JPS62175907A - Video tape recorder - Google Patents

Abstract

PURPOSE:To know in a short time the contents of the previous recording on a tape at the time of re-recording, by providing a reproducing head of a PCM sound signal in advance of a recording head by a time portion required for a processing at the time of recording and reproduction, and discriminating a signal which has been reproduced by this reproducing head so that an alarm signal can be generated, at the time of recording. CONSTITUTION:A figure A shows a reproducing signal from reproducing heads 9A, 9B, this signal is supplied to an envelope detecting circuit 15 and an envelope shown in a figure B is detected. This envelope signal is supplied to latching circuits 16A, 16B, and also, a latch pulse shown in a figure C is supplied to the circuits 16A, 16B, and a latch signal shown in a figure D is taken out from the latching circuit 16A, 16B. On the other hand, by a decoder 12, decoding is executed as shown in a figure E, and at the time point of the end of this decoding period, when many errors exist in a reproducing demodulated data from the heads 9A, 9B and cannot be corrected, an error signal is generated as shown in a figure F at every head 9A, 9B. Subsequently, the error signal from this decoder 12, and the latch signal from the latching circuits 16A, 16B are supplied to a discriminating circuit 18, and the previously recorded signal is discriminated.

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a videotape recorder for professionals used in broadcasting stations and the like. [Summary of the Invention] The present invention provides a method for recording and reproducing a PCM audio signal in place of a synchronization signal on a so-called synchronization track in a video tape recorder called, for example, the SMPTE-C format. , is provided ahead of the recording head by the time necessary for processing during recording and reproduction, so that during recording, the signal reproduced by this reproduction head can be discriminated and an alarm signal can be issued. [Prior Art] In a so-called SMPTE-C format video tape recorder, two heads are provided on a rotating drum, and this drum is rotated at a rate of one revolution per field. A magnetic tape is wound diagonally over nearly 360 degrees of the circumferential surface of the magnetic tape and is transported at a predetermined speed. The video period of the video signal is recorded on one of the two heads mentioned above, and the signal is recorded on the other head during the period when this head is separated from the magnetic tape (synchronization period). is being done. That is, FIG. 3 shows the recording pattern of the magnetic tape recorded in this manner. In the figure, the magnetic tape is divided into two parts in the width direction, and video period signals are recorded on diagonal tracks by one of the above-mentioned heads on the wide part, and the other head is recorded on the narrow part. The signal of the synchronization period is recorded on the diagonal track by the head. In addition, between these parts and on both side edges of the magnetic tape, there are control tracks recorded by fixed heads, respectively.
First, second and third audio signal tracks are provided. By the way, in such a format, if a so-called time base collector is used for the playback signal, even if the synchronization period signal is lost, as long as the video period signal is obtained, the regular video signal can be reproduced without any problem. . Therefore, in the above format, it has been considered to record a digitized PCM audio signal in place of the synchronization period signal on a diagonal track in the narrow portion. That is, in the above-mentioned conventional format, audio signals are recorded in analog form using a fixed head, but such analog recording suffers from significant deterioration, especially when dubbing is repeated. On the other hand, if recording is done digitally, the problem of deterioration during dubbing will be solved. The applicant of the present application previously proposed a video tape recorder that took these points into consideration (Special Training No. 180257/1982). That is, FIG. 4 is a block diagram of the PCM signal system for this purpose, and in this block diagram, the input terminal (41)
The analog audio signal supplied to the AD conversion circuit (43) is supplied to the AD conversion circuit (43) through the 10 circuit (42) and converted into digital data. This data is supplied to the data bus (44). The data on this data bus (44) is stored in the memory (
45) and stored. Furthermore, the data stored in the memory (45) is supplied to an encoder (47) via a data bus (46), where it is encoded by adding a predetermined error correction code, rearranging, etc. The data from the memory (45) is then supplied to the modulation circuit (48), and a signal based on the modulated data is supplied to the recording head (50) through the recording amplifier (49) to synchronize the magnetic tape (51). Recording is performed on a diagonal track in a narrow portion corresponding to the track. Furthermore, during playback, from the tape (51) to the playback head (5
The signal reproduced in step 2) is supplied to the demodulation circuit (54) through the reproduction amplifier (53), and the recorded digital data is demodulated. This fit (circulated data) is supplied to the data bus (55) (56), and this data bus (
55) The data in (56) is supplied to the memory (45), and is also supplied to the first and second decoders (57), respectively.
(5B). Further, the address of the data detected by the demodulation circuit (54) is supplied to the memory (45) via the address bus (59). The data that has been subjected to predetermined sorting, error correction, and other decoding is transferred from the memory (45) to the data bus (45).
4). The data on this data bus (44) is supplied to the DA conversion circuit (60) and converted into an analog audio signal, and this signal is passed through the 10 circuit (42) to the output terminal (
61). Further, the signal from the digital signal input terminal (62) is supplied to the data bus (44) through the digital 10 circuit (63), and the signal from the data bus (44) is supplied to the data bus (44) through the digital 10 circuit (63).
Digital signal output terminal (64) through circuit (63)
It is taken out. Furthermore, during editing, data from other video tape recorders etc. is supplied to the editing control circuit (66) through the terminal (65), and data from this circuit (66) is supplied to the data bus (44). The control signal detected by the circuit (66) is sent to the memory (45) via the auxiliary bus (67).
). Furthermore, FIG. 5 shows a time chart of recording and reproducing operations of this apparatus. Vertical lines in the figure are field boundaries. In this figure, A is a recording operation, for example, a field

