JP2512027B2 - PCM signal recording device - Google Patents

Description

The present invention relates to a device for recording a PCM signal on a magnetic tape, and more particularly to a device for recording a PCM signal in a format for multimode setting corresponding to a recording area or recording density. Regarding recording device.

[Conventional technology]

There are 8 mm video, digital audio tape recorder (DAT), etc. as a device for recording or reproducing a PCM audio signal on a magnetic tape. The 8mm video standard is recorded in "8mm video standard that achieves both compactness and recording characteristics" by Nikkei Electronics (1983.5.23). Here, as the performance of PCM audio, sampling frequency s related to audio reproduction band, signal-to-noise ratio (hereinafter referred to as S / N), number of quantization bits N _S related to distortion, PCM of 8mm video For voice, s = 31.5kHz, Ns
= 10 bits (10-8 companding). Broadcast satellite bs−
In satellite broadcasting using 2, there are two kinds of PCM audio of A bit and B mode, s = 32kHz, Ns = 14 bits (14-10 quasi-instantaneous companding) in A mode, s = 48kHz in B mode, Ns ＝
It is 16 bits (linear).

On the other hand, as PCM voice of audio credit, s = 44.1 kHz and Ns = 16 bits (linear) in a compact disc. In addition, as for DAT that can be recorded and played back, s = 48kHz, Ns = 16 bits (linear) is standard as recorded in "Outline of DAT standardization", IEICE Vol.70 No.1 (1987-1). In addition, s = 32kHz, 44.1kHz can also be supported.

The s of the 8 mm video described above is twice the horizontal synchronizing signal h (.apprxeq.15.75 kHz) of the video signal, and has a lower frequency than other digital audio formats. Even in Ns, it is as low as 10 bits due to the limitation of the recording area of PCM audio.

[Problems to be solved by the invention]

In the above conventional technique, when 8 mm video PCM voice is evaluated as digital audio, there is a problem that it is inferior to other PCM devices in terms of voice reproduction band, S / N and distortion.

An object of the present invention is to improve the sound quality that can be evaluated as digital audio of 8 mm video PCM signals.

[Means for solving problems]

The purpose of the above is to sample a voice analog signal at a sampling frequency of 48 kHz, convert it into a 16-bit digital signal, and divide it into 8-bit symbol data, and use it for synchronizing signals, control signals, error correction codes, etc. Is added to form a data frame synchronized with the field of the video signal, and the first signal system code-modulated in symbol units and the 16-bit digital signal are digitally compressed to 12 bits, and a 12-bit signal is further added. The second set (24 bits) is divided into 8 bits and 3 symbols, a data frame is constructed by using this, and a second signal system for code-modulating is provided.
First PCM recording area capable of recording the signal of the second signal system, and a second PC capable of recording the signal of the second signal system
This is achieved by providing an M recording area and selecting and recording the first and second recording areas.

[Action]

In the above means, by converting a 16-bit digital signal sampled at 48 kHz into 8-bit 2-symbols, signal processing and code modulation can be facilitated, and the PCM recording area can be expanded to reduce the recording density. The PCM signal can be recorded without expanding the recording area by compressing the digital signal of 12 to 12 bits and reducing the recording density to 3/4. The circuits can be shared by processing the 8-bit signals in both systems, and high-quality PCM can be achieved by high-quality recording by symbol-based code modulation.
The signal can be recorded and reproduced.

〔Example〕

Hereinafter, the present invention will be described with reference to examples. FIG. 1 is a block diagram of a PCM signal recording apparatus showing the present invention. Reference numeral 1 is an analog input terminal, 2 is a digital input terminal, 3 is an analog / digital converter (hereinafter referred to as ADC), 4 is a changeover switch, 5 is a symbol data generation circuit, and 6 is a compressed symbol data generation circuit. Reference numeral 7 is a changeover switch, 8. is a digital signal processing circuit, 9 is a time axis compression circuit, and 10 is a code modulation path. 11 is a mode control circuit, 12 is a system controller, and 13 is a control line. The basic operation will be described below.

