JPS60212871A - Video tape recorder - Google Patents

Abstract

PURPOSE:To make completely a video signal and a sound signal in phase coincident with each other, by providing offsets on cylinders of a recording and reproducing rotary head and reproducing rotary head, and synchronizing an time-compressed sound signal with a reproduced video signal by using a buffer memory, reading and extending the result for operation. CONSTITUTION:A recording and reproducing head is put on a location which precedes a monitor reproducing head by two fields by providing offsets on the cylinders of the recording and reproducing head; and reproduces a digitized sound signal by the recording and reproducing head and reproduces a video signal by the monitor reproducing head, at the time of reproduction. The reproduced digitized sound signals are supplied to a format decoder 203 which performs reverse conversion to time-series samples including error correcting operations through a demodulator 202 and successively written in buffer memories 207, 208, and 209 in the unit of fields. Then the written sound signals are read out by means of start signals synchronous to the video signals supplied to a terminal 217 and outputted to a terminal 216 after they are subjected to extending operations. Therefore, phases of the videos and sounds can be made coincident completely with each other.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a video tape recorder having a function of recording and reproducing digitized audio signals.

2. Description of the Related Art Structures and Problems Therein In recent years, rotary hexagonal scan type video tape recorders (hereinafter simply referred to as VTRs) have been widely used for both business and home use. In this case, the video signal is recorded and played back by a head attached to a rotating cylinder, and the audio signal is recorded and played back by a fixed head.However, as the tape speed decreases and the length of time increases, it is relatively difficult to improve the quality of the audio signal compared to video. The situation is now. Under these circumstances, as a method for dramatically improving the quality of audio signals, a system of recording and reproducing using a rotary head with a high relative speed, similar to video signals, is beginning to show signs of being put into practical use. A simple method is to perform FM modulation with the audio signal, frequency multiplex it with the video signal,
Alternatively, the method of deep recording in the thickness direction of the tape is used for home use
Developed by TR. However, such a method cannot be said to be sufficient in terms of quality such as continuity for each field, band, and S/N. Therefore, so-called PCM, which converts audio signals into digital codes and records and reproduces them, is attracting attention as a method that can reproduce high-quality audio in the truest sense. For example, in the case of a small home VTR called 8m/m video, the magnetic tape is wound around the cylinder at an angle greater than 18o0, and a compressed digitized audio signal is recorded in that part in units of one field. A reproduction method is used. Although this method overcomes the conventional quality-related drawbacks, one problem arises.

That is, it is the phase difference between video and audio. Since recording is performed in field units, first, during recording, one field is recorded for the video signal in terms of processing time such as compression, and then one field is used for processing such as error correction and expansion during playback, for a total of two fields (one frame). ) Rif voice overlapping signal is delayed. Home VTR
In this case, it may not be a problem perceptually, but in the case of professional use such as broadcasting, this delay becomes impossible to ignore if editing by dubbing is repeated. According to the literature, experimental results have shown that viewers feel a 3-frame delay, although it depends on the program. Therefore, for business use, complete synchronization of video and audio is required as a basic performance.

OBJECT OF THE INVENTION The present invention solves the above-mentioned conventional problems by recording a high-quality digitized audio signal together with a video signal on the same tape, and eliminating phase lag between the video and audio during recording and playback. The purpose of the present invention is to provide a VTR device that does not require any cables.

Structure of the Invention The present invention has a recording head that is housed in a rotating cylinder and has a pre-reproduction function, and a reproduction head that is provided downstream of the recording head, and the recording head and the reproduction head are arranged at the same point. The position of the rotary cylinder is set so that the time difference to be traced is one frame, and the phase alignment of the video and audio can be realized by controlling the buffer memory of the digital audio signal.

Description of examples FIG. 1 is a block diagram showing an outline of an embodiment of the present invention.

