JPH079685B2 - Video tape recorder - Google Patents

Description

Detailed Description of the Invention

[Field of Industrial Application] The present invention relates to a video tape recorder for professionals used in broadcasting stations and the like. SUMMARY OF THE INVENTION The present invention, for example, in a video tape recorder called SMPTE-C type format, when recording and reproducing a PCM signal in place of a synchronization signal in a so-called synchronization track,
This PCM signal reproducing head is provided for each head of the video period for which the application is different, and it is possible to sequentially read the PCM signals reproduced by the heads with the same tracking during tape variable speed reproduction and perform continuous PCM signal demodulation. It is something to do. [Prior Art] In a so-called SMPTE-C type video tape recorder, two heads are provided on a rotating drum, and this drum is rotated at a rate of one rotation per one field, and at the same time, the circumference of the drum is rotated. The magnetic tape is wound diagonally over nearly 360 degrees of the surface and transported at a predetermined speed. The video period of the video signal is recorded in one of the two heads described above, and the signal is recorded in the other head during the period (synchronization period) in which the head is separated from the magnetic tape. Has been done. That is, FIG. 4 shows a recording pattern of the magnetic tape thus recorded. In the figure, the magnetic tape is divided into two in the width direction, a signal in the video period is recorded on an oblique track by the above-mentioned one head in the divided wide portion, and the other in the divided narrow portion. The signal of the synchronization period is recorded on the diagonal track by the head. A control track, a first audio track, a second audio track, and a third audio signal track, which are recorded by a fixed head, are provided between these parts and on both side edges of the magnetic tape. By the way, in such a format, if a so-called time base collector is used for the reproduction signal, even if the signal in the synchronization period is lost, a regular video signal can be reproduced without trouble as long as the signal in the video period is obtained. . Therefore, it has been considered to record a digitized PCM audio signal in the above-mentioned format instead of the signal in the synchronization period on an oblique track in a narrow portion. That is, in the above-mentioned conventional format, the audio signal is analog-recorded by the fixed head, but in such analog recording, the deterioration is remarkable especially when the dubbing is repeated. On the other hand, if the recording is performed digitally, the problem of deterioration during dubbing can be solved. The applicant of the present application has previously proposed a video tape recorder (Japanese Patent Application No. 60-180257) in consideration of such a point. That is, FIG. 5 is a block diagram of a PCM signal system for that purpose. In this block diagram, the analog audio signal supplied to the input terminal (41) is supplied to the AD conversion circuit (43) through the IO circuit (42). , Converted to digital data. This data is supplied to the data bus (44). The data on the data bus (44) is supplied to and stored in the memory (45). Further, the data stored in the memory (45) is supplied to the encoder (47) through the data bus (46), and encoding such as addition of a predetermined error correction code and rearrangement is performed. Then, the data from the memory (45) is transferred to the modulation circuit (4
8) is supplied to the recording head (50) through the recording amplifier (49) and is modulated by the data to be supplied to the recording head (50), and the diagonal portion of the narrow portion of the magnetic tape (51) corresponding to the above-mentioned synchronous track is supplied. Recorded on the track. During playback, the tape (51) to the playback head (52)
The signal reproduced in (4) is supplied to the demodulation circuit (54) through the reproduction amplifier (53), and the recorded digital data is demodulated. This demodulated data is the data bus (55) (56)
The data of the data buses (55) and (56) are supplied to the memory (45) and to the first and second decoders (57) and (58), respectively. The demodulator circuit (5
The address of the data detected in 4) is the address bus (5
It is supplied to the memory (45) through 9). Then, the data that has been subjected to predetermined rearrangement and decoding such as error correction is supplied from the memory (45) to the data bus (44). The data of the data bus (44) is supplied to the DA conversion circuit (60) to be an analog audio signal, and this signal is taken out to the output terminal (61) through the IO circuit (42). The signal from the digital signal input terminal (62) is supplied to the data bus (44) through the digital IO circuit (63), and the signal from the data bus (44) is output as a digital signal through the IO circuit (63). Taken out to the terminal (64). Further, during editing, data from another video tape recorder or the like is supplied to the editing control circuit (66) through the terminal (65), and the data from this circuit (66) is transferred to the data bus (44).
The control signal detected by the circuit (66) is also supplied to the memory (45) through the auxiliary bus (67). Further, FIG. 6 shows a time chart of the recording / reproducing operation of this apparatus. Vertical lines in the figure are field boundaries. In this figure, first, A is a recording operation,

The signal AD-converted in the period of [0] is encoded in the first half of the next field [1], time-axis-compressed and read in the latter half of this field [1], and the recording heads (50A) (50B) are read. Will be recorded at. The recording is divided into two tracks. On the other hand, B is a reproducing operation, and for example, the signals reproduced by the reproducing heads (52A) and (52B) in the first half of the field [-2] are from the second half of the field [-2] to the next field. Decoded in the first half of [-1], and then the next field

The time axis is expanded during the period [0], DA converted, and taken out. Therefore, in the device described above, the same field

