GB2254977A

GB2254977A - Receiver for letterbox television signals

Info

Publication number: GB2254977A
Application number: GB9208801A
Authority: GB
Inventors: Teunis Poot; Franciscus Wilhelmus Vreeswijk; Marcellinus Joseph Jo Annegarn
Original assignee: Philips Electronics NV
Current assignee: Koninklijke Philips NV
Priority date: 1992-04-23
Filing date: 1992-04-23
Publication date: 1992-10-21
Anticipated expiration: 2012-04-23
Also published as: DE4312739A1; GB2254977B; ITMI930777A1; FR2690591B1; IT1264155B1; KR930022881A; ITMI930777A0; GB9208801D0; FR2690591A1

Description

225)4977 Receiver for letterbox television signals.

1 The invention relates to a receiver for letterbox television signals, i.e. extended definition television signals in which a wide aspect ratio picture and at least one horizontal bar jointly form a standard aspect ratio television picture. These compatible standard aspect ratio pictures can be received by standard television receivers.

Such letterbox television signals are known from William F. Schreiber's lecture "6 MHz single channel HDTV systems" presented at the HDTV Symposium in Ottawa, October 1987. The horizontal bars are used to transmit enhancement signals for improving the quality of the wide aspect ratio picture. Although these enhancement signals are processed to reduce their visibility, standard receivers would see bars of moving noise - the enhancement signals - in these areas. The annoyance level could be reduced to some extent by proper signal design. The usual overscan setting on most receivers would make the bars smaller. If desired, an inexpensive adapter could blank out the noisy bars. New NTSC receivers could have this blanking arrangement built in at negligible cost. Schreiber does not disclose how and when this blanking arrangement is to be operated.

The international application WO-A-91/11882 discloses that in addition to scrambled additional information in the lines of the noisy bars, a recognition signal could be transmitted in th vertical blanking interval or in the lines of the noisy bars, which recognition signal would enable an intermediate generation of 4:3 receivers to recognize the lines belonging to the noisy bars and to set these lines to the black level.

It is an object of the invention to provide a user-preference adaptive and simple method of reducing the visibility of the at least one horizontal bar. For this purpose, one aspect of the invention provides a receiver as set out in the main claim. Advantageous aspects of the invention are set out in the subclaims.

2 The invention thus relates to a standard aspect ratio television receiver which also displays the horizontal bars; an extended definition receiver would display a wide aspect ratio picture without the horizontal bars. The standard aspect ratio television receiver is equipped with an additional control signal decoder for the additional control signal which is transmitted along with the extended definition television signal to control the various decoding operations of an extended television receiver. This control signal decoder may control the blanldng arrangement for eliminating the noisiness of the bars when a letterbox television signal is received. In accordance with the invention, the television receiver also includes a zoom processor controlled by the control signal decoder for removing the at least one noisy horizontal bar from the visible part of the standard aspect ratio display device. Even when the horizontal bars do not convey enhancement signals, it is an advantage to use an automatic zoom processor which shows all of the height of the wide aspect ratio picture on the standard aspect ratio display. A user control signal selects between the zoom processor and the blanIdng arrangement, so that if the user would like to watch all of the width rather than all of the height of the wide-screen image, he is able to do so.

In an advantageous embodiment, the user may also indicate which option (zooming or blanling) should be automatically selected upon receipt of a letterbox television signal; the user control signal may then be used to select the other one of the two options.

When the additional control signal indicates the aspect ratio of the wide aspect ratio picture, for example, whether this aspect ratio is 14:9 or 16:9, the disturbance reduction control signal advantageously depends on this aspect ratio of the wide aspect ratio picture so that the blanldng or zooming operation is adjusted to the aspect ratio of the wide aspect ratio picture.

It has to be noted that in the article "Marktfibersicht, Fernsehspafl mit 16:9" which appeared in the German periodical Funkschau 1/1992, pp. 34-36, television receivers are described which have a 16:9 aspect ratio display. To compensate for the nowadays lacIdng 16:9 programmes, these new television receivers offer the opportunity to zoom. Thereby, the television picture appears to be watched from a closer distance. The picture of original 4:3-format pictures is, however, cut at the upper and lower sides.

Ile above-mentioned and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

3 In the drawing:

Fig. 1 shows a block diagram of a prior art embodiment of a receiver; and Fig. 2 shows a block diagram of an embodiment of a receiver in accordance with the present invention.

In Fig. 1, input television signals are applied to a video decoder 1 for carrying out all operations normally performed on television signals. The video decoder 1 supplies its output signals to a display device 3. A switch 5 is inserted between the video decoder 1 and the standard aspect ratio display device 3, which switch may apply the output signal of an arrangement 7 rather than that of the video decoder 1 to the display device 3. The arrangement 7 supplies a black level signal. The switch 5 is controlled by an additional control signal decoder 9 which is arranged to detect whether the received television signal includes a recognition signal indicating the horizontal bars of a letterbox television signal. If such a letterbox television signal is received, the decoder 9 operates switch 5 so that it connects the output of the arrangement 7 to the display device 3 during the horizontal bar or bars.

