (QAM) symbol constellations of either 64 or 256 points. The function of the carrier recovery cycle in the unit 25 compensates for symbol point offset and symbol point rotation caused by the jitter and frequency at the carrier frequency introduced by the transmission channel and the instability of the signals. oscillators in the low noise block descending converter (LNB) as it is known. The carrier recovery cycle of the unit 25 derives a carrier offset value representing the symbol point rotation induced by the frequency error between the transmitted carrier frequency and derived from the selected PTC. The offset carrier offset value is used by the carrier recovery cycle of the unit 25 to compensate for the symbol rotation induced by this frequency error. The value of carrier phase shift in the illustrative mode does not change significantly between the different PTCs. Consequently, once the carrier offset value for a PTC is derived it is stored by the controller 17 and applied to the carrier recovery cycle of the unit 25 to expedite the re-selection of the system 12 towards other PTCs. The time required to re-select system 12 to a different PTC is reduced by applying the stored carrier offset value to the carrier recovery cycle of unit 25 because the offset value accelerates the convergence of the recovery cycle. . In order to compensate for the frequency drift and other variations that affect the convergence of the recovery cycle, the controller 17 causes the carrier offset value to be periodically derived and updated. The system 12 may alternatively be configured to derive a specific carrier offset value for each PTC for use in compensating the carrier recovery cycle. The unit demodulator 25 also incorporates an equalizer function used in conjunction with the carrier recovery cycle for the purpose of compensating for transmission channel disturbances and for reducing intersymbol interference, as is known. In addition, a switch in the unit 25 applies a series of decision thresholds to the corrected output from the carrier recovery cycle to recover the data symbol sequence which is the input to the demodulator 25. The switch is configured by the controller 17 either for a QAM symbol constellation of 64 points or 256 points in response to the Control C signal configuration. The video data output retrieved from the unit 25 is provided to the differential decoder 30. The unit 25 recovers also the sampling and synchronization clocks that correspond to the transmitter clocks and are used for time control of the operation of the processor 20, the demodulator 25 and the differential decoder 30. The clocks are derived within the unit 25 in accordance with known principles by means of the derivation of a phase and the error signal of the time control based on a comparison of the input of the disconnector and the output data. The derived error signal is filtered and applied to the control input of a controlled voltage crystal oscillator to generate the clocks. Alternatively, a clock frequency greater than two times the speed of the symbol can be used as a sampling clock. The output of demodulator 25 is optionally differentially decoded by unit 30 and passed to multiplex 35. Differential encoding / decoding is a known technique used to overcome the problem associated with the potential phase ambiguity in the derived carrier and the constellation of recovered symbol. The controller 17 determines whether the input data is to be decoded interleaved from parameters within the input data or, arbitrarily selects the interleaved decoding as part of an iterative initialization process. This initialization process is used to properly configure the system 12 to acquire and decode the received input data, as will be discussed later in connection with FIG. 2. If the controller 17 selects an interlaced decoding mode, either differentially decoded data is used. from the decoder 30 or demodulated data from the unit 25 are passed through the multiplex 35 to the interleaver decoder 40. The decoder 40 applies interlaced decoding principles to detect the code sequences in interleaved encoded data from the multiplex 35. The decoder 35 determines from the data symbols received from the multiplex 35 the most similar corresponding sequence of bits that would have been encoded interleaved by the encoder and therefore identifies the corresponding transmitted data symbols.The resulting retrieved original data is provided by means of the multiplex 45 to the unit 50. However, if the controller 17 selects a non-interlaced decoding mode, either differentially decoded data from the decoder 30 or demodulated data from the unit 25 is provided to the unit 50, by means of the multiplex 35 and 45, deviating m. interleaver decoder 40. 10 The output from multiplex 45 is mapped in data segments of byte length, deinterleaved and corrected Reed-Solomon error in accordance with principles known by unit 50. In addition, unit 50 provides a validation correction of Direct Error or closing indication to the controller 17. The correction of the Error Reed-Solomon is a known type of Direct Error Correction. The FEC closing indication signals indicate that the Reed-Solomon error correction is synchronized for the data that is being corrected and is providing a valid output. The corrected output data from unit 50 is processed by the transport processor compatible with MPEG 55. Individual packets comprising particular program channel content or, Program Guide information, are identified by their Packet Identifiers (PIDs) Processor 55 separates the data in accordance with the type of based on analysis of Packet Identifiers (PIDs) contained within the header information and provides the synchronization and error indication information used in the subsequent decompression of video data. Individual packages comprising a selected program channel 5 are identified and assembled using PID's contained in a Master Program Guide (MPG). However, the PIDs that identify the MPG packets are predetermined and stored in the internal memory of the controller 17. Therefore, / ^ W. after the controller 17 determines from the indication With FEC closure provided by unit 50 that system 12 is producing valid data to transport processor 55, the MPG that is present in each PTC can be acquired without additional PID information. Using the control signal C, the controller 17 configures the transport processor 55 to select the data packages comprising the MPG. The processor 55 couples the PID's of input packets provided by the multiplex 45 with previously loaded PID values in the control registers within the unit 55 by the controller 17. The controller 17 acquires a complete MPG by accessing and assembling MPG packets that are identified and captured by the processor 55. The information in the MPG that enables the controller 17, together with the processor 55, to identify data packets comprising individual programs, is called a map. channel.

