MXPA98000509A - Waveform generator for the insertion of data in televis digital signals - Google Patents

Abstract

The present invention relates to a digital waveform generator that complies with different vertical blanking interval (VBI) standards, and is inserted into the vertical blanking interval portions of a digital component video signal. A buffer zone receives the symbols carrying data from the vertical blanking interval for a particular vertical blanking interval service according to a user's data syntax, which identifies a television line where they are going to insert the vertical blanking interval data. A symbol processor responds to the information provided by the syntax. This information indicates the number of pixels (picture elements) represented by symbol, a symbol transition time, and the number of symbols carrying data to be inserted in the portion of the vertical blanking interval. The symbol processor provides the data of the vertical blanking interval in a format according to the particular vertical blanking interval service. A timing circuit responds to a start time provided by the syntax to insert the data from the vertical blanking interval. A level control circuit adjusts to the data level of the vertical blanking interval before being inserted into the vertical blanking interval portion, in response to the amplitude values provided by the syntax.

Description

WAVEFORM GENERATOR FOR THE INSERTION OF DATA IN DIGITAL TELEVISION SIGNALS BACKGROUND OF THE INVENTION The present invention relates to the communication of digital television signals, and more particularly, to a waveform generator useful for providing a digital television signal with data of a type conventionally carried in the set-up interval. vertical white (VBI) of an analog television signal. Examples of these data, hereinafter referred to as "user data", include subtitling data (CC), vertical interval time code (VITC), non-real-time video data (e.g., test signals Vertical Interval-VITS), sampled video data, North American Basic Teletext Specification (NABTS), World System Teletext (WST), data from the European Broadcast Union (Union de European Transmission) (EBU), and Nielsen Automated Measurement of Lineup (Nielsen Automated Alignment Measurement) data (AMOL). The digital transmission of television signals can deliver video and audio services of a much higher quality than analog techniques. Digital transmission schemes are particularly suitable for signals that are transmitted via a cable television network, or via satellite to cable television affiliates, and / or directly to home satellite television receivers. It is expected that digital television transmitter and receiver systems will replace existing analog systems, just as digital compact discs have replaced analog photographic discs in the audio industry. One way of transmitting compressed video data to a receiver is in the form of packets contained within a packet data stream. Typically, packets carrying compressed video data are multiplexed with other packets, for example, which carry corresponding audio data and the control information necessary to reconstruct a television signal. A standard for transporting digital television signals in this way is the MPEG-2 standard, details of which can be found in the International Organization for Standardization, ISO / IEC 13818-1, Standard International, November 13, 1994, entitled "Generic Coding of Moving Pictures and Associated Audio: Systems " (Generic Coding and Motion Movies and Associated Audio: Systems), recommendation H.222.0, incorporated herein by reference. Other details of video syntax and semantics for MPEG-2 video can be found in the International Organization of Standardization, ISO / IEC 13818-2, International Standard, 1995, entitled "Generic Coding of Moving Pictures and Associated Audio: Video "(Generic Coding for Motion Picture and Associated Audio: Video), recommendation H.262, also incorporated herein by reference. Another standard for the transport of digital television data in a packet stream is the Advanced Television Systems Committee (ATSC) Digital Television Standard A / 53 (Digital Television Standard A / 53 of the Advanced Television Systems Committee (ATSC)) , approved April 12 and September 15, 1995, incorporated herein by reference. The ATSC Digital Television Standard is based on the ISO Video Standard (IEC MPEG-2, the Digital Audio Compression Standard (AC-3), and the ISO / IEC MPEG-2 Systems Standard. MPEG-2 (and the similar system DigiCipherR II, owner of General Instrument Corporation, the assignee of the present one), forms a transport stream, or a transport multiplexing of a contiguous set of fixed-length packets. transports using a hierarchical structure, where a sequence header is followed by different extensions, user data, an image group header ("GOP"), optional user data, an image header, and so on. The sequence header provides information for a sequence of images, which will generally include more than one group of images. This information includes, for example, horizontal and vertical size values, aspect ratio, frame and bit index, and quantization parameters for the video data. You can also include a user data extension that, among other things, provides additional data to be used by the decoders. The DigiCipherR II standard provides for the transport of additional user data after the sequence header, in order to identify a DigiCipherR II signal, and the use of any special video compression techniques used within a sequence, including the special DigiCipherR prediction. and the block movement estimate. In both MPEG-2 and DigiCipherR II syntax, a sequence display extension is provided which contains, for example, video format information and color description, in addition to the sequence extension and user data. A subsequent group group header provides, among other information, a time code. Subsequently, an image header is provided that includes different information pertaining to a corresponding image in a sequence of images to be displayed. Then an image extension is provided, and finally, the data of the real image that will be decoded and played to be viewed. It is noted that the MPEG does not specify the order in which different extensions (such as the sequence display extension) or the user data must be transmitted beyond the fact that it must be after the sequence extension and before the header of the image group (if provided) or the image header. MPEG does not require the sending of image group headers, and these headers can be overridden in particular implementations. In a practical transmission system, it may be necessary to include additional data at different times for specific purposes, such as providing subtitling, VITS, auxiliary real-time video, Teletext, and AMOL data. These additional data may be carried in the vertical blanking interval (VBI) portions of an analog television signal, and are referred to herein as "VBI user information," "user data," or "user information." user".

Many standards have been developed for services provided by means of waveforms carried in the lines of the vertical blanking interval of analog and composite video. Digital video compression systems tend to employ algorithms optimized for the characteristics of two-dimensional motion video. These algorithms are generally not suitable for the compression of the video waveforms present in the lines of the vertical blanking interval of the analog video. The waveform character of the vertical blanking interval is very different, compared to the active video. The transmission without compression for these lines is very intense in bandwidth, such as the sending of samples of 8 or 10 bits of 704 or 720 pixels (image elements) of luminance and chrominance. For example, 720 values of luminance and chrominance in the resolution of 8 bits and 30 Hz, require 345,600 bps, while the information transported by these lines only represents 480 bps for subtitling, and 6,720 bps for the North American Basic Teletext Specification . As the transition to digital video proceeds, the demand to transport and reconstruct services from the vertical blanking interval continues. Digital video distribution systems are expected to reconstruct the vertical blanking interval, as well as active video, even when using digital video compression techniques. Accordingly, there is a need for algorithms, syntax, and semantics specifically for the compression of video lines in the vertical blanking interval, which allow for an efficient and flexible alternative for developing the syntax and semantics of user data. specific waveforms of the vertical blanking interval. It would be convenient to provide a generic transport semantics and syntax for digital television data, which accommodates different types of user information of the vertical blanking interval, which may or may not be used at any given time. This scheme would make possible the economic management of the bandwidth while providing flexibility with respect to the transport of the user information from the vertical blanking interval. In addition, it would be convenient to provide a waveform generator to provide digital waveforms that meet the different waveform standards of the vertical blanking interval, in response to the generic transport syntax. The present invention provides a generic waveform generator that enjoys the aforementioned advantages.

