JPS639379A - Magnetic recorder - Google Patents

Abstract

PURPOSE:To enjoy a still picture of very high picture quality well worthy of looking by extracting 1 unit picture such as 1 frame or 1 field of moving picture and making PCM still picture recording of it while recording moving picture. CONSTITUTION:PCM still picture recording is made at a period of 240 frames such as frame pictures F1, F241..., or, at a period of 8 seconds. When PCM still picture recording of a frame picture F1 is terminated thus, next still picture frame cycle TC is started, and here, a frame picture F241 is PCM still picture recorded over 420 continuous PCM tracks. Thus, as 1 frame of moving picture is PCM recorded automatically at a fixed period while photographing of the moving picture is being made, when the picture is reproduced later and projected on a television picture or a hard copy is made, a reproduced still picture of very high picture quality that can be comparable with, though not equal to, a silver salt photograph can be enjoyed.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a magnetic recording device such as a video tape recorder (VTR), and in particular to a magnetic recording device having a simple configuration and a high-quality still image recording function. Regarding equipment.

(Prior art) Recently, cameras and V
A so-called camera-integrated VTR that incorporates a TR is gaining popularity.

After all, this type of camera-integrated VTR is small!
! Its feature is its large size, making it suitable for carrying around on trips or sports days for video manipulation, but various improvements have been made in terms of image quality to the point that it is sufficient for general use.

For example, the image pickup tube and image sensor, which are said to be the heart of a video camera, are becoming more sensitive and have higher resolution.
In this case, the number of pixels has increased to about 250,000, the resolution has been improved by about 30%, and smear and moire phenomena have been reduced.

Regarding circuits, efforts have been made to improve the S/N ratio by improving emphasis circuits and comb filters.

Furthermore, since the camera and VTR are directly connected, a circuit that mixes the luminance signal and chrominance signal and a circuit that separates both signals are omitted, so the bands of the luminance signal and chrominance signal are no longer compressed, and the resolution increases. There is also the advantage of improved color reproducibility that is unique to integration.

By the way, when taking video, it is common to take videos of moving people or objects, and it is rare to actively take pictures of still things.In fact, when playing back, you only want to take a single frame of the video that you think is important. I often view still images by playing them back.

When playing still images on a VTR, image blur and noise appear, but this is a tracking error phenomenon that occurs because the head does not accurately trace the video track where the image to be played is recorded. However, recently, playback heads specifically designed for still images have been installed to reduce blur and noise.

In recent years, video printers that convert video images into hard copies have been developed, so it is thought that the ability to easily print and enjoy video still images will become popular.

(Problem to be solved by the invention) However, unlike videos, still images have considerably high image quality because the information contained in a single image that does not change over time is viewed as visual information. is required. Therefore, if the reproduced video signal contains jitter, dropouts, etc., image deterioration phenomena such as shaking, distortion, color unevenness, and noise may appear in the image, and the still image may not be able to withstand close attention. Moreover, when such still images are hard-copied, the low image quality becomes even more noticeable.

Therefore, video, especially camera-integrated VT as mentioned above,
Although the popularity of R has been remarkable, it is still far from as good as silver halide photography in terms of image quality, and users prefer VTRs with built-in cameras or portable separate cameras for video shooting, and silver halide still cameras for still images. It is used differently,
Sometimes they are forced to carry both a video camera and a still camera.

Therefore, if we consider the video system by dividing it into the imaging system, the recording system, and the computer copy system, we can see that in the imaging system, the development of 400,000 pixel CCD is progressing, and the appearance of the CCD is likely to be imminent, as well as the hard copy system. The image quality of these systems has recently improved considerably, and it is only a matter of time before it reaches a level that is satisfactory for practical use. Therefore, the remaining recording system is the starting point, and although various signal processing circuits have been developed or improved to improve image quality, still images of high quality sufficient for viewing have not been obtained.

In view of these problems, an object of the present invention is to provide a magnetic recording device that records high-quality still images by extracting one unit image of the moving image at regular intervals while recording the moving image. do.

