Television – Nonpictorial data packet in television format – Data separation or detection
Reissue Patent
1999-12-16
2002-04-02
Kostak, Victor R. (Department: 2611)
Television
Nonpictorial data packet in television format
Data separation or detection
C348S467000, C348S478000, C375S240260
Reissue Patent
active
RE037620
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to the communication of digital television signals, and more particularly to a band-width efficient scheme for providing user data in a digital television data stream without the need to reserve space for the user data in advance. Examples of such user data include closed caption data, non-realtime video data (e.g., vertical interval test signal—VITS), sampled video data and automated measurement of lineup (AMOL) data.
Digital transmission of television signals can deliver video and audio services of much higher quality than analog techniques. Digital transmission schemes are particularly advantageous for signals that are broadcast via a cable television network or by 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 phonograph records in the audio industry.
One way to transmit the compressed video data to a receiver is in the form of packets contained within a packetized data stream. Typically, packets carrying compressed video data are multiplexed with other packets, e.g., carrying corresponding audio data and control information necessary to reconstruct a television signal. One standard for transporting digital television signals in this manner is the MPEG-2 standard, details of which can be found in the International Organisation for Standardisation, ISO/IEC 13818-1, International Standard, 13 Nov. 1994 entitled “Generic Coding of Moving Pictures and Associated Audio: Systems,” recommendation H.222.0, incorporated herein by reference. Further details of the video syntax and semantics for MPEG-2 video can be found in International Organisation for Standardisation, ISO/IEC 13818-2, International Standard, 1995 entitled “Generic Coding of Moving Pictures and Associated Audio: Video,” recommendation H.262, also incorporated herein by reference.
In the MPEG-2 system (and the similar DigiCipher® II system proprietary to General Instrument Corporation, the assignee hereof) a transport stream, or transport multiplex is made up of a contiguous set of fixed length packets. The video sequence is transported using a hierarchical structure in which a sequence header is followed by various extensions, user data, a group of pictures (“GOP”) header, optional user data, a picture header, etc. The sequence header provides information for a sequence of pictures, which in general will include more than one GOP. This information includes, for example, horizontal and vertical size values, aspect ratio, frame and bit rate, and quantization parameters for the video data. A user data extension can also be included which, among other things, provides additional data for use by decoders. The DigiCipher® II standard provides for the transport of additional user data after the sequence header, in order to identify a DigiCipher® II signal and the use of any special video compression techniques used within a sequence, including DigiCipher® special prediction and block motion estimation.
In both the MPEG-2 and DigiCipher® II syntaxes, a sequence display extension containing, e.g., video format and color description information, is provided in addition to the sequence extension and user data. A subsequent group of pictures header provides, among other information, a time code. Thereafter, a picture header is provided which includes various information pertaining to a corresponding picture in a sequence of pictures to be displayed. A picture extension and, ultimately, the actual picture data to be decoded and reproduced for viewing, is then provided. It is noted that MPEG does not specify the order in which various extensions (such as the sequence display extension) or the user data must be transmitted beyond the fact that they must be after the sequence extension and before the GOP header (if provided) or the picture header. MPEG does not require GOP headers to be sent, and such headers may be bypassed 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 closed captioning, VITS, auxiliary real time video, and AMOL data. Such additional data may be carried in the vertical blanking interval (VBI) portions of a television signal, and is referred to herein as “VBI user information.” Typically, the insertion of such VBI user information would require a transport syntax to allocate and reserve fixed length portions into which the VBI user information is inserted. If the VBI user information is not used, the fixed length portions would be unusable for other information and bandwidth would be wasted.
It would be advantageous to provide a transport syntax for digital television data that would accommodate various types of VBI user information which may or may not be used at any given time, without requiring space to be reserved for the information in advance. Such a scheme would enable the economical management of bandwidth while providing flexibility as to the transport of VBI user information. The present invention provides a transport method and apparatus enjoying the aforementioned advantages.
SUMMARY OF THE INVENTION
In accordance with the present invention, a bandwidth efficient method is provided for using a digital television data stream to transport variable amounts of different types of information carried in a vertical blanking interval (VBI) portion of a television signal. Information to be transported is extracted from portions of input video data that correspond to vertical blanking intervals of successive video frames. First identifiers are provided for the extracted information. The first identifiers specify a count of a particular type of information associated with the identifier. The first identifiers and the associated information are inserted into VBI related portions of the digital television data stream. The data stream, including the first identifiers and the information, is then communicated to a receiver. The first identifiers enable the adjustment of the data stream to accommodate variable amounts of different types of information without space being reserved for specific amounts and types of information in advance.
Second identifiers can be provided for the extracted information. The second identifiers designate a priority of the particular type of information specified by the first identifiers. In an illustrated embodiment, the first and second identifiers precede the information associated therewith in the data stream. Each second identifier follows a counterpart first identifier. Thus, the syntax provides a first identifier specifying a count of a particular type of information, followed by a second identifier specifying a priority of the information, followed by the information itself. It should be appreciated that each type of information (i.e., “construct,” the size of which is dictated by the count) may include a priority, such that a video picture can include constructs of various priorities.
The extracted information can comprise, for example, one or more of closed caption data, non-realtime video data, sampled video data and AMOL data, referred to herein as VBI user information because it is provided in the VBI portions of a television signal. When the extracted information comprises non-realtime video data, the syntax provides sequence numbers and segment numbers for portions of the non-realtime video data. When the extracted information comprises AMOL data, identifiers are provided to designate whether the AMOL data is null data represented in an abbreviated form. For example, where the AMOL data comprises a string of zeros, the string can be runlength coded to avoid the need to send the entire string of zeros, thereby saving bandwidth. The syntax can also provide identifiers to designate parity values for the AMOL data.
In the illustrated embodiment, the digital television data stream is assembl
Hoogenboom Chris
Moroney Paul
Nuber Ray
General Instrument Corporation
Kostak Victor R.
Lipsitz Barry R.
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