SUMMARY OF THE INVENTION In accordance with the present invention, there is provided an apparatus for generating digital waveforms that comply with different services of the vertical blanking interval (VBI) to be inserted into the portions of the vertical blanking interval of a digital component video signal. A buffer zone receives a plurality of symbols carrying data from the vertical blanking interval for a particular vertical blanking interval service, according to a user data syntax, which identifies a television line in the that the vertical blanking interval data will be inserted. A timing circuit responds to a start time (provided by the syntax) for a first symbol to perform the insertion of data from the vertical blanking interval into the vertical blanking interval portion of the video signal of digital component at a time dictated by the particular service of the vertical blanking interval. A symbol processor responds to the information provided by the syntax. This information indicates (i) a number of pixels (picture elements) represented by symbol, (ii) a transition time for the symbols, and (iii) the number of symbols that carry data to be inserted in the portion of the vertical blanking interval. The symbol processor provides the data of the vertical blanking interval in a format dictated by the particular service of the vertical blanking interval. A level control circuit may be provided to adjust the data level of the vertical blanking interval, before being inserted into the vertical blanking interval portion in response to at least one amplitude value provided by the syntax . Optionally, a multilevel amplitude modulation of the vertical blanking interval data can be provided. In a first embodiment used for vertical blanking interval data having a single symbol pulse response, the symbol processor comprises a transition processor for detecting a transition in the vertical blanking interval data, and to generate a transition waveform in response to the detected transition. The transition waveform complies with the format dictated by the particular vertical blanking interval service. Elements are provided to combine the transition waveform with the vertical blanking interval data, to provide the digital waveform to be inserted in the vertical blanking interval portion of the television line identified by the syntax . The transition processor may further include a memory for storing the transition data, to generate the transition waveforms. The transition waveform may be a ramp or a non-linear function, for example. In a second embodiment used for vertical blanking interval data having a single symbol and / or multiple symbol impulse response, the symbol processor implements a finite impulse response (FIR) function (equivalent, for example). example, to a finite impulse response filter (FIR)) to generate a sequence of data symbols representing the data of the vertical blanking interval for the particular vertical blanking service, to be inserted in the vertical blanking interval portion of the television line identified by the syntax. A memory may also be provided for storing the finite impulse response data for the vertical blanking services according to a transition type of the vertical blanking interval services which is defined by the syntax, wherein the element to implement responds to the finite impulse response data stored to implement the finite impulse response function for the particular service of the vertical blanking interval. Alternatively, an infinite impulse response (IIR) filter or equalizer can be used. In any case, the filter can be implemented in a look-up table. The impulse response data can be downloaded into memory, in conjunction with the service of the vertical blanking interval, or in an independent manner. Moreover, the first and second modalities can be realized in a single implementation. A corresponding method is also presented.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a block diagram of a digital video encoder embodying the present invention. Figure 2 is a block diagram of a video decompression processor embodying the present invention. Figure 3 is a block diagram of a first embodiment of a pixel generator (pixels) for generating a vertical vertical blanking interval waveform from the user data carried in a data stream of digital video in accordance with the present invention. Figure 4 is a block diagram of a second embodiment of a pixel generator (pixels) for generating a vertical vertical blanking interval waveform from the user data carried in a data stream of digital video, when the impulse response time of the transmission standard of the vertical blanking interval is greater than the symbol time. Figure 5 is a graph illustrating the frequency response of the interpolator of Figure 4.

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an efficient method and apparatus in bandwidth, to utilize a digital television data stream, to convey varying amounts of different types of information conventionally carried in the vertical blanking interval portion. of an analog television signal. The information of interest is a subset of a type of user data referred to as "image user data", to distinguish it from "sequence user data" in an MPEG, ATSC, or DigiCipherR II transport stream. This subset, referred to herein as user information of the vertical blanking interval, comprises information such as subtitling data, sampled video data, NABTS, WST, EBU data, and Nielsen AMOL data. Each of these categories of image user data is updated in each image. The image user data is conveyed in portions of successive video frames corresponding to the lines of the vertical blanking interval. Each line of the vertical blanking interval is represented by 720 8-bit luminance samples and 720 8-bit chrominance samples before being processed in accordance with the present invention. The present invention resulted from the realization that most of the standard waveforms of the vertical blanking interval can be represented as pulse modulated amplitude (PAM) data (eg, such as data with no return to zero (NRZ). )) modulated on the luminance portion of a video signal. These waveforms can be classified by their impulse form, its number of pixels per symbol, its symbol relationship to the time of elevation, its waveform start time within the video line, and the applicable video system (ie, the video standard). Since none of the standards specify significant data correlation from line to line or from frame to frame, each line of the vertical blanking interval can be processed independently of any other line in the vertical blanking interval. Moreover, the impulse shape specifications allow the different waveforms of the vertical blanking interval to be categorized into waveforms that require a pulse form less than the duration of a duration symbol (such as shapes). waveforms that are not Teletext), and waveforms that require a momentum form of more than one symbol (such as Teletext waveforms). The present invention capitalizes on the embodiments stipulated above with respect to the different waveform formats of the vertical blanking interval, to provide a waveform generator that is compatible with different data types of the vertical blanking interval , which communicates in a stream of digital television data. A single state machine is provided that can reconstruct most of the different waveforms of the vertical blanking interval. The state machine allows the following parameters to be programmed: the field number of the particular line of the vertical blanking interval, the line number of the particular line of the vertical blanking interval, the symbol rate used by the standard of the particular waveform of the vertical blanking interval, the start sample number CCIR-601 of the standard, the rise time of the standard (relation of symbol duration to transition), the CCIR value -601 of the standard for the symbols "0" and "1" without return to zero, the number of symbols in the waveform of the standard, and the vector of the values of the symbols in the waveform of the particular line of the Vertical blanking interval. As will be appreciated by experts in this field, "CCIR-601" is a standard promulgated by the International Radio Consultive Committee for the coding and filtering of digital components. Table 1 summarizes the key attributes of the known vertical blanking interval waveform standards. The phrase "vertical blanking interval service" is used herein to refer to any of the aforementioned standards, as well as to any other data format, protocol, or vertical blanking interval system. The aforementioned standards apply to 525-line video systems (NTSC and PAL / M) or 625 lines (PAL with the exception of PAL / M).

Each standard provides some portion of the waveform as a Timing Reference and Synchronization Pattern for the purpose of symbol synchronization. Also, each provides a fixed number of Data Bits per video line, some of which can be provided for the purpose of error detection. Each one modulates the data bits on the video line by means of some Modulation technique, and using different Amplitudes to represent different values of data bits. Finally, each waveform uses a nominal Symbol Rate (sometimes referenced to the video line speed [fh]) and a Impulse Form (symbol) (often specified with a time of elevation [tr] or form of High Cosine impulse with a particular value of Alpha). The unique attributes of the particular standards are enhanced in a bold type.