In addition, the MPG advantageously contains the channel map information that allows the identification of packets comprising individual programs for all PTC's and for the different transmission coding formats. Different channel mappings are associated with different coding formats since the maximum number of Physical Transmission Channels (PTC's) is determined by the transmission width for a particular encoding format. As previously explained, the use of a coding format that provides greater immunity to signal noise results in less bandwidth available for the transmission of program content. The channel mappings may also be varied to allow variation in the program content transmitted between different transmission areas or to allow the change, i.e. the addition or removal of services, in normal transmission operations. The controller 17 uses the channel map information in the MPG acquired to identify the packets that comprise the SC video channel that the user selected to view. The processor 55 couples the PID's of input packets provided by the multiplex 45 with PID values of the SC video channel previously loaded into control registers within the unit 55 by the controller 17. In this way, the processor 55 captures the packets of the SC video channel and the forms in an MPEG compliant data stream containing the compressed audio and video data representing the SC program content of the selected video channel.

The audio and video data compressed from the processor 55 are decompressed by the MPEG decompressor 60 to provide audio and video output data to the audio processor 70 and to the video processor 65. The processors 65 and 70 format the audio and video signals to be suitable for reproduction of the unit 75. It should be noted that the MPEG compatible data stream incorporating the MPEG output by the processor 55 can provided alternatively to a storage device for storage (not shown to simplify the drawings). The controller 17 employs the process of Figure 2 to select and configure the processor 20, the demodulator 25, the differential decoder 30 and the interleaver decoder 490 for receiving a variable transmission coding format signal, as previously described in connection with FIG. 1. The process of FIG. 2 automatically and adaptively selects the system 12 for receiving signals that are variable in: a) the number and frequency location of the channels that are transmitted, b) the type of signal coding for example encoded interleaved or non-interleaved or, differential or non-differential encoded, and c ) the demodulation format eg modulation formats that use symbol constellations of 64 or 256 elements. The process of Figure 2 is used when the FEC closure indication provided by unit 50 (Fig. 1) indicates that closure has not been achieved. Such a condition may occur at the first energization moment or after a change of transmission coding format in the encoder, for example. In the illustrative process of Fig. 2, the input data to the system 12 is differentially coded and intertwined encoded or not coded neither differentially nor interleaved. After the start in step 100 of FIG. 2, a carrier phase shift value is derived in step 105 in the manner previously described in relation to FIG. 1. The carrier phase shift value is derived by an initial PTC. for example PTC = 0, and applied by controller 17 in step 105 to the carrier recovery cycle of unit 25. In step 110, controller 17 is programmed to iteratively execute process steps 115-150 of Fig. 2 for each PTC, starting with the first PTC (PTC = 0) until the FEC closure has been achieved for one of the PTCs. In step 115, the controller 17 configures the demodulator 25 for a QAM 64 modulation format symbol constellation and configures the multiplexes 35 and 45 to provide the output from the demodulator 25 to the unit 50 by bypassing the decoder 30 and the decoder. interleaving 40. If the controller 17 determines in step 120 that the FEC closure has not been reached by the unit 50, the controller 17 executes step 125 to configure the demodulator 25 for a QAM modulation format 64. In addition, the controller 17 in step 125, it configures the decoder 30 and the decoder 40 to differentially decode the output data from the demodulator 25 to provide differentially decoded and decoded data interleaved to the unit 50 by means of the multiplexes 35 and 45. If the controller 17 determines in step 130 that the FEC lock has not been reached by the unit 50, the controller 17 executes step 135 to configure the demodulator 25 for a QAM 256 modulation format symbol constellation. Also the controller 17, in step 135, configures the multiplexes 35 and 45 to provide output data from the demodulator 25 to the unit 50 by diverting the decoder 30 and the interleaver decoder 40. If the controller 17 determines in step 140 that the unit 50 has not reached the FEC lock, the controller 17 executes the step 145 to configure the demodulator 25 for a QAM 256 modulation format. In addition the controller 17 in step 145, it configures the decoder 30 and the decoder 40 to differentially decode and interlaced the output data from the demodulator 25 to provide differentially decoded data and interleaved to the unit 50 by means of the multiplexes 35 and 45. If the controller 17 in step 150 determines that the unit 50 has not reached the FEC close after the iteration through steps 115-15 0 for each of the PTCs (PTC 0-32), the controller 17, in step 155, provides a system error indication to the user. This may be in the form of a panel light indication or a default image display on the reproduction apparatus 75, or an error message carried by a telephone line or other type of fault indication. However, if the unit 50 achieves the FEC closure for any of the PTCs in steps 120, 130, 140 or 150, the controller 17 executes the step 160. In step 160, the controller 17 stores in its internal memory the value of carrier phase shift, the modulation format (either QAM 64 or 256) and the type of encoding (either coded interleaved or non-interleaved) for the PTC for which the FEC lock was acquired. After completion of steps 155 or 160 the process of Fig. 2 ends in step 165. Controller 17 employs the process of Fig. 3 to acquire a Master Program Guide (MPG) from an input signal that contains Physical Transmission Channels (PTCs). The process of Fig. 3 is used after the process of Fig. 2 to select system 12 to a particular PTC. However, the process of Fig. 3 can also be used whenever the acquisition of a new MPG is desired to follow a change of transmission coding format in an encoder. After the start in step 200 of FIG. 3, the controller 17 searches for the data output from the multiplex 45 (Fig. 1) for the MPG data packets. As previously described in connection with Figure 1, the controller 17, in step 205, preloads the internal registers within the processor 55 with the MPG PID values. The processor 55 couples the MPG PID values against the PID values of the data packet input from the multiplex 45 and captures the identified MPG data packets. After detection of the MPG data packets in step 210, the controller 17, in step 240, transfers the MPG packets captured by the processor 55 into the internal memory. The controller 17 continues the process of step 240 until a complete, valid and error-free MPG has been acquired, decoded and assembled in the internal memory. If the controller 17 determines in step 245, that a complete, valid and error-free MPG has been obtained, the process of FIG. 3 is completed and ends in the stage 260. If the controller 17 determines, in step 245, that a complete, valid and error-free MPG has not been acquired, the controller 17 configures the system 12 (Fig. 1) to receive the next PTC in step 215 , for example the PTC number 1 if the current PTC is zero.