In FIG. 1, 101 is a video signal output terminal, 102 is a YC separation circuit that separates a luminance signal and a color difference signal from a composite video signal, and 103 is a YC separation circuit that separates two color difference signals R-Y and B-Y signals, for example, in one horizontal scan. A C signal compression circuit that compresses each period (hereinafter referred to as 1H) into one system, 104 is an FM modulator, 105 is a recording amplifier (RECAMP) that drives the recording head, and 106 is an audio signal. The input terminal consists of two stereo input terminals, an L channel and an R channel. 107 is an AD converter, and 108 is a format encoder that adds an error correction code and an error detection code to the digitally converted audio data and configures a recording format. , 109 is a modulator, 110 is a tape, 111 rotary cylinders, 112 is a playback booster (PBAMP), 113
114 is an FM demodulator, 114 is a TBC that absorbs jitter components and expands a color difference signal, 115 is a YC synthesis circuit that generates a composite video signal from a luminance signal and a color difference signal, 116 is a video signal output terminal, and 11 is a demodulator. , 118 is a format decoder that performs inverse conversion from the recording format to time-series samples including error correction operations, 119 is a DA converter, 1
20 is an audio signal output terminal. FIG. 2 shows a detailed configuration of the format decoder 118 shown in FIG.
1 is a reproduction signal input terminal, 202 is a demodulator, and 203 is a first
In FIG. 118, there is a format decoder, a 2o4 block synchronization separation circuit, 205 is an error detection circuit, 206 is an error correction circuit, and 207, 208, and 209 are memories that can store one field of digitized audio data. A and memory B, memory C 1210 is an address selection switch that selects the address counter output and supplies write and read addresses to memories 207, 208, and 209, and 211 supplies addresses to write playback signals to memories 20 and 208, 209. a first address counter that
212 is a second address counter that supplies write and read addresses for data transfer between the memories 207, 208, and 209 and the error correction circuit 206;
3 is a third address counter that supplies the memory 207, 208, 209 with an address based on the frequency expansion clock of the time series sample; 214 is a data bus; 216 is an average value interpolation circuit; and 216 is supplied from the video signal processing system. This is a start signal input terminal for initializing the third address counter 213. FIG. 3 (1 is a layout diagram of the head attached to the rotating cylinder shown in FIG. 1 111, and is a view of the rotating cylinder from above, 3o1 is the tape, 302 is the cylinder, 303, 304 is the erasing head, 305.306 is a brightness signal recording/reproducing head, 30
7.308 is a color difference signal recording/reproducing head, 309.31
0 is a head for reproducing color difference signals, and 311 and 312 are heads for reproducing color difference signals. Figure 3 (bl is a side view of the cylinder compared to Figure 3 (al), and the numbers are the same as Figure 3 (a). Figure 4 is a diagram showing the recording pattern on the tape, and 401 is a diagram showing the recording pattern on the tape. A track 402 on which a luminance signal Y and a digitized audio signal (i.e., R channel of PCM) are recorded.
is a track on which the color difference signal C and the R channel of PCM are recorded. Figure 6 shows that there are 2
The two playback heads (see Figure 3(a) % lead, playback, do 306-308, and monitor playback heads 309-31
The types of signals detected in step 2) are separated. 6th
7 and 7 are diagrams showing approximate time charts of video signals and audio signals recorded and reproduced in small units of one field (1e, emE)'r.

The operation of the video tape recorder of this embodiment having the Kjs as described above will be explained below.

Composite video signal input from terminal 101 (for example, NTS
C signal) is converted into a luminance signal (Y signal) by the YC separation circuit 102.
The component and two color difference signals (C signals) R-Y and B-Y signals modulated by the Kalani subcarrier and superimposed thereon are separated.

The C signal is subjected to time axis compression of % every 1H by the C signal compression circuit 103, and a compressed C signal is generated by dividing the 1H interval into front and back. YC separated 2 channel video signal FiF
FM modulated by M modulator 104, RECAMPl 06
A recording/reproducing head (306 to 3 in Fig.
08) and recorded on tape.

On the other hand, an audio signal is input from the terminal 106.

The R stereo signal is converted into digital data by an AD converter 107, and then converted into a recording signal format by a format encoder 108.

Conversion to the recording signal format is performed by writing into the memory in the format encoder in units of one field, performing high-speed reading using a time-axis compressed clock, and generating an error correction code at the time of reading. By controlling the order of write and read addresses, data strings can be interleaved. Furthermore, the data is divided into blocks every several samples, and an error detection code and a block synchronization code are added to each block. format encoder 10
The output of the two channels of 8 is converted from NRZ data into an appropriate modulation code by a modulator 109. RECAMPl
The video signal and each field are switched by the OS and recorded on the tape. Figure 6 shows video and audio signals #n~
A time chart is shown when #(n+3) field signals are recorded. In this way, the video and audio are set to 1 when recording.
A field phase difference occurs. Figure 4 shows the recording tracks on the tape. The windings from 00 to 1800 to /linda are video signal (y, c) recording sections, and the rear windings 1800 and above are PCM recording sections. Then, the adjacent recording/reproducing head 306.30 shown in FIG.
6 and 307.308, two tracks are recorded simultaneously.