The reproducing heads (52A) and (52B) are provided three or more fields ahead of the recording heads (50A) and (50B) in order to extract the audio signal at [0]. That is, FIG. 7 shows the rotary drum as viewed from above. In the figure, (71A) and (71B) are recording heads for audio signals, and (72A)
(A) (72B) is the playback head for checking the recording of the audio signal, (73B)
A) (73B) are audio signal reproducing heads, and (74A) (74B) are audio signal reproducing heads for variable speed reproduction of video signals. Furthermore, (81) is a recording / playback head for video signals, and (82)
Is a variable speed reproducing head for video signals, and (83) is an erasing head for video signals. Here, there are a total of eight recording / reproducing heads for audio signals, and three recording / reproducing heads for video signals. Providing a total of eleven heads in a balanced manner is especially important for recording / reproducing for video signals. This is impossible when the arrangement of the head (81) and the variable speed reproducing head (82) is set to 120 degrees by the standard of the SMPTE-C type format, for example. Therefore, as shown in the figure, the dummy head (9
0) is provided, and a total of 12 heads are arranged at an angle of 30 degrees. That is, in the figure, the recording heads (71A) (71B), the erasing head (83), the recording / reproducing head (81), the dummy head (90), the reproducing heads (72A) (72B) are rotated counterclockwise from the position at 3 o'clock in the figure. ), Playhead (82), playhead (73
A) (74A) (73B) (74B) are arranged in this order. The heads (72A) and (72B) are set so as to trace the same track recorded by the heads (71A) and (71B).
(71B) is provided with a step that follows the track by 1/3 track, and the heads (73A) and (73B) are
Against B) The head (74A) (7
4B) is provided with a step that follows the heads (73A) and (73B) by 1/3 track. As a result, appropriate tracking is performed for each recording track, and recording of audio signals with consideration of time delay for a predetermined field is also performed for video signals recorded and reproduced by the heads (81) (82). Playback is performed. By the way, in the above video tape recorder,
For example, there is a demand for performing variable speed reproduction within a range of several percent over a long period of time, such as reproducing a tape recorded for 60 minutes in 55 minutes or conversely reproducing a 55 minute tape in 60 minutes. In this case, the reproduction of the video signal uses a head capable of performing tracking correction, so that one track is eliminated or the same track is repeatedly reproduced when the tracking correction reaches the limit for the tape which is reproduced at variable speed. It can be done without problems. On the other hand, in the case of the conventional analog recording, the time axis of the audio signal is changed as it is by simply shifting the tape. It should be noted that, within the range of several%, the fluctuation of the frequency due to the change of the time axis is not a problem. However, in the recording / reproducing with the above-mentioned PCM signal, when the tape is transferred at a variable speed, tracking cannot be performed in a predetermined cycle, and normal reproduction cannot be performed. On the other hand, if tracking correction is also performed on the PCM signal, the continuity of the PCM signal will be lost when tracks are eliminated or repeated playback is performed as described above, and normal audio signal demodulation such as noise generation in the transient part will not occur. I can not do it. [Problems to be Solved by the Invention] As described above, in the conventional technique, there is a problem that the reproduction of the PCM signal cannot be normally performed when the variable speed reproduction is performed. [Means for Solving the Problems] The present invention provides a rotary drum provided with a first head for recording / reproducing a video period of a video signal and a second head for recording / reproducing a period other than the video period. Recording and reproducing by the first head and recording by the second head on each part of the magnetic tape that is diagonally transferred on the peripheral surface of the rotating drum and is divided into two in the width direction. In a video tape recorder provided with a third head (82) which is capable of tracking correction and reproduces a signal in the video period, a PCM signal is generated by a head corresponding to the second head. When performing recording / playback of
A fourth head (73A) (73B) corresponding to the second head, which corresponds to the reproduction by the first head, and the third head.
And a fifth head (74A) (74B) corresponding to the above-mentioned second head corresponding to the time of reproduction by the above head, the magnetic tape is transferred at a speed different from that for recording, and the third head is transferred. While reproducing the video period, the PCM signals reproduced by the heads of the fourth and fifth heads on which the tracking is the same are sequentially demodulated (decoder (3), (1
0)) and a frequency different from that at the time of recording the demodulated signal corresponding to the different speed (frequency conversion circuit (26)).
It is a video tape recorder which is designed to read at the clock of. [Operation] According to this, since all the PCM signals are reproduced, it is possible to demodulate them and obtain good audio signals. [Embodiment] In FIG. 1, a clock signal from a master clock circuit (20) is supplied to a drum motor control circuit (21) to rotate a head drum (22) at a predetermined speed. Then, the signal reproduced from the tape (51) by the variable speed reproducing head (82) provided on the head drum (22) is transmitted through the reproducing amplifier (23) and the reproducing circuit (24) to the video output terminal (2
5) is taken out. Further, the clock signal from the master clock circuit (20) is supplied to the frequency conversion circuit (26),
A second clock signal, the frequency of which is converted according to the gear ratio, is formed, and the second clock signal is supplied to the capstan motor control circuit (27) to drive the capstan (28) at an arbitrary speed. . As a result, the tape (51) is transported at an arbitrary speed. And the head (8
The tracking deviation of 2) is detected by the reproducing circuit (24), and the tracking control signal is supplied to the tracking correction means such as the bimorph plate (29) provided at the base of the head (82). As described above, the variable speed reproduction of the video signal is performed. Further, the signals from the heads (73A) (73B) are supplied to the reproducing circuit (2) through the reproducing amplifier (1). The PCM signal reproduced by this is supplied to the decoder (3), and error correction, rearrangement, etc. are performed. And the digital data from this decoder (3) is switched (4)
Is written in the memory (5) through the, the data from the memory (5) is supplied to the DA conversion circuit (6), and the converted analog audio signal is taken out to the output terminal (7). The signals from the heads (74A) (74B) are supplied to the reproduction circuit (9) through the reproduction amplifier (8), and the PCM signal reproduced here is subjected to error correction and rearrangement by the decoder (10). It is supplied to the switch (4). Then, the switch (4) is switched to the side where the normal decoder is performed by the signals from the decoders (3) and (10). Further, the clock signal from the master clock circuit (20) is supplied to the decoders (3) and (10) and also to the memory (5) to write data. Further, the second clock signal from the frequency conversion circuit (26) is supplied to the memory (5) to read the data and is also supplied to the DA conversion circuit (6). Therefore, in this device, for example, a time chart when the tape speed is high is as shown in FIG. That is, in the figure, A is the scanning locus of the heads (73A) and (73B), B is the track pattern on the tape, and C is the scanning locus of the heads (74A) and (74B). Here, when the tape speed is high, the track pattern is relatively narrow. Further, in this figure, if a range of 1/2 of the center of the head width (shown with a diagonal line at the left end in the figure) is in the track, it is assumed that the track is reproduced, and each head (73A) ( 73B), (74A) and (74B), the tracks of the numbers shown in the figure are reproduced, and the PCM is displayed as shown in D and E of the figure.
You can get the signal. Then, by decoding this signal, writing it in the memory (5), and reading it by the second clock signal proportional to the tape speed, a continuous reproduction signal can be obtained as shown in FIG. Further, FIG. 3 is a time chart when the tape speed is slow, where A is the scanning locus of the heads (73A) and (73B), and B is the time chart.
Indicates a track pattern, and C indicates a scanning locus of the heads (74A) (74B). Here, when the tape speed is low, the track pattern is relatively wide. By this, each head (73A) (73B) and (74A) (74
As shown in D and E in the same figure, the PCM signal is taken out from B), and this signal is decoded, written in the memory (5), and read by the second clock signal proportional to the tape speed. A continuous reproduction signal can be obtained as shown in FIG. In this way, the signal from the PCM signal track is reproduced, but according to the above-mentioned device, the head (73A) (73B)
Since there is a step between (74A) and (74A),
A normal reproduction signal can always be obtained from either head within a predetermined speed range, and by decoding this signal and reading it continuously, it is possible to obtain a continuous reproduction signal without omission or duplication. it can. In the above description, the decoders (3) and (10), the switch (4), and the memory (5) are configured separately, but in reality, the configuration is as shown in the conventional PCM audio system configuration. It is realized by expanding the capacity of the memory in this and performing appropriate address operation. [Advantages of the Invention] According to the present invention, since all PCM signals are reproduced, it is possible to demodulate the PCM signals and obtain good audio signals.

