Television – Nonpictorial data packet in television format – Data format
Patent
1991-12-12
1994-10-11
Groody, James J.
Television
Nonpictorial data packet in television format
Data format
348468, 348466, H04N 7087, H04N 708
Patent
active
053551702
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention refers to a method for the transmission of preferably periodically repeated teletext data in a television signal wherein on the transmitter side, complementary data for a respective teletext page is transmitted in addition to the teletext basic data of conventionally constructed teletext pages, and wherein, on the receiver side, the teletext data is separated from the television signal, the data belonging to a particular teletext page is collected and the basic data and the complementary data of a desired teletext page are intermediately stored and processed in such a way that the characters allocated to the basic data are made to appear at those character positions where no complementary data is present, and that the characters allocated to the basic data working in conjunction with the complementary data are made to appear at those character positions where complementary data is present. Such a method is known from "Rundfunktechnische Mitteilungen", vol. 27 (1983), issue 3, pages 116 through 134. The invention also refers to a facility for carrying out the method.
With the conventional teletext system at present in use in Europe (with the exception of France), only the so-called "level 1" of the teletext standard WST (world system teletext) is made use of; the system possesses only a limited basic character set for texts and graphic representations. Special characters, fine textures or color hues cannot be reproduced using this "level 1" system. To avoid these shortcomings the WST standard provides, particularly in its expanded stages "level 2" and "level 3", for the transmission of complementary data in so-called pseudo rows (also called "ghost rows") which have addressable row numbers which are not used by the "level 1" but are kept unoccupied in the transmission format. Several rows with the same row number must be used, as required, for the transmission of the required quantity of complementary data as can be seen in FIG. 1 for row number #26 (cf. also the above-mentioned publication "Rundfunk-technische Mitteilungen").
As the teletext receiver does not receive any information concerning the number of pseudo rows transmitted in association with a particular teletext page (basic data), the decoder does riot "know" whether, which and, if applicable, how many pseudo rows have been broadcast for a teletext page. A correct evaluation can, therefore, only be performed if the desired teletext page and all associated pseudo rows are received in full. Moreover, additional storage capacity for every teletext page which is to be stored, for example, 4 kByte, must be kept permanently available in the decoder which cannot be used otherwise in case no pseudo rows are transmitted.
In view of this, it is the object of the invention to render possible an improved transmission or processing of complementary data with a method or a facility respectively of the aforementioned type while also guaranteeing complete compatibility with existing teletext receivers which work according to "level 1".
SUMMARY OF THE INVENTION
The above object generally is solved according to the invention by a method for the transmission of preferably periodically repeated teletext data in a television signal wherein on the transmitter side, complementary data for a respective teletext page is transmitted in addition to the teletext basic data of conventionally constructed teletext pages with the complementary data for a respective page of teletext being transmitted in the form of one or more associated complementary pages; and wherein, on the receiver side, the teletext data is separated from the television signal, the basic data and the complementary data belonging to a particular teletext page are collected, the complementary page(s) allocated to a desired teletext page is/are intermediately stored separately from the associated teletext page(s), and the basic data and the complementary data of a desired teletext page are processed in such a way that the characters allocated to the basic data are
REFERENCES:
patent: 4614972 (1986-09-01), Motsch et al.
patent: 4698677 (1987-10-01), Kinghorn et al.
patent: 4953022 (1990-08-01), Bugg
Review HF. XIII, No. 10, 1987, Ophain Be Seiten 283-296; Ir K. van Bruwaene: "De Evolutie van Teletekst", Royal Television Society Journal, vol. 18, No. 5, Oct. 1980.
London GB, pp. 43-45; J. P. Chambers, "Potential of Extended Teletext".
Electronic Components and Applications, vol. 6, No. 1, 1984, Eindhoven NL, pp. 15-29; J. R. Kinghorn "Computer Controlled Teletext".
Eitz Gerhard
Moll Gerhard
Groody James J.
Metjahic Safet
Telefunken Fernseh und. Rundfunk GmbH
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