By the way, if you just want to add a still image recording function,
Since various still image recording devices are available, it is easy to incorporate them into video, and in fact, such attempts have been made to date.However, they all involve significant weight and price. In other words, in order for a video with a still image recording function to become popular among general users, it is necessary to support higher image quality, but it also requires an increase in weight. A magnetic recording device that satisfies such requirements has not yet been realized.For example, it should not require a mechanism or increase the cost significantly.However, a magnetic recording device that satisfies such requirements has not yet been realized.

Therefore, another object of the present invention is to realize a magnetic recording device that can record high-quality still images with little increase in weight and at low cost, in order to provide a well-balanced and popular product. There is a particular thing.

(Means for Solving the Problems) The configuration of the present invention that achieves the above object is such that a magnetic tape travels in a state in which it is wound diagonally at a predetermined angle around a cylinder to which a rotating magnetic head is attached, and the magnetic head is attached to the magnetic tape. In a helical scanning magnetic recording device in which the analog video signal of a moving image is recorded for one unit image such as one field or one frame each time the top is scanned diagonally, the time is divided into a part of one scanning period of the magnetic head. A means for recording a PCM still image is provided, and the PCM still image recording means includes a means for converting an analog video signal of a moving image into a digital video signal, and a means for capturing a digital video signal for one unit image at a fixed period. means for extending the time axis at a predetermined rate; and means for converting the time axis expanded digital video signal for one unit image into a PCM signal and recording it over a plurality of consecutive head scanning periods at a constant cycle. , is characterized by.

(Function) In the present invention, a moving image and a still image are recorded together in a time-divided manner each time the magnetic head scans the magnetic tape. Moving images are magnetically recorded in the form of analog video signals as usual, but still images are magnetically recorded in the form of PCM signals.

Such a still image is given as one unit image of a moving image, for example, one frame, and is obtained by being extracted from the moving image at a constant period.

The extracted digital video signal for one unit image is time-axis expanded at a predetermined rate, and then transferred to a PC by a predetermined amount.
It is recorded in a part of the head scanning period in the form of an M signal, and a plurality of head scanning periods are responsible for recording the entire one unit image.

Then, once one PCM still image is recorded, one unit image of the moving image is extracted again, and that one unit image is recorded as a PCM still image on the same magnetic tape via the same magnetic head in time division as the moving image recording. The image will be recorded.

In this way, when a moving image is recorded for a certain period of time, a portion (one frame) of the moving image is recorded as a PCM still image at regular intervals during that time.

The reproduced still images obtained from the PCM still image recording of the present invention are not affected by time hash errors due to jitter components due to PCM recording, and are resistant to dropouts and other characteristic deterioration, so they have extremely high image quality and are sufficient for viewing. It is durable and has excellent storage stability.

(Embodiment) An embodiment in which the present invention is applied to an 8 mm video will be described below with reference to FIGS. 1 to 5.

S1 Video format First, the 8 mm video format will be outlined with reference to FIGS. 4 and 5.

As is well known, 8mm video is produced by the ``8mm Video Conference''.
The main differences from the conventional VH5 system and β system are the narrower tape width, audio signal recording method, and tracking method.

FIG. 4 shows the track arrangement on a magnetic tape for 8 mm video. The tape width is 8 mm, and the material is coated or vapor-deposited metal tape. Each track is formed diagonally on the magnetic tape by helical scanning in the same manner as before, but on the extension of the video track TRV, which corresponds to a period of 180° head scanning, a PCM) rack corresponding to a period of 36° head scanning is formed. TRP is provided. Each video track TRV has a video signal (V 1deo)
is recorded using the low-pass conversion color difference signal recording method as in the past, and the FM audio signal (AF'M) and the traversing pilot signal (TPS) are recorded in a frequency multiplex manner. On the other hand, in each PCM rack TRP, an audio signal is time-compressed and recorded in PCM, and a tracking pilot signal (TPS) is superimposed and recorded. However, this PCM recording is treated as an option, and dubbing (after recording) is also possible.

As shown in FIG. 5, the PCM track TRP is usually 18
A drum wrap of o° is obtained by increasing the angle by 36°. As you can see from the head position in this figure, one video node CH-1 is connected to video track TRY.
When recording ends, the other video head CH-2 performs PCM recording on the next PCM track TRP.

Again in FIG. 4, a cue track TRQ for recording a cue signal and an audio track TRA for recording an after-recording audio signal, each using a fixed head, are optionally provided on both the upper and lower sides of each scanning track TR.

