DE3613230A1 - Magnetic video recorder/player - Google Patents

Abstract

In slow-motion playback, a control unit (20) controls the feed rate of a magnetic tape (1) and the rotational speed of a rotating drum in such a way that they are 1/nth of that of normal recording. Reproduced signals received from a video head (2) are time-base compressed by an A/D converter (7), a first image memory (8), a memory control circuit (9), a second image memory (10), a D/A converter (11) and a switch (12), so that they are output repeatedly for predetermined intervals. <IMAGE>

Description

Magnetic video recorder / player

DESCRIPTION The invention relates to a magnetic video recorder / reproducer from the helical scan system, and in particular it relates to a magnetic one Video recorder / reproducer, the noise-free playback in the time stretching method enables.

Referring now to Figures 7 and 8, two typical examples are given from conventional means for performing noise-free time stretcher reproductions described.

In one of the conventional systems, a tape drive shaft motor is used not rotated continuously to drive a magnetic tape, but step by step to repeat the sequence Turn - Hold - Turn - Hold ..., this will make the Follow normal playback - idle playback - normal playback - idle playback ... repeated during Zeitstretcher playback. An establishment of such a system is provided with special video heads, one of which is an exclusive one Video head for still images in addition to a normal video head to prevent blurring the still images during reproduction is prevented and a noise-free reproduction is enabled, these video heads become in full time count for time stretcher playback switch controlled.

Fig. 7 shows the scanning locations of the respective video heads on one Magnetic tape patterns in time stretch reproduction in such a device and the dispensing envelopes the one from the video heads video signals output at that time. In Fig. 7, numeral 1 denotes a magnetic tape, and numeral 20 denotes Video tracks, references H1 and H2 indicate the locations of the video heads at intervals of still images, reference character E denotes reproduction of the output envelopes, reference number Ti and T3 denote idle frame intervals in which the same fields are repeated are reproduced, and reference symbol T2 denotes a normal reproduction interval (Frame feed).

Instead of incrementally driving the tape drive axle motor and the Using special video heads in the manner set out above is a other conventional system, the time stretch playback through a frame memory carried out. Namely, a magnetic tape becomes continuous at one speed Driven l / n times the recording speed so that only fields are faded out achieve adequate noise-free video output signals and make the video signals discrete can store in the image memory while video signals from the output of the Frame buffers are interpolated with respect to the remaining fields, thus time stretch playback is performed.

Fig. 8 shows the scanning positions of a video head in time stretch reproduction by such a device and the enveloping output waveform of video signals, output from the video head. In Fig. 8, reference numerals denote and symbols identical to those in Fig. 7, the same parts, and in video signals obtained at an interval T4 are written in the image memory, while repeating the image of a k-th field stored in the image memory is displayed in a following interval T5, i.e. an interval for a field, which can receive a following complete shell.

The conventional facilities are of the structure listed above, the first set-up requires a special motor and a complicated motor control, thus, the tape drive shaft motor satisfactorily incrementally counteracts its moment of inertia is put in rotation while a special video head and a complicated one A facility to control it is required so that images are free of noise and blurring can be achieved in still image reproduction. In the second facility is moving the tape so slowly that it is difficult to get sufficiently noise-free with an ordinary one Video head to read the signals while the time stretching images thus obtained are discontinuous are composed by interrupted fields and are not represented uniformly can be.

It is therefore an object of the invention to provide a magnetic video recorder / reproducer to provide clear and uniform time-stretching images through an ordinary video head can achieve absolutely no noise.

This object is achieved by the magnetic according to the invention Video recorder / reproducer that reproduces signals in the manner that is used in time stretch reproduction both the speed of a magnetic tape with l / n and the speed of rotation a rotating drum are multiplied by i / n to obtain the reproduced signals with time base compression by a time base compression device are outputted while video signals by repeatedly outputting the same Output signals at intervals in which there is no output from the time base compressor happens to be interpolated.

According to the invention, a video head accurately reproduces the scanning of video tracks on the magnetic tape, thereby producing clear and uniform time-stretching images through the Using an ordinary video head achieved absolutely no noise.

