Television – Nonpictorial data packet in television format – Including teletext decoder or display
Patent
1996-02-07
1998-04-28
Peng, John K.
Television
Nonpictorial data packet in television format
Including teletext decoder or display
348465, 348467, H04N 700, H04N 1100
Patent
active
057451842
DESCRIPTION:
BRIEF SUMMARY
This invention relates to the transmission of closed caption and other auxiliary digital information in a compressed video transmission environment.
BACKGROUND OF THE INVENTION
Current standard video signals such as PAL or NTSC include vertical intervals, or fields, having a plurality of horizontal line intervals, e.g. 262.5 lines per field in NTSC video systems. The beginning of each vertical and horizontal interval is identified by respective vertical and horizontal sync pulses that are included in a composite video signal. During a portion of each vertical interval, information in the video signal may not be intended for display. For example, a vertical blanking interval spans approximately the first 20 horizontal line intervals in each field. In addition, several line intervals adjacent to the vertical blanking period, e.g. line 21, may be within an overscan region of a video display and will not be visible.
The lack of displayed image information during blanking and overscan intervals makes it possible to insert an auxiliary information component, e.g. teletext or closed caption data, into these intervals. Standards such as Federal Communications Commissions (FCC) Regulations define the format for each type of auxiliary information including the positioning of the information within a vertical interval. For example, the present closed captioning standard (see e.g. 47 CFR 15,119 and 73.682) specifies that digital data corresponding to ASCII characters for closed captioning must be in line 21 of field 1. The FCC specified format provides for two eight-bit digital data words in each occurrence of line 21, field 1. The closed caption specification may be extended to provide for closed caption format data in line 21 of every field. The data in each word represents one ASCII format character. Closed caption signal data format that complies with the FCC standard is depicted in FIG. 1.
Recent (1993) developments in digital technologies have made practical the transmission of video signals in digital compressed format, allowing the transmission of more than one television signal in the same bandwidth as a conventional analog television signal. However the video compression processes tend not to be conducive to transmitting the digital codes such as the closed caption information contained in the vertical blanking intervals. The present invention therefore comprises a method and apparatus for transmitting and receiving closed caption information, for example, in a compressed video transmission/storage system.
SUMMARY OF THE INVENTION
Apparatus for compressing video information including digital data in horizontal or vertical blanking intervals of analog video signals includes circuitry for retrieving such digital data. The retrieved digital data is formatted into auxiliary digital data packets. The analog video signal is compressed according to, for example, the MPEG compression protocol and the auxiliary digital data packets are included in the frame/picture headers of the compressed video signals.
In a further embodiment including a receiver of compressed video signal with auxiliary digital data packets conveying closed caption data, for example, the compressed video signal and the auxiliary digital data packets are separated. The auxiliary digital data packets are encoded into analog closed caption signal format. The compressed video signal is decompressed into standard video signal format and combined with the analog closed caption signal for application to a television receiver or VCR.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an amplitude/time waveform drawing of a standard closed caption analog signal.
FIG. 2 is a block diagram of a video signal compression/transmission system embodying the present invention, which system includes circuitry for transmitting closed caption-like data as digital data rather than video data
FIG. 3 is a block diagram of apparatus for processing and extracting closed caption-like data from analog television signals.
FIGS. 4 and 5 are block diagrams of alternative re
REFERENCES:
patent: 5148272 (1992-09-01), Acampora et al.
patent: 5168356 (1992-12-01), Acampora et al.
patent: 5400401 (1995-03-01), Wasilewski et al.
patent: 5493339 (1996-02-01), Birch et al.
ISO/IEC JTC 1/SC 29 N 147, 20 Apr. 1992, Tokyo, Japan, pp. 78-85, "Coded Representation of Audio, Picture Multimedia and Hypermedia Information".
Herrmann Eric P.
Kurdyla Ronald H.
Peng John K.
Srivastavh Vivek
Thomson Consumer Electronics Inc.
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