The tracking pilot signal (TPS) is based on the automatic track Φ finding (ATF) method, and TPS of four different frequencies f1 to f4 selected within the band of approximately 100kHz to 160kHz are sequentially sent to each scanning track TR. recorded. Then, during reproduction, a tracking servo is applied so that head displacement is detected based on the frequency difference between the TPSs on both sides and accurate tracing is performed. Therefore, in 8 mm video, fixed head type control tracks are not provided.

The 8mm video format has been outlined above, but according to this embodiment, as will be described later, a part of the video is recorded as a PCM still image on the 8mm video PCM rack TRP. PCM still image recording is performed in almost the same PCM format as PCM audio recording. In this way, the PCM encoder for PCM audio is used as is for the still image recording function.

Real” L-in-law! Figure 1 shows the main configuration of the 8 mm video according to this embodiment.

In this figure, light from a subject passes through a lens 10 and forms an image on the imaging surface of a CCD 12.

The CCD 12 converts the image formed thereon into an electrical signal and stores it, and is driven by a drive circuit 14 to perform horizontal and vertical scanning and output a video signal. This video signal is supplied to the camera processing circuit 16, where it undergoes signal processing such as noise reduction and gamma correction.

From the camera process circuit 16, the luminance signal Y and the color signal C into which the synchronization signal S has been inserted are supplied to the modulation-recording circuit 18, where the luminance signal Y is FM modulated and the color signal C is FM-modulated.
The frequency is converted from 58 MHz to approximately 743 kHz and subjected to phase conversion (PI) processing at that time. The modulation/recording circuit 18 outputs a video signal Video which is a mixture of the FMrJ degree signal YFM and the low frequency conversion color signal Co. The signal is mixed with the AFM and sent to the magnetic head 28.3 via the changeover switch 25.26.
0 alternately with a field period.

Note that 20 is a microphone that provides the audio signal AU to the FM modulator 22.

The magnetic head 28.30 is attached to a slit 32a in the substantially center of the cylinder 32, and is driven to rotate by a spindle motor 34 at the same number of rotations as the frame frequency (30 rotations per second). A magnetic tape 36 is wound diagonally 221 degrees around the cylinder 32 and is run at a constant speed by a tape running mechanism such as a capstan.
30 alternately scans the magnetic tape 36 diagonally, and each time an analog signal such as a video signal Video is recorded on the video track TRY.

A magnet piece and a fixed head (not shown) are attached to the cylinder 32, and the fixed head connects the magnetic head 28.30.
A pulse PG representing the rotational phase of is generated, and this pulse P
G is applied to the servo circuit 38. The servo circuit 38 is
The pulse PG is the reference pulse P from the synchronization signal generation circuit 40.
Controls the spindle motor 34 so that the rotation of the head is synchronized with the reference pulse PS by comparing the phase with S, and
A servo is applied to the capstan motor 42 to keep the traveling speed of the magnetic tape 36 constant.

The servo circuit 38 also sends switch switching signals SW1. to SW1 to the switches 25 and 2θ, respectively. Give SW2.

The components described so far are standard equipment for 8mm video, and are almost common to the VH8 system and the β system.

Next, the PCM still image recording system of this embodiment will be explained. From the camera process circuit 16, a luminance signal Y and a color difference signal RY,
B-Y is output, and their analog signals Y, R-Y,
B-Y is, for example, 4 according to the component encoding method.
: A selection switch 50 with a sampling frequency having a 1:1 relationship. The signals are converted into digital signals YD1 (RY)D and (B-Y)D by A/D conversion 552.54. Therefore, in the case of 4:1:1 component encoding, the changeover switch 40 switches to the terminals 50a and 50b once each within a period in which the luminance signal Y is sampled four times, and thereby The color difference signals R-Y and B-Y are each sampled once. Such a switching operation of the changeover switch 50 is performed in response to a switching signal SQ from the synchronization signal generator 40. Further, a clock signal CL for sampling and A/D conversion is applied from the synchronization signal generator 40 to the A/D converters 52 and 54.