These and other features and usefulnesses of the invention emerge from the description of exemplary embodiments with the aid of the figures. 1 shows a schematic block diagram according to a first embodiment of a magnetic video recorder / reproducer according to the invention; Fig. 2 is a timing chart for explaining the operation of the embodiment shown in Fig. 1; Fig. 3 is a schematic block diagram of a second embodiment of the invention; Fig. 4 is a schematic block diagram of a third embodiment of the invention; Fig. 5 is a timing chart showing the reverse playback operation in each of the embodiments; 6A and 6B are vector diagrams showing the principle of the invention, showing tape speed, the relative speed between the tape and a video head, and the angular relationships therebetween; Fig. 7 is a schematic block diagram showing the video tracks and scanning locations of video heads on a magnetic tape when time stretched playback by conventional four head system means and the playback of the output jackets therefrom; and Figure 8 is a schematic diagram showing the video tracks and scan locations of a video head on magnetic tape when time stretched playback by conventional two head and image storage system devices.

Before describing the preferred embodiments, first the principle of the invention is described with reference to FIGS. 6A and 6B. Figures 6A and 6B are vector diagrams showing the relationship between the feed rate of a magnetic tape in a helical scan type magnetic video recorder / reproducer and the relative speed between a video head driven by a rotating Drum is rotated, and the magnetic tape.

In Fig. 6A, Vh means the relative speed between the video head and the magnetic tape moving at a speed Vt, and the video head performs scanning at an angle. # through, through, which is spanned by Vh and Vt, whereby video signals are recorded on the magnetic tape. The symbol 8 denotes the angle of inclination of the scanning location of the video head when the tape is stopped (Vt = 0), this angle corresponds to the angle of tilt of the rotating drum. The symbol Vhg then designates the relative speed at this point in time. Between &commat; e and and # 0 has the following relationship: Vh. sin # tanO Vh Vh.cos + Vt Assuming that both the rotating speed Vhg of the rotating drum and the tape feeding speed Vt are multiplied by a factor of 1 / n (n = 2, 3, ...), the relative speed also becomes Vh multiplied by l / n. As can be seen from Fig. 6B, there is shown the vector relationship obtained by multiplying the rotating speed Vh0 of the rotating drum and the tape feeding speed Vt by 1 / n. In the triangle defined by Vhg, Vt, and Vh, when Vh0 and Vt are both multiplied by / n, 00 remains unchanged and a triangle similar to the original one is obtained as shown in Fig. 6B, and so Vh becomes 1 as well / n multiplied. The relative speed Vh0 at standstill of the tape is proportional to the rotational speed of the rotating drum, and therefore this rotational speed is represented by Vh0 for ease of illustration if Vh -W (l / n). Vh Vt + (ion) Vt (n = 2, 3, ...), then the following relationship is also established between @ O and and 8: whereby it is understandable that the scanning is performed parallel to the original video tracks on the magnetic tape at an angle θ. In other words, all of the video tracks can be faithfully scanned.

The reproduction cycle of the output video signals, i.e. the interval between a horizontal sync signal and a subsequent horizontal sync signal, is multiplied by n.

The above discussion applies accordingly to a magnetic video recorder / reproducer of the helical track type through- out when the magnetic tape is in reverse Moved towards the above. In this case e0> e and the velocity -Vt.

The invention is carried out on the basis of the above principle, and Fig. 1 shows a first embodiment thereof.

Referring to Figure 1, there is shown a video head 2 recorded on magnetic tape Reads video signals. Thus, at the output of the video head 2 there is an FM luminous density signal (hereinafter also referred to as brightness signal) and low-frequency converted Signals composed of chrominance signals (hereinafter also referred to as color signal). In the first embodiment, the tape feeding speed and the rotating speed become a rotating drum to which the video head 2 is attached by a controller 20 controlled in time stretch playback, 1 / n times that of normal recording is. The control device 20 has devices for switching the time constants etc.

the control characteristics such as servo characteristics of the various Motor control systems, depending on the speed of rotation of the rotating Drum and the tape feed speed so that the video head 2 the tracks samples correctly in every type of time stretch playback. The output signals from the video head 2 is fed to a preamplifier 3. The frequency compensation characteristic of the preamplifier 3 is suitably provided by a circuit (not shown) switched depending on the reproduced signal frequency. While namely the speed of rotation of the rotating drum multiplied by the factor n of the l / n Speed of this embodiment is changed, the frequency band becomes the reproduced signals are changed in response, and therefore the reproduced Signals are amplified in a frequency compensation characteristic that is most suitable for the frequency band of the reproduced signals.

The output signals from the preamplifier 3 become an A / D converter 7 supplied, which is operated according to clock signals of frequency (l / n) fCLK. Output signals from the A / D converter 7 are fed to a first image memory 8. It is also a second image memory 10 is provided, and a memory control circuit 9 controls this Writing to / reading from the first and second image memories 8 and 10, respectively.

