KR940000460B1 - Recording system - Google Patents

Abstract

The system and method includes an A/D converter for converting an NTSC composite analog signal into a digital signal, a Y/C separator for separating a luminance signal and a chrominance signal, first and second subnyquist sampling portions for compressing the transmission amount of the luminance signal and chrominance signal into half, a mixer for alternately arranging the chrominance signals output from the second subnyquist sampling portion, vector quantizers for classifying 8 data into 4 groups and two-dimensionally vector-quantizing respective groups, error correctors for adding an error correcting bit to the output of the vector quantizers, modulators for converting 8-bit data output from the error correctors into 10-bit data, a delay for delaying the chrominance signals output from the modulator, and a head drum for recording one frame of the luminance signal and chrominance signals output from the modulator.

Description

Digital signal recording system and recording method using the same

1 is a schematic diagram showing a digital signal recording system according to the present invention;

2A and 2B show a structure of data for recording on a tape and a format recorded on a tape according to the present invention.

3 is an enlarged view of a tape format according to the present invention.

4 is an enlarged view of a format of a VHS type tape according to the prior art.

* Explanation of symbols for main parts of the drawings

1: A / D converter 2: Digital luminance / color signal separator

3: SubNyquist Sampler 4: Mixer

5: Hadamard Converter 6: Vector Quantizer

7; Error corrector 8: Modulator

9 delay unit 10 head

11: head drum 20: tape

The present invention relates to a digital signal recording system and a recording method using the same, and more particularly, to convert an analog composite TV signal into a digital component signal and record it on a cassette tape or an external digital signal for high resolution. The present invention relates to a system for directly inputting component signals to a cassette tape and a recording method thereof.

In general, the development trend of video tape recorders focuses on long time recording by high quality and high density recording method. When pursuing high quality, digital recording rather than analog recording is advantageous in terms of image quality and recording time. Conventional analog composite NTSC signals consist of 320 lines of luminance signals and 120 to 40 lines of color signals, whereas the recently announced digital recording method encodes video signals to 520 lines of luminance signals in accordance with international standards. Is set to 260 lines, the component recording method is adopted for recording digital signals.

In general, in the recorder of a digital video tape recorder, analog-to-digital image and audio input signals are analog-to-digital converted and input to a digital processing unit. In this case, a bit rate is compressed and a code for error correction is added. do. The error-corrected data is recorded on the magnetic tape by the magnetic head through a modulation process, that is, a recording incubation process.

In realizing a digital video tape recorder adopting the above principle in general use such as home use, firstly, high density recording technology which reduces the tape occupancy area per bit, and secondly, compression of data transmission amount which reduces the number of data of the image to be recorded. Technology and thirdly, improvement as a recording medium is required. However, there are other problems in the process of realizing the above improvement. For example, if the recording density is increased, an error occurrence rate is increased, and if the image compression is excessive, a problem of deterioration in image quality occurs.

Therefore, the characteristics of the recording may depend on which realization means specifically accomplishes the above-described basic functions in the digital signal recording system. In the field of the technical field to which the present invention pertains, different independent recording systems have been developed and announced as means for realizing the above-described basic functions.

In connection with this, the present invention combines several conventional circuit means, but improves the recording characteristics of the digital signal having new specifications regarding the circuit operation characteristics of the main part and the operation characteristics of the mechanism part which operates in response to the output signal of the circuit. Its purpose is to provide a records system.

It is another object of the present invention to provide a recording method for giving a new tape recording form for the simplification of the head mechanism of a digital signal recording system, i.e., a digital video tape recorder.

The following describes the present invention in more detail with reference to the accompanying drawings.

In FIG. 1, which is a schematic diagram of a digital signal recording system according to the present invention, the A / D (analog-digital) converter 1 performs A / D conversion of an NTSC composite signal, where the sampling frequency is four times the subcarrier frequency. This is 14.3MHz.

