JPH02285888A - Method and circuit device for forming auxiliary signal - Google Patents

Abstract

PURPOSE: To reduce residual time errors into several seconds in case of time correction by calculating the curve passage characteristics of sine wave of a reference signal with extremely high phase/amplitude accuracy and further adding the reference signal to an analog video signal as an auxiliary signal together with a horizontal synchronizing signal. CONSTITUTION: A programmable fixed value memory 9 stores a data word having the amplitude value of curve passage characteristics of the auxiliary signal while depending on an address. In this case, eight amplitude values are respectively filed in the programmable fixed value memory 9 for each vibration cycle of a reference signal R. Further, this programmable fixed value memory 9 stores data having the curve passage characteristics of a horizontal frequency synchronizing pulse S and both colorless areas Uv and Un . When reading this programmable fixed value memory 9, by impressing an address signal, the auxiliary signal is supplied in the format of the data word for following signal processing.

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Field of Application The invention is based on the method specified in the preamble of claim 1.

BACKGROUND OF THE INVENTION In an earlier patent application filed by the applicant (German Patent No. 96 75 6 741), an apparatus has been proposed for detecting all time base errors in HDTV video signals extracted from magnetic tape. This HDTV video No. 1 has six rear black signals in the area of the horizontal 94-win erasure section that have a reference signal consisting of a plurality of packets of sinusoidal vibrations, similar to the color synchronization signal in a color video signal. In contrast to the color synchronization signal transmitted on the shoulder or bank porch, this reference signal is superimposed galvanically on the average gray value within the horizontal blanking return. The frequency of the reference signal is combined with the frequency of the clock pulse signal using the following equation.

1 clock pulse auxiliary signal (Σ (2n+4)) =
f n=0 Therefore, the clock pulse frequency is f. Wow, 2 sweetfish””
27) When vfHz and the integer is n=i, the frequency of the reference signal is fM -3,375 MHz.

This frequency f. Furthermore, the clock pulse signal with the
It is combined with a frequency that is 864 times the horizontal frequency of the TV video signal. A reference signal added during horizontal frequency blanking on the recording side is used to correct for time errors present in the reproduced HDTV video signal. In this case, the respective time error is calculated using a special phase detector using the phase of the reproduced reference number 1g.

Problems to be Solved by the Invention It is an object of the present invention to calculate the curve profile of a sine wave of a reference signal with extremely precise phase and amplitude accuracy in a method of the type described at the beginning, and to further synchronize the reference signal with horizontal synchronization. It is added to the analog video signal as an auxiliary signal along with the signal.

Means for solving the problem This problem is solved by the features indicated in the characterizing part of claim 1.

This configuration has the following advantages: the digital form and therefore highly accurate derivation of the reference and synchronization signals applied on the recording side reduces the residual time error during time error correction to a few nanometers and seven cants. It has the advantage of

Claim it-can be constructed as indicated in the dependent claims. The advantage of waiting is the attenuation due to the 5tn(X)/X function form of the D/A converter used during D/A conversion! Note: The reduction in frequency characteristics due to the attenuation characteristics of the low-pass filter used during low-pass filtering can be compensated for as follows. This can be compensated for by having data values correspondingly stored in the programmable fixed-value memory corresponding to the "amplitude profile of the auxiliary signal of the predistorted 11 sinusoids". This makes it possible to use a slow Bessel filter device without group running.

Description of examples Next, embodiments of the present invention will be described using the drawings.

In the block diagram of FIG. 1, the color components of an analog video signal can be seen at terminal 1. The horizontal frequency blanking interval A of this video signal is combined with the diagnostic auxiliary signal of the negative synchronization pulse S of the horizontal frequency synchronization signal and the reference signal R in the gray phase.
has been inserted. The reference signal R has a frequency of 3375M
It contains 1Q pieces of sine 'tb' of Hz.

