JPH01318371A - Video signal processing method - Google Patents

Abstract

PURPOSE:To eliminate the disturbance of a digital signal by setting the luminance level of a video signal to a high value in periods adjacent to the digital signal on a recording medium in a field where the digital signal is not inserted. CONSTITUTION:Character signals are inserted to 14-16th and 21th lines in the vertical flyback time of the first field of the video signal, and white is set throughout in active periods in 13-16th, 20th, and 21st lines of the vertical flyback time in a second field. Since these lines are adjacent to lines where character signals are inserted in a first field with respect to a pattern on a tape in the long-time mode of a home video tape recorder of a VHS system, white is set throughout to raise the FM carrier frequency, and the crosstalk suppressing effect is increased. Thus, the digital signal like a character signal is satisfactorily decoded without error.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a video signal processing method, and particularly to a video signal processing method suitable for recording and reproducing by a video signal recording and reproducing apparatus (such as a VTR) using guard panless recording. The present invention relates to a video signal processing method for inserting a digital signal such as a teletext signal into a part of a vertical retrace period of a video signal.

(Prior Art) An example of a digital signal inserted into a part of the vertical blanking period of a video signal is a teletext signal (hereinafter referred to as a character signal). This character signal is a Y3 type digital signal as shown in FIG. 7, and consists of a clock run-in, a framing code, and a data packet (data block and diec code) from the beginning of the digital signal string, and the clock frequency is 5. 727272 MHz.

This character signal is inserted into a predetermined horizontal scanning period (line) within the vertical retrace period of the video signal, and as shown in FIG. 21 lines (277th, 278th .
279 and 284th line).

In addition, a videotape recorder with guard panless recording (
In VTR), especially when playing back using a video head that is wider than the video track width (for example, in long-time mode), as shown in the 1~Rack pattern shown in Figure 9, Adjacent 1 to Rack [The reproduced signal is disturbed by Kostalk.

As a countermeasure against this crosstalk, Tsutomi recorded by changing the azimuth angle of the head between adjacent racks.
Azimuth loss reduces crosstalk from adjacent racks, and this effect becomes greater as the recording frequency becomes higher.

(Problem solved by the invention) However, when a digital signal such as a character signal is inserted every field, crosstalk of low frequency components may be mixed in. The problem is that the original digital signal is disturbed by the signal, causing many errors and not being decoded correctly.

Therefore, an object of the present invention is to provide a video signal processing method that solves the problems of the conventional techniques described above.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a video signal processing method for inserting a digital signal into a part of a vertical blanking period of a video signal. signal 1
It is inserted every other field, and in the field where it is not inserted, the pyroxene level of the video signal is set to black for at least the adjacent 1! Provided is a video signal processing method characterized in that the digital signal is set higher than the video signal level, and the digital signal is inserted into a part of the vertical blanking period of the video signal. It is inserted into every other field of the signal, and in the field where it is not inserted, the recording level of the frequency modulated pyroxene signal is optimized for at least a period on the recording medium that is adjacent to the digital signal insertion period in the field where it is inserted. The present invention provides a video signal processing method characterized in that the signal is set lower than the recording level.

(Embodiment) In an embodiment of the video signal processing method according to the present invention, as shown in FIG. In addition, in the second field, as shown in the figure, the signals are inserted, for example, the 13th, 14th, 15th .
In the 16th and 20th, 21st lines (276th, 277th, 278th, 279th, and 283rd, 284th lines counting from the beginning of the first field), the active period (i.e., excluding the horizontal retrace period of one line) period) to 100% white.

Here, if we consider the phase of the color subcarrier, NT
The SC signal has 4 fields in one period -4 = In this case, the '53 and 4th fields are treated in the same way as the 1st and 2nd fields, respectively (
The same applies hereafter).

In the second field, these lines were selected because, for example, in the long mode (EP mode) of a home video tape recorder (VTR) using As each line is lined up as shown in Figure 2, the above line (the line surrounded by O in the figure) is the line where the character signal of the first field is inserted (the line surrounded by O in the figure). This is because they are adjacent.

Further, the reason why the accedip period is set to 100% white is as follows.

In Tsutomi and home VTRs, when recording luminance signals by frequency modulation (FM), the FM frequency of the sync chip is set low and the white side is set high. A method that expands the luminance signal band to high frequencies (
In S-V)-18), the sink chip! i, 4
MHz, ioo% white is said to be 7.0 MIIz.