The signal AD-converted during the period [0] is encoded in the first half of the next field [1], compressed in the time axis and read out in the second half of this field (1), and sent to the recording head (50A) (50B). Recorded at. Note that recording is performed by dividing into two tracks. On the other hand, B is a reproduction operation, and for example, the signal reproduced by the reproduction head (52A) (52B) in the first half of field [-2] is transmitted from the second half of this field (-2) to the next field. It is decoded in the first half of [-1], then time-axis expanded in the period of the next field (0), DA converted, and extracted. Therefore, in the above-mentioned device, the same field

In order to extract the audio signal at [0], the playback head (528) (52B
) is provided three or more fields ahead of the recording heads (508) and (50B). That is, FIG. 6 shows the rotating drum viewed from above. In the figure, (71A) and (71B) are recording heads for audio signals, (72A) and (72B) are playback heads for checking recording of audio signals, (73A) and (73B) are playback heads for audio signals, and (74A) ( 74B> is an audio signal playback head when the video signal is played back at variable speed.Furthermore, (81) is a video signal recording/playback head, and (82)
(83) is a variable speed playback head for video signals, and (83) is an erase head for video signals. Here, there are a total of 8 heads for recording and reproducing audio signals, and 3 heads for video signals, for a total of 11 heads.
Providing a well-balanced head (particularly a recording/playback head (81) for video signals and a variable speed playback head (82))
This is not possible, for example, if the alignment is defined at 120 degrees by the SMPTE-C format standard. Therefore, as shown in the figure, a dummy rad (9
0), and a total of 12 heads are arranged at angles of 30 degrees. That is, in the figure, counterclockwise from the 3 o'clock position in the figure, the recording head (71A) (71B), the erasing head (71B),
83), recording/reproducing head (81) dummy head (90)
, playback head (72A) (72B), playback head (82), playback head ('73A) (74A)
(73B) (74B'') are arranged in this order.The head (72^) (72B) is the head (71A').
The head (71A') (71B) is provided with a step that is one track behind the head (71A') (71B) so as to trace the same track recorded by the head (71B). )
The head (74A) (74B) is provided with a step that is three tracks ahead of the head (71B), and the head (74A) (74B) is provided with a step that is one track behind the head (73A) (73B). As a result, appropriate tracking is performed for each recording track, and audio signals are also recorded taking into account the time delay of a predetermined field for the video signals recorded and reproduced by the heads (81) and (82). Playback occurs. However, in the video tape recorder using magnetic recording as described above, since the tape can be reused, the tape used for recording is not necessarily new. In this case, if the tape on which the necessary material images, etc. have been recorded is mistakenly re-recorded, the necessary images, etc. may disappear, resulting in an irreversible accident. However, in the conventional technology, in order to check such recording, it is necessary to perform playback once, and even if so-called fast-forward playback is performed, an extremely long time is required. On the other hand, in the above-mentioned video tape recorder for recording and reproducing PCM audio signals, a reproducing head is provided at a position preceding the PCM audio signal by a predetermined field. This application focuses on this point. [Problems to be solved by the invention] As mentioned above, in the conventional technology, it is not possible to know the contents of the previous recording on the tape when re-recording, and it takes an extremely large amount of time to check this. There were some problems, such as: [Means for Solving the Problems] The present invention has a rotating 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. The first head and the second head record on each part of the magnetic tape, which is diagonally transferred along the circumferential surface of the rotating drum, divided into two parts in the width direction. In a video tape recorder configured to perform recording processing, an audio signal is subjected to recording processing (encoder +41) including AD conversion and time compression and is supplied to the heads (7A) (7B) corresponding to the second head for recording. In this case, a head corresponding to the second head on the rotating drum calculates the time required for the recording process during recording, and the time axis expansion and DA conversion corresponding to the above recording process during playback. Regeneration processing (including