The first and the second image memory 8 and 10 are correspondingly with one terminal 12a and another terminal 12b of a switch 12 are connected. A switchable connection 12c of the switch 12 is connected to the connection side 12a for Reading from the first image memory 8 switched while going to the other terminal side 12b is switched to read from the second image memory 10. The switchable connection 12c is connected to a D / A converter 11, which is based on clock signals of the frequency fCLK is operated. The A / D converter 7, the first and second image memories 8 and 10, the memory control circuit 9, the D / A converter 11 and the switch 12 constitute a time base compression means for compressing the reproduced signals time base type and interpolation means for interpolating the video signals at intervals in which there is no output from the time base compressor takes place.

The time base compressors and Interpolation device obtained from the FM brightness signals and the low frequency converted Signals composed of color signals are reproduced in a luminance signal processing circuit 4 supplied. This doubled luminance signal processing circuit 4 is to be carried out of reproduction processes, i.e. frequency demodulation of the brightness signals, suitable, and the time constant, etc. of this circuit 4 become dependent on the value n the "l / n-multiplied speed" switched. Continue to be the above listed together set signals to a reproduced color signal processing circuit 5 supplied. This doubled color signal processing circuit 5 is for processing of reproduction processes, i.e. high-frequency conversion of the color signals. Finally, a mixer 6, which is a circuit that demodulates the frequency Receives brightness signals and the high-frequency converted color signals, these Signals together.

The operation of the first embodiment will now be described.

FIG. 2 shows the write / read times of the image memories shown in FIG 8 and 10, and the operation for time stretch reproduction is referred to described on this timing diagram.

In the time stretcher playback, the rotation speed becomes the rotating drum and the feed speed of the magnetic tape by the control device 20 controlled so that it is 1 / n times as large as when it was recorded, as here above Fig. 2 shows the case for n = 3.

The signals reproduced in such a state are transmitted by the The preamplifier 3 is amplified in order to then be introduced into the A / D converter 7. Of the A / D converter 7 digitizes the received analog video signals, as in the Clock frequency (l / n) fCLK are received, whereby the data in the first image memory 8 can be written. The frequency fcLK becomes depending on the frequency band the signals to be treated are determined. At that time, the playback speed is 1 / n times the recording speed, and therefore the field or field cycle is the reproduced signals nV.

as shown in Fig. 2, in which the symbol V is the original Field refresh rate indicates. After a lapse of (n - 1) V from the beginning of the Writing that begins Reading the first image memory 8. To this Time, the reading is carried out at the clock frequency fCLK, i.e. the clock frequency is n times that of the A / D conversion. At the same time, read output signals from the first image memory 8 into the second image memory 10 with the clock frequency fCLK written. In other words, writing to and reading from the first image memory 8 and writing to the second image memory 10 are performed with respect to this sub-image ended at the same time. After the termination of such an operation with reference to a k-th field of the video signal becomes a following (k + l) -th field subsequent written into the first image memory 8.

Thereafter, the process of the case of the k-th sub-image is repeated. However, until reading from the first image memory 8 begins, the data will be out the second image memory 10 is read at the clock frequency fcLK, which is identical that of repeated writing (n - l) times.

The read output signals from the first and second image memories 8 and 10 thus obtained are converted into D / A converter 11 through switch 12 which is operated at the clock frequency fCLK, and they are in it by converted from digital to analog.

Then the signals go into the doubled brightness signal processing circuit 4 and introduced into the doubled color signal processing circuit 5, in which they the frequency demodulation and the high frequency conversion by the respective Circles are subject, then they are merged by the mixer 6 and as the composite video signals are output Thus, in the In the first embodiment, the tape feed speed and the rotation speed the rotating drum is so controlled in time stretch playback that it is l / n times as much are like recording, which makes the video head faithful to the scanning of the tracks and clear time-stretching images can be achieved with absolutely no noise at an arbitrary speed multiplied by 1 / n by an ordinary one Video head. Furthermore, the reproduced signals are in a compressed time base output while the signals are identical to the compressed time base output signals are for interpolation by the interpolation device in the intervals, if no such compressed time base output is received, are output, whereby the images are obtained sequentially and are clear and uniform Images are displayed.

Fig. 3 shows a block diagram of a second embodiment of the invention. The feature of this embodiment is that a duplicated signal processing circuit 4, a doubled color signal processing circuit 5 and a mixer 6 in the first Stage of the time base compression device and interpolation device provided to allow the time base compression and interpolation of the composite video signals are performed after the reproduction signal processing of the luminance signals and the color signals.

Corresponding parts in this embodiment are similar in operation those of the first embodiment described above while the effect the same is also similar to that of the first embodiment.