Here, the sampling frequency and the number of quantization bits in A/D conversion greatly affect the image quality, so they must be secured at a certain value or higher, and must be selected at least within the Nyquist band. The frequency is required to be 2 MHz or more, preferably 3 MHz or more, and the number of quantization bits is 5 or more bits for the luminance signal Y+S and 3 or more bits for the color difference signals RY and B-Y. However, as the number of bits increases, the processing circuit becomes more complex and the cost increases, so this must also be taken into consideration. In the case of this embodiment, since the digital data of the 8 mm video format is 8 bits, the quantization bits are selected to be 8 bits accordingly. The sampling frequency is
For example, the image quality specifications for still images are: ■The frequency characteristics of the luminance signal Y are almost flat up to 4.2MHz, ■The color difference signals R-Y, B
-Y frequency characteristics are set to be almost flat up to 1.0MHz, END of PASSBAND/5TART
of, 4.2X1.3X2:10.92M when using a filter with a 5TOPBAND ratio of 1:1.3
Selected to be H2-(+) or higher. By the way, in 8 mm video, the amount of data bits per field, ie, each PCM), the amount of data focus written in rank TRP is determined to be 1050 words (one word is 8 bits).

Therefore, in the PCM still image recording of this embodiment, each PCM
CM) If 18 minutes of the video signal is recorded in the PCM rack TRP, the sampling frequency fs for the luminance signal Y is 8 (3/2 ll ) =8X 1
From 050-(2), 700 fH(+11.OIM
Hz), which satisfies the condition (1) above.

In this case, the sampling frequency r s/4 for the color difference signals R-Y and B-Y is 175f (42,75MHz)
becomes. Also, since 2H of the video signal is recorded in PCM per one rotation of the cylinder 32, if the number of pre-scanning lines in one frame is 420, one frame (one frame) of image is recorded in PCM still image in 7 seconds. will be done.

Now, the digital signals YD, (RY)D, (B-Y)D output from the A/D converters 52 and 54 are written in one frame at a writing speed synchronized with the sampling frequency fs. It is input into memory 56. Then, when the magnetic head 28 or 30 scans the PCM rack TRP, 18 minutes of the video signal is recorded in the PCM rack TRP.
8 minute digital signal YD, (RY)D, (B-Y)
D is output from the frame memory 56 at a predetermined reading speed and supplied to a PCM encoder 68, which will be described later. In this way, in the frame memory 56, the digital signals YD,
18 minutes of (R-'Y)D and (B-Y)D are read out during a 36° forward scan period, and one frame is read out in a total of, for example, 7 seconds. , time axis expansion of the digital signal is performed. Note that such write/read operations of the frame memory 56 are controlled by a memory controller 58. The controller 58 is supplied with a clock signal CK from the synchronization signal generation circuit 40 and a control signal CT from the system controller 60.

PCM encoder 88 is commercially available for use with 8 mm video and provides error correction processing and modulation similar to that for PCM audio recording. That is,
An 8-word, 2-parity cross-interleave code is used as an error correction code, and an address, synchronization signal, parity, etc. are added to the data. A CRC code for error detection is also added. Note that the data includes an ID word for indexing in addition to the video signal. Therefore, in the case of this embodiment, this ID word may be used to locate the beginning of a still image, for example. In addition, a type of FM modulation called bi-phase modulation is used for modulation, and with this, the recording system after the PCM encoder 68 can mix analog signals and PCM signals.
It can be shared with signals.

Thus, the digital signals YD, (RY)D.

CB-Y)D is converted into a PCM signal with an error correction code added by the PCM encoder 68 for each IH, and recorded on the PCM track TRP of the magnetic tape 36 by the magnetic head 28.30 via the changeover switch 25.28. It is now possible to do so. In addition, the changeover switch 25.28 is
Switching signal SW1. from servo circuit 38. 1 by SW2
They are alternately closed during each head scanning period.

That is, when the head 28 scans the tape 36, the switch 25 is closed and the switch 26 is opened. Then, the switch 25 first starts the PCM recording period (PCM recording period).
M) During the rack scanning period), the terminal is switched to 25A and P is
The PCM signal from the CM encoder 68 is sent to the head 28, and during the next video recording period (video track scanning period), the terminal 25B is switched to send the analog video signal Video from the mixer 24 and the FM audio signal AFM to the head 28. send. Similarly, during the period when the head 30 scans the tape 36, the switch 26 is connected to the terminal 26A.