In FIG. 2a, a horizontal frequency blanking interval A is shown with a front colorless area U, . . . , a synchronization pulse S, a reference signal R and a rear colorless area TJh. Both colorless chain acids T7V and Uh have zero amplitude in the image area.
Exists within the range of % to 100%, which is the level Ov to 0
．． 7v and 0.35 when the image shake is 50%
Corresponds to V.

The synchronizing pulse S of the synchronizing signal occupies an amplitude range of OV to -0, 6V of the entire amplitude range IVI3B.

As mentioned in the introduction, this reference signal is combined in frequency and phase with the horizontal synchronization signal of the HDTV video signal. For this reason, the horizontal synchronization signal HD (32 μs 71 scan line period), which is transmitted at the terminal 2 simultaneously with the analog video signal, is guided to the phase control loop 3. From the output side of this loop, a clock pulse signal CLK is collected which is phase-combined with 864 times the horizontal frequency of the HDTV video signal and has a clock pulse frequency of 27.2%. This clock pulse 1 word CLK, the horizontal #wave erase signal AH applied to terminal 4, and further terminal 5
The vertical housing synchronization signal 2v guided through the logic stage 6 is combined to become one control signal. This shrine#
No. 1g is transferred via the reset stage γ to the control input of the address meter dad. The output side of the address counter 68 is connected to a 9-bit 1-bit address bus, on the one hand to the address input side of a fixed value memory 9 (FROM) capable of 7'o programming, and on the other hand to the control stage 10. ing. The U control stage 10 detects the address value provided in OvC at the end of the return erase period. Its purpose is reset stage 7
This is to reset the address counter 8 to a predetermined initial address value via the .

Depending on the address, data words with the amplitude values of the curve profile of the auxiliary signal are stored in the programmable fixed value memory 9.

In this case, eight amplitude values are stored in the programmable fixed value memory 9 for each oscillation period of the reference signal R. Furthermore, data are stored in this programmable fixed value memory 9, which includes the curve profile of the horizontal frequency synchronization pulse S and the two colorless areas Uv, Ufi. When reading this programmable fixed value memory 9, the application of the address signal supplies auxiliary signals in the form of data words for further signal processing. The data retrieved from the output of the programmable fixed-value memory 9 are conducted via an 8-bit wide data bus to a D/A converter 11, where they are converted into corresponding analog values. D/A converter 1
1 is connected to a clamp stage 13 via a low-pass filter 12. This clamping stage is controlled by the horizontal frequency flange pulse signal H8, and the rear uncolored area U
The auxiliary signal present in analog form in h is DC voltage clamped to a predetermined DC voltage potential. Another clamping stage 14 is provided in a transmission channel provided for the transmission of HDTV video signals. The signals provided at the outputs of clamping stages 13 and 14 are connected to summing stage 1.
5 is added. Therefore, in the horizontal frequency blanking interval of the HDTV video signal taken from the output terminal 16, an auxiliary signal is inserted which is extremely accurate with respect to phase p and amplitude.

Reset stage 7, address counter 8, programmable identification value memory 9, control stage 10 and D/A converter 1
1 is led to the clock pulse signal CLK prepared by the logic stage 6.

The D/A converter 11 has an amplitude decay curve that follows the function 5in(X)/X. The low-pass filter 12 downstream of the D/A converter 11 also has a predetermined ui width attenuation profile. This characteristic is represented by a Bessel function in this embodiment, and decreases at high frequencies. The continuous frequency of the low-pass filter 12 formed as a Bessel low-pass filter is approximately 6×2, and this selection makes it possible to ignore the group transit time error of the Bessel low-pass filter. I can do it. Therefore, means for correcting the group running time error can be omitted. In particular, only one frequency is transmitted.