On the other hand, it is known that in the case of azimuth recording, the higher the frequency of the crosstalk component is, the more the crosstalk from the adjacent 1~rack is suppressed due to the azimuth effect.
By making the track adjacent to the character signal 100% white, the FM carrier frequency becomes higher and the effect of crosstalk suppression becomes greater.

In addition, when inserting a character signal in the first field, unlike when inserting a character signal in the second field, the character signal is not adjacent to the picture part (the 22nd line of the first field), so the above 100 The advantage is that even if %white is inserted, this will not appear on the screen as crosstalk.

Note that the present invention does not necessarily have to be limited to inserting a character signal into the first field in this way; in particular, when either field is not specified, field discrimination is not necessary, so the circuit is It has the advantage of being simple. In this case, if a character signal is inserted into the second field, there will be crosstalk from the picture on the 22nd line of the first field, but in this case the adjacent
-Rack can take the above-mentioned crosstalk countermeasures on the 21st line, so it can be improved to some extent.

In addition, in a field where a character signal is not inserted, instead of making the active period of the line adjacent to the character signal on Dave 100% white as described above, it should be set to black level (black level), or it should be set to black level from the beginning. In this case, the data may be transmitted without doing anything.

In this case, compared to the 100% white case, [1 stoke suppression effect is inferior, but for the reason described below,
Compared to the case where character signals are inserted into both fields, the adverse effects of crosstalk are greatly improved.

In other words, a part of the character signal is shown in Figure 3 (a), but in a VTR, emphasis is usually performed before frequency modulation ("M") during recording, so FM modulation is actually The waveform that enters the device at = 7 - is as shown in Figure 3 (b). At this time, the instantaneous frequency of the FM at the tip of the downward whisker is the above-mentioned S -
In the case of VHS type FM carrier setting, for example, approximately 4.
3MH2, approximately 5.9 of the FM carrier at black level.
Since it is quite low compared to MIIz, it will jump into the adjacent track, so if character signals are inserted into both fields, the effect of crosstalk will be small.

Next, an example of a video signal processing circuit that implements the video signal processing method according to the present invention will be described. FIG. 4 shows its block diagram, and FIG. 5 shows waveforms of each part in FIG.

It should be noted that each waveform in FIG. 5 is the waveform at the corresponding reference numeral shown in FIG.

In FIG. 4, a video signal input to an input terminal 1 is supplied to a sync separation circuit 2, where a sync signal is extracted. Furthermore, while the vertical synchronization signal (waveform shown in FIG. 5(b)) is extracted by the vertical synchronization separation circuit 3, the signal becomes high level in the first field as shown in FIG. 5(C) by the field discrimination circuit 4. , a pulse (hereinafter referred to as a field discrimination pulse) which becomes low level in the second field is created.

Next, this field discrimination pulse and the synchronization signal extracted by the synchronization separation circuit 2 are supplied to the AND circuit 5, and their AND output (that is, the synchronization signal output only to the first field) is supplied to the gate pulse generation circuit 6. is fed to one input of In addition, the above field discrimination pulse and the vertical synchronization signal extracted by the vertical synchronization separation circuit 3 are ANDed.
These A N +) outputs (that is, vertical synchronization signals output only in the first field) are supplied to the other circuit 7 of the gate pulse generation circuit 6 .

Then, in the first field, the gate pulse generating circuit 6 generates a revealing gate pulse as shown in FIG. 5(d) for inserting a character signal at a prescribed position on a prescribed line using these manual inputs as a time reference. Output.

On the other hand, the video signal input to the input terminal 1 is supplied to the clamp circuit 8 and is clamped there.

This clamped video signal is output by the switch circuit 9 as = 1
0- supplied to one input terminal. Further, the other input terminal of the switch circuit 9 is supplied with a character signal read out from a memory 10 in which character signals are stored.

Therefore, in the first field, when the gate pulse shown in FIG. 5(d) is output from the gate pulse generation circuit 6 and supplied to the memory 10 and the switch circuit 9, the character signal from the memory 10 is At the same time that reading of the data starts, the switch circuit 9 is switched from the clamp circuit 8 side to the memory 10 side, and a character signal is inserted.