The signal waveform shown in FIG. 2A shows the structure of the data to be recorded on the tape. The minimum structure unit of the synchronization block is 2H, which is the minimum unit of the Hadamard transform in the Hadamard transporter 5A (5B) described later. Is because it is composed of 2H. In the NTSC composite system, since the color signal is multiplexed with the luminance signal as shown in FIG. 2A, the digital Y / C (luminance signal / color signal) separator 2 is employed to provide the digital output of the A / D converter 1. The output is separated into a luminance signal and a color signal. The Y signal output from the Y / C separator 2 is applied to the first sub-nyquist sample device 3A, while the color signal from the Y / C separator 2 (strictly the color difference signal) RY (BY Is applied to the second sub-knit sample device 3B. In the recording system of the present invention, it is possible to input and record digital component signals of international standard for high picture quality in order to enhance the use thereof. Looking at the frequency spectrum of these component signals, the luminance signal and the color difference Since the signals are separated, the Y signal, which is the luminance signal among the digital component signals, is directly directed to the first sub-Nyquist sample device 3A, and the RY and BY signals, which are color signals, are respectively the second sub-Nyquist sample device 3B. To be applied to. The bit rate of the Y signal applied to the first sub-Nyquist sample device 3A is about 95 Mbps, and the amount of transfer of the BY and RY signals applied to the second sub-Nyquist sample device 3B is about 47.5 Mbps. It is. Each of these sample devices 3A and 3B reduces the sampling frequency so that the transmission amount of the input data is halved. The mixer 4 alternately arranges the R-Y signals and the B-Y signals, which are the color difference signals that are compressed and output by the second sub-knit sample device 3B, in order.

The Hadamard transformers 5A and 5B respectively output 8-bit Y signals output from the first sub-Nyquist sample apparatus 3A and 8-bit BY and RY signals output from the mixer 4, respectively. The length is compressed to about 5 bits on average. The Hadamard transform used in the Hadamard transformers 5A and 5B divides a plurality of pixels of an orthogonal transform into one block and distributes each block to a component that is more independent of the pattern coefficient determined at the sampling point, that is, has less correlation. do.

Hadamard conversion of the video signal has a frequency component that is proportional to the energy distribution of the signal. At this time, many bits are allocated to a large power component and fewer bits are assigned to a small power component, thereby enabling bit detection. In this embodiment, eight pixels are divided into one block to perform two-dimensional eighth order Hadamard conversion to reduce eight-bit data constituting each pixel according to eight Hadamard conversion coefficients.

The vector quantizer 6A and 6B classify the above-mentioned Hadamard transformed eight kinds of data components into four groups of two and perform two-dimensional vector quantization for each group. This operation is to minimize the quantization error by setting a representative point applied to the statistical distribution of the signal and quantizing it in two dimensions, so that the number of bits can be saved by about 0.5 bits by vector quantization.

Thus, the 8-bit data applied to the input terminal of the Hadamard transformer (5A) (5B) is subjected to Hadamard conversion and then compressed again to 4.5-bit data through the vector quantization process, the amount of transmission data is about 24Mbps Decreases.

The error correction unit 7A (7B) executes a double encoding function that divides the screen into a plurality of blocks and adds error correction bits in both horizontal and vertical directions. In this embodiment, RS (Reed-Solomon) Coding system using code is adopted. This feature has a high correction capability for the error on the burst, and the code length can be freely selected.

The modulators 8A and 8B convert the 8-bit data output from the error corrector 7A and 7B into 10-bit data, respectively. And a wide range of detection windows. Here, 8 bits per pixel (levels 0 to 255) correspond to quasi-equilibrium data containing five "1s", where the number of quasi-equilibrium data is ₁₀ C ₅ = 252 Replenish by selecting 2 each from ₁₀ C ₄ and ₁₀ C ₆ . As a result, the modulators 8A and 8B output Y signals, RY and BY signals at a transmission rate of 30 Mbps for each channel.