Table 1: Summary of Vertical Waveform Interval Waveform Standards Different conclusions were drawn when comparing the different waveform standards of the vertical blanking interval stipulated in Table 1. These include: 1. All waveforms can be represented as non-return to zero (NRZ) data modulated on the luminance of the video signal, including the bi-phase modulated symbols of EBU 3217, but the nominal luminance values representing the symbols "0" and "1" without return to zero (NRZ) differ from wave form to shape cool. 2. Impulse Shape specifications can be classified as waveforms that have a momentum shape less than a time symbol duration for non-Teletext waveforms, and waveforms that have a form of greater momentum of a symbol for Teletext waveforms. 3. None of the standards specifies significant line-to-line or frame-to-frame correlation of data - therefore it is convenient to handle each line of the vertical blanking interval (VBI) independently of any other line of the staging interval in vertical white (VBI). 4. The VITC synchronization bits are best handled simply as data bits.

. The number of CCIR-601 samples per symbol has a range by a factor of 13 over all waveforms. 6. The ratio of the symbol to the time of elevation is 1.5 to 8.5 on all waveforms that are not Teletext. 7. The symbol rate of the waveforms has a range by a factor of 21. 8. The required sample of the waveforms, in relation to the first sample CCIR-601, is from 27 samples before the shows CCIR-601 zero, up to 80 samples, after sample zero with a nominal value of 26 samples after sample zero. In view of the above conclusions, it has been determined that a single state machine can be created to reconstruct all these waveforms from the vertical blanking interval, if the following parameters can be programmed in the state machine: 1. The field number of the particular vertical blanking interval line, 2. The line number of the particular vertical blanking interval line, 3. The symbol speed of the standard, 4. The start sample number CCIR-601 of the standard, 5. Standard rise time (symbol transition duration), 6. The CCIR-601 value of the standard for symbols "0" and "1" without return to zero (NRZ), 7 The number of symbols in the waveform of the standard, 8. The vector of values of the symbols in the waveform of the particular line of the vertical blanking interval. A state machine providing programmability of the above parameters is disclosed below for use in the reconstruction of each of the different waveforms of the vertical blanking interval, in connection with Figure 3. Before discussing the state machine, novel syntax according to the present invention is disclosed, in conjunction with an exemplary embodiment of an encoder and decoder structure. Figure 1 illustrates, in a block diagram form, an encoder for processing raw digital video data into a user data syntax, wherein variable amounts of different types of user information can be communicated from the blanking interval vertical, in a digital television data stream. The user data syntax may include pulse modulated amplitude (TAM) data, such as non-zero return data (NRZ), referred to herein as "luma NRZ". It will be appreciated that although the non-return to zero (NRZ) data are referred to in the particular illustrative examples, other pulse modulated amplitude (PAM) schemes may be used. The gross digital video, such as the video that complies with the standard of the Society of Motion Picture and Television Engineers (SMPTE), gets into a serial 12 receiver by means of the terminal 10. The serial receiver puts the data in series, which are put in a parallel format. The serialized data is stored in a buffer zone 14, which may comprise a conventional first-in-first-out (fixed) register. A syntactic video analyzer 16 interprets the syntax of the data put in series, and separates different information, such as that which identifies the start of a new line, the start of a new frame, and the raw data of luminance and chrominance. The luminance and chrominance data are input to a demultiplexer 18, where they are separated into portions of data corresponding to the vertical blanking intervals of successive video frames (eg, lines 1-21 of an analog television signal NTSC counterpart), and the active video portions of those frames. The demultiplexer 18 also determines whether the synchronization of the acquired data stream has been lost, and if so, produces a "loss of synchronization" signal to a video compression processor 22, which also receives the active video that is received. is going to compress. The video compression processor is a type well known in the art, such as described in U.S. Patent Nos. 5,376,968; 5,235,419; 5,091,782; or 5,068,724. It is noted that some user data types that are classified as vertical blanking interval data may not reside in the actual vertical blanking interval. For example, the programming alignment information used by the A.C. Nielsen Company for market research, and referred to as "Automated Alignment Measurement" (AMOL) is inserted in line 22 of field 2 of each television frame in the transmission standard of the National Television Systems Committee (National Committee of Television Systems ) (NTSC). Line 22 is an active video line, and therefore, a decoder can begin to process the active video with line 23 instead of line 22 for NTSC signals. Within a sequence of 30 frames, the AMOL line will typically be present for each frame, but the data for most frames will generally be null. In order to accommodate the AMOL data, it is assumed that the vertical blanking interval extends to line 22 instead of line 21. The data contained in the portions of the vertical blanking interval of the input signal of digital video, are produced from the demultiplexer 18 to the direct access memories (RAM) 20, which include both a direct luminance memory and a chrome direct access memory. The direct access memories store the data until they are required by a syntax processor 24, which extracts the user information from the vertical blanking interval, and constructs a syntax that makes it possible to transport the information in an efficient manner in the portions of the vertical blanking interval of a digital television data stream, to communicate to a corresponding decoder, for example, at a location of the end user. The syntax provided by the syntax processor is stored in a first-in-first-out (FIFO) logger of headers 28, which is used to assemble the transport headers for, for example, an MPEG or DigiCipher ^ II implementation of the digital television data stream. The first-in-first-out (FIFO) headers register, provides the syntax information to a barrel changer 30 which combines the header with the active video compressed from a video encoder 26. The video encoder 26 encodes the compressed video from the video compression processor 22 in a well-known manner using, for example, Huffman coding, to provide code words (CW), code word lengths (CL), and data labels that identify the information encoded The output from the barrel changer 30 is a data stream containing the active video separated by headers that contain the necessary information to decode the active video. This data stream is stored in a video buffer zone 32, which provides the data on a base as needed, to a packer 34. The packer is a conventional component that assembles the data into transport packets in accordance with a standard transport current, such as the digital television standard ATSC, MPEG-2, or DigiCipherR II. The functions of the syntax processor 24, as far as they are relevant to the present invention, are described below using the formal grammar used by the ATSC and MPEG transport standards. This grammar is a syntax of the type of the C language, and is a method to describe the continuous and possibly variable velocity bit streams, instead of specifying a procedure program and its functions as in the computation language C. The first column of the syntax contains the element of the syntax. The second column gives the length of the elements of the syntax in bits, and the third column identifies the type of syntax. The types are bslbf (first the bit to the left of the bit string), and uimsbf (first the most significant bit without sign). The header "user_data () { ....}." Indicates that the syntax elements inside the keys are a named set, and can be invoked anywhere in the syntax simply by using the designation "user_data ()". A conditional display of bit structures can be indicated with the usual "if" tests (if), and the usual relationship operators well known in the C language are also available. Cycle structures are possible, and they use the header syntax of standard cycle C. The syntax table is accompanied by a set of semantics, which provides definitions for each field of previously undefined syntax, and which places limitations on its use.The following syntax of data bit stream of the image user (where the shaded areas represent the standard ATSC user data syntax, and the unshaded areas represent the syntax in accordance with the present invention. ion), and the semantics of the bit stream, illustrate a preferred embodiment of the present invention: Semantic Extensions of Image User Data: ad_type_data_type - An 8-bit integer (values in the range [1: 255] that indicate the type of additional data constructions following the field.) This field will have the value 01 in hexadecimal, for indicate that the additional data is luma NRZ data. additional_data_length - An unsigned 16-bit integer (values in the range [0: 65535]) that indicates the length in bytes of additional data constructions following the field. the same additional_data_data_field, but includes the following additional_data for the given additional_data type, up to, but not including, the subsequent additional_data of any other additionaldata_data types. count_number_nrz - a 5-bit integer (values in the range [0:31]) indicates the number of constructions luma NRZ following the field. All these constructions must be presented in the intended order of line and field exhibition. priority_luma_nrz - a number between 09 and 3 that indicates the priority of constructions in the reconstruction of the image, where there are different levels of hardware capacity. For luma NRZ constructs, a fixed number of lines can be labeled per visual display field as zero priority. field_number - the field number, in order of visual display, from which the data of the vertical blanking interval, interpreted in table 2, originated.