Fig. 2 shows an embodiment of a receiver in accordance with the present invention. Elements which correspond to those shown in Fig. 1 have the same reference numerals. However, in accordance with an aspect of the present invention, the arrangement 7 may supply a colored signal like a blue background, or some nicelooking pattern, instead of a simple black level signal. The crux is that the original horizontal bars, which may convey enhancement signals which look like noise, are replaced by something which is more pleasing to the eye.

The additional control signal decoder 9 is advantageously arranged to detect whether the received television signal includes an additional control signal intended to control the decoding operations of an extended television decoder. If this additional control signal is received, the decoder 9 determines whether the received signal is a letterbox signal having a wide aspect ratio picture and at least one horizontal bar. As in the PALplus TV system, wide-image pictures having either a 14:9 or a 16:9 aspect ratio may be transmitted in a letterbox format between black bars, the output 4 signal of the decoder 9 is advantageously adapted to the aspect ratio of the wide-screen picture actually transmitted so as to affect only the black bars.

In a preferred embodiment of the invention, the additional control signal decoder 9 is formed from a teletext decoder which is adapted to decode the additional control signal of an extended letterbox television signal as well. Further details about the additional control signal and how it is to be decoded may be found in the nonprepublished European patent application No. 92.200.407.2 filed on 13.02.92 (PHN 13,988), incorporated herein by reference.

The standard aspect ratio receiver may use the blanked bars to display additional status information, like time-information (graphical or alphanumerical), program information, or status information of other audiolvideo equipment like the VCR or the satellite tuner.

In the embodiment of the receiver in accordance with the present invention shown in Fig. 2, the output signal of the video decoder 1 is now applied to a zoom processor 11 which is controlleA by the additional control signal decoder 9 so as to substantially remove the horizontal bar or bars from the visible part of the standard aspect ratio display device 3. However, it will be evident that this zoon-dng operation will cause loss of some side panel information at the left and right sides of the picture. In accordance with the invention, the user may therefore apply a user control signal USC to the zoom processor 11 for disabling the zooming operation and to the switch 5 for enabling the blanking operation, so as to obtain a display of the whole wide image picture with blanked horizontal bars, just as in the embodiment shown in Fig. 1.

In an advantageous embodiment, the user may also indicate which option (zooming or blanking) should be automatically selected upon receipt of a letterbox television signal; the user control signal may then be used to select the other one of the two options.

Since the introduction of PALplus may be done step by step on a program by program basis, letterbox pictures may be transmitted without the black bars 30 containing vertical resolution enhancement signals. As a modification of the PALplus TV system, we propose to include in the black bars a digital data signal, carrying either a sound or a data service like teletext when no vertical resolution enhancement signals are transmitted. The digital data signal is hidden as much as possible, around the black level, and is DC-free. An error correction is added to make the signal robust against the impairments of the (terrestrial) channel. An enhanced decoder comprises a detector coupled to the IF stage and synchronized by a sync separation circuit. The detector is followed by an error correction decoder whose output is applied to a sound decoder or to a data service decoder. It will be evident that the adaptive zooming/blanldng arrangement of the present invention is also suitable to reduce the visibility of this digital data signal in the same manner as the visibility of the image display enhancement signals is reduced.

It will be evident that those skilled in the art is able to design many 10 alternatives which fall within the scope of the following claims.

Claims

Claims:

6 1. A television receiver for receiving extended television signals to be displayed on a standard aspect ratio display device, said extended television signals conveying a wide aspect ratio picture together with at least one horizontal bar so as to form a standard aspect ratio picture, the receiver comprising: means for decoding an additional control signal encoded with said extended television signals, so as to flu-nish a disturbance reduction control signal; and disturbance reduction means coupled to receive said disturbance reduction control signal for reducing the visibility of said at least one horizontal bar, wherein said disturbance reduction means include:

zoom processor means for substantially removing said at least one horizontal bar from a visible part of said standard aspect ratio display device; means for replacing said at least one horizontal bar by another signal; and means for selecting between said zoom processor means and said replacing means in response to a user control signal.
2. A television receiver as claimed in claim 1, further comprising preference setting means for indicating whether said zoom processor means or said replacing means should be automatically enabled in dependence upon said disturbance reduction control signal, whereby said user control signal disables the automatically enabled means and enables the other one of said zoom processor or replacing means.
3. A television receiver as claimed in claim 1, wherein said additional control signal indicates an aspect ratio of said wide aspect ratio picture, and said disturbance reduction control signal depends on said aspect ratio of said wide aspect ratio picture.
4. A television receiver substantially as described herein with reference to Figure 2 of the accompanying drawings.
5. Any novel feature or novel combination of features disclosed herein either explicitly or implicitly whether or not it relates to the same invention as that claimed in any preceding claim.