The Y signal output from the modulator 8A is recorded on the magnetic tape through the head 10 on the drum 11, while the RY and BY signals output from the modulator 8B are about 1/480 second with respect to the Y signal. Since there is a time difference, the color difference signals RY and BY are recorded on the magnetic tape by the head 10 on the drum 11 via the delay unit 9 having a delay period of about 1/480 seconds.

In the digital video signal recording system according to the present invention, the mechanism for driving the head drum is configured so that the conventional 1 / 2-inch VHS system mechanism can be used as it is. By the way, in the conventional configuration, the two-channel two-head recording method is employed in the case of recording an analog signal on the magnetic tape. However, in the present invention, two heads are provided for two channels per channel.

The recording data per frame constituting the screen consists of 60M bits x 1/30 (seconds) ≒ 2M bits. In the embodiment of the present invention, one frame of data, i.e., 2M bits, is divided into eight tracks. Thus, data recorded in each track is 0.25 (= 2M bits / 8) M bits. However, in consideration of the use of the 1/2 inch VHS mechanism, the width of the tape should also be used to correspond to 1/2 inch, and the tape has a track length of about 97.39 mm. Therefore, with respect to the plurality of bits recorded in one track, the length occupied by each bit is 97390 µm? 0.25 M bits? 0.380 µm. Since the two bits constitute one wavelength, the shortest recording wavelength lambda is 0.76 mu m. In the conventional analog video tape recorder, the head drum is rotated at 1800 rpm, whereas in the digital video tape recorder according to the present invention, the head drum is recorded as 2 M bits per frame in a two channel four head method. Is designed to rotate at 3600 rpm.

FIG. 2B is a diagram for explaining a recording method in the case of recording a signal that has undergone data compression and modulation with respect to the signal of FIG. 2A on a tape.

Data of one frame is divided into eight tracks (n-3) (n-2)... As shown in FIG. As recorded in (n + 2) (n + 3), the two fields constituting the frame occupy four tracks each. Each track consists of 65.6 blocks.

In Fig. 2B, the odd tracks n-3, n-1, n + 1, n + 3 are tracks for recording luminance signals, and even tracks n-2, n ( n + 2) (n + 4) are tracks for recording the color difference signals RY and BY.

FIG. 2B (b) shows a form in which the video signal is recorded on two adjacent tracks of the tape in the 2H period shown in FIG. 2A. In one block of the n-3 track, which is one of the odd tracks, the luminance signals Y1 and Y2 appear in the 2H period, and in one block of the n-2 track, which is one of the even tracks, the color difference signals RY1, ( BY) 2 is entered. (C) of FIG. 2b shows a detailed structure of each block shown in (b) of FIG. In the figure, the number in parentheses in each section indicates the word length occupied by that section, and one block consists of a total of 460 words. SYNC is a sync block, ID is a field number indicating the order of the sync block, SBi is a subblock of the i-th (i = 1, 2, 3, 4) data, Ci is a CRCC for SBi, (Cyclic Redundancy Check Code), PARITY is a 4-word RS code, and RUNUP is a 2-word clock recovery data.

In the past, video tape recorders used analog signals to record data within a frequency range of less than 10 MHz. In digital video tape recorders, the amount of data is approximately 60 Mbits (30 MHz) by converting analog signals to digital. As described above, the recording density must be high in order to record it as described above.

Accordingly, in the present invention, the head is used as an alloy laminated film type (LAM) head. This alloy laminate head consists of a magnetic core that is stacked by exchanging an amorphous metal layer of Co-Nb-Zr-Ta and an insulating layer of thin SiO ₂ on a ceramic substrate. It has features. In addition, the format of the tape is configured as shown in Figures 2b and 3b, and the tape material is preferably a metal deposition tape, but the original fabric of the 8mm video tape cut to 1/2 inch By using it, high density recording of 30 MHz was enabled.