Table 2. Field Number for Image User Data line_despided - a 5-bit integer (values in the range [1:31]) that gives the line offset from where the Lumen NRZ data originated in relation to the base vertical blanking interval frame line (line 10) from field 1 of 525 lines {NTSC and PAL / M.}., line 273 of field 2 of 525 lines, line 6 of field 1 of 625 lines {all PAL except PAL / M.}., and line 319 of field 2 of 625 lines), as specified in CCIR report 624-4. start_start - a 9-bit unsigned integer (values in the range [0: 511]) that indicates the sample of the reconstructed luminance line where the transition to the first Luma NRZ symbol will start. show_initiated will be in the same units as the CCIR 601 samples, and will be in relation to the first sample of the CCIR 601 reconstructed frames. increment_nrz - an unsigned 6-bit integer (values in the range [1:63]), which indicates the Luma NRZ symbol clock increment value, and take values that describe, together with the modulo_nrz, the relation of the Luma NRZ symbol clock with a reference of 27 MHz. see the semantics of the modulo_nrz for more details. modulo_nrz - a 10-bit unsigned integer (values in the range [2: 1023]), which indicates the value of the Luma NRZ symbol clock module, and takes values that describe, along with the increment_nrz, the clock ratio of Luma NRZ symbol with a reference of 27 MHz. Specifically, the increment_nrz and the modulus_nrz are related to the speed of the Luma NRZ symbol as: increment_nrz / modulo_nrz = symbol velocity Luma NRZ / frequency_recie_sistema where: frequency_recie_sistema is specified in ISO / IEC 13818 -1 as 27 MHz + 30 ppm, and the value of the increment_nrz must not exceed the modulo_nrz-l. amplitude_0 - an unsigned 8-bit integer (values in the range [1: 254]), which indicates the amplitude where Luma NRZ symbols of zero value will be reconstructed in amplitude units of CCIR 601 reconstructed frames. amplitude_l - an integer unsigned 8-bit (values in the range [1: 254]) that indicates the amplitude at which the Lumen NRZ symbols of a value of 1 will be reconstructed, in units of amplitude of CCIR 601 reconstructed frames. form_pulse - an integer without 2-bit sign indicating the shape of the impulses that will be used to reconstruct this line of Luma NRZ. The meaning of form_pulse is defined in Table 3.

Table 3. Impulse Form relation_symbol_to_transition - an unsigned 8-bit integer (values in the range [16: 255]), which indicates the relationship of each symbol duration Luma NRZ to each symbol transition duration between the amplitudes specified by amplitude_0 and amplitude_l, and have units of 2"4 (0.0625). This field describes symbols with a symbol to transition ratio of 1.0 to 15.9375 nrz_alfa - an unsigned 5-bit integer (values in the range [0:31]), which indicates the value of Alpha for the high cosine filter, whose impulse shape describes each Luma NRZ symbol with units of 2"5 (0.03125). This field describes Alpha values from 0.03125 to 1.0. The meaning of nrz alpha is defined in Table 4.

