JPH0770007B2 - 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 provides a reproducing head for a PCM audio signal in the case of recording and reproducing a PCM audio signal in place of a synchronous signal in a so-called synchronous track in a video tape recorder called SMPTE-C format, for example. The recording head is provided ahead of the recording head by the time required for the recording / reproducing process so that the signal reproduced by the reproducing head can be discriminated and an alarm signal can be issued during recording. [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. 3 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. 4 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. 5 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 in the latter half of the field [1], and then output to the recording heads (50A) (50B). 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. 6 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 video tape recorder using the magnetic recording as described above, since the tape can be reused, the tape used for recording is not necessarily so-called new. In that case, if the tape is re-recorded by mistake on the tape on which the necessary material images and the like are recorded, the necessary images and the like may be erased, and an accident may occur irretrievably. However, according to the conventional technique, in order to check such recording, it is necessary to perform reproduction once, and even if so-called fast-forward reproduction is performed, an extremely long time is required. On the other hand, in the above-described video tape recorder for recording / reproducing a PCM audio signal, a reproducing head is provided at a position preceding by a predetermined field for reproducing the PCM audio signal. The present application focuses on this point. [Problems to be Solved by the Invention] As described above, in the conventional technique, the contents of the previous recording on the tape cannot be known at the time of re-recording, and it takes a very long time to check this. There was a problem such as this. [Means for Solving the Problems] The present invention has a rotary drum provided with a first head for recording a video period of a video signal and a second head for recording a period other than the video period. Then, the recording by the first head and the recording by the second head are performed on each part of the magnetic tape, which is diagonally transported on the peripheral surface of the rotary drum, divided into two in the width direction. In a video tape recorder adapted to be performed, a recording process including AD conversion and time base compression of an audio signal to a head (7A) (7B) corresponding to the second head (encoder (4))
In the case of performing recording by supplying the PCM audio signal, the time required for the recording process at the time of recording and the recording process at the time of reproduction from the head corresponding to the second head on the rotary drum. A third head (9A) (9B) is provided at a position preceding by more than the time required for the reproduction processing (decoder (12)) including the corresponding time axis expansion and DA conversion, and the third head is used at the time of reproduction. The reproduction signal from the head is reproduced to reproduce the audio signal, and the level of the signal reproduced by the third head during recording (envelope detection circuit (15)) and presence / absence of the PCM audio signal ( Decoder (12))
Discriminating (circuit (18)) to output a warning signal (terminal (19)) based on at least the presence / absence of normal signal recording and the presence / absence of the PCM audio signal. [Operation] According to this, since the signal previously recorded is reproduced by the head that preceded at the time of recording, it is possible to easily generate the alarm signal by discriminating this. [Embodiment] In FIG. 1, an analog audio signal supplied to an input terminal (1a) is supplied to an AD conversion circuit (2a), converted into digital data, and digitally supplied to an input terminal (1d). The audio signal is supplied to the IO circuit (2d). Then, the signals from these circuits (2a) and (2d) are selected by the switch (3) and supplied to the encoder (4), and predetermined rearrangement, redundant bit addition, etc. are performed to form a PCM audio signal. It This PCM audio signal is supplied to the modulation circuit (5) to be a predetermined recording signal, and is passed through the recording amplifier (6).
It is supplied to the PCM voice recording heads (7A) and (7B) and recorded on the tape (8). Further, the video signal supplied to the input terminal (21) is supplied to the recording circuit (22) to be a predetermined recording signal, and this signal is passed through the recording amplifier (23) and the recording side contact of the recording / reproducing changeover switch (24). Supplied to the video recording / playback head (25),
Recorded on tape (8). Furthermore, the signal reproduced from the recording / reproducing head (25) from the tape (8) is supplied to the reproducing circuit (27) through the reproducing side contact of the switch (24) and the reproducing amplifier (26), and the reproduced video signal is output terminal. Taken out at (28). In addition, the signal from the head (9A) (9B) is reproduced by the playback amplifier (1
0) to the demodulation circuit (11). The PCM audio signal demodulated by this is supplied to the decoder (12), and error correction, rearrangement and the like are performed. And the digital data from this decoder (12) is converted to DA converter (13
a), the converted analog audio signal is taken out to the output terminal (14a) and the digital data is transferred to IO.
It is taken out to the output terminal (14d) through the circuit (13d). Further, the signal from the reproduction amplifier (10) is supplied to the envelope detection circuit (15), the detected envelope signal is supplied to the latch circuits (16A) and (16B), and the reproduction of the heads (9A) and (9B) is performed. The latch pulse corresponding to the period is transmitted through the terminals (17A) (17B) to the latch circuit (16A) (1
6B). The signals from the latch circuits (16A) and (16B) are supplied to the discrimination circuit (18), and at the same time, an error indicating uncorrectable corresponding to the signals from the heads (9A) and (9B) from the decoder (12). The signal is supplied to the discrimination circuit (18), and the signal discriminated here is taken out to the output terminal (19). In this device, the PCM audio playback head (9A) (9A
B) is about, for example, about the recording heads (7A) (7B) It is provided ahead of the field. Therefore, by operating the playback system below this head (9A) (9B) during recording, this head (9A) (9B) can reproduce the signal of the previous recording on the tape before recording. Therefore, the previously recorded signal can be discriminated. That is, in the time chart of FIG. 2, FIG. A shows a reproduced signal from the reproducing heads (9A) and (9B), and this signal is supplied to the envelope detection circuit (15) so that the envelope as shown in FIG. To be detected. This envelope signal is supplied to the latch circuits (16A) and (16B),
The latch pulse as shown in Figure C is the circuit (16A) (16B)
Is supplied to the latch circuits (16A) and (16B), and a latch signal as shown in FIG. On the other hand, in the decoder (12), decoding is performed as shown in FIG. 8E, and at the end of this decoding period, the head (9A)
When the reproduced demodulated data from (9B) has many errors and cannot be corrected, an error signal is generated for each head (9A) (9B) as shown in FIG. The error signal from the decoder (12) and the latch signal from the latch circuits (16A) and (16B) are discriminated by the discrimination circuit (1
The signal supplied to 8) and previously recorded is discriminated. That is, in the discrimination circuit (18), discrimination is made, for example, at time point t ₀ after the latch signal and the error signal for the same reproduction signal are aligned, and if both latch signals are low potential at this time, they are recorded first. It is determined that there is no signal. When both the latch signals have a high potential and the error signals have a low potential, it is determined that the previously recorded signal is a signal including a PCM audio signal. Further, when the latch signals are both high potentials and the error signals are also high potentials, it is determined that the previously recorded signal is a signal including a conventional synchronization signal. In the above-mentioned device, even if the tape on which the signal including the PCM audio signal is recorded is normally managed, the tape on which the signal including the conventional sync signal is recorded may not be managed well. Conceivable. Therefore, when the discrimination circuit (18) further discriminates the signal including the PCM audio signal, the recording is allowed as it is, and only when the signal including the synchronization signal is discriminated, the alarm signal is generated and the recording is further stopped. Processing can be performed. Further, in the above-mentioned device, when only one of the latch signals has a high potential, it is considered that one of the error signals is discriminated to discriminate the recording and that the other head is clogged. In this case, when one of the rotary heads is clogged, the other heads are also in a state close to that, so it is necessary to perform cleaning of the heads. Further, when the latch signals are both high potential, one of the error signals is low voltage and the other is high potential, it is determined that the signal includes the PCM audio signal, and the head on the other side is attenuated in the high frequency range. This means that the head has reached the end of its life, and it is possible to perform processing such as replacement of all the heads as described above. [Effect of the Invention] According to the present invention, since the previously recorded signal is reproduced by the head that precedes the recording, it is possible to easily generate the alarm signal by discriminating the reproduced signal. .