This circuit shows a PCM signal generation unit for storing an audio signal as a PCM signal on a magnetic tape or the like, and the audio signal input to the analog input terminal 1 is sampled at the sampling frequency s in the ADC circuit 3. At the same time, each sampled data is converted into a 16-bit digital signal. This 16
The bit-one-word digital signal is sent to the symbol data generation circuit 5 and the compressed symbol data generation circuit 6 via the changeover switch 4. Further, the PCM audio signal input to the digital input terminal 2 is the same as the digital signal generated by the ADC circuit 3, and when the digital input terminal side is selected by the changeover switch 4, the PCM audio signal is
It is sent to the symbol data generation circuit 5 and the compressed symbol data generation circuit 6. The symbol data generation circuit 5 converts the input 1-word 16-bit digital signal into 8-bit unit symbol data. Further, the compressed symbol data generation circuit 6 compresses the input 1-word 16-bit digital signal into a 12-bit digital signal. This compression is so-called instantaneous digital compression for reducing the voice deterioration of the voice signal and lowering the transmission rate. The compressed 12-bit digital signal is converted into 8-bit 3-symbol data by dividing two sets (for example, L channel and R channel) of 24 bits into three. The output signal of the symbol data generation circuit 5 or the output signal of the compressed symbol data generation circuit 6 is input to the digital signal processing circuit 8 via the changeover switch 7. The digital signal processing circuit functions to interleave the input symbol data, add a simultaneous signal, a control signal, an error correction code and the like to form a block, and synthesize the block to generate a data frame. . The block and data frame configurations can be changed according to the mode control circuit 11. (Details will be described later.) The time axis compression circuit 9 time axis compresses the input data frame according to the mode and the recording area. The code modulation circuit 10 code-modulates the signal of the compressed data frame on a symbol-by-symbol basis (for example, converts 8 bits of 1 symbol into a modulation signal of 10 bits). The code-modulated modulated signal is sent to a recording circuit (not shown).

The above is a description of the basic operation of the present invention. Hereinafter, the recording method and circuit operation will be described in detail using a specific example. FIG. 2 is a block diagram showing a circuit of the 8 mm video PCM audio recording device. PCM audio of 8mm video is recorded by compressing the PCM signal on the time axis in the PCM area on the extension of the video track. The block will be described with reference to FIG. The circuits having the same numbers as those in FIG. 1 have the same functions. In the digital signal processing circuit 8 , 14 is a block generation circuit, 15 is a data frame generation circuit, 16 is an interleave processing circuit, 17 is a header signal generation circuit, and 18 is an error correction code generation circuit. 19 is an asynchronous absorption circuit, 20 is a video modulation circuit, and 21 is a video signal input terminal. 23 is a recording amplifier,
Reference numeral 24 is a cylinder having a rotary head, and 25 is a magnetic tape. The symbol generation circuit 5 inputs 16 bits 1
The word sampling data is converted into 8-bit symbol data. As shown in FIG. 3, the 8 bits of the sampling data input in the same sequence as L ₀ , R ₀ , L ₁ ... , The lower 8 bits are converted into symbol data. The compressed symbol data generation circuit, as shown in FIG.
After digitally compressing the bit sampling data to 12 bits, for example, the above 8 bits of L ₀ ′ data are symbol data.
Converted to Lou, and the upper 8 bits of R ₀ ′ data are converted to symbol data Rou. Then, the lower 4 bits of the L ₀ ′ data and the lower 4 bits of the R ₀ ′ data are combined to generate 8-bit symbol data L Rol. As a result, 8-bit unit symbol data similar to that of the symbol data generation circuit 5 can be obtained. The two types of symbol data are the same 8-bit data, but when compared in terms of information amount, the output of the compressed symbol data generation circuit 6 has been compressed by 3/4 of the information.