Table 4. NRZ Alpha word_count - an unsigned 5-bit integer (values in the [0:31] range), which indicates the number of bit_marker and blue_number_nrz pairs that follow this field. word_luma_nrz - a 22-bit string of luma NRZ symbols, such that the first bit received is the value of the first luma symbol NRZ reconstructed on the video line as it is displayed from left to right. The words_number_nrz will be received in the order in which they will reconstruct their symbols on the video line as shown from left to right. constant_count - an unsigned 5-bit integer (values in the range [0:21]), which indicates the number of_wave_nrz bits that follow this field. bits_luma_nrz - a single bit that represents the luma_nrz symbol that will be reconstructed in the video line. The bits_luma_nrz will be received in the order in which their symbols will be reconstructed in the video line, subsequently to the symbols reconstructed from any_luma_nrz_words, as shown from left to right. The above syntax is assembled by the syntax processor 24 illustrated in Figure 1. In the preferred embodiment, the syntax processor is implemented in the firmware. After the syntax is added to the digital video data, the resulting data stream is packaged and output from the packer 34 to provide the final transport stream to communicate to a set of decoders. Figure 2 is a video decompression processor block diagram (i.e., decoder) for processing a received data stream containing the user data syntax of the vertical blanking interval detailed above. The video decompression processor (VDP) incorporates a memory manager 130 which directs a dynamic direct access memory (DRAM) 122, to store and retrieve the video data necessary to reconstruct a television program in a receiver. The processor, generally designated 120, is a direct processor designed to decode both the transport layer (ie, the control information and other non-video information), as well as the video layer of the stream of compressed bits tucked in. by means of terminal 110, sometimes referred to as the "transport packet interface" of the video processor. In terminal 114, a user processor interface is provided, which may comprise, for example, a busbar controller M 150, for controlling the video data processor. This interface configures different registers in the processor 120 as is well known in this field. An interface is provided with dynamic direct access memory (DRAM) 122 via address lines 124 and data lines 126. In the example illustrated in Figure 2, dynamic direct access memory (DRAM) 122 has a 9-bit address port, and a 32-bit data port. A video output interface 138 is provided for the reconstructed and decompressed video, which, for example, can be output as a luminance (Y) and chrominance (Cr, Cb) multiplexed 27 MHz, 8-bit signal from the standard CCIR 656. A test interface can be provided via terminal 182 to a conventional JTAG (Joint Test Action Group) 160 controller. The JTAG is a standardized limit scan methodology used for the board level test, to detect faults in the packet and board connections, as well as internal circuits. The video decompression processor 120 receives a clock signal via the terminal 112. The clock provides the timing information that is used, for example, to enable a transport syntax parser 132 to retrieve the timing information and the video information from the transport packets contained in a packet data stream inserted through the terminal 110. An acquisition and error management circuit 134 using a program clock reference (PCR), and decodes the time stamp (DTS) detected by a syntactic parser of video syntax 140, to synchronize the start of the decoding of the image. This circuit establishes vertical synchronization, and provides global synchronization for all decoding and visual display functions. The video layer is stored in a buffer zone (first-in-first-out, FIFO), configured in dynamic direct access memory (DRAM) 122 by memory manager 130. The syntax parser of video 140 receives the output of compressed video data from the first-in-first-out (FIFO) register of the direct data access memory (DRAM) by means of the memory manager 130, and separates the vector information of movement of the coefficients that describe the video information. The coefficients are processed by a Huffman decoder 152, an inverse quantizer 154, and a reverse discrete cosine transformation (IDCT) processor 156. The motion vectors are retrieved and used to direct the previously decoded video frames required to reconstruct a current video frame. In particular, a motion vector decoder 142 decodes the motion vectors received from the video syntax parser 140, and passes them to a prediction address generator 144. The prediction address generator provides the necessary address information to retrieve, through the memory manager 130, the necessary anchor frame data (i.e., intra-frame) (I) or prediction frame (P)) to enable the prediction calculator 146 to provide a prediction signal necessary to reconstruct a current frame block. The differential decoder 148 combines the prediction data with the decoded coefficient data to provide decompressed video data. The decompressed data is stored in appropriate buffer zones of the dynamic direct access memory (DRAM) 122 by means of the memory manager 130. It should be appreciated that the video decompression processes performed by the decoder of the motion vector 142, the prediction address generator 144, the prediction calculator 146, the differential decoder 148, the Huffman decoder 152, the inverse quantizer 154, and the discrete cosine transformation 156, are generally conventional and well understood by those skilled in the art. The memory manager 130 schedules all the activity on the address and data bus bars of the dynamic access memory (DRAM) 124, 126, and efficiently directs the dynamic direct access memory (DRAM) 122. The memory manager ensures that all data transfer requirements of the first-in-first-out (FIFO) logger portion of dynamic direct access memory (DRAM) 122, the video syntax parser are met 140, and the video reconstruction circuit 136 (as well as the prediction computer 146 and the differential decoder 148). The video reconstruction circuit 136 calculates a current image, and processes the user data of the vertical blanking interval, in order to insert the desired user data to be produced on the video output line 138. It should be appreciated that there may also be other user data different from the user data of the vertical blanking interval present, and that the user data that is available may be stored temporarily before being processed and produced. The video output 138 will contain the user information of the processed vertical blanking interval, together with the decompressed active video, in the original format presented to the serial receiver 12 illustrated in FIG. 1. The dynamic direct access memory (FIG. DRAM) 122 is illustrated as an external memory. It should be appreciated that, in future implementations, and as memory technology advances, dynamic direct access memory (DRAM) 122 may be provided as an internal memory inside the video decompression processor. The dynamic direct access memory (DRAM) is mapped to provide different zones of decoding buffer and video output, as well as a buffer zone of first-in-first-out (FIFO) circular for the stream of compressed input video bits. Dynamic direct access memory (DRAM) can also be used to provide a buffer zone of the test pattern, a buffer area of vertical interval test signals, and a visual display of subtitling that reorders the buffer zone, as well as to store different data of the image structure necessary to properly display the decoded video frames. Dynamic direct access memory (DRAM) can be reinitialized by means of memory manager 130, to provide different memory maps, as required, when modifying variables such as PAL or NTSC video, memory configuration of 8 or 16 Mbits, and if frames B are present. As indicated above, the memory manager 130 schedules all activity on dynamic direct access memory (DRAM) busbars, including the first data logger's data transfer requirements. in entering-first out (fixed) entry, the video syntactic analyzer, and the video reconstruction circuit. The memory manager also performs the required refresh of dynamic direct access memory (DRAM) in a conventional manner. For example, the same row of each of two or four dynamic direct access memories (DRAMs) can be refreshed simultaneously. When a packet-bit stream, which contains compressed video data, is input to the terminal 110 of the video decompression processor 120, the video frames represented by the compressed data are reconstructed one at a time. Initially, a complete video data frame will have to be received and stored in the dynamic direct access memory (DRAM) 122. The information for the subsequent video frames may comprise a subset of the complete video frame which, when added to the prediction data from the previous video frame (stored in the dynamic direct access memory (DRAM) 122), will give as result the reconstruction of a complete framework. Figure 3 is a block diagram of a pixel generator (pixels) for generating a vertical vertical blanking interval waveform from the user data carried in a stream of digital video data according to with the syntax described above. The waveform generator may be part of the video reconstruction circuit 136 of Figure 2, or it may be provided independently of the video reconstruction circuit, for example, for commercial applications where greater flexibility is desired, albeit with a potentially greater expense. The waveform generator can accommodate the different parameters for the vertical blanking interval standards AMOL, VITC, and EBU stipulated in Table 1. Each of these vertical blanking interval services has a corresponding number of pixels (image elements) by symbol. The subtitling services, AMOL, VITC, and EBU have pulses with an impulse response time that is less than the time of a symbol, referred to herein as the impulse response of a single symbol. Teletext services have a pulse response of multiple symbols, where the pulse response time is several symbols. In Figure 4 a waveform generator is described for services that have a pulse response of multiple symbols. The services with a impulse response of a single symbol each have a corresponding rise time, a total transition time, and a number of pixels (image elements) per transition. This information is summarized for each type of service in Table 5.