28B, while the switch 25 is in an open state.

The system controller 60 receives the system clock SC from the synchronization signal generation circuit 40 and also receives the system clock SC from the servo circuit 3.
It receives the head phase pulse PG from 8, gives instructions to the memory controller 58 to write and read data in the frame memory 56, and controls other parts of the system.

In addition, in FIG. 1, the tracking pilot signal (T
A circuit for recording PS) is omitted.

Actual "E Example 0 Work" L Next, referring to FIG. 2, the operation of PCM still image recording according to this embodiment will be explained.

In Fig. 2 (A), the images taken by the CCD 12 are Fl,
F2. F3. . . . This shows how a moving image is formed by changing frame by frame one after another. Each frame image Fl is, as described above, in the form of an analog video signal V [deo], which is transmitted through two consecutive video doors on the magnetic tape 36 shown in FIG.
T Rv+Ial T Rv, +bc;: Recorded.

Now, PCM still image recording according to this embodiment is performed at a constant period TC.
In FIG. 2, frame images Fl,
F241, . . . PCM still image recording is performed at an 8 second period in terms of 240 frames per hour.

First, the frame image Fl is taken into the frame memory 56 shown in FIG.

B-Y is converted into digital signals YD, (RY)D, and (B-Y)D at a predetermined sampling frequency and quantization bits, and the data is input to the frame memory 56. The above data input for one frame is performed under the control of the system controller 60.

The frame image Fl thus taken into the frame memory 56 is recorded over a plurality of consecutive PCM racks TRP, 1-TRP, J in the form of a PCM signal every IH after a predetermined period of time. In this example, the number of effective scanning lines is 42.
Since it is 0, there are 420 PCM) racks T R
P , 31a - T RP , 18 min PC in 240b
M signals Fl-PI to Fl-P420.6 (each recorded, and the recording time is 7 seconds. In addition, PCM) rack TRP, 3! 30 PCMs before a) Rack T
Still image data is not recorded in RP, Ia-TRP, and 30b (with a lapse of 1 second), but header HE, control data CD, etc. are recorded.

In this way, when the PCM still image recording of the frame image F1 is completed, the next still image frame cycle TC begins, and here the frame 1m image F241 is recorded in the PCM over 420 consecutive 20M tracks in the same manner as described above. Still images are recorded.

As mentioned above, in this embodiment, while video recording is performed without interruption in accordance with the 8 mm format,
One frame (one frame image Fl) in the video is selected at a fixed period, and an 8 mm format PCM) rack (area) is selected.
PCM still images are recorded.

Therefore, the head 28, 30 or the playback head may rotate unevenly, or the tape 3B may expand or contract.

When running unevenness occurs, the reproduced signal will be accompanied by jitter, but P
Since jitter is effectively removed from the PCM signal reproduced from the CM) rack during the PCM reproduction process, a reproduced still image without shaking or distortion can be obtained. This reproduced still image is created by connecting 18 minutes of PCM signals read from each of the 420 PCM racks mentioned above and generating one standard analog video signal for one frame through PCM demodulation and D/A conversion. formed by

In addition, dropouts inevitably occur in VTRs due to scratches on the tape or head, adhesion of dust, etc., but these can be easily restored by the powerful error correction ability of PCM. %, the effect of dropout is almost eliminated and good reproduced still images can be obtained. In addition, various image quality deterioration phenomena associated with analog recording are hardly observed in still images recorded in PCM according to this embodiment, and the recording stability and reproduction repeatability are also excellent.

In this way, according to this embodiment, one frame of the video is automatically recorded in PCM at a fixed period while the video is being shot, so that it can be played back later in PCM and displayed on a TV screen or as a hard copy. If you do this, you can enjoy extremely high-quality still image playback comparable to that of silver halide photographs.In addition, the magnetic head 28. Since it is recorded in PCM format, no special mechanism is required and there is no increase in weight or shape.
M) Since PCM still images are recorded using a rack in almost the same PCM format as PCM audio, the PCM encoder for PCM audio can be used as is for the still image recording function, reducing costs. There are advantages.

That is, the 8 mm video according to this embodiment is a popular camera-integrated video that is lightweight, low cost, and has the functions of a high-quality still camera.

