Title of Invention	METHOD FOR THE RECOVERY OF A VIDEO SIGNAL.
Abstract	TITLE: METHOD FOR THE RECOVERY OF A VIDEO SIGNAL. The invention relates to a method for the recovery of a video signal. According tot he invention, an adaptive equalizer 2 is used, the characteristics of which are adjusted to the conditions of a transmission channel by means of the digital data signals that are concomitantly transmitted in addition to the analogue signal components in a video signal. This adjustment is then used for analogue signal components of the video signals. The teletext signal can advantageously be used for the adjustment.

Title of Invention

METHOD FOR THE RECOVERY OF A VIDEO SIGNAL.

Abstract

TITLE: METHOD FOR THE RECOVERY OF A VIDEO SIGNAL. The invention relates to a method for the recovery of a video signal. According tot he invention, an adaptive equalizer 2 is used, the characteristics of which are adjusted to the conditions of a transmission channel by means of the digital data signals that are concomitantly transmitted in addition to the analogue signal components in a video signal. This adjustment is then used for analogue signal components of the video signals. The teletext signal can advantageously be used for the adjustment.

Full Text	Method for the recovery of a video signal The invention relates to a method for the recovery of a video signal. Prior art Video signals which are transmitted via a channel are, as a rule, influenced by the channel characteristics. This applies, in particular, to channels which are susceptible to interference, such as the terrestrial transmission of TV signals. Signal interference may occur due to ambient influences on the transmission path. There is thus an interest in compensating for this interference in the receiver and in obtaining an optimal reproduction quality. In the case where the channel characteristics are known in the receiver, interference can be eliminated by means of suitable compensation measures, such as e.g. an equalizer. However, knowledge of the channel characteristics is not provided e.g. in the case of terrestrial transmission. In order to ensure interference-free reception even in the case of such transmission channels which are subject to interference, an adaptive equalizer can be used. It is then necessary, however, to transmit a reference signal with the useful signal, from which reference signal the corresponding compensation parameters are then derived by the adaptive equalizer. For capacity reasons, however, such reference signals are not prescribed by the transmitter. Invention The invention is based on the object of specifying a method for the recovery of a video signal which, without an additional reference signal, to the greatest possible extent eliminates channel interference which influences the quality of the video signal. The object is achieved by means of the features specified . Advantaggeous developments are reproduced According to the invention, an adaptive equalizer is used which is trained by the digital data signals, such as e.g. teletext data, that are concomitantly transmitted in a video signal. An adaptive equalizer adapts itself independently in order to compensate for unknown or time-variable channel characteristics. An input signal which is , interfered with by the channel is changed by the adaptive equalizer until a desired output signal is present. Since adaptive equalizers cannot judge when a desired analogue output signal is present given an analogue input signal, the digital data signal that is concomitantly transmitted with the analogue input signal is advantageously used for the adjustment of the adaptive equalizer. It is preferable for the adaptive equalizer to be adapted to the optimal reception condition during the transmission duration of the digital data signals and for this adjustment then to be maintained during the transmission duration of the analogue signals. Drawings Furthermore, an exemplary embodiment for a circuitry realization for the method according to the invention is described with reference to the accompanying drawing. A signal is fed to an adaptive equalizer 2 via a reception device 1. The adaptive equalizer 2 comprises, in particular, an adj us table filter unit 5, via which the video signal is fed to an output 6. In addition, the video signal is fed via a window stage 3 to an evaluation stage 4 for digital data signals. A control output of the evaluation stage 4 is connected to the adjustable filter unit 5 The output of the evaluation stage likewise leads to the output 6 of the adaptive equalizer 2. Further processing stages (not shown) for the video signal are connected to the output 6. In order to eliminate the influence of channel- dictated interference on the video signal, the digital data signals are used to modify the filter characteristics of the adjustable filter unit 5 in such a way as to minimize the interference for the output signal. By means of a window stage 3 and an evaluation stage 4, the operation for altering the filter characteristics of the adjustable filter unit 5 is limited to the period of time in which digital data signals are present. As soon as the digital data signals are no longer present, the filter characteristics of the adjustable filter unit 5 are frozen for example via a control line by means of a corresponding signal. The method according to the invention is suitable? for any signal transmission methods and for signals which contain not only analogue information but also digital data signals which have a sufficiently high staistical probabilitv. WE CLAIM: 1. A method for recovery of video signals with analogue signal components and digital data components, wherein said digital data components are transmitted concomitantly to said analogue signal components for the purpose of providing additional information to the TV user, said method comprising the steps of : providing the video signals to an adaptive equalizer (2); windowing the video signals for the separation of the digital data components; generating a control output from the separated digital data components; applying the video signals to a filter within the adaptive equalizer (2); and adjusting characteristics of the filter based upon the control output for correcting the analogue signal components. 2. The method according to claim 1, wherein digital teletext data are used as the digital data components of the video signals. 3. The method according to claim 1, wherein the filter characteristics are altered only when digital data components are present. The invention relates to a method for the recovery of a video signal. According to the invention, an adaptive equalizer 2 is used, the characteristics of which are adjusted to the conditions of a transmission channel by means of the digital data signals that are concomitantly transmitted in addition to the analogue signal components in a video signal. This adjustment is then used for analogue signal components of the video signals. The teletext signal can advantageously be used for the adjustment.