In the digital signal processing circuit 8 , the block generation circuit 14 adds a synchronization signal, a control signal,
A block is generated by adding the block address, the validity, and the error correction codes C1 and C2. FIG. 5 is a configuration diagram showing the block. The block 26 uses the synchronization signal 27 (SYN
C), control signal 28 (ID), block address 29 (B.ADDRE
SS) and parity signal 30 (PARITY) each has a symbol portion of 4 symbols in total, data 31 (DATA) is 30 symbols, C2 outer code 31 (C2-PARITY) is a symbol, and C1 inner code 33 (C1- PARITY) consists of 44 symbols, 4 symbols in total. The synchronization signal 27 is for positioning the head of the block. The control signal 28 is data other than voice, such as a music station number, or data such as stereo / monaural identification. The block address 29 is a block number for forming a data frame. Parity 30 is a control signal
28, a block address 29 is a code for error detection. The data 31 is the above-described symbol data, which is the data after the data is dispersed by the interleave processing circuit 16. C2
The outer code 32 and the C1 inner code 33 are codes generated by the error correction code generation circuit 18.

Next, a data frame obtained by combining the above blocks will be described. 6 and 7 are configuration diagrams showing a data frame. The data frame 34 in FIG. 6 is the mode A, the seventh
The data frame 40 in the figure shows the configuration in the mode B. Mode A is a so-called 16-bit linear recording mode in which 16 bits of sampled data are converted into 8 bits and 2 symbols, and is a case where the output signal of the symbol data generation circuit 5 is used by the changeover switch 7. Mode B is a so-called non-linear recording mode in which 16 bits of sampled data are compressed to 12 bits, in which an output signal of the compressed symbol data generating circuit 6 is guided by the changeover switch 7.
The block 26 is used for both the data frame 34 and the data frame 40 blocks. In data frame 34 ,
Block 26 uses 108 blocks (B). 35 is a header part, 36 is DATA-I, 37 is DATA-II, 38 is C2 outer code, 39
Is the inner code of C1. DATA-I 36 is obtained by converting even-time sampling data and DATA-II 37 is converting odd-time sampling data into symbol data.

The total amount of DATA for DATA-I 36 and DATA-II 37 is 30 x 108 = 32
It is 40 symbols and its capacity is determined by the following reasons.
The input sampling data is 48 k × 2 = 96 k words per second with a sampling frequency of 48 kHz and two L channels, and when converted into symbol data, it is twice as large as 192 symbols. On the other hand, the frequency of the data frame is equal to the field frequency of the image and is 60 / 1.0 for the color NTSC system.
With 01Hz, the number of symbols required in one data frame is
192k ÷ (60 / 1.001) = 3203.2 symbols. Therefore, it fits efficiently within the DATA amount of 3240 symbols. At this time 3
6.8 The processing for generating the remaining amount of symbols and generating a fraction will be described later (description of asynchronous absorption).

Next, the error correction code will be described. As shown in Fig. 6, the system of the C1 inner code and the system of the C2 rank code have an oblique relationship with each other and C2
The outer code line is a system that is completed within one frame, which is a so-called oblique complete reading type. When the Reed-Solomon code is used as the correction code, the code configuration of the C2 outer code is RS (36, 30). The C1 inner code has an RS (40, 36) configuration, or an RS (41, 37) configuration when the block address 29 is added to the information. The reason for adding the block address 29 to the information is to prevent a large error due to erroneous detection of the block address during reproduction.

Next, the data frame 40 corresponding to the non-linear recording in mode B will be described. As in mode A, the number of data symbols required in the data frame is obtained. Since the symbol data of three symbols is generated from the two sampled data in the case of the mode A, the number of data symbols required in the mode B is three quarters of the mode A. That is It is a symbol. FIG. 7 shows an example of a data frame that efficiently covers this capacity. Basically, it differs from the data frame 34 in FIG. 6 in that blocks are 82 blocks. The total of DATA-I 42 and DATA-II 43 is 2460 symbols.

As described above, when the mode A and the mode B are used, only the number of blocks is different because the data amount as information is different.
The number of bits in one symbol, the header configuration, and the error correction code configuration can be made equal, and the circuit configurations of mode A and mode B can be shared.