In the second field, since the synchronization signal and the vertical synchronization signal as a time reference do not enter the gate pulse generation circuit 6, the gate pulse shown in FIG. 5(d) is not output. Therefore, in the second field, the following processing is performed.

The pulse obtained by inverting the field discrimination pulse shown in FIG.
2, and their AND output (that is, a synchronization signal output only to the second field) is supplied to one input of the gate pulse generation circuit 13. In addition, a pulse obtained by inverting the above field discrimination pulse by the inverter 11 and a vertical synchronization signal are supplied to the AN1) circuit 14, and their AND output (that is, the vertical synchronization signal output only for the second field) is gated. It is supplied to the other input of the pulse generating circuit 13. Then, in the second field, the gate pulse generation circuit 13 uses these inputs as a time reference to set a predetermined position of a predetermined line to a partial level (for example, 100% white) as shown in FIG. 5(f). A gate pulse as shown is created and output.

Therefore, in the second field, the gate pulse generator circuit 13 outputs the gate pulse shown in FIG. It is switched to the E side, a constant level E (for example, 100% white) is output, and this period is set to, for example, 100% white.

As described above, the waveform shown in FIG. 5(a) or FIG. 5(e) is alternately output from the output terminal 16 for each field.

Next, another embodiment of the video signal processing method according to the present invention will be described.

In this embodiment, in the field where the character signal of the video signal is not inserted, the recording level of the FM luminance signal is set lower than the optimum recording level for the period adjacent to the character signal on the tape, as shown in FIG. 6(b). If set lower, crosstalk can be suppressed even further.

If this is done, the S/ of the reproduced signal in this part will deteriorate, but since it is during the vertical retrace period and will not be visible on the screen, there will be no substantial problem.

In the above-mentioned embodiment, it was explained that character signals are inserted in the 14th, 15th, 16th and 21st lines of the first field, but character signals are inserted only in some of these lines. Furthermore, it may be inserted into other lines within the vertical retrace period.

In addition, in the second field, not only the above example,
For example, all the acquisition periods in the 10th to 21st lines of this field may be set to 100% white.

(Effects of the Invention) As described above, the video signal processing method of the present invention can be applied to a signal system where there is a lot of crosstalk from adjacent tracks, such as the long-time mode of a home video tape recorder (VTR). Even when a video signal processed by the method according to the present invention is passed through, it is possible to successfully decode a digital signal such as a character signal inserted in a part of the vertical retrace period of the video signal without error.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a waveform of a vertical blanking period of a video signal according to an embodiment of the video signal processing method according to the present invention, and FIG. 2 is a diagram showing a pattern on a tape in a long-time mode of a home VTR. FIG. 3 is a diagram showing the waveform of a part of a character signal, FIG. 4 is a block diagram showing an example of a video signal processing circuit implementing the video signal processing method according to the present invention, and FIG. 5 is a diagram showing each part of FIG. 4. FIG. 6 is a diagram showing waveforms according to another embodiment of the video signal processing method according to the present invention, FIG. 7 is a diagram showing the signal form of a character signal, and FIG. 8 is a diagram showing the insertion of a character signal. FIG. 9 is a diagram showing the relationship between the track pattern of guard panless recording and a wide video head. DESCRIPTION OF SYMBOLS 1... Input terminal, 2... Synchronization separation circuit, 3... Vertical synchronization separation circuit, 4... Field discrimination circuit, 5, 7
．． 12.14...AND circuit, 6.13...Gate pulse generation circuit, 8...Clamp circuit, 9.15...
・Switzerland circuit, 10...Memory, 11...Inverter, 16...Output terminal. Patent Applicant Kakimoto, Representative of Victor Japan Co., Ltd.
Japanese yam 3m

Claims (2)

[Claims] (1) In a video signal processing method in which a digital signal is inserted into a part of the vertical blanking period of a video signal, the digital signal is inserted into every other field of the video signal, and in the field where it is not inserted, A video signal processing method characterized in that the brightness level of the video signal is set higher than the black level for at least a period on a recording medium adjacent to a digital signal insertion period in the field to be inserted. (2) In a video signal processing method in which a digital signal is inserted into a part of the vertical retrace period of a video signal, the digital signal is inserted into every other field of the video signal, and in the field where it is not inserted, A video signal processing method characterized in that the recording level of a frequency modulated luminance signal is set lower than the optimum recording level for at least a period adjacent to a digital signal insertion period on a recording medium in the field to be inserted.