Table 5. Characteristics of the Vertical Blanking Interval Service (VBI) The category of impulse response service of a single symbol has the characteristic that there are four or more pixels (image elements) at the CCIR 601 sampling rate per symbol. As can be seen in Table 5, subtitling has the maximum number of pixels (picture elements) per symbol (for example, approximately 27). For impulse response services of a single symbol, there is no overlap from one symbol to the next. The response time of the symbol is characterized by its transition and the full amplitude portion. The transition portion of a symbol can be downloaded as part of the service, or it can be resident in a transition memory (Read Only Memory (ROM), or Direct Access Memory (RAM)), as provided in the generator of transition 218 of Figure 3. The use of read-only memory (ROM) is more efficient in terms of hardware complexity and channel efficiency. A square sine transition will work for all the different services of the vertical blanking interval (VBI). The data to be inserted into a vertical blanking interval waveform in a decoder is inserted by means of a symbol input 200, and entered in a first-in-first-out logger (FIFO) ) 202. The data is inserted in the vertical blanking interval by reproducing the symbols through a pixel generator (picture elements). The pixel generator (picture elements) will be provided with the high and low levels to insert (amplitude_0 and amplitude_l) by means of terminal 201, the frame line number where the data will be inserted (derived from field_number and line_despired) by means of terminal 203, the type of transition (derived from form_pulse) by means of terminal 205, the number of symbols to be inserted (derived from word_count and last_count) by means of terminal 207, the modulo_nrz and increment_nrz by means of terminals 209 and 211, respectively, the relation_symbol_to_transition by means of terminal 213, and the start time of the first symbol (initial_spec) by means of terminal 215. All this information is specific to the type particular of vertical blanking interval data to be inserted, and is provided by means of the syntax defined above. The video data into which the data of the vertical blanking interval is to be inserted is inserted into the waveform generator via the terminal 217. The video data is provided, for example, in a CCIR 656 format. conventional, and are coupled with a multiplexer 254. The multiplexer also receives a gate signal from an insert window generator 248, which makes it possible for the multiplexer to produce the vertical blanking interval data during a time window which is , for example, of 704 pixels (image elements) in length. In order to insert the data of the vertical blanking interval in the video at the appropriate location, a line count of the video data is maintained, and compared with the desired insertion line. This function is provided by a line detector 244 and a line time generator 246, which receives the current line information from the video data via the terminal 217. The line time generator 246 is enabled by the line detector 244, when the line on which the data of the vertical blanking interval is to be inserted, is detected by the line detector. Then the line time generator keeps track of the pixels (picture elements) for that video line, and provides the pixel count (picture elements) of the video line, up to the insert window generator 248, in order to provide the appropriate insertion window of, for example, 704 active pixels (image elements). When a zero data of the correct line arrives, the line time generator 246 also signals a start time detector (counter) 214, which starts a count down for the pixel time (image element) of start dictation for the sample_info information obtained from the syntax. The down counter of the starting pixel (image element) 214 enables a symbol clock generator 210, which, in turn, cleans a symbol counter 212. The symbol clock generator 210 receives the modulo_nrz and the increment_nrz from the syntax. Once the symbol clock generator is initiated in response to the detector 214, the time of the symbol is derived by incrementing a counter by the numerator of the time fraction of the symbol over the time of the pixel (image element). The counter module is the denominator of the fraction. If desired, the numerator and denominator can be multiplied by a constant to simplify hardware implementation. The symbol clock generator 210 produces a symbol clock to enable the first-in-first-out (FIFO) recorder to set the vertical blank interval data from the first-in recorder to the clock. first out (FIFO) 202. It also provides the fraction of the time of the symbol representing a current sample for a transition time scale circuit 216, described below. The symbol clock works until the symbol counter 212 counts the number of symbols specified by the word_count and long_count from the syntax, at which time a stop signal is generated. The stop signal also cleans the shift recorder 206 in the data path of the vertical blanking interval. The vertical blanking interval data exchanged through the recorder 206 is monitored by a transition signal detection circuit 208. The presence or absence of a transition is detected by comparing the previous transmitted symbol with the current symbol which is going to be transmitted. If they are equal, the same value is generated and transmitted. If there is a difference between the two symbols, then the transition generator 218 is selected, which may comprise, for example, a read-only memory (ROM), or a direct access memory (RAM). The transition generator 218 stores the data to generate multiple transition functions, one for each type of transition that is supported, for the data pulses of the vertical blanking interval for different vertical blanking interval (VBI) standards. . The particular transition function selected for the current vertical blanking interval data is determined by the transition type specified by the syntax-driven value of the syntax, and put into transition generator 218 via terminal 205. For example , the transition function can provide the pulse-form as a high or rectangular cosine pulse.