Next, asynchronous absorption between the cycle (field) of the mode frame and the sampling cycle will be described. As described above, the number of symbol data required for one data frame is 323.2 symbols by calculation. If the fractional 0.2 symbols are omitted for the sake of simplicity, 3203 symbols are required and the capacity of the data frame example in FIG. 6 is 3240 symbols. In other words, the difference of 37 symbols becomes an empty area. By the way, it is necessary to record the data frame period on the tape in synchronization with the field period of the video signals simultaneously recorded. On the other hand, the amount of voice data can be sampled. Since the field period and the sampling period are originally unrelated, they are in an asynchronous state. Even if the audio data is divided based on the field period, it does not always become 3203 symbols. Therefore, an asynchronous absorption circuit 19 that synchronizes in a long cycle by increasing or decreasing the number of symbol data to be recorded for each frame is provided. In the above-mentioned empty area (37 symbols), the object can be achieved by increasing or decreasing the symbol data by several tens of symbols in units of data frame. From this point of view, the 0.2 symbol generated in the above calculation can be absorbed (a negligible amount). If the amount of symbol data to be written is changed for each data frame, it is necessary to identify the amount of symbol data on the reproducing side. Therefore
If the identification code is written using the area of ID28 or the like, the amount of symbol data can be known on the reproducing side.

Next, returning to the block diagram in FIG. 2, the circuit operation will be described. The data frame obtained by the digital signal processing circuit 8 is time-axis compressed corresponding to the PCM recording area on the magnetic tape by the time-axis compression path 9. Video signal and PC
The recording pattern of the M signal is shown in the pattern diagram of FIG. There are recording tracks diagonally on the magnetic tape, and the video signal 46 is divided into 180 ° corresponding to the angle of the rotary head, and the PCM signal 47 is divided into 36 ° on the extension of the track and recorded. The PCM signal 47 has a PCM data area, a preamplifier area in the front thereof, and an after-recording margin area in the rear thereof, and the PCM data area is 26.32 °. In order to record one data frame described above in this area, it is necessary to compress the data frame by 23.32 ° / 180 ° on the time axis. The compressed PCM signal is processed by the code modulation circuit 10 (for example, 8-10).
It is modulated, time-divided with the video signal, and recorded on the magnetic tape via the recording amplifier 23 and the head. Here, the linear recording density and the recording wavelength of the time-base compressed PCM signal will be described. NTSC
Format 8mm video B mode data frame 40
When recording (FIG. 7), the number of line symbols in one data frame is 44 × 82 = 3608 symbols. 1 symbol 8
Since it is a bit, the total number of bits in one data frame is 2886
It will be 4 bits. The compression rate is 26.32 ° / 180 ° and the data frame frequency is The transmission rate becomes Becomes Since the relative speed between the head and the tape is about 3.752m / s, the linear recording density per inch is Is.

The shortest recording wavelength when using 8-10 modulation is Becomes

This wavelength is used for CCIR in the standardized conventional method.
It is close to λmin (= 0.54μm) of 8mm video and is at a practical level.

Next, the linear recording density and the recording wavelength in the A mode are obtained. According to the data frame configuration diagram in FIG. 6, the total number of symbols in one data frame is 44 × 108 = 4752 symbols.
The total number of bits is 38016 bits, calculated as in the previous example, the transmission rate is 15.58Mbps and the linear recording density is 105.5KBPI.
Becomes

The shortest recording wavelength λmin is 0.385 μm. Recording at this wavelength can be realized by a ME (Metal-Evaporation) tape, which has better frequency characteristics than the conventional MP (Metal-Particle) tape.

