Method for decoding image/sound data contained inteletext data of a digital television signal

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The invention relates to a method for receiving data transmitted in a television signal.

In the conventional Teletext system currently used in Europe (with the exception of France), the so-called "Level 1" of the Teletext standard WST (World System Teletext) is used. Level 1 teletext allows texts and graphic representations to be displayed with a restricted basic character set on a screen. A teletext page consists of a head row and 23 rows.

As is known from German Patent DE 39 14 697 C2, further supplementary data for special characters, fine structures and color shadings can be transmitted with Level 1 in addition to text pages. At the receiving end, the associated supplementary data are temporarily stored in addition to the Level 1 text page and are displayed on the screen together with the relevant Level 1 page. The fine structures are transmitted pixel by pixel in special supplementary pages without using compression methods.

It is also known from published British patent application GB 2146878A to provide for a simplified selection of Teletext pages by means of search words. In addition to the search words, which are displayed on the screen together with a given Teletext page in a 24th row, associated page numbers are transmitted in a hidden manner in a further row.

It may be desirable to display images and image sequences, for example, together with a text page, and to reproduce sounds, by mainly utilizing the already existing circuitry for digital signal processing in a receiver. Such existing circuitry may include circuitry for image and sound decoding. Such feature may be used in the future to supplement text service.

In accordance with an inventive feature, the display of images and the reproduction of sounds, if necessary, are provided following a request by the user. A text-image-sound link table is transmitted together with the text, image and sound data. The decoder retrieves the image and sound data in accordance with the text-image-sound link table. A code that is also transmitted is used for selectively applying the retrieved image and sound data to the display screen and to a sound transducer such as a loudspeaker, respectively.

FIG. 1 shows a diagrammatic representation of a digital television receiver having a text decoder, the facilities for image and sound decoding and the corresponding transducers, according to an aspect of the invention;

FIG. 2 shows a diagrammatic representation of a text page with the text-image-sound link table according to the invention and the associated image and sound data;

FIG. 3 shows a text page with a program preview and the search words emphasized by the decoder in accordance with the text-image-sound link table;

FIG. 4 shows the text page according to FIG. 3 with an image associated with a particular program designation;

FIG. 5 shows the text page according to FIG. 3 with an image associated with a further program designation; and

FIG. 6 shows a special page, of the type forming a TV program guide, in which images for program designations of various broadcasting stations are displayed together with the associated broadcasting times.

FIG. 1 shows a block diagram of a television receiver for digital transmission. A digital television signal containing non-teletext picture and sound information encoded in, for example, digital techniques and also teletext information encoded in digital techniques is applied via a switch 10 to an image decoder 20 which decodes the television image data and displays them on the screen via a switch 30. The television signal is also applied via a switch 80 to a sound decoder 90 which reproduces the decoded sounds in a loudspeaker. In addition, a text decoder 40, controlled by remote control, separates the text, image and sound data derived from the incoming digital television signal and temporarily stores them in a memory 70. Upon a request by the user, a desired text page is supplied from the memory 70 via a switch 50 to a character generator 60. The requested text page is displayed on the screen via the switch 30.

In addition, the decoder loads a separate text-image-sound link table and searches for search words. The search words are entered in the table under the requested page and are displayed in a suitable manner on the screen together with the associated text page. If the user desires further information on one of the subjects mentioned in the search words, he selects the relevant search words by means of, for example, a movable marker or cursor. The decoder then searches in the text-image-sound link table for a code and for addressing information associated with the selected search word. If the data retrieved according to the addressing information are identified by the code as being image data, the image data are applied from the memory via the switch 50 and 10 to the image decoder 20 and displayed on the screen via the switch 30. If, on the other hand, sound data are identified by the code, they are applied from the memory to the sound decoder 90 via the switch 80 to provide an audio signal to the loudspeaker.

FIG. 2 diagrammatically shows the text-image-sound link table with a text page and associated image and sound data. For example, the text-image-sound link table `1FA`contains, under the page number of text page `301`, a search word `weather`. The search word `weather`is associated in the table with a code `B` identifying image data, and with an address word `1FA 001`, providing the address of the associated image data. In addition, further sound data can be retrieved with the same search word in accordance with the address word `1FA 0010` and a code `T` identifying sound data. In addition, the text-image-sound link table contains further entries with codes and addresses under the search word `JOYrobic` for text page `301` and for text page `302`. In addition, further codes are possible for image and sound data which are automatically retrieved and applied to the corresponding transducer directly when the text page is retrieved, without request by the user.

To explain the invention, FIG. 3 shows a text page with a program preview page according to the invention. The decoder marks or highlights the search words `weather`, `JOYrobic`, etc., in the selected text page `301` in accordance with the text-image-sound link table. It is also possible for the decoder to display the search words that are valid for a selected text page in a separate area on the screen.

FIG. 4 shows the program preview page `301` after selection of the search word `weather` by the user. Instead of the associated image being displayed, image sequences can also be reproduced.

FIG. 5 shows the program preview page `301` after selection of the search word `JOYrobic`.

FIG. 6 shows a format for distinctly displaying images of program designations for a TV program guide. In this arrangement, the text decoder assembles the images, which have been appropriately reduced in size, from designations of various broadcasting stations (in this case from ARD and ZDF). The images are assembled with the associated broadcasting times in a special overview page by means of the text-image-sound link table. In addition, the user can use the remote control to display other designations at other broadcasting times or from other broadcasting stations.

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