Also shown in Figure 3 (ta) is 1. erase head 303.304
In the recording mode, it is necessary to operate at the same timing as the recording command so as to erase the portion to be recorded in advance. In the case of this embodiment, each head for erasing, recording, and +1+-1 magnetic monitor playback is 600 m
Since it is placed at the angle of , erase it, record it with
The playhead time difference is 5 fields.

The reproducing operation is carried out using the FLJ raw head attached to the cylinder 111 in FIG. 1 (the advance reproducing head 305 in FIG. 3(a)
-3o8 and monitor playback heads 309-312) are subjected to processing such as amplification and equalization and waveform shaping in the PBAMP 112, and the video signal is input to the FM demodulator 113 and demodulated. Although the demodulated Y and C video signals are not shown in the figure, H synchronization and ■ synchronization are detected, and at that timing the TBCl for jitter absorption is detected.
It is written in 14. The expansion operation of the C signal is also performed using TBCl.
This is realized by operating the readout of 14.

The YC synthesis circuit 116 restores the original composite video signal and outputs it from the terminal 116.

On the other hand, the PCM signal is separated from the video signal by the PBAMP 112 and demodulated by the demodulator 117. Further, a format decoder 118 performs inverse format conversion including error correction operations. L channel returned to time series sample,
The R channel audio data is converted into an analog signal by a DA converter 119 and output from a terminal 120.

The present invention is constructed based on the basic operation described above, but the detailed operation which is the key point of the invention will be explained below. In the present invention, in the reproduction mode, the type of reproduction head to be used and the signal to be reproduced are selected according to the table shown in FIG. That is, in the simultaneous playback mode in which recording results are monitored simultaneously while recording, the playback head is the monitor playback head 309 to 312, and when editing using two VTRs, the playback head on the recorder side is the recording head 305 to 308.・This is the playback head, but in other modes, P
CM playback is performed using the recording/playback head 3 with advance playback function.
05 to 308, the video signal is played back by the monitor playback head 30.
Performed from 9 to 312. Recording/playback heads 306-308
The angle formed by the monitor playback heads 309 to 312 is 60°.
In the case of mounting the head shown in FIG. 3(b), the height position is set to have an offset of two fields. In other words, the recording and playback heads 305 to 308 and the monitor and playback heads 309 to 312 trace the points traced by the recording and playback heads 306 to 308 to the monitor playback, and the points traced by the dos 309 to 312 are 2 fields and 10% fields later at fc time. The height difference is set. Therefore, as shown in Fig. 7, the playback signals have the relationship shown in Fig. 7 (b) in the case of the simultaneous monitor mode and the recorder during editing, and in other cases, the relationships shown in Fig. 01 and 2. .

Moving on to the explanation of the operation of the format decoder shown in FIG. 2, the 11f raw signal inputted from the terminal 201 is demodulated by the demodulator 202, and then the block synchronization code is detected by the synchronization uF circuit 204. .

The demodulated data flowing through the data bus 214 is first written into the memory IJA 207 in units of one field, and the writing operation continues sequentially to the memory B2O3 and the memory C209 field by field. In this case, although not shown, the demodulated data clock is supplied as a clock pulse to the first address counter 211, initialized at the detected block synchronization, and error detection is performed so that data is written to the memory only when there is no error. The output of the circuit 206 is supplied as an enable signal to the first address counter 211. The address selection switch 210 sequentially transfers the output address of the first address counter 211 to the memory A207,
Memory B2081 is alternately supplied with ν to memory C209. After the write operation to the memory is completed and a waiting time corresponding to the phase fluctuation of the jitter is provided, the second address counter 2
12 is generated, and the clock frequency divided from the jitter-free crystal oscillator is counted to generate an address signal. During this time, for example, writing and reading operations are repeated multiple times in sample word units to the memory A 207 via the address selection switch 210, and the data bus 207
4, the error correction circuit 206 generates an error correction circuit using codes and data, and performs error correction operations. The detection results of the error detection circuit 206 are also transferred to the data bus 214.
The data are stored together with the data in the memories A, B, and C in sample word units.

