DE29516956U1 - Device for evaluating the signal strength of a television signal received with a tuner - Google Patents

Description

Device for evaluating the signal strength of a television signal received with a tuner

The invention relates to a device for evaluating the signal strength of a television signal of a television program received with a tuner , which also has teletext signals within the television signal.

Television sets, whether they are standard television receivers with a picture tube, video recorders or similar, must be programmed manually for the respective installation location using conventional technology in a complex manner in order to assign the receivable channels to program numbers. It is advisable to program the most frequently tuned television channels to low program numbers in order to enable the quickest and most easily remembered access to the most frequently tuned channels via low program positions.

There have been suggestions to automatically save the receivable stations to the program positions. To do this, it is necessary to recognize the station names or program names during an automatic search run.

Theodor-Heuss-Straße 1 D-38122 Braunschweig Federal Republic of Germany

Telephone 0531 / 28 14 0-0 T«1M*£.·* 0531/28 140 28

For television programs that also broadcast teletext signals, the station name can be taken from the teletext page, since the station name is always shown at a specific place on the screen on a teletext page and can be evaluated. The sorting of the television programs is preferably done in accordance with a priority list stored for a specific reception country, in which the television programs are sorted according to the frequency of switching on or the historical creation of these programs.

The problem with the automatic setting routine of the television is that some television programs can be received on several television channels, so that the lowest program slot provided for this television program should be programmed with the television channel on which this television program can be received best, i.e. on which it has the highest signal strength.

When setting up the television manually, you will visually compare the various channels on which a television program is received in order to find the supposedly best channel. Such a comparison is difficult to automate.

Furthermore, it is known from IEEE Transactions on Broadcasting, Vol. 37, No. 2, June 1991, pp. 35 - 43, that deviations of the signals from their mean values can be evaluated in order to measure the signal-to-noise ratio of television signals.

Based on the problem of comparing the signal strength of television signals of a television program received with a tuner, the device according to the invention is characterized in that it has an evaluation stage for a predetermined area of the teletext page to form an evaluated signal, a memory for temporarily storing the evaluated signal, a comparison stage for comparing an earlier stored evaluated signal with a later evaluated signal to generate an error signal in the event of

non-matching signals and a counter for the number of error signals generated for a test cycle containing a specified number of comparisons.

The device according to the invention therefore does not use a conventional method for evaluating the signal strength of a television signal, but rather refers to areas of a teletext page that are essentially unchanged over time, so that for a test

cycle, identical signals can be assumed in this area. The assessment of the signal quality is based on the evaluation of the signals in this area and the performance of comparisons of a currently evaluated signal with a previously evaluated signal. If a complete match is found, no error signal is generated, whereas if there is a deviation between the compared signals, a signal representing an error is produced. A large number of such comparisons are carried out in a test cycle, with the number of error signals produced representing an inversely proportional measure of the quality of the signal. This method is based on the idea that the compared signals are identical on the transmitter side and that a lack of match can be attributed to interference caused by poorer reception quality.

The device according to the invention therefore enables the assessment of the reception quality of a received television program, without having to take into account varying image content of the currently broadcast television program.

The area of the teletext page where the time display for the various television programs appears in a standardized manner is particularly suitable for carrying out the comparison with the device according to the invention. This time display is updated by the transmitter every 40 ms, so that it can be assumed that the television signal transmitted is constant over a test cycle. It should be noted that a test cycle can be repeated.

will only extend over a few seconds on a regular basis, because comparisons are preferably carried out several times per second. In order to adapt to the updating of the time display, it may be useful, for example, to carry out the comparison every 40 ms, whereby it may be sufficient to evaluate only part of the time display (without using any seconds display).

It is advisable to always use the previous evaluated signal as the evaluated signal to be compared. If the relatively unlikely case occurs that the time display, which regularly records hours and minutes, changes during the test cycle when changing from one minute to the next, this will only result in a single error signal, while the subsequent signals will not result in error signals if reception is perfect.

The device according to the invention allows assessments of the signal strength or the reception quality of the received television program for any purpose for which knowledge of this information is essential. According to the invention, the method or device for forming a ranking between television signals of the same television program that can be received on several channels is used for the automatic program allocation of a television set.

The invention will be explained in more detail below using the flow chart shown in the drawing:

At the start of the text cycle, a loop counter is set to 1. Furthermore, a counter for the error rate is set to 0. It is then checked whether a stable tuner signal is present. If this is not the case,

an error signal is produced and the error rate is increased by 1. This ends the respective test loop in this case.

However, if a stable tuner signal is detected, the system switches to a teletext page and checks whether a valid teletext page is being received. If this is not the case, an error signal is generated and the error rate is increased by 1. In this case, too, the test loop would be completed.

However, if a valid teletext page is received, the time (hours:minutes) is read from this page. For the first test loop, the time read is saved as "old hour time and old minute time" in order to be available as a comparison value for the next test loop. After the time signal has been saved, the loop counter is increased by 1 and it is checked whether 25 test loops have already been carried out, since in the example shown a test cycle should contain 25 comparisons. If the test cycle is not yet completed, i.e. the loop counter is at a value between 1 and 25, a waiting period of 40 ms is waited before the test loop starts again to check whether a stable tuner signal has been received.

Once the first test loop has been completed, the next test loop compares the time read from the teletext page with the "old time" (hours:minutes).

If a deviation is detected during the comparison, the error rate is increased by 1 and the newly read time is saved as the "old time" for the next test loop.

If, however, no deviation is found during the comparison, i.e. the same hour and minute information is available, the new time is also saved, but this corresponds to the previously saved time without increasing the error rate. The loop counter is then increased by 1 again and a new test loop is started, unless the loop counter reaches a value > 25. If this is the case, the test cycle is completed and the accumulated error rate is evaluated as the test result. A high error rate is an indicator of a

poor reception quality, i.e. a low signal strength of the received television signal.

Although the embodiment shown is designed for a comparison of the time display on the teletext page, the invention can also be easily applied to other stable displays on the teletext page, for example for the respective logo of the television program in question.

Li/bk

Claims (5)

Device for evaluating the signal strength of a television signal of a television program received with a tuner, which also has teletext signals within the television signal, characterized by an evaluation stage for a predetermined area of the teletext page to form an evaluated signal, a memory for temporarily storing the evaluated signal, a comparison stage for comparing an earlier stored evaluated signal with a later evaluated signal to generate an error signal in the event of non-matching signals and a counter for the number of error signals generated for a test cycle containing a predetermined number of comparisons. 2. Device according to claim 1, characterized in that the evaluation stage is set for the evaluation of the area of the teletext page standardized for the time display. Theodor-Heuss-Straße 1 D-38122 Braunschweig Federal Republic of Germany Tetefea ..0531/28 14 0-0 • Fax |··&rgr;.531 / 28 140 28 3. Device according to claim 1 or 2, characterized in that the evaluation stage is designed to evaluate the time display appearing at a standardized position on the teletext page. 4. Device according to one of claims 1 to 3, characterized in that several comparisons per second can be carried out with the evaluation stage. 5. Device according to claim 4, characterized in that the evaluation stage is designed to carry out a comparison every 40 ms. GRAMM, LINS & PARTNER
Li/bk