Further, as a means of increasing the recording wavelength, that is, reducing the recording density, there is expansion of the PCM recording area. For example, if the data area of the PCM recording area is expanded to about 1.3 times that of the conventional (26.32 °) and the area is 34.82 °, the recording density is 79.7K in mode A.
It becomes 60.5KBPI in BPI mode B. As a result, the reliability in recording and reproducing can be improved as much as the recording density is lowered. An example of an extended pattern of the PCM recording area will be described with reference to FIG. The conventional PCM recording area 47 is 36 ° (data part is 26.32
゜), and adding + 8.5 ° extension area 48 to this, PCM
The total recording area is 44.5 ° and the data area is 34.82 °. With this expansion, linear (voice) track 49
Narrows like a truck 50. The standard format of 8mm audio is FM multiplex audio, and the audio by this linear track is provided as an accessory, so there is no major system problem.

Next, the operation of controlling the expansion of the PCM recording area will be described. The circuit for controlling the area control and the data frame transmission rate corresponding to the mode A and the mode B is the second
It is the time axis compression circuit 9 in the figure. Table 1 shows the linear recording densities of the conventional area and the expanded area.

According to Table 1, in the tape capable of recording 80 KBPI, the area can be selected by selecting the A mode and the area or area can be selected by selecting the mode B. For tapes that can record 100 KBPI, all areas can be handled. In addition, only the mode B and area correspond to the tape that enables recording equivalent to 60 KBPI. With the above combination, the optimum system can be selected for each tape, and the change in signal processing by switching is only the presence or absence of compression of sample replacement data and the change in the number of blocks in the data frame. Since the 1-symbol configuration, the correction code configuration, etc. are made the same, it is simple in terms of system and hardware.

Next, another embodiment will be described. FIG. 9, FIG. 10, and FIG. 11 are a block configuration diagram, a mode A data frame configuration diagram, and a mode B data frame configuration diagram, respectively, when the video signal format uses the CCIR method. In the A mode data frame 52 , the block 51 is composed of 103 blocks, and in the B mode data frame 58 , the block 51 is 98 blocks.
It consists of blocks. The present embodiment basically has the same functions and effects as the example using the NTSC system.

In the following embodiment, the data frame is in a format in which the C1 inner code system and the C2 outer code system are orthogonal to each other. FIG. 12 is a block configuration diagram thereof. A data frame 66 in FIG. 13 shows a data frame structure corresponding to the mode A, and a data frame 72 in FIG. 14 shows a data frame structure corresponding to the mode B. The C1 inner code is generated in the vertical block,
The code configuration is, for example, RS (32, 28). The C2 outer code is generated in the horizontal direction between the blocks, and its code structure is, for example, RS (36,30) in mode A and RS (29,23) in B mode. C2
The outer code has four sets in the horizontal direction, and only the code is arranged at the center. This is for dispersing the odd-numbered sampled data and the even-numbered sampled data to increase the burst error correction length. Also in the above embodiment, the symbols are all composed of 8 bits, and by controlling the mode A, the mode B and the PCM recording area, high-density recording is possible according to the performance of the tape, and the system is very simple. The effect is as follows.

In the above-described embodiments, the mode A and the mode B data frame configuration are switched by changing the number of blocks. However, as another method, a method of fixing the number of blocks and changing the number of symbol data in a block is used. There is also.

The slanting (interleaving) of the diagonal lines of the C2 outer code in FIG. 6 and FIG. 7 is optimized in the mode A and the mode B in the interleaving distances in the mode B. It is possible to reduce the switching of the above). However, when the burst error correction length in mode A is insufficient, interleaving suitable for each mode can be performed.

In Table 1, when the areas are selected so that the recording densities are the same (or close) in the mode A-area method and the mode B-area method, the transmission rate of the signal system becomes the same. This has the effect of sharing analog circuits.

The mode A and mode B identifying means can be performed by using a mode identifying code in the area of the control signal 28 of each block and detecting it. In the above-mentioned method, it can be determined after the detection circuit of the digital data operates. Therefore, if a method of frequency-multiplexing (or time-division-multiplexing) the mode identification and pilot signals into a PCM signal area, a preamplifier area, a video signal, or the like is used separately from the content of the data frame, the identification processing is easy and fast.