Likewise, if the MPG data is not detected by the processor 55 in step 210, the controller 17 similarly configures the system 12 to receive the next PTC in step 215. However, if the controller 17 determines, in the stage 220, which has been searched in all available PTCs without success, the Controller 17 indicates a system error to the user in step 230. Estro may take the form of a panel luminous indication or, a default image display on the reproduction apparatus 75, or any error message conveyed by a line telephone or other type of fault indication.

If the controller 17 determines, in step 220, that the search has not been made in all available PTCs, the controller 17, in step 225, executes the previously described selection process of FIG. 2 from step 115 ( Fig. 2) for the PTC selected in step 215 (Fig. 3). This portion of the process of Fig. 2 is used to select system 12 towards the PTC selected in step 215 (Fig. 3). After selecting the system 12 towards the new PTC in step 225, the controller 17 repeats the process of Fig. 3 to acquire an MPG that starts with step 205. The execution of the process of Fig. 3 is completed and ends in step 260 after the generation of an error indication in step 230 or, after step 245 and the successful acquisition of an MPG. Controller 17 employs the process of Fig. 4 to provide a selected video channel or program guide information for display from an input signal containing multiple Physical Transmission Channels (PTCs) and variable modulation and coding formats. The process of Fig. 4 is used following the acquisition of an MPG by the process of Fig. 3 for example. After the start in step 300 of FIG. 4, the controller 17, in step 305, determines from the selection information provided from a remote control unit whether a user has requested a video channel or a guidance program for visualization. If a video channel (SC) has been selected, the controller 17 in step 310 determines on which PTC the selected channel SC is transmitted using the previously stored MPG information. In step 315 the controller 17 determines whether the PTC of the selected channel is different from the PTC to which the system 12 is currently selected. If the PTC of the selected channel is different from the current PTC, the controller 17, in step 320, configures the system 12 with the carrier phase shift value, the modulation format (either QAM &4 or 256) and the type of coding (whether interlaced or non-interlaced) of the required PTC. The modulation format and the type of coding of the PTC required are determined by the controller 17 from the parameters within the stored MPG data. The carrier phase shift value for the required PTC is obtained by the controller 17 from the previously stored phase shift data determined in the acquisition process of Figure 2. In step 325, the controller 17 performs the previously described selection process of Fig.2 from step 115 (Fig. 2). This portion of the process of Fig. 2 is used to select system 12 for the PTC that was determined in step 310 (Fig. 3) and on which the selected video channel is transmitted. However, in step 315, if the PTC of the selected video channel SC eß is the same as the PTC for which the system 12 is currently selected, the controller 17 bypasses the steps 320-325 and continues the process of with the stage 330 * In step 3305 the controller 17 uses the MPG data to identify the packets comprising the SC video channel that the User selected to view. As described in relation to Fig. 1, the processor 55 couples the PIDs of the incoming packets 5 provided by the multiplex 45 with the PID values of the SC video channel previously loaded into the control registers within the unit 55 by the controller 17. In this manner, the processor 55 in step 335, controlled by the controller 17, captures the SC video channel packets and forms them within a stream data compatible with MPEG which contains compressed audio and video data representing the SC program content of the selected video channel. In step 365, the compressed audio and video output data from the processor 55, driven by the controller 17, are decompressed by the MPEG decoder 60 to provide audio and video output data to the audio processor 70 and the video processor 65. Furthermore, in step 365, the processors 65 and 70 format the audio and video signals for make them suitable for reproduction through the unit 75.

The process of Fig. 4 ends in step 370. However, if in step 305 a program guide is requested for viewing by the user of the video receiver, the controller 17 in step 350 determines whether it has been requested a Special Program Guide (SPG) or an MPG. The MPG is transmitted on each PTC and contains all the information required to identify and assemble packages comprising a selected video channel program or an SPG. In contrast, an SPG is an optional guide and can only be transmitted over a limited number of PTCs, for example PTC = 0. In addition, there are many different SPGs and an individual SPG can contain information only on selected video channels. In the illustrative process of Fig. 4, an SPG is transmitted over zero PTC. Therefore, if in step 350 an SSPG is requested for display, the controller 17 in step 360 sets the required PTC as zero and continues the execution of the process of Fig. 4 from step 315 in the previously described manner. However, if in step 350 an MPG is requested for display, the controller 17 in step 355 retrieves the MPG data previously stored in the internal memory and in conjunction with the processor 55, forms a representative MPG stream. The