JPS6037890A - Magnetic reproducing device - Google Patents

Abstract

PURPOSE:To eliminate noise bars in case of variable speed reproduction by outputting and storing a reproduced signal from a recorded magnetic tape if the level of this signal is high and outputting a stored reproduced signal of the preceding field if the level of this signal is low. CONSTITUTION:When the level of the reproduced signal from a recorded magnetic tape 1 is higher than a preliminarily set prescribed value, the reproduced signal is not only outputted but also stored in a field memory 8. When the level of the reproduced signal does not reaches the prescribed value, the circuit is so switched that the reproduced signal is not outputted but a reproduced signal of the preceding field which is stored in the field memory 8 is outputted. Thus, the low-level reproduced signal is not outputted but only the sufficiently high-level reproduced signal is outputted in case of variable speed reproduction at a high speed, and a high-quality picture without noise bars is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic reproducing device that outputs only a sufficiently high level reproduction signal using a field memory.
An object of the present invention is to provide a magnetic reproducing device capable of obtaining a high-quality reproduction screen without noise bars during variable speed reproduction.

When a video tape recorder cuts a recorded magnetic tape, the video head crosses the 1-rack pattern of the tape, resulting in noise bars on the playback screen. A separate feature was installed to prevent noise bars from appearing on the playback screen.

However, the conventional method has the disadvantage that the control circuit is complicated to achieve the above-mentioned control, and the speed that does not completely generate noise bars is limited to about 0 to 3 times the speed, so the range of use is narrow. Ta.

The present invention eliminates the above-mentioned drawbacks, and an embodiment thereof will be described below with reference to the drawings.

The figure shows a block system diagram of an embodiment of the magnetic reproducing device according to the present invention. In J3 shown in the figure, when performing variable speed reproduction, the FM signal reproduced from the recorded magnetic tape 1 to the video heads 2+ and 22 of the first channel 11 and the second channel is supplied to the video signal processing circuit 4 via the preamplifier 3. Bidet A
While being used as a signal, it is supplied to an envelope detector 5 and subjected to envelope detection.

Here, the tape 1 is running at a speed that is, for example, double the normal speed.A capstan motor is applied to the tape 1. A phase comparator 12 compares the phase of a signal whose frequency is divided to four times that of the control signal during normal running and the control signal reproduced from the tape 1 by the control head 11. The detected phase comparison error voltage and the capstan motor 1
3 is divided into 1/4 by a frequency divider 14 and mixed with the voltage converted by a frequency-voltage converter 15 in a mixer 16, and this mixed voltage is supplied to a drive circuit 17. The rotation of the capstan motor 13 is controlled using the drive signal obtained. As a result, the tape runs at four times the speed of normal running while being phase-locked.

In this way, the playback screen based on the signals taken out from the video heads 2+ and 22 will have noise bars placed at different positions in the vertical direction for one field (this will cause the video heads 2+ and 22 to trace the guard band of tape 1 due to variable speed playback). The vertical positions of these three noise bars are fixed as long as the tape 1 is running at four times the normal speed.

, the signal whose envelope has been detected by the L envelope detector 5 is supplied to the comparator 6 and can be compared with the threshold C. If the envelope is equal to or higher than the same value C (FM>C), the signal is at L level, for example, and the envelope is lower than the threshold C ( F M
If <C), for example, a switching signal of ]-Lulbel is extracted. The interlocking switches Sz and S2 are connected to the terminal M by the L level (FM>C) of the switching signal, and to the terminal a by the L level (FM<C) of the switching signal.

During the period when the envelope of the FM signal from the preamplifier 3 is equal to or higher than the threshold value C, the output j of the video signal processing circuit 4 is switched to the switch S.
The signal is taken out from the output terminal 7 via the switch S1 and supplied to the CRT (not shown), where it is displayed as an image, while it is also supplied via the switch S1 to the video field memory 8, where it is written in a predetermined pixel area. It will be done. The field memory 8 is, for example, a RAM having a pixel area for one field, writes the video signal from the video signal processing circuit 4 into each predetermined pixel area, and rewrites the data one after another in response to newly supplied video signals. It is said to be composed of

Here, when the envelope of the FM signal becomes below the threshold C, the video signal of the previous field written in the field memory 8 is taken out from the output terminal 7 via the switch S2. The video signal is not taken out from the output terminal 7 and is not written into the field memory 8.