The beginning and end of the transition are dictated by the directions placed to the transition generator from the transition time scale circuit 216, which scales the fraction of the time of the symbol according to the ratio of the symbol to the duration of the transition. transition from terminal 213, and modulo_nrz from terminal 209. The scaled fraction of time of the symbol represents the position of the sample in time within the rise time of the data pulse of the vertical blanking interval. The transition process is repeated until the detection circuit 220 determines that the address exceeds the range of read-only memory (ROM) or direct access memory (RAM) of the transition generator, at which time, the symbol has reached 100 percent of its final value. Then, an output multiplexer (selector) 242 selects the final value for the current and remaining pixel (pixels) of the pixels (pixels) of that symbol. The selection logic 222 controls the multiplexer 242 based on the initial detection of a transition, by the transition detection circuit 224, and the termination of the transition determined by the circuit 220. A look-up table (LUT) 236 (stored, for example, in read-only memory (ROM)), it converts each bit of data output from change recorder 206, at an 8-bit level that is finally scaled to the appropriate luminance level for the particular type of user data that are being processed. For example, the query table (LUT) 236 can convert a binary "0" in the 8-bit word 00001111, and a binary "1" in the 8-bit word 11110000. This mapping is arbitrary, and any number can be selected. Other desired 8-bit levels for binary "1" and "0". The 8-bit level from the query table output (LUT) 236 is provided to the multiplexer 242, which selects this level for the output, unless a transition is in progress, as indicated by the selection logic 222 , in which case, the transition function is produced from the transition generator 218. The data stream exiting from the multiplexer 242, is then scaled to the required output levels, in response to the values of amplitude_0 or amplitude_l delivered by the user data syntax via terminal 201. An output multiplexer 254 inserts the resulting vertical blanking interval data on the video stream from terminal 217, for the insertion window provided by generator 248. The insert window corresponds to the duration of the active video. Multiple vertical blanking interval services can be inserted with the generator of Figure 3. Additional circuits are needed to load the variables required to run the generator on a line-by-line basis. The data is entered into a first-in-first-out (fixed) common logger. In the implementation shown, all clocks are working at 13.5 MHz, unless otherwise indicated. This is half the speed of the standard MPEG, ATSC, and DigiCipher II system clock. The data that comply with EBU 32187, have the property that the transition time is slightly longer than the symbol time. This can be overcome by selecting a transition function that has a time from 10 percent to 90 percent slower in relation to the entire transition. The filter specified for the wave configuration data of EBU 3217 is Gaussian transition. A Gaussian window transition can provide better performance than the square sine. The teletext services can be supported in a similar manner, as disclosed for the vertical blanking services described in connection with Figure 3. To support teletext, the waveform generator must handle a pulse response which, as noted above, is of a duration greater than a symbol. An example implementation of this vertical blanking interval waveform generator is illustrated in Figure 4. The first-in-first-out (FIFO) logger of vertical blanking interval data 310, the change recorder 312, symbol counter 316, symbol clock generator 320, start time detection circuit 322, scale and offset circuit 306, multiplexer (selector) 308, insert window generator 332, the line detection circuit 330, and the line time generator 328 of Figure 4, are equivalent to the similarly named elements of Figure 3. In order to handle the impulse responses of multiple service symbols of teletext, which can be from 1.89 to 2.36 samples per symbol at a sampling of 13.5 MHz, a read-only memory (ROM) of transmission filter (Tx) 302, and an interpolation filter 314 are provided. and appreciate that the filter 302 can also be implemented in the direct access memory (RAM) if desired, particularly if the impulse response of the desired format is to be downloaded instead of being stored locally in the read-only memory (ROM). . Any of these downloads will be at a fixed speed of number of samples per symbol. The syntax for this download can be provided according to the C language type syntax discussed above. The interpolator is used to generate the 13.5 MHz speed of the pixels (picture elements). The difference in speed is the increase of the interpolator. The data to be inserted is entered in the first-in-first-out (FIFO) register 310 via terminal 303. The data is inserted in the vertical blanking interval by reproducing the symbols through the generator of pixels (image elements). The pixel generator (picture elements) is provided with the start time of the first pixel (picture element) of the symbol by means of terminal 315, the number of pixels (picture elements) per symbol (increment / module) by means of the terminals 311 and 309, the high and low levels (amplitude_0 and amplitude_l) to insert by means of the terminal 300, the impulse response of the signaling system (transition type) by means of the terminal 301, the number of symbols to be inserted by means of terminal 307, and the field and line number where the data will be inserted by means of terminal 305. Video data put into terminal 317 is provided in CCIR format 656. The count of lines are derived and compared with the desired line of insertion in circuits 330, 328, and 322. When the zero data of the correct line arrives, a downward count is initiated for the start pixel (image element) time. in circuit 322, which enables the symbol speed clock generator 320 at the appropriate time. The 704 pixel window generator (pixels) 332 is enabled by the line time generator 328. As in the waveform generator of Figure 3, the time of the symbol is derived by increasing one counter per the numerator of the fraction "symbol time / pixel time (image element)", where the increment "INCR" is the numerator, and the module of the counter is the denominator of the fraction. In addition to receiving the module and the increment via terminals 309 and 311, respectively, the symbol clock generator 320 receives the system clock (e.g., 27 MHz) by means of terminal 313. By making the symbol clock generator, for example, at 27 MHz, instead of at 13.5 MHz, a double symbol speed clock is generated. The enable entry of the first-in-first-out (FIFO) register 310 receives the symbol clock from a splitter 318, which divides the output of the clock generator 320 by two. This is necessary, because the generator of the symbol clock provides a clock of twice the speed of the symbol. Once the specified number of symbols have been produced from the first-in-first-out (FIFO) recorder, the symbol clock for the current television line is disabled. All subsequent data symbols are forced to the low (zero) state. These symbols are not data, but rather they fill the rest of the 704-pixel window (image elements) with low-status data. The read-only memory (ROM) of the transmission filter 302 generates two samples per symbol. The transmission change recorder 312 is loaded with the transmission symbols at the speed of the symbol, when the start time has arrived. The logger is initialized to a low state at the end of each insertion. The transmission data for the duration of the impulse response is applied to the read-only memory (ROM) from the change recorder 312. The read-only memory (ROM) stores a pulse response query table calculated in advance in accordance with well-known techniques. By storing the results of the finite impulse response (FIR) calculation in the read-only memory, it is not necessary to store the finite impulse response (FIR) coefficients to calculate the results. The finite impulse response (FIR) appropriate for the particular transition to be provided in the waveform of the vertical blanking interval (VBI) is taken from the query table (LUT) when the memory is directed only read (ROM) by the type of transition via terminal 301. The output of the transmission filter is provided to an interpolator filter 314 by means of the register 304. The interpolation filter converts the velocity data from two samples per symbol to 13.5 MHz samples. An example of an appropriate interpolation filter is described by the following finite impulse response coefficients (FIR): Ag = aμ 0 oí μ A¡ = μ2 + (a + Dμ A2 = otμ + (a + 1) μ + 1 A3 = otμ - o¿μ where o; it is defined as 0.5. μ is the time for the sample to interpolate. The frequency response 400 of this interpolator (Paralntr) and the transmission impulse responses 402, 404, 406, and 408 for the different teletext standards, as well as the VideoCipher standard which owns the original assignee of the present invention, are illustrated in Figure 5. It can be seen that the interpolator clearly has influence over the transmitted frequency response. This frequency response error can be corrected (predistort) in the transmission filter 302 to minimize its impact. It is a requirement that the transmission spectrum and its images are well controlled before interpolation. This is the case for the data signal types described. If the speed of pixels (picture elements) per symbol is less than about 3 samples per symbol, a larger number of samples per symbol would be required. The data supplied to the interpolator 314 is twice the speed of the symbol. The actual data transfers are presented coinciding with the 27 MHz ticking. The interpolator output is read at 13.5 MHz. The time interpolation variable is supplied to the 13.5 MHz speed filter. A 324 time generator and a circuit of scale 326, allow the numerical representation of μ to be consistent with the numerical system of the filter hardware, and independent of the value of the current module. The data stream has to be scaled up to the required output levels. This can be done, for example, with a multiplication and addition per pixel (picture element) provided by the scaling and offset circuit 306. The output multiplexer 308 inserts the data from the vertical blanking interval from the scaling circuit. scale and offset 306 on the CCIR video stream from terminal 317, for the 704 pixel window (pixels). There are several alternative ways to implement the functions provided by the waveform generating circuits of Figure 3 and Figure 4, and the specific modalities illustrated by no means are limiting. For example, the scale and phase shift can be done earlier in the process, than as illustrated. In the embodiment of Figure 4, any of a variety of known interpolators can be used. Moreover, in the multiple symbol mode, lower data rates can be supported, having impulse responses with more samples per symbol. All current teletext standards are supported by two samples per symbol. Additionally, the pulse modulated amplitude (PAM) of M-levels (multiple levels), with M 2, can be supported using the waveform generator of Figure 4. In these implementations, with M > 2, there would be the register base 2 of M bits per symbol supplied to the read-only memory (ROM) of the transmission filter. With M = 2, there would be one bit per symbol supplied to the read-only memory (ROM) of the transmission filter.

It should now be appreciated that the present invention provides a method and apparatus for communicating user information in a digital television data stream. The user information is a type that is conventionally carried as data with no return to zero (NRZ) in the vertical blanking interval of an analog television signal. The user's data is transported in a user data syntax, which has been supplemented with different fields. These include a field of additional data type, a luma NRZ account and priority, field number, out of phase line, start sample, increment and NRZ module, amplitude values, pulse shape information, and word count information and remaining in relation to user data, which are carried in the form of words luma NRZ. Although the invention has been described in connection with a preferred embodiment, it should be appreciated that various adaptations and modifications may be made thereto without departing from the spirit and scope of the invention as set forth in the claims.