resultant representative MPG datastream provided by the processor 55 in a representative MPEG data stream containing compressed audio and video data. In step 365, the compressed audio and video output data from the processor 55 is decompressed by the MPEG decoder 60 to provide audio and video output data to the audio processor 70 and the video processor 65. step 365, processors 65 and 70 format the audio and video signals to make them suitable for reproduction by means of unit 75. The process of figure 4 ends at stage 370. The principles of the invention also apply to training, coding and transmission of a data stream that incorporates an MPG as described herein. The principles of the invention apply to the formation of an MPG that incorporates channel map information that allows the identification of packets comprising individual programs for all PTCs and for the different transmission coding formats. The principles of the invention apply similarly to the formation of an MPG that incorporates parameters indicative of the modulation format and the type of coding. A data stream formed in accordance with the principles of the invention can be used for communication in a variety of applications including video server or PC type communication via telephone lines, for example. A stream of video program data formed to incorporate an MPG in accordance with the principles of the invention can be recorded on a storage medium and transmitted or re-transmitted to other servers, PCs or receivers. In addition, a video program can be stored in an interlaced or non-interlaced encoded form, for example. If the program is stored in an interlaced coded form, the stored program guide information including the data of the modulation format and the type of coding, facilitates the demodulation and decoding of the program by the receivers subsequent to the recovery and re-transmission of the program. Program. If a program is stored in non-interleaved encoded form, upon retrieval of the program from a storage medium, a server can modulate and encode the program in an interlaced fashion in accordance with the modulation data and encoding type carried in the program guide. . The program can then be re-transmitted to other receivers that can use the modulation data and coding type in the program guide information to facilitate the demodulation and decoding of the program. Similarly, in said type of video server the application that involves the retransmission of programs, a server may remodulate the program data for transmission in accordance with the program guide information. Fig. 5 shows a flow chart of a process for forming the program guide information and incorporating the program guide information into a video program data stream for transmission in variable transmission coding formats. After the start in step 400 of FIG. 5, the parameters are generated in step 405 which indicate the modulation format and the type of coding used for the transmission of each of the PTCs. In step 410, channel maps are generated that identify the data packets comprising individual video programs and their accompanying audio data that are to be transmitted over each of the PTCs. In step 415, the indication parameters of the modulation format and the type of coding, generated in step 405, are incorporated into the channel maps, thereby associating a PTC with a particular transmission coding format and programs. of particular videos. The program guide format 5 can be of a variety of types. For example, you can meet the requirements of the Program Specific Information (PSI) specified in section 2.4.4 of the standard MPEG systems or ^ Can meet the high-definition television (HDTV) signal ^^^ * standard "Digital Television Standard for HDTV Transmission" of 12 April 10, 1995, prepared by the Committee of Advanced Television Systems of the United States (ATSC). Alternatively, it can be formed in accordance with the property or customer requirements of a particular system. In step 420, the program guide information is formed incorporating channel maps and parameters of modulation format and coding type. The program guide information is incorporated into a video program data stream in step 425 to form a video output program. In step 430, the video output program data is process to be suitable for transmission to another device such as a receiver, video server or storage device for recording on a storage medium, for example. The process executed in step 430 includes known coding functions such as data compression, Reed-Solomon coding, interleaving, mixing, optional interlaced coding, differential coding and modulation. The process is completed and terminated at step 435. The architecture of Fig. 1 is not exclusive. Other architectures may be derived in accordance with the principles of the invention 5 to achieve the same objectives. In addition, the functions of the system elements 12 of Fig. 1 and the process steps of Figs. 2-5 can be implemented in whole or in part within the programmed instructions of a microprocessor. In addition, the principles of the invention apply to any form of guidance of electronic program compatible or not with MPEG. Furthermore, although the described system receives variable transmission QAM modulation formats and interleaved or non-interleaved encoded data, it is only illustrative. The principles of the invention can be applied to systems receiving other types of coding signal, not only of qptional interlaced coding and other modulation formats not only QAM that include forms of Impulse Amplitude Modulation (PAM).