Next, the overall format structure of the tape has been described with reference to FIG. 3, and for convenience of explanation, the tape format structure of the tape according to the conventional VHS method for recording an analog signal will be described with reference to FIG.

As described above, since the recording system according to the present invention uses the mechanism of the existing 1 / 2-inch NHS type video tape recorder, the width of the tape is 1/2 the size of the tape.

Conventionally, as shown in FIG. 4, although the audio track a is placed on the upper portion of the tape 20 'except the video signal recording field c, in the present invention, the video head records the audio signal. As shown in d and l of FIG. 3, the audio track is set in the video signal recording field 9 via gaps f and k at both ends of the video track. In addition, the control signal is recorded in the control track (i) (d) provided at the lower end of the tape in FIG. 3 and FIG. In the tape 20 of the present invention, the cue signal track b is arranged at the upper end of the tape, that is, at the position of the audio track 7 in FIG.

On the other hand, in the tape 20 'of FIG. 4, a gap b is provided between the audio track 1 and the control track arranged at both ends of the video signal recording field c. On the other hand, in the tape 20 of FIG. 3, the cue signal track b and the control track i are arranged above and below the video signal recording field g via the gap c and j. . In addition, in the tape of FIG. 3, the gap (a) (h) is provided in the upper end and the lower end in order to prepare for the occurrence of the error at the time of tape running. The dimensions of each track of the tape shown in the figures of FIGS. 3 and 4 are shown in Tables 1 and 2 below.

TABLE 1

TABLE 2

As can be seen from Table 1, the lengths of the various gaps (a) (c) (h) (j) set on the tape are 0.10 mm, the width of the cue signal track (b) is 0.95 mm, and the video / audio The width of the signal recording field g is 10.60 mm, and the control track i is 0.7 mm. In addition, the recording method according to the present invention adopts the double azimuth method. The azimuth angle α according to the present invention is ± 15 degrees, which is different from the ± 6 degree which is the azimuth angle β according to the conventional VHS method. . Since the head drum rotates at 3600 RPM, the head drum of the present invention having the same diameter as the head drum of the 1 / 2-inch mechanism has a circumferential speed Vd.

Vd = π × D × W

= π × 62 × 60 = 11686.724 [mm / sec]

It becomes

Therefore, the relative speed Vr between the head and the tape is as follows.

Where Vt is the velocity of the tape and? Is the drum lead angle corresponding to the track recording angle at the time of tape stopping, which is 5.935 degrees.

Therefore, the track inclination angle (track recording angle) θ1 of the actual tape is as follows.

θ1 = tan-1 [Vdsinθ / (Vdcosθ-Vt)]

= 5.956 degrees

That is, the inclination angle θ1 of the track according to the present invention is θ1 = 5.956 degrees, while the inclination angle θ2 of the track according to the prior art is θ2 = 5.935 degrees.

The relative velocity Vr is as follows.

Vr = (Vr ² + Vd ² -2VtVd cosθ1) ^1/2

= {(41.708) ² + (11686.724) ² -2 × 41.708 × 11686.724 × cos5.935} ^1/2

= 11645.240 [mm / sec]

On the other hand, the length P of the width of the video track is obtained by the following procedure.

In addition, the video track e is reduced by [length of audio track x 2] + [length of gap f (k)]. The length of the gap f (k) is 0.50 mm, and the length of the audio track d (l) is set to 1.617 mm.

The length of the audio track is calculated by the following process. The recording speed and the recording wavelength of the audio track (d) (l) are 2 Mbps and 0.76 mu m, similarly to the recording speed and the recording wavelength of the video track (e), respectively. Here, the total length Lt of the audio tracks d and l is as follows.

Therefore, the length Ls of each audio track d (l) is

Ls = Lt / 2 = 1.583 [mm / track]

Becomes

As described above, according to the present invention, the digital recording system according to the new standard can be obtained by employing the 1 / 2-inch mechanism part according to the conventional VHS system without large change.

