Note: Descriptions are shown in the official language in which they were submitted.
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~O 91/03127 - 1 - PCT/EP90~01323
Method for transmission and automatic reception of data
signals in a television signal
DESCRIPTION
The invention relates to a transmission method
according to the preamble of patent claim 1 as well as a
reception method according to the preamble of patent
claim 3. Methods of this type are known from the research
report BBC RD 19~8/1 of March 19~8 from the British
Broadcasting Corporation.
For the transmission of data signals in a television
signal, the UK videotext (teletext) specification (cf. BBC
Research Report BBC European 1988/1) provides for a
specially identified videotext line to be used
asynchronously with a videotext cycle. This videotext line
is a so-called "pseudo line" which is not evaluated by
videotext decoders for the so-called "level 1" of the
videote~t standard WST ~World System Teletext). In the
pseudo lines for the e~panded stages "level 2" and "level 3"
of the WS~ standard, supplementary data, with regard to the
limited basic character set of "level 1", is transmitted in
order to present special characters, fine structures or
shades of color. In the case of a data signal transmission
independent of this, then, in particular, software data for
the remote programming of personal computers can be
transmitted ("tele-software").
The videotext broadcasting and networking facilities
used by ARD and ZDF in the Federal Republic of Germany and
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Berlin (west) are, like the videotext receivers at present
available on the German market, just as incapable of
transmitting or, respective~, evaluating pseudo lines, in
particular if they are inserted into the videotext cycle
independently from the videotext page structure. With this
in mind, the transmission of data signals provided for in
the UK videotext was not incorporated in the television te~t
specification of ARD/ZDF/DBP.
The object of the invention consists of specifying a
transmission o~ data signals in a television signal which is
compatible with the television text specification of
ARD/ZDF/DBP. Further, with such a compatible data signal
transmission, every effort will be made to create a
particularly simple, aut:omated possibility for the reception
and for the evaluation of the data signals.
This task, with respect to the transmission of data
signa]s, is solved by the characterizing features of patent
claim 1. With respect to the reception of such transmitted
data signals, the task is solved by the characterizing
features of the non-subordinate patent claim 3.
The invention will be explained in more detail by means
of the drawings. They show:
:
Fig. 1 a schematic representation of a special
videotext page transmitted and received according
to the invention;
Fig. 2 a block circuit diagram of an embodiment
example for the construction of circuitry on the
broadcasting and reception sides for carrying out
the method according to the invention; and
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WO 91/03127 - 3 ~ PCl'/EP~0/01323
Fig. 3 a bloc~ circuit diagram for the receiving
section merely indicated as a circuit bloc~ in
Fig. 2.
The special videotext page represented schematically in
Fig. 1 is transmitted in a non-cyclic manner in the
videotext cycle and consists of a packet of data signals.
The length of the pac~et can be varied in order to ensure
matching with the respective type Or application. As a
matter of practicability, the length of the data pac~et is
matched to the number of lines available in each television
field. These do not necessarily always need to be lines in
the vertical blanking interval (picture flybac~) although
this type of application is the most common. If,
specifically, no section of the image is transmitted in the
television signal, then practically all the lines of each
field are available for the transmission of the data
sigrlals .
As Fig. 1 illustrates, each special videotext page
consists of a pac~et overhead of, for example, 24 x 8 bits
as well as a control and/or user data packet of, for
example, 40 x 8 bits. The packet overhead is located in the
first row ~0 of the special videotext page, while the
control and/or user data are distributed over the row~ #1
through #23 of the special videotext page.
In the schematic circuit diagram for the facilities on
the broadcasting and reception sides for carrying out the
method according to Fig. 2, the user data is generated on
the broadcasting side in a data source 1 and transmitted to
a coder 2, coding the user data into the videotext code, as
a "data transmission". The coded data transmission,
presented as separate block 3, is formed in the packet ;'
formatter 6 into a user data packet.
. . .. : ~ . :, . , .. , , :: . :: : . . . :, . :, .. : . :
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Wo 91/03127 - 4 P(T~EP90/01323
The coding arl~ the formation of the pac~et in bloc~s 2
and 6 is carried out under the control of a control circuit
5 which con~erts lhe presets, ~-ith respect to the data format
of the data packets coming from a control input 4, into
correspon~ing control information for the blocks ~ and 6.
Tlle n user data packets created by tlle pac~et formatter
6 are illustrate~ in Fi~. 2 as blocks 8l through 8n. Ad~ecl
to these user data pac~ets will be - as can be seen from
Fig. 1 - a control data packet, shown as block 9 in Fig. 2
and generated by a control packet generator 7 controlled by-
the control circuit 5. The user data packets 8I through 8n
and the control data packet 9 are fed as a special ~ideotext
page according to Fig. 1 from the packet transmitter 10 to a
videotext computer 12. Hereby, the packets 8l through 8n
receive the packet overhead and the control and u~er data in
the ~esired format according to Fig. 1.
The non-cyclic data stream being sent out from the
packet transmitter 10 is mixed with the cyclic data stream
of the "normal" videotext pages, indicated as a rotary
magazine 11, by the videotext computer 12, i.e. it is
incorporated as a special page between two "normal"
videotext pages. The videotext computer 12 feeds the
videotext data (which now contains the special page
according to the invention) in the conventional way to an
adding stage 13 which inserts the videotext data into a
video signal in accordance with the television standard, for
example, into the lines provided for this in the vertical
blanking interval of each field.
The video signal, with the inserted videotext data
including the invention-type special videotext page, is sent
along the transmission path 14, schematically illustrated as
a line (broad band cable link, optical wave guide link,
terrestrial broadcasting route, satellite broadcasting
. . ~ . . . ~ , ... . - . : .
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Wo 91/03127 - 5 - PCT/EP90/01323
route), to the receiver 15 which is shown in more detail in
Fig. 3-
The televi~ion tuner 159 of the receiver 15 shown inFig. 3 converts the video/videotext signal transmitted, for
example, at high frequency, into a baseband signal which is
separated from the videotext component in a videotext data
separation stage :154. The received videotext data stream at
the output of the data separation stage 159 is constantly
scanned by a videotext page acquisition stage 157 for the
appearance of the special vldeotext page number
preprogrammed on the receiver side. This preprogramming is
carried out via a page number input 155 which is connected
to a control circuit 153 which in turn controls the
acquisition stage 157. When the selected special videotext
page number appears in the received videotext data stream,
the special page is decoded anà temporarily stored in the
videotext page memory 158.
The videotext special page which has been temporarily
stored is then checked under the control of the control
circuit 153 in an evaluation stage 152 to see whether a
control data packet provided for control on the receiver
side is contained in it and, if the answer is affirmative,
whether its data transmission identification code coincides
with a preprogrammed identification code on the receiver
side. This latter preprogramming is carried out by an
indentification code input 156 which is connected to the
control circuit 153.
When the identification codes coincide, the special
videotext page which has been temporarily stored, and if
applicable, all subsequent special videotext pages received
under the same special videotext page number, is processed
in the evaluation stage and decoded in the downstream
decoder 151. The resulting data signal corresponds to the
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dat,a t,ransmission at the output of the data source 1 ,
(Fig. 1). This data si~nal can, for example, be stored and
further processed in a personal computer.