A third head (9^) (9B) is provided at a position that precedes the sum of the time required for the decoder (12)),
At the time of playback, the reciprocal signal from the third head is subjected to the playback processing to reproduce the audio signal, and at the time of recording, the third head
Distinguish the signal played by the head (circuit (18))
This is a video tape recorder that can output an alarm signal (terminal (19)). [Operation] According to this, since the signal previously recorded by the head that preceded during recording is reproduced, this can be discriminated and an alarm signal can be easily generated. [Example] In FIG. 1, an analog audio signal supplied to an input terminal (1a) is supplied to an AD conversion circuit (2a), where it is converted into digital data, and a digital audio signal is supplied to an input terminal (1d). The audio signal is supplied to 10 circuits (2d). The signals from these circuits (2a) and (2d) are selected by a switch (3) and supplied to an encoder (4), where they are rearranged in a predetermined manner, redundant bits are added, etc., and a PCM audio signal is formed. Ru. This PCM audio signal is supplied to a modulation circuit (5) and made into a predetermined recording signal, which is then passed through a recording amplifier (6) to a PCM audio recording head (7A).
(7B) and recorded on tape (8). In addition, the video signal supplied to the input terminal (21) is supplied to the recording circuit (22) and made into a predetermined recording signal, and this signal is sent to the recording amplifier (23) and the recording/playback switch (24).
The video signal is supplied to the video recording/reproducing head (25) through the recording side contact point of the video recording head (25), and is recorded on the tape (8). Furthermore, the tape (8) is played back using the recording/playback head (25).
The generated signal is supplied to the reproduction circuit (27) through the reproduction side contact of the switch γ(-(24) and the reproduction amplifier (26), and the reproduced video signal is taken out to the output terminal (28). Signals from the heads (9A) and (9B) are supplied to the demodulation circuit (11) through the reproduction amplifier (10).As a result, the 1!L modulated PCM audio signal is supplied to the decoder (12), which performs error correction and Then, the digital data from the decoder (12) is supplied to the DA conversion circuit (13a), the converted analog audio signal is taken out to the output terminal (14a), and the digital data is sent to the 10 circuits. (13d) to the output terminal (14d). Furthermore, the signal from the reproduction amplifier (lO) is supplied to the envelope detection circuit (15), and the detected envelope signal is supplied to the latch circuit (16A') (16B). At the same time, latch pulses corresponding to the playback periods of the heads (9A) and (9B) are applied to the terminals (17A) (
17B) through the latch circuit (16A) (16
B). This latch circuit (16A)
(16B) is supplied to the discrimination circuit (18), and each head (9^) from the decoder (12)
Corresponding to the signal from (9B), an error signal indicating uncorrectability is supplied to the discrimination circuit (18), and the signal discriminated here is taken out to the output terminal (19). Then, in this device, go to PCM audio playback.
A) (9B) is the recording head (7A) (7B)
For example, it is provided in advance by about 3 fields. Therefore, when recording, this head (9A) (9B)
By operating the following playback system, this head (9
A) In (9B), the previously recorded signal on the tape before recording can be reproduced, and thereby the previously recorded signal can be discriminated. That is, in the time chart of FIG. 2, A in the same figure shows the reproduction signal from the reproduction head (9^) (9B),
This signal is supplied to the envelope detection circuit (15) to detect the envelope as shown in Figure B.This envelope signal is supplied to the latch circuit (16^) (16B), and the envelope as shown in Figure B is detected. A latch pulse as shown in is supplied to the circuit (16^) (16B), and the latch circuit (