In the above description of the embodiment, mode A is sampled at 48 kHz, 16-bit (linear) 2-channel system, mode B is set at 48 kHz.
Although it uses the kHz sampling, 12-bit (non-linear) 2-channel system, according to the data capacity of each, for example, in mode A, 32 kHz sampling, 16-bit, 2-channel marking,
44.1kHz sampling, 16-bit, 2-channel method, 32kHz sampling, 12-bit (non-linear), 4-channel method can be used. Also, in mode B, 44.1kHz sampling, 12
Bit (non-linear), 2 channel system, 32kHz sampling, 1
2-bit (non-linear), 2-channel or 3-channel method, 32 kHzg sampling, 16-bit, 2-channel method, etc. can be used.

[Effect of the Invention] According to the present invention, the PCM signal of 8 mm video or the like corresponds to the performance or recording area of the tape and the mode is diversified, but the complicated switching of the signal processing circuit is reduced, It has the effect of enabling high-density recording and improving the quality of PCM audio.

[Brief description of drawings]

FIG. 1 is a basic block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram showing another embodiment, FIG. 3 is a configuration diagram of symbol data, and FIG. 4 is a configuration diagram of compressed symbol data. . 5, 9, and 12 are block diagrams showing data blocks, and FIGS. 6, 10, and 13 are block diagrams showing mode A data frames, FIG. 7, FIG. 11, and FIG. FIG. 14 is a block diagram showing a mode B data frame. Fig. 8 shows 8 mm
It is a pattern diagram which shows the tape format of a video. 1 ... Analog input terminal, 2 ... Digital input terminal,
3 ... Analog / digital converter, 4, 7 ... Changeover switch, 5 ... Symbol data generation circuit, 6 ... Compressed symbol data generation circuit, 8 is digital signal processing circuit, 9
…… Time axis compression circuit, 10 …… Code modulation circuit, 11 …… Mode control circuit, 26 , 51 , 64 …… Data block, 34 , 40 ,
52 , 58 , 66 , 72 ... data frame, 46 ... video signal, 47 ... PCM signal area, 48 ... extended area.

Front page continuation (72) Inventor Seiichi Saito, 292 Yoshida-cho, Totsuka-ku, Yokohama, Kanagawa Hitachi Appliances Research Laboratory (72) Inventor Takao Arai, 292, Yoshida-cho, Totsuka-ku, Yokohama, Kanagawa Hitachi, Ltd. Home Appliance Research Laboratory (56) Reference JP 61-96574 (JP, A) JP 61-87277 (JP, A)

Claims (4)

(57) [Claims] 1. A recording apparatus for converting a PCM signal into symbol data, generating a block from a plurality of the symbol data, generating a frame from the plurality of blocks, time-axis-compressing and recording the medium. A first symbol generation circuit for generating a symbol data by unitizing a plurality of bits of the PCM signal as one symbol, and generating a different number of symbols per frame;
Symbol generation circuit, a mode switching circuit that outputs a mode signal, a switching circuit that switches the outputs of the first symbol generation circuit and the second symbol generation circuit according to the mode signal, and the first symbol generation circuit. Circuit or a PCM signal recording device provided with a frame generation circuit for generating a plurality of frames with different numbers of symbol data according to the mode switching signal from the plurality of symbol data generated by the second symbol generation circuit . 2. The recording apparatus according to claim 1, wherein the frame generation circuit blocks from a plurality of the symbol data generated by the first symbol generation circuit or the second symbol generation circuit. And a frame having a different number of blocks according to the mode switching signal. 3. The recording apparatus according to claim 1, wherein the frame generation circuit uses a plurality of the symbol data generated by the first symbol generation circuit or the second symbol generation circuit, A PCM signal recording device, characterized in that a block having a different number of symbol data is generated by the mode switching signal to generate a frame. 4. The recording apparatus according to claim 1, further comprising a time compression circuit for switching the time axis compression rate of the frame data generated by the frame generation circuit according to the mode signal. PCM signal recorder.