Full Text

Method for the recovery of a video signal
The invention relates to a method for the
recovery of a video signal.
Prior art
Video signals which are transmitted via a channel
are, as a rule, influenced by the channel
characteristics. This applies, in particular, to channels
which are susceptible to interference, such as the
terrestrial transmission of TV signals. Signal
interference may occur due to ambient influences on the
transmission path.
There is thus an interest in compensating for
this interference in the receiver and in obtaining an
optimal reproduction quality.
In the case where the channel characteristics are
known in the receiver, interference can be eliminated by
means of suitable compensation measures, such as e.g. an
equalizer. However, knowledge of the channel
characteristics is not provided e.g. in the case of
terrestrial transmission. In order to ensure
interference-free reception even in the case of such
transmission channels which are subject to interference,
an adaptive equalizer can be used. It is then necessary,
however, to transmit a reference signal with the useful
signal, from which reference signal the corresponding
compensation parameters are then derived by the adaptive
equalizer. For capacity reasons, however, such reference
signals are not prescribed by the transmitter.
Invention
The invention is based on the object of
specifying a method for the recovery of a video signal
which, without an additional reference signal, to the
greatest possible extent eliminates channel interference
which influences the quality of the video signal.
The object is achieved by means of the features
specified .
Advantaggeous developments are reproduced
According to the invention, an adaptive equalizer
is used which is trained by the digital data signals,
such as e.g. teletext data, that are concomitantly
transmitted in a video signal.
An adaptive equalizer adapts itself independently
in order to compensate for unknown or time-variable
channel characteristics. An input signal which is ,
interfered with by the channel is changed by the adaptive
equalizer until a desired output signal is present. Since
adaptive equalizers cannot judge when a desired analogue
output signal is present given an analogue input signal,
the digital data signal that is concomitantly transmitted
with the analogue input signal is advantageously used for
the adjustment of the adaptive equalizer.
It is preferable for the adaptive equalizer to be
adapted to the optimal reception condition during the
transmission duration of the digital data signals and for
this adjustment then to be maintained during the
transmission duration of the analogue signals.
Drawings
Furthermore, an exemplary embodiment for a
circuitry realization for the method according to the
invention is described with reference to the accompanying drawing.
A signal is fed to an adaptive equalizer 2 via a
reception device 1. The adaptive equalizer 2 comprises,
in particular, an adj us table filter unit 5, via which the
video signal is fed to an output 6.
In addition, the video signal is fed via a window
stage 3 to an evaluation stage 4 for digital data
signals. A control output of the evaluation stage 4 is
connected to the adjustable filter unit 5 The output of
the evaluation stage likewise leads to the output 6 of
the adaptive equalizer 2. Further processing stages (not
shown) for the video signal are connected to the output
6.
In order to eliminate the influence of channel-
dictated interference on the video signal, the digital
data signals are used to modify the filter
characteristics of the adjustable filter unit 5 in such a
way as to minimize the interference for the output
signal.
By means of a window stage 3 and an evaluation
stage 4, the operation for altering the filter
characteristics of the adjustable filter unit 5 is
limited to the period of time in which digital data
signals are present. As soon as the digital data signals
are no longer present, the filter characteristics of the
adjustable filter unit 5 are frozen for example via a
control line by means of a corresponding signal.
The method according to the invention is suitable?
for any signal transmission methods and for signals which
contain not only analogue information but also digital
data signals which have a sufficiently high staistical
probabilitv.
WE CLAIM:
1. A method for recovery of video signals with analogue signal
components and digital data components, wherein said digital data
components are transmitted concomitantly to said analogue signal
components for the purpose of providing additional information to
the TV user, said method comprising the steps of :
providing the video signals to an adaptive equalizer (2);
windowing the video signals for the separation of the
digital data components;
generating a control output from the separated digital data
components;
applying the video signals to a filter within the adaptive
equalizer (2); and
adjusting characteristics of the filter based upon the
control output for correcting the analogue signal components.
2. The method according to claim 1, wherein digital teletext
data are used as the digital data components of the video signals.
3. The method according to claim 1, wherein the filter
characteristics are altered only when digital data components are
present.
The invention relates to a method for the recovery of a video signal.
According to the invention, an adaptive equalizer 2 is used, the characteristics of which are adjusted to the conditions of a transmission channel by means of the digital data signals that are concomitantly transmitted in addition to the analogue signal components in a video signal. This adjustment is then used for analogue signal components of the video signals. The teletext signal can advantageously be used for the adjustment.

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Patent Number

216366

Indian Patent Application Number

938/CAL/1999

PG Journal Number

11/2008

Publication Date

14-Mar-2008

Grant Date

12-Mar-2008

Date of Filing

29-Nov-1999

Name of Patentee

DEUTSCHE THOMSON-BRANDT GMBH,

Applicant Address

HERMANN-SCHWER-STR.3, D-78048, VILLINGEN-SCHWENNINGEN, GERMANY, A GERMAN COMPANY.

Inventors:

#	Inventor's Name	Inventor's Address
1	ERBAR MAXIMILIAN	SCHALMENAECKER 30 D-78052 VILLINGEN-RIETHEIM, GERMANY.
2	LIN JINAN	GANGHOFERSTR.11 D-85521 OTTOBRUNN, GERMANY, A CHINESE NATIONAL.

PCT International Classification Number

H04N 5/21

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	19857030.9	1998-12-10	Germany