Fig. 4 shows a block diagram of a third embodiment of the invention. The feature of the third embodiment is that the time base compression means and Interpolation device for brightness signals independently of which are intended for color signals, thus compressing and interpolating of the brightness signals after frequency demodulation and the low frequency converted Color signals happen separately from one another.

Although in this embodiment the memories and the like in the Numbers are increased in comparison with the first and second embodiments both the luminance signals and the color signals at low frequency levels into the appropriate time base compression device and interpolation device entered, and therefore, the A / D conversion and D / A conversion can be performed at low clock frequency levels be performed. It is therefore not necessary to add expensive A / D and D / A converters use, which can save costs. It can also be clear and smooth continuous images with this embodiment absolutely without noise just like with of the first and second embodiments can be achieved.

Although the above description of the embodiment in consideration of the case where the time stretcher playback has been made in the forward direction has been performed, i.e., the value n is the "1 / n multiplied speed" a positive integer, the video tracks can play back faithfully even in that case n = -2, -3, ..., i.e., the case where the rotation of the rotating Drum and the advance of the tape in the reverse direction are done by a similar procedure. In this case, however, the repetition cycle becomes the outputted Video signals changed two, three, ... times in the opposite direction In In this case, the reverse time stretcher reproduction can be performed by-von a first image memory 8 is read in reverse, i.e. one after the other of the last written data as shown in the timing diagram is shown in FIG. In this case, too, can be clear and smooth successive Images with absolutely no noise can be obtained, similar to the previous ones corresponding embodiments.

Furthermore, the special case for driving the belt can be reversed Direction can be used, namely when n = -1, and thus noise-free backward reproduction can be performed smoothly without a second image memory 10, i.

only with a first image memory 8 in this case.

Claims (7)

Magnetic Video Recorder / Playback PATENT CLAIMS 1. Magnetic Video recorder / reproducer featured by a helical scan system by: control means (20) for controlling the speed of advance of a magnetic tape and the rotation speed of a rotating one built with a video head Drum so that they can be played l / n times (n: positive whole number larger than two) that of normal recording in the forward direction and correspondingly in the reverse direction are; Device for compressing the time base (7, 8, 9, 11, 12), which in a Video signal processing system is provided for time stretcher playback and delay functions with a variable amount of delay to compress reproduced Having signals in a time base fashion; and interpolation device (9 - 12), those in the video signal processing system in time stretcher reproduction for interpolating output video signals by repeatedly outputting the same output signals at intervals when there is no output from the device for compressing the Time base takes place, is provided. 2. Magnetic video recorder / reproducer according to claim 1, characterized characterized in that the means for compressing the time base and the interpolation means for direct processing of signals reproduced by the video head, are suitable. 3. Magnetic video recorder / reproducer according to claim 1, characterized characterized in that the means for compressing the time base and the interpolation means for processing composite video signals reproduced from the by the video head Signals are demodulated, are suitable. 4. Magnetic video recorder / reproducer according to claim 1, characterized characterized in that the means for compressing the time base and the interpolation means for the independent processing of luminance signal components and chrominance signal components, separated from the signals reproduced by the video head are. 5. Magnetic video recorder / reproducer according to one of the claims 1 to 4, characterized in that the device for compressing the time base and the interpolation device have: one in sync with Clock signals of a predetermined frequency working A / D converter (7) for converting from inputted input analog signals into digital signals, a first image memory (8) for storing output signals from the A / D converter, a second image memory (10), a memory control device (9) for reading from in the first image memory stored content at a speed of n times the frequency of the clock signals, for writing the same in the second image memory during the repeated reading of contents stored in the second image memory at the speed of n times the frequency, a switching device (12), the read output signals from the first image memory at one terminal thereof while receiving read output signals from the second frame buffer on its other port to receive signals by switching to the one terminal outputs when read signals from the first image memory output and by switching to the other terminal when there is no read signal is output from the first image memory, and one in synchronism with clock signals D / A converter (11) operating at the frequency of n times the said clock signals for converting output signals from the switching device into analog signals. 6. Magnetic video recorder / reproducer according to one of the claims 1 to 5, further characterized by a preamplifier (3) for amplifying from the magnetic head reproduced signals, the control device also the Frequency compensation characteristic of the preamplifier in response to the speed of rotation the rotating drum and the feed speed of the magnetic tape switches. 7. Magnetic video recorder / reproducer according to one of the claims 1 to 6, characterized in that the control device also controls the control characteristic the corresponding motor control systems contained in the magnetic video recorder / reproducer are present in response to the speed of rotation of the rotating drum and the feed speed of the magnetic tape switches.