JPS6260175A - Video tape recorder - Google Patents

Abstract

PURPOSE:To attain the accurate record and reproduction of PCM signals by supplying the video signals and the PCM sound signals produced with the sampling frequency asynchronous with those video signals for each prescribed number of fields in case the PCM signals are recorded and reproduced by a video tape recorder in place of the synchronizing signals and completing a format within said prescribed field unit. CONSTITUTION:The 1st head which records and reproduces a video period of video signals to a rotary drum is provided to a video tape recorder of an NTSC color system together with the 2nd head which record and reproduces the periods excluding the video period. Then a magnetic tape fed obliquely is divided in two parts in its width direction and these two tape parts have contacts with the 1st and 2nd heads respectively. In such a constitution, at every four fields are divided into 50 blocks for each unit of 200 fields when the PCM signals having a 44.1kHz sampling frequency is recorded and reproduced by the 2nd head. Then each field of an optional block consists of 735 samples. While other 49 blocks contain three fields of 736 samples and a single field of 735 samples.

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, for example, in a video tape recorder called SMPTE-C type format, when a PCM audio signal is recorded and played back in place of a synchronous signal on a so-called synchronous track, a sampling frequency that is asynchronous with the video signal is used. By formatting the formed PCM audio signal in units of a predetermined number of fields so as to be completed within each field, asynchronous PCM audio signals can be recorded and reproduced favorably. [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 rotation per field. A 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 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 signals for the video period are recorded on diagonal tracks by one of the above-mentioned heads on the wide part, and the signals of the video period are recorded on the diagonal tracks in the narrow part. The signal of the synchronization period is recorded on the diagonal track by the head. Note that between these portions and on both side edges of the magnetic tape, there are provided a control track and first, second, and third audio signal tracks recorded by fixed heads, respectively. 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 conventional formant described above, the audio signal is recorded in analog form using a fixed head, but in such analog recording, the deterioration is significant 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 has previously developed a video tape recorder that takes these points into consideration. That is, FIG. 4 is a block diagram of a PCM signal system for this purpose. In this block diagram, an analog audio signal supplied to an input terminal (11) is supplied to an AD conversion circuit (3) through a 10 circuit (2), The data is converted into digital data. This data is supplied to the data bus (4). The data on this data bus (4) is supplied to the memo and stored therein. Furthermore, the data stored in the memo (January 5) is transferred to the data bus (
6) to the encoder (7), where the encoder (7) performs encoding such as addition of a predetermined error correction code and rearrangement. The data from the memory (5) is sent to the modulation circuit (8).
A signal based on the modulated data is supplied to the recording head (10) through the recording amplifier (9), and is applied to the diagonal track in the narrow portion of the magnetic tape (11) corresponding to the above-mentioned synchronous track. recorded. The configuration of the rotating drum on which the recording head (10) is provided is shown in FIG. In the figure, the drum is rotated clockwise, and 12 (m) heads are provided on its periphery at angular intervals of 30 degrees.The digital audio signals are recorded and reproduced by, for example, two heads. Counterclockwise from the position, the audio signal recording head (10^) (IOB>video signal erasing head (31), the video signal recording/playback head (32)
), dummy head (33), audio signal recording/recognition playback head F (34A) (34B), video signal variable speed playback head (35), audio signal one playback head (36^), variable speed One reproduction head (37A) for audio signals for reproduction, and the other corresponding heads (36B) and (37B) are provided. Furthermore, during playback, from the tape (11) to the playback head (1
2) ((34A) (34B) (36A)
(36B) (37A) (37B)) The signal reproduced by the demodulation circuit (13) passes through the reproduction amplifier (13).
4) and the recorded digital data is demodulated. This tlUM data is transferred to the data bus (15)
, (16) and this data bus (15)
(16) data is supplied to Memo January 5), and
The signals are supplied to first and second decoders (17) and (18), respectively. Further, the address of the data detected by the demodulation circuit (14) is transferred to the memory (5) via the address bus (19).
). The data that has been subjected to predetermined rearrangement, error correction, and other decoding is supplied from the memory (5) to the data bus (4). The data on this data bus (4) is supplied to the DA converter circuit (20) to be converted into an analog audio signal, and this signal is taken out to the output terminal (21) through the 10 circuit (2). Further, the signal from the digital signal input terminal (22) is supplied to the data bus (4) through the digital 10' circuit (23), and the signal from the data bus (4) is supplied to the digital signal through the 10 circuit (23). It is taken out to the output terminal (24). Furthermore, during editing, data from other video tape recorders etc. is supplied to the editing control circuit (26) through the terminal (25), data from this circuit (26) is supplied to the data bus (4), and the circuit The control signal detected at (26) is supplied to the memo via the auxiliary bus (27). Furthermore, FIG. 6 shows a time chart of recording and reproducing operations of this apparatus. The vertical lines in FIG. 6 indicate 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 (108) (IOB ) is recorded. On the other hand, B is a playback operation, and for example, field [-2]
The signal reproduced by the playback head (36A) (36B) in the first half of is decoded from the second half of this field [-2] to the first half of the next field (-1),
Further fields