Amplitude attenuation losses due to the D/A converter 11 and the low-pass filter 12 are stored in a programmable fixed value memory 9.
can be compensated for by means of correspondingly predistorted amplitude values in the form of data words. The signal curve of the reference signal R, shown in dashed lines in FIG. 2a, illustrates this compensation process. The voltage-time diagram shown in Figure 2 shows two complete scan line periods H4 of the analog video signal applied to terminal 1. A voltage assigned to the synchronization signal HD and the horizontal blanking signal AH in a time-corresponding manner.
Show a time diagram. The address signal is applied to the address input of the programmable fixed value memory 9 only during the horizontal frequency blanking period, as shown in FIG. 2e.

a reference signal 2 and a synchronization signal of horizontal frequency, and a fixed temporal assignment of said reference signal and synchronization signal in relation to a fixedly defined scanning instant in the auxiliary signal being formed; By deriving the auxiliary signal in analog form, a sinusoidal waveform is formed which is substantially independent of the tolerances of the analog components, so that the phase and width characteristics of the formed auxiliary signal are influenced in a component-dependent manner. Things will go away.

By means of the auxiliary signal formed by the present invention, HDTV @
The residual time error due to time error correction on the playback side of the silver tape device can be limited to about 3 ns. This is HDTV
This corresponds to approximately one-sixth of one pixel in the video signal.

As mentioned above, in the present invention, an auxiliary signal tone having a plurality of oscillation periods of the reference signal and one horizontal synchronization pulse each can be provided during the blanking period of the horizontal frequency.

Furthermore, the amplitude of the auxiliary signal can be determined by corresponding data values in a programmable fixed value memory.

Roughly speaking, the frequency of the clock pulse signal may be related to an even multiple of the frequency of the auxiliary signal, for example eight times.

Effects of the Invention The invention makes it possible to generate an auxiliary signal that can reduce the residual time error to a few nanoseconds during time correction.

A voltage-time diagram for explaining the operation of the block diagram is shown.

3... Phase control loop, 6... Logic stage, 7... Reset stage, 8... Address counter, 9... Fixed value memory, 10... Control stage, 11... D /A converter, 1
2...Low pass filter, 13.14...Clamp stage, 15...Addition stage.

Claims (1)

Claims: 1. A method for forming an auxiliary signal which is combined in frequency with a synchronization signal of a video signal and added to said video signal in the region of a horizontal frequency blanking period, comprising: deriving a combined clock pulse signal such that the frequency of the clock pulse signal is multiple times the frequency of the auxiliary signal; and during the blanking period of each horizontal frequency, said derived clock pulse signal a fixed value memory (9) which is programmable and stored in dependence on the signal profile of said auxiliary signal;
), and the data signal obtained at the output of the programmable fixed value memory (9) is D/A converted and, after low-pass filtering, inserted into the video signal. 1. A method for forming an auxiliary signal, characterized in that the auxiliary signal is used as an auxiliary signal for 2. Claim 1, wherein the low-pass filtering is performed by a Bessel low-pass filter, and the cut-off frequency of the low-pass filter corresponds to approximately twice the frequency of the auxiliary signal.
Method described. 3. The signal attenuation of the auxiliary signal during the D/A conversion and the low-pass filtering is compensated by data words previously correspondingly corrected in a programmable fixed value memory. Method described. 4. A circuit arrangement for implementing the method according to claim 1, comprising a clock pulse generator (3) coupled with horizontal synchronization pulses of a video signal;
An address counter (8) for counting the clock pulses taken from 3) and a programmable fixed value memory (9) are provided, in which case the address input side of this fixed value memory is connected to said address counter. a D/A converter (11) on the data output side of the programmable fixed value memory (9); a low-pass filter (12) connected to the output side, and a summation that brings together the video signal and the auxiliary signal taken from the output side of the low-pass filter (12) in the region of horizontal frequency blanking. A circuit device characterized in that a stage (15) is provided. 5. The circuit arrangement as claimed in claim 4, further comprising a horizontal frequency-controlled clamping stage (13, 14) intermediately connected in the signal line of the summing stage (15).