Claims (10)

An A / D converter 1 for converting an NTSC composite analog signal into a digital signal; A Y / C separator 2 for separating the digital output of the A / D converter 1 into a luminance signal having a transmission amount of 95 Mbps and a color difference signal having a transmission amount of 47.5 Mbps; First and second sub-Nyquist sample devices 3A and 3B for compressing the transmission amounts of the luminance signal and the chrominance signal output from the Y / C separator 2 in half; A mixer (4) for sequentially arranging R-Y and B-Y color difference signals which are compressed and output from the second sub-Nyquist sample device (3B) sequentially; Hadamard transformer 5A, which compresses the length of the luminance signal Y in 8-bit units and the color difference signals RY and BY in 8-bit units to about 5 bits on average, respectively, output from the first sub-Nyquist sample device 3A and the mixer. ) 5B and; The vector quantizer 6a for dividing the eight types of data components Hadamard transformed by the transformers 5A and 5B into four groups and performing two-dimensional vector quantization for each group to reduce the number of bits by 0.5 bits ( 6b) and; Error correction unit 7A (7B) for outputting data of 24 Mbps transmission amount for each channel by adding an error correction bit using a Reed-Solomon (RA) code to the output of the vector quantizer 6A (6B). Wow ; Modulators 8A and 8B for converting 8-bit data output from error correction 7A and 7B into 10-bit data using an 8-10 block code system; A delay unit 9 for delaying the R-Y and B-Y signals output from the modulator 8B for a period of about 1/480 seconds; A head drum having four heads 10 and dividing one frame of the luminance signal Y and the color difference signal RY, BY outputted from the modulator 8B and the delay unit 9 into eight tracks and recording them on the tape 20. And a digital signal recording system comprising: (11). The digital signal recording system according to claim 1, wherein the mechanism for driving the head drum is constituted by a 1/2 inch VHS mechanism, and the rotation speed of the head drum is 3600 rpm. 2. The digital signal recording system according to claim 1, wherein the head (10) is composed of an alloy laminate head. The digital signal recording system according to claim 1, wherein the tape (20) is formed by cutting a fabric of 8 mm video tape into a width of 1/2 inch as a metal deposition tape. In driving the tape zone with a plurality of tracks in order to record digital signals on the tape, a gap area (a) (h) is provided at the top and bottom of the tape, and inside the gap area (a) (h). A cue signal track (b) for recording a cue signal and a control track (i) for recording a control signal are respectively installed in adjacent portions of the cue signal track (b) and the inside of the cue signal track (b) and the control track (i). The video signal recording field (g) is provided through the gap (c) and (j), and the audio track (d) and (l) is provided through the gap (f) and (k) above and below the video track (e). Digital signal recording method characterized by the above-mentioned. 6. The digital signal recording method according to claim 5, wherein the adjacent tracks are set at an angle of about 15 degrees. 7. The digital signal recording method according to claim 6, wherein each video track and the inclination angle θ1 are set at θ1 = 5.956 degrees. 6. The width of the tape is 12.65 mm, the width of the gap (a) (c) (h) (j) is 0.10 mm, the width of the cue signal track (b) is 0.95 mm, the control track ( i) The width of 0.7 mm, the video / audio signal recording field (g) is 10.60 mm, the length of the audio track (d) (l) is 1.617 mm, the audio track (d) () (l) and the video track. The length of the gap (f) (k) between (e) is 0.50 mm, and the width of each video track is set to 18 占 퐉. The digital signal recording method according to claim 5, wherein one frame of TV screen data is recorded by dividing it into eight tracks, but the luminance signal Y, the color difference signals R-Y, and B-Y are recorded in different adjacent tracks. 10. The apparatus of claim 9, wherein each track is divided into a plurality of blocks, each block comprising one sync block, a field number block indicating the order of the sync blocks, four sub blocks for storing data, and these sub blocks. And a CRCC block for the block and a parity block including an RS code added by an error correction process.

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