Claims (17)

1. In a system for receiving a digital data stream representing video information encoded in one of a plurality of different formats and transmitted in one of a plurality of transmission channels, a method for acquiring data transmitted on a transmission channel, characterized by the steps of: a) selecting a transmission channel of said plurality of channels; b) select a modulation format; c) select to receive the modulation format; d) determine if valid data is being received on the selected transmission channel; and e) repeating steps a-d.

2. A method according to claim 1, characterized in that the selection step comprises configuring a demodulator.

3. A method according to claim 1, characterized in that the selection step comprises configuring a decoder.

4. A method according to claim 1. characterized in that the step of repeating comprises repeating steps a-d until valid data is received.

5. In a system for receiving a data stream representing video information encoded in one of a plurality of different formats and transmitted in one of a plurality of transmission channels, a method, for acquiring data transmitted on a transmission channel, characterized by the steps of: a) selecting a transmission channel of said plurality of channels; b) select a type of coding; c) select to receive the type of coding; d) determine if valid data is being received on the selected transmission channel; and e) repeating steps a-d.

6. A method according to claim 5, characterized in that the type of coding is selected from a plurality of coding types.

A method according to claim 1, further characterized by the steps of: e) repeating steps a-d until valid data is received; f) capturing the program guide information on the selected transmission channel; and g) re-selecting to receive a transmission channel in response to the program guide information.

8. A method according to claim 1 or claim 7, further characterized by the step of selecting a type of coding.

9. A method according to claim 8, characterized in that the step of repeating comprises repeating steps a-d for each of a plurality of coding types.

10. A method according to any one of claim 1 or claim 7, characterized in that the plurality of coding types includes interlaced and non-interlaced coding.

11. A method according to any one of claim 1 or claim 7, characterized in that the plurality of coding types includes error correction coding types.

12. A method according to claim 7, characterized in that the selection and re-selection steps configure a demodulator.

13. A method according to claim 7, characterized in that the selection and re-selection steps configure a decoder

14. A method according to claim 1 or claim 7, characterized in that the repetition step comprises repeating the stages ad for each transmission channel of the plurality of channels.

15. A method according to claim 1 or claim 7, characterized in that the step of repeating comprises repeating steps a-d for each of a plurality of modulation formats.

16. A method according to claim 15, characterized in that the plurality of modulation formats includes modulation formats of different symbol constellation size.

17. A method according to claim 1 or claim 7, characterized in that the valid data is indicated from an error coding function.