[Brief description of drawings]

FIG. 1 is a block diagram of an example of the present invention, FIG. 2 is a diagram for explaining the same, and FIGS. 3 to 6 are diagrams for explaining the video tape recorder previously proposed. (4) is an encoder, (7A) and (7B) are PCM audio recording heads, (9A) and (9B) are PCM audio reproducing heads, (12) is a decoder, (15) is an envelope detection circuit, and (18) is a discrimination circuit. , (19) are output terminals.

Claims (1)

[Claims] 1. A rotary drum provided with a first head for recording a video period of a video signal and a second head for recording a period other than the video period, and a peripheral surface of the rotary drum. A video tape recorder in which recording by the first head and recording by the second head are respectively performed on each portion of the magnetic tape that is diagonally transported and divided into two in the width direction. In the case of performing recording by supplying a PCM audio signal that has been subjected to recording processing including AD conversion and time base compression to an audio signal corresponding to the second head, A head equivalent to the head precedes by a time equal to the sum of the time required for the recording process at the time of recording and the time required for the reproduction process including the time axis extension and DA conversion corresponding to the recording process at the time of reproduction. 3rd in position A head is provided, and when reproduced, the reproduction signal from the third head is subjected to the reproduction processing to reproduce the audio signal, and at the time of recording, the level of the signal reproduced by the third head and the presence or absence of the PCM audio signal. Is a video tape recorder capable of issuing an alarm signal based on the presence or absence of recording of a normal signal and the presence or absence of the PCM audio signal.