Claims (22)

1. NOVELTY OF THE INVENTION Having described the foregoing invention, it is considered as a novelty, and therefore, property is claimed as contained in the following: CLAIMS 1. An apparatus for generating a digital waveform according to a syntax of user data of a vertical blanking interval service (VBI) to be inserted into the portions of the vertical blanking interval of a digital video signal, this apparatus comprising: a symbol processor for receiving data of the blanking interval vertical blank from the vertical blanking interval service, and to provide the vertical blanking interval data in a format that is compatible with the vertical blanking interval service according to the data syntax of the vertical blanking interval. user; providing this syntax a start time for a first symbol of a plurality of symbols carrying the data of the vertical blanking interval, and indicating (i) a number of pixels (picture elements) represented by a symbol, (ii) a transition time for these symbols, and (iii) the number of symbols that carry the data of the vertical blanking interval; and a timing circuit for effecting the insertion of the vertical blanking interval data into a portion of the vertical blanking interval of a television line identified by the syntax according to the start time. The apparatus according to claim 1, characterized in that it further comprises: a buffer zone coupled with the symbol processor for temporarily storing the vertical blanking interval data. The apparatus according to claim 1 or 2, characterized in that it further comprises: a level control circuit for adjusting the data level of the vertical blanking interval before being inserted into the interval portion of Vertical blanking in response to at least one amplitude value provided by said syntax. The apparatus according to claim 3, characterized in that: the level control circuit provides the amplitude modulation of M-levels (multiple levels) of the vertical blanking interval data, with M > 2. The apparatus according to claim 3, characterized in that: the level control circuit provides amplitude modulation without return to zero of the vertical blanking interval data. The apparatus according to claim 1, characterized in that: the data of the vertical blanking interval of the vertical blanking interval service have a pulse response of a single symbol; the symbol processor comprises a transition processor for detecting a transition in the vertical blanking interval data, and for generating a transition waveform in response to the detected transition, which is compatible with the staging interval service in vertical white; and the apparatus further comprises an element for combining the transition waveform with the vertical blanking interval data, to provide the digital waveform for insertion into the vertical blanking interval portion of the television line identified by said syntax. 7. The apparatus according to claim 6, characterized in that the transition processor further comprises: an element for generating a transition function for the vertical blanking interval service, according to a transition type thereof, defined by said syntax; generating the transition waveform according to the transition function. The apparatus according to claim 7, characterized in that the transmission processor further comprises: a memory for storing the transition data to generate the transition function; the element to generate responds to the stored data to generate the transition function. The apparatus according to claim 1, characterized in that the data of the vertical blanking interval have a pulse response of multiple symbols, this symbol processor comprising: an element for implementing a response function pulse, to generate a sequence of data symbols representing the data of the vertical blanking interval for the vertical blanking interval service. The apparatus according to claim 9, characterized in that it further comprises: a memory for storing pulse response data for the vertical blanking interval service according to a transition type thereof defined by said syntax; the element to be implemented responds to the stored impulse response data, to implement the impulse response function for the vertical blanking interval service. The apparatus according to claim 10, characterized in that: the impulse response data is downloaded into the memory to store the impulse response data. 12. A method for generating a digital waveform according to a user data syntax of a vertical blanking interval service (VBI), to be inserted into the vertical blanking interval portions of a signal from digital video, this method comprising the steps of: receiving the data from the vertical blanking interval from the vertical blanking interval service; providing the vertical blanking interval data in a format that is compatible with the vertical blanking interval service according to the user's data syntax; the syntax providing a start time for a first symbol of a plurality of symbols carrying the data of the vertical blanking interval, and indicating (i) a number of pixels (picture elements) represented by a symbol, (ii) a transition time for these symbols, and (iii) the number of symbols that carry the data of the vertical blanking interval; and inserting the vertical blanking interval data into a vertical blanking interval portion of a television line identified by said syntax, according to the start time. The method according to claim 12, characterized in that it comprises the additional step of: placing the data of the vertical blanking interval before the providing step in the buffer zone. The method according to claim 12 or 13, characterized in that it comprises the additional step of: adjusting the data level of the vertical blanking interval before being inserted into the vertical blanking interval portion , in response to at least one amplitude value provided by said syntax. The method according to claim 14, characterized in that: the level adjustment step provides the amplitude modulation of M-levels (multiple levels) of the data of the vertical blanking interval, with M > 2. The method according to claim 14, characterized in that: the level adjustment step provides an amplitude modulation without return to zero of the data of the vertical blanking interval. 17. The method according to claim 1 of claim 12, characterized in that the data of the vertical blanking interval of the vertical blanking service, have a pulse response of a single symbol, this method comprising the additional steps of: detecting a transition in the vertical blanking interval data, and generating a transition waveform in response to the detected transition, which is compatible with the vertical blanking interval service; and combining the transition waveform with the vertical blanking interval data, to provide the digital waveform, to be inserted into the vertical blanking interval portion of the television line identified by said syntax. The method according to claim 17, characterized in that it comprises the additional step of: generating a transition function for the vertical blanking interval service according to a transition type thereof, ned by said transition syntax; this transition waveform is generated according to the transition function. 19. The method according to claim as claimed in claim 18, characterized in that it comprises the additional step of: storing the transition data to generate the transition function; answering the step of generating the stored data to generate the transition function. 20. The method according to claim as claimed in one of claims 12 to 19, characterized in that the data of the vertical blanking interval has a pulse response of multiple symbols, and which comprises the additional step of: implementing a function pulse response to generate a data symbol sequence representing the vertical blanking interval data for the vertical blanking interval service. The method according to claim 20, characterized in that it comprises the additional step of: storing the impulse response data for the vertical blanking interval service according to a transition type thereof, ned by said syntax; answering the step of implementing the stored impulse response data, to implement the impulse response function for the vertical blanking interval service. The method according to claim 21, characterized in that it comprises the additional step of: downloading impulse response data; where the step of storing responds to the step of downloading. SUMMARY OF THE INVENTION A digital waveform generator complies with different vertical blanking interval (VBI) standards, and is inserted into the vertical blanking interval portions of a digital component video signal. A buffer zone receives the symbols carrying data from the vertical blanking interval for a particular vertical blanking interval service according to a user's data syntax, which identifies a television line where they are going to insert the vertical blanking interval data. A symbol processor responds to the information provided by the syntax. This information indicates the number of pixels (picture elements) represented by symbol, a symbol transition time, and the number of symbols carrying data to be inserted in the portion of the vertical blanking interval. The symbol processor provides the data of the vertical blanking interval in a format according to the particular vertical blanking interval service. A timing circuit responds to a start time provided by the syntax to insert the data from the vertical blanking interval. A level control circuit adjusts the data level of the vertical blanking interval before being inserted into the vertical blanking interval portion, in response to the amplitude values provided by the syntax.