16A) A latch signal as shown in the figure is taken out from (16B>. On the other hand, the decoder (12) performs decoding as shown in figure E, and at the end of this decoding period, the head (9A)
) When the reconstructed 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 launch signal from the latch circuits (16A) (16B) are then supplied to a discrimination circuit (18) to discriminate the previously recorded signal. That is, in this discrimination circuit (18), discrimination is performed at a time point t after the latch signal and error signal for the same reproduced signal are together, and if both the latch signals are at low potential at this time, it is determined whether the latch signal and error signal for the same reproduction signal were recorded first. It is determined that there is no signal. Further, when both the latch signals are at high potential and both the error signals are at low potential, it is determined that the previously recorded signal is a signal containing a PCM audio signal. Further, when both the latch signals are at high potential and the error signals are both at high potential, it is determined that the previously recorded signal is a signal containing a conventional synchronization signal. In the above-mentioned apparatus, even if tapes on which signals including PCM audio signals are recorded are properly managed, tapes on which signals including conventional synchronization signals are recorded may not be managed properly. Conceivable. Therefore, when the discrimination circuit (18) further discriminates a signal containing a PCM audio signal, recording is permitted as is, and
It is possible to perform processing such as generating an alarm signal and stopping recording only when a signal including a synchronization signal is determined. In addition, in the above-mentioned device, if only one latch signal has a high potential, recording is determined by determining the error signal on one side, and it is also possible that the head on the other side is clogged. In this case, when one of the rotating heads becomes clogged, the other heads are also in a similar state, so it is necessary to clean the heads. Furthermore, when both latch signals are at high potential, one error signal is at low potential, and the other is at high potential, it is determined that the signal includes a PCM audio signal, and high-frequency attenuation is applied to the other side's navel and do. This means that the head has reached the end of its lifespan, and it is possible to perform a process such as replacing all the heads as described above. [Effects of the Invention] According to the present invention, since the signal recorded earlier by the head that preceded during recording is reproduced, it has become possible to discriminate this and easily generate an alarm signal. .

[Brief explanation 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 previously proposed video tape recorder. (4) is encoder, (7A) (7B) is PCM audio recording head, (9A) (9B) is PCM audio playback head, (12) is decoder, (15) is envelope detection circuit, (18) is discrimination circuit , (19) are output terminals. Fig. 0 of the a-claw side of He-Uba; 70-tsuk diagram of the PCM series

Claims (1)

[Scope of Claims] A rotating 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; on the magnetic tape that is being transferred diagonally.
In a video tape recorder in which recording is performed by the first head and recording by the second head in each divided portion, an audio signal is sent to the head corresponding to the second head.
When recording is performed by supplying a recording process including conversion and time axis compression, a head corresponding to the second head on the rotating drum calculates the time required for the recording process during recording and the time required for playback. A third head is provided at a position that is at least the sum of the time required for playback processing including time axis expansion and DA conversion corresponding to the above-mentioned recording processing of time, and the playback signal by this third head is The above-mentioned playback processing is performed to play back the above-mentioned audio signal, and at the time of recording, the above-mentioned third
A video tape recorder that can distinguish the signals played by the head and issue an alarm signal.