[Brief description of drawings]

FIG. 1 is a block diagram of an example of the present invention, FIGS. 2 and 3 are diagrams for explaining the same, and FIGS. 4 to 7 are diagrams for explaining the video tape recorder proposed previously. . (3) (10) is a decoder, (6) is a DA conversion circuit, (20)
Is a master clock circuit, (26) is a frequency conversion circuit,
(73A) (73B) is PCM playback head, (74A) (74B) is PCM
It is a variable speed reproducing head.

Claims (1)

[Claims] 1. A first head for recording / reproducing a video period of a video signal, and a second head for recording / reproducing a period other than the video period.
Recording on the magnetic tape which is obliquely transferred on the peripheral surface of the rotary drum and is divided into two parts in the width direction by the first head. In a video tape recorder provided with a third head which performs reproduction and recording / reproduction by the second head, and which is capable of tracking correction and reproduces a signal in the video period, it corresponds to the second head. When recording / reproducing a PCM signal with the head, the fourth head corresponding to the second head corresponding to the reproduction with the first head and the third head corresponding to the reproduction with the third head. A fifth head corresponding to the second head is provided, and the magnetic tape is transferred at a speed different from that for recording to reproduce the video period by the third head, and the fourth and the fourth heads are reproduced. 5 The PCM signal reproduced by the head on the side where the tracking is the same in the head is sequentially demodulated, and the demodulated signal is read with a clock having a frequency different from that at the time of recording corresponding to the above different speeds. Video tape recorder.