[Print color Although one embodiment has been described above, the present invention is not limited to this (various modifications and changes are possible within the scope of the technical idea. For example, sampling frequency, I quantization The characteristics, recording time mode, etc. can be selected as appropriate, and some examples are shown in FIG.

In FIG. 3, specification A is selected in the embodiment described above.

B specification is for the case where H blank (horizontal blanking period) is not recorded, and the sampling frequency is reduced accordingly due to the high image quality specification, but the number of effective pixels (PIXEL), recording PCM) rack number and The recording time is the same as the A specification.

The C specification uses a line-sequential method that records the color difference signals R-Y and B-Y alternately for each IH, and under the condition that no H blank is recorded.
PCM) This is a method in which 2H worth of video signals are recorded in PCM ranks. With this specification, the number of recording racks (PCM) and recording time are each halved, but the image becomes somewhat rough because the sampling frequency is low.

The D specification has the same conditions as the C specification, but the sampling frequency is relatively high to prioritize image quality, and the recording PC
M) The number of racks and recording time have increased slightly.

Although the above four specifications have been illustrated, other specifications are of course possible. In addition, in the embodiment described above, the PC
Although M still images are recorded, it is also possible to record on a field-by-field basis.

Although the present invention is advantageously applied to 8mm video as described above, it is also applicable not only to camera-integrated VTRs of other standards, but also to portable separate-type VTRs, and even to so-called stationary VTRs. It is also possible to apply this method to record television images as PCM still images.

(Effects of the Invention) As described above, according to the present invention, while recording a moving image, one unit image such as one frame or one field of the moving image is extracted at a fixed period and it is recorded as a PCM still image. For example, in the case of a camera-integrated video, one frame of the video is periodically transferred to the PC while the video is being recorded.
If you later reproduce the image using PCM and display it on a television screen or make a hard copy, you can enjoy extremely high-quality still images that are suitable for viewing.

In addition, since the present invention records PCM still images on a common magnetic tape using the same magnetic head as that used for video recording, it does not require any special mechanism and is a well-balanced and popular product that is lightweight and low cost. can be provided.

In particular, when the present invention is applied to 8 mm video, a special advantage is obtained in that the circuit for PCM audio in the 8 mm video format can be used as is.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the main configuration of an 8 mm video to which an embodiment of the present invention is applied; FIG. 2 is a diagram for explaining the operation of PCM still image recording according to the above embodiment; 4 is a diagram showing some example specifications of PCM still image recording of the present invention, FIG. The tape winding in the millimeter video format is a diagram showing the angle. 14...Camera process circuit, 25.28 song selection switch, 28.30...Magnetic head, 32.
...Ninda, 36-track magnetic tape, 38-track servo circuit, 40...sync signal generation circuit, 5o song changeover switch, 52.54...A/D conversion! ,
56... Frame memory, 58 memory controller, 60 song system controller, 68...
...PCM encoder.

Claims (4)

[Claims] (1) A magnetic tape runs diagonally around a cylinder equipped with a rotating magnetic head at a predetermined angle, and each time the magnetic head scans the magnetic tape diagonally, the analog video signal of a moving image is In a helical scanning magnetic recording device that records one unit image such as a field or one frame, PCM is time-divided into a part of one scanning period of the magnetic head.
Means for recording a still image is provided, and the PCM still image recording means includes means for converting the analog video signal of the moving image into a digital video signal, and a means for capturing the digital video signal for one unit image at a constant cycle and storing the digital video signal. means for expanding the time axis at a predetermined rate; and means for converting the time axis expanded digital video signal for one unit image into a PCM signal and recording it over a plurality of consecutive head scanning periods at a constant cycle. A magnetic recording device comprising: (2) The magnetic recording device according to claim 1, wherein the PCM signal is recorded in a PCM area that is an extension of a moving picture track in which the analog video signal of the moving picture is recorded. (3) The magnetic field according to claim 2, wherein the digital video signal for one unit image is recorded in the PCM area for one horizontal scan of the image in each of the plurality of consecutive head scanning periods. Recording device. (4) The magnetic recording device according to claim 1, wherein an audio signal is frequency multiplexed and recorded on a moving picture track on which an analog video signal of the moving picture is recorded.