In this case, although the video heads 2+ and 22 are played back at a lower level for each channel in the vertical direction, the video signal of the previous field whose level is normal and is written in the field memory 8 only during this period is reproduced. It is replaced and taken out. That is, during the period in which the first field is played back at a low level by the video head 21, the video signal of the second field that was played back by the video head 22 in the immediately preceding second field and written to the field memory 8 is taken out. During the period in which the second field is played back at a low level by the video head 22, the video signal of the first field that was played back by the video head 21 in the previous first field and written to the Feel Mono 7 is extracted, and the result is Therefore, even if there is a period in which the level is played back at a low level, only the video signal at the normal level is always taken out from the output terminal 7, and no noise bar is generated on the playback screen.

At this time, if the running speed of 7-1 is selected so that the noise bar position on the screen by the 1st C11 video head 21 is the same as the noise bar position on the screen by the 2011th video head 22, then The normal deA signal will not be written into the pixel area of the field memory 8 forever, and a normal screen cannot be imaged. Therefore, as in this embodiment, if the running speed of the tape 1 is selected so that the noise bar position by the video head 21 and the noise bar position by the video head 22 are in the vertical direction of the screen, the field memory by each video head is Since the pixel areas that are not written to the 8 are different from each other, it is possible to extract the normal video signal of the previous field obtained by the other video head during a period corresponding to the noise bar position by the other video head.

As a result, only the part corresponding to the noise bar on the screen for one field becomes a screen in which the pixels of the previous field are embedded, but since the pixels of the previous and following fields are similar, the screen as a whole becomes an almost natural screen. , there is almost no problem in practical use.

Note that the running speed of the tape 1 is not limited to the method of selecting an even multiple of the normal speed as in the above embodiment, but the dividing ratio of the frequency divider 10°14 may be selected as appropriate. The speed may be selected to be a speed other than an integral multiple or an integral fraction of the normal speed.

In this case, the noise bar is not fixed at a fixed position in the vertical direction of the screen but always moves up and down, but in this case as well, a screen without noise bars can be obtained by the method explained in the figure.

Further, the location of the video field memory is not limited to after the video signal processing circuit as in the above embodiments, but may be located before or in the middle of the video signal processing circuit 4, for example.

As described above, the magnetic reproducing apparatus according to the present invention outputs the reproducing signal and stores it in the field memory when the level of the reproducing signal from the recording magnetic tape is set in advance. Since the configuration is configured so that when the level of the reproduced signal does not reach a predetermined value, the reproduced signal is output (U) and the reproduced signal of the previous field stored in the field memory is output. It is possible to output only a sufficiently high-level playback signal without outputting a low playback signal, which makes it possible to obtain a high-quality screen without noise bars, and to control tape running so that the video head does not cross the track pattern. It does not require complicated control compared to conventional equipment that prevents
Because we are not performing special control like in the past,
For example, C, which performs continuous variable speed playback, does not produce noise bars and has the advantage of having a wider range of use than conventional devices.

[Brief explanation of the drawing]

The figure is a block system diagram of an embodiment of the device of the present invention. DESCRIPTION OF SYMBOLS 1... Magnetic tape, 2+, 22... Video head, 4... Video signal processing circuit, 5... Envelope detector, 6... Comparator, 7... Output terminal, 8
...Video field memory.

Claims (1)

[Claims] When the level of the playback signal from the recorded magnetic tape is equal to or higher than a predetermined value, the playback signal is output and stored in the field memory, and when the level of the playback signal does not reach the predetermined value, the playback is performed. 1. A magnetic reproducing device characterized in that it is configured to switch to output a reproduced signal of a previous field stored in the field memory without outputting a signal.