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

To extract the signal at [0], use the playback head (36A) (36B)
must be provided three or more fields in advance of the recording head (IOA) (IOB). In the case of the above-mentioned device, the mounting positions of the reproducing heads (36A) (36B) on the rotating drum are the recording head (IOA) (
Since it is 120 degrees ahead of IOB), the actual advance amount is 3-field. By the way, in such a device, the video signal system is NTS
When driven by the C color method, the field frequency is about 59.94Hz, and the sampling frequency rs, which is an integral multiple of this, is, for example, about 44.94Hz.
056kHz. On the other hand, many general PCM devices have an fs of 44.1 kHz. Therefore, such a signal is sent to the PC.
It was proposed to record up to an amount of M on the above-mentioned videotape recorder. However, in that case, since fs is not an integer multiple of the field frequency, a fraction will occur for each field during recording. It is conceivable that the fractional portion be recorded without being recorded, and that each be treated as a dropout during playback, but this may impair the quality of the playback signal due to the PCM signal. Also, using a so-called rate converter, rs can be changed to 44.
Although it is possible to convert from 1 kHz to 44.056 kHz, such a device would have a complicated circuit and would significantly increase the product price. [Problems to be Solved by the Invention] As mentioned above, in the conventional technology, when driven in accordance with the NTSC color system, it is difficult to record a PCM signal with a sampling frequency of 44.1 kHz well. There was a problem that it could not be done. Means for Solving Problems c] The present invention complies with the NTSC color system and includes a first head for recording and reproducing a video period of a video signal, and a second head for recording and reproducing a period other than the video period. The magnetic tape is diagonally conveyed along the circumferential surface of the rotating drum, and the magnetic tape is divided into two parts in the width direction. In a video tape recorder in which recording and reproduction are performed by the second head, the sampling frequency is 44.1kHz in the head corresponding to the second head.
When recording and reproducing a PCM signal of z, the unit is 200 fields, and these 200 fields are divided into 50 blocks of 4 fields each, and each field of any one block among these 50 blocks is composed of 735 samples. This is a video tape recorder in which each field of the other 49 blocks is composed of three fields of 736 samples and one field of 735 samples (FIG. 1). [Operation] According to this, all the samples can be recorded by predetermined formatting, so that recording and reproduction of asynchronous PCM signals can be performed satisfactorily and accurately. [Example] By the way, the above-mentioned PCM signal with rs of 44.1k) Iz has one field period (approximately □59.
94 seconds) has a PCM signal of 735.735 samples. Therefore, when considering a 200 field period, the number of samples is 147,147 samples, which is an integer. Therefore, as shown in Figure 1A, 200 fields are divided into 50 blocks of 4 fields each.
For example, all four fields of the first block [1] are composed of 735 samples, and the other blocks [2] to
In [50], the first field is formed to have 735 samples, and the other three fields are formatted to consist of 736 samples. This will result in 200
The total number of samples after the field has passed is 1471.
There are 47 samples, and all the samples can be recorded on the tape. The PCM signal supplied for this purpose has 735.735 samples per field, as shown in FIG. Therefore, in the first field of the first block [1], only 735 samples are recorded out of the supplied 735.735 samples, so for this fraction of 0.735 samples, the memory for 1 sample is used to store 2 For field 2, the memory for 2 samples is used to carry over to field 3 for a total of 1.47 samples of the carryover and the fraction in this field, and for field 3, a total of 2.235 samples. The memory for 3 samples is used to carry over to the 4th field, and in the 4th field, the memory for 3 samples is used for a total of 2.94 samples to carry over to the second block (
Carry over to 2). Furthermore, in the first field of block [2], the memory for 4 samples is used for 3.675 samples, which is the sum of the carryover portion and the fraction in this field, and the samples to be recorded in the field 2 are carried over to field 2. Since the number of samples is 376, the memory for 4 samples is used for the 3,41 samples that are reduced from the carryover and carried over to the field 3, and in the field 3, the memory for the 3,145 samples that was also reduced is Then, the memory for 4 samples is used to carry over to the 4th field, and in the 4th field, the reduced 2.88 samples are carried over to the third block [3] using the memory for 3 samples. Thereafter, the carryover amount is reduced by 0.06 samples for each block, and in field 4 of the 500th block [50], the carryover amount becomes O. In this way, "S is a PCM signal of 44.1kHz