The setting must be such that the total time for writing to memory falls within one field. After the correction operation is completed, the third address counter 213 is initialized by a start signal synchronized with the video signal supplied from the terminal 217 (this operation only needs to be performed once after the reproduction signal Vi starts to be detected). )1, supplied to the memory via the address selection switch 210 from the third address counter 213 for decompression operation. In this way, the memories A, B, and C 207 to 209 are controlled by the address selection switch 210 so that each address counter 211, 21
2,213 addresses are selected and the operations are controlled so that they do not overlap with each other. Therefore, in Figure 7,
As shown in c, the decompression operation is timed by a start signal synchronized with the video signal, so the video output and audio output are synchronized on a field-by-field basis. data bus 21
For uncorrectable errors, the data expanded through 4 is corrected by average value interpolation in an average value interpolation circuit 215, and is outputted from a terminal 216.

With the above-described configuration and operation, in normal playback, the video and audio are perfectly synchronized and no phase shift occurs even if dubbing is repeated, as shown in FIG. 7C. Also the 7th
Regarding the simultaneous playback mode, which is the mode in which the case shown in b in the figure occurs, and the case of the recorder during editing, the former is originally a function to check the recorded content, and when the simultaneous playback output is used as a dubbing input at the same time, Unthinkable.

Since the latter is also a recorder, there is no case where the playback output is recorded again. In both cases, the monitor screen and the sound are shifted by one frame, but this cumulative effect does not pose a problem, and if the embodiment of the present invention is used, the phases of the screen and the sound match.

Further, in this embodiment, an example of 2-channel recording using YC separation has been described, but it is obvious that the present invention can also be applied to 1-channel recording in which recording is performed on the same YC track. In either case, since the video and audio portions are separate areas that are spatially separated, a so-called post-recording function in which images and audio can be recorded independently can also be realized. Especially in the case of 2CH recording, Lch.

Rch also has the advantage of being able to do post-recording independently.

Effects of the Invention In the video tape recorder of the present invention, the recording/preceding playback head is placed two fields ahead of the monitor playback head, and during playback, the advance playback head plays back a digitized audio signal and the monitor playback head plays back a video signal. In addition, by synchronizing the readout and expansion timing of digital audio data from the buffer memory with the video signal, it is possible to perfectly match the phases of video and audio.
Previously, even if dubbing was repeated, there was a problem.

It is possible to eliminate the lag between the screen and the sound, which has a great effect.

Furthermore, since images and sounds are recorded in separate areas, dubbing is possible, and in the case of 2CH recording, dubbing can be done for each L channel and R channel.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a video tape recorder according to an embodiment of the present invention, FIG. 2 is a block diagram showing an example of the configuration of a format decoder according to an embodiment of the present invention, and FIG.
Figure (a) is a top view of the head arrangement in the cylinder of the embodiment of the present invention, Figure 3 (bl is a side view of the head arrangement of the same cylinder, Figure 4 is a recording pattern diagram according to the embodiment of the invention, The figures are operation mode diagrams according to the embodiment of the present invention, FIG. 6 is a time chart diagram of recording signals according to the embodiment of the present invention, and FIG.
The figure is also a time chart diagram of the reproduced signal. '1
08...Format encoder, 111...
...Rotation/linda, 118...Format decoder, 207.208.209-7 Yield memory A
, B, C, 210...address selection switch,
211, 212, 213...address counter,
217...Start signal input terminal, 305,3
06゜307.308...recording/playback head, 3
09°310, 311, 312...Monitor playback head. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 1! 1 Shi------111----------------------
Figure 3 (C1l Figure 41!l Figure 5 Figure 6 α Figure 7 (Labor 1 □

Claims (2)

[Claims] (1) A rotary head scan type video tape recorder that digitizes audio signals and then compresses the time and records and plays back in a different area from the video signal, which includes a rotary head for recording and playback and a rotary head for playback that is capable of monitor playback. , an offset corresponding to the field time difference is provided at the height position of the recording/reproducing rotary head and the reproducing rotary head on the cylinder, and the digitized audio signal is transmitted at the throat to the recording/reproducing rotary head; 1f1 has a mode in which a video signal is detected by a rotary head for reproduction, writes a reproduced digitized audio signal in a field unit to a buffer 1 memory,
A video tape recorder comprising means for reading and decompressing time-series digital audio data from the buffer 1 memory in synchronization with a reproduced video signal. (2) The video signal is split into a luminance signal and a color difference signal, which are separated into independent channels, and the audio signal also corresponds to the video signal, and the left and right channels are independent, and the two channels are simultaneously recorded together with the video signal. The videotape recorder according to item 1.