JPH0377590B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for reproducing a PCM (Pulse Code Modulation) signal, and more specifically, to a method for reproducing an analog signal well even if data dropout occurs during PCM recording and reproducing. The present invention relates to a reproduction method that allows for.

When recording and reproducing PCM signals using a recording medium such as a magnetic tape, drop-out of the signal becomes a problem due to dust, scratches, deformation, etc. of the magnetic tape. For this reason, in the PCM recording and playback system for audio signals using a VTR, there are two methods: recording the same PCM signal twice to compensate for dropouts, and recording both the PCM signal and the corresponding analog signal on magnetic tape. There are methods to compensate for dropouts by recording them in the dropout, methods to detect dropouts and perform linear interpolation using data before and after the dropout, and methods to approximately compensate for dropouts by holding data before the dropout. Adopted. According to the method described above, it is possible to compensate for dropout to some extent, but it is not only impossible to compensate completely, but also good compensation is impossible if an easy compensation method such as hold is adopted. Furthermore, if a compensation method such as interpolation is adopted, there is a drawback that the interpolation calculation becomes troublesome.

Therefore, the purpose of the present invention is to make it possible to significantly reduce the effects of dropout relatively easily.
The purpose of the present invention is to provide a method for reproducing PCM signals.

To achieve the above object, the present invention provides data obtained by sampling an analog signal at a constant period and sequentially converting it into a digital signal, without arranging the data in the order of sampling. By dividing the data into data blocks consisting of a plurality of data blocks and sequentially recording on a recording medium as an array of at least first and second comb-shaped information data blocks including data in the data blocks intermittently in the order of sampling. In the method for reproducing a PCM signal using a recorded recording medium obtained by the method, sequentially reproducing the first and second comb-shaped information data blocks from the recording medium,
The data arrangement is the same as that obtained by sampling the analog signal at a constant period and converting it into a digital signal without writing the reproduced first and second comb-shaped information data blocks into the memory as they are. The present invention relates to a method for reproducing a PCM signal, which is characterized in that the data is written back into the array, the data is read from the memory in the order of the array, and the data read from the memory is converted into an analog signal. Note that the first and second comb-shaped information data blocks are written into the memory as they are, and the first and second comb-shaped information data blocks are arranged in the same order as the analog signal sampling order without being read out from the memory as they are. It can be returned and read out. According to the present invention, even if dropout occurs during reproduction, a signal close to the original signal can be reproduced based on the first and second comb-shaped information data blocks. Since the first and second comb-shaped information data blocks are returned to the sampling order of the analog signal by writing to or reading from the memory, this arrangement can be easily and quickly performed.

Embodiments of the present invention will be described below with reference to the drawings.

First, referring to FIG. 1, which shows the recording section of a PCM recording and reproducing apparatus using a TVR according to the present invention,
When an analog signal such as an audio signal is input to the sample and hold circuit 2 from the input terminal 11, the analog signal is sampled and held at a predetermined sampling rate determined by a clock signal provided from the clock signal generator 3. The sample and hold circuit 2 includes an analog-to-digital converter, that is, A-D.
Since the converter 4 is connected, the sampled and held analog signal is converted into a digital signal. Digital signals are output in parallel from the A-D converter 4, but PCM signals are output in series by the scratch pad memory 5 and the parallel-to-serial converter 6 at the output stage of the A-D converter. It is considered a signal. P.C.M.
Signals are written into the memory 5 sequentially by address designation by the write address circuit 8. Reading of data written in the memory 5 is performed by addressing by the read address circuit 9, but in the case of this embodiment, the data is not read in the order in which it was written in the memory 5, but instead consists of a plurality of consecutive pieces of data. one data block first
The first comb-shaped data block and the second comb-shaped data block are divided into a comb-shaped data block (a block containing information in a comb-shaped shape) and a second comb-shaped data block. The same data block is read out at different times, and then the same data block is read out repeatedly. For such special signal arrangement methods,
This will be described later with reference to FIG.

A parity check bit generation circuit 10 provided in the branch circuit 7 is a circuit that forms a data parity bit and applies it to the parallel-to-serial converter 6. Therefore, the parallel-to-serial converter 6 outputs a PCM signal with a parity bit added.

Output of parallel-serial converter 6 and synchronization signal circuit 11
The vertical synchronization signal 14 and frame synchronization signal 15 shown in FIG. 3 given from the synchronization signal circuit 11 are added to the PCM signal, and the composite PCM It becomes a signal. The above-mentioned vertical synchronization signal 14 is generated in response to the vertical synchronization signal of the television signal, is a signal that largely distinguishes between data streams, and is also used at the editing point of the tape. The frame synchronization signal 15 mentioned above is a subdivision synchronization signal that subdivides the vertical synchronization signals, and is a signal that serves as a reference for reading out one or more pieces of data. The above-mentioned composite PCM signal is, for example, “1”.
This is a three-value signal consisting of "0" and "-1".

Such a composite PCM signal is sent to the FM modulation circuit 1.
6. FM recording is performed on the magnetic tape 20 by a VTR 19 comprising a recording amplifier circuit 17, a magnetic head 18, etc.

Next, the recording method will be explained in detail with reference to FIG. Digital signals corresponding to analog signals are written into the memory 5 in the order of sampling, but are not read out in the order of writing. For example, data blocks A, B, C, D, E, each consisting of 128 words,
Even if F, G, etc. are written in this order, they are not read out in this order. Figure 3B shows the order in which data blocks are read.By reading data at a speed approximately twice the data writing speed, the same data can be read twice within the same time as the writing time. Reading out. In Fig. 3B, A, B, C, ... without dashes indicate the first read data blocks, and A', B', C', ... with dashes indicate the second read data blocks. It shows. Therefore, after reading the first data block A, the same data is read again and the first data block for double recording is written.
A', and after the first data block A has been repeatedly read out, the second data block B is read out. Data blocks A, B, C, etc. each consist of 128 words, and when writing,
As shown in FIG. 3A, the data blocks are regularly arranged from A ₀ , A ₁ , A ₂ , ...A ₁₂₇ .
At the time of reading, the data are not read out in the order shown in FIG. 3A, but in the order shown in FIG. 3C.

That is _