It can be recorded on a video tape recorder driven by the TSC color system. In this case, formatting can be performed extremely easily by simply using a memory containing 736 samples for one field plus 4 samples. Furthermore, FIG. 2 shows an example of a signal flow when performing the above-described formantization. In the figure, a video signal supplied to an input terminal (50) is supplied to a recording circuit (51), modulated into a predetermined recording signal, and then passed through a recording/reproducing switch (52) to a video signal recording/reproducing head (32). supplied to In addition, the signal reproduced by the head (32) is transferred to the switch (5).
2) to a reproduction circuit (53), and a predetermined demodulated video signal is taken out to an output terminal (54). Furthermore, during recording, synchronization signals etc. from the recording circuit (51) are supplied to the servo circuit (55), and the drum motor (56)
etc. are synchronously controlled. On the other hand, the "S" supplied to the input terminal (22) is 44.1kHz.
The PCM audio signal of z is supplied to the memory (60), and the clock signal in this signal is supplied to the address control circuit (61), so that each sample with fs of 44.1kHz is sequentially written to the memory (60). be included. Further, the signal previously reproduced by the reproduction head (36A') <36B) is supplied to the field number detection circuit (63) through the reproduction circuit (62), and the field number of the track to be recorded is determined from the detected field number. It is calculated and supplied to the address control circuit (61). This causes 735 or 736 samples per field to be sequentially read from memory (60) from this field number according to the format described above. This read sample is passed through the recording circuit (64) to the recording head (I).
OA) (10B). Further, during reproduction, the signal from the reproduction circuit (62) is supplied to the memory (65), and the field number from the detection circuit (63) is supplied to the address control circuit (66), and each field is divided according to the above-mentioned format. 735
Or 736 samples are written sequentially. Furthermore, the terminal (
The 44.1kHz clock signal supplied to the address control circuit (67) is supplied to the address control circuit (66), and the PCM signal read out in synchronization with this clock signal is sent to the DA conversion circuit (68).
The signal is converted into an analog audio signal and taken out to an output terminal (21). Note that the memories (60) and (65) actually correspond to 1 (which may be fixed, as in the memo January 5 of the block diagram mentioned above). Also, when editing, etc., if a PCM signal formatted as described above is input, it is only necessary to carry over the samples according to the field number, and in this case, the memory for 3 samples is extra. It's enough. Furthermore, if an effect such as a cross-fade is used at the editing point, the three samples carried over may be removed. [Effects of the Invention] According to the present invention, all samples can be recorded by predetermined formatting, so that asynchronous PCM
It has become possible to record and reproduce signals with good quality and accuracy.

[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 conventional technology. (IOA) (1OB) is the recording head, (11) is the magnetic tape, (21) is the audio output terminal, (22) is the PCM input terminal, (36A) (36B) is the playback head, (
6o) (65) is a memory, (61) (66) is an address control circuit, (62) is a reproduction circuit, (63) is a field number detection circuit, (64) is a recording circuit, (67) is a clock signal, ( 68) is a DA conversion circuit.

Claims (1)

[Scope of Claims] A rotating drum conforming to the NTSC color system and provided with a first head for recording and reproducing a video period of a video signal and a second head for recording and reproducing a period other than the video period. The first head records and reproduces data, and the second head records and reproduces information on each part of the magnetic tape that is diagonally conveyed along the circumferential surface of the rotating drum. In a videotape recorder configured to perform the following steps, when recording and reproducing a PCM signal with a sampling frequency of 44.1 kHz using a head corresponding to the second head, the unit is 200 fields. Divide the field into 50 blocks of 4 fields each, each field of any one of these 50 blocks consists of 735 samples, and each field of the other 49 blocks consists of 7 samples.
A video tape recorder constructed of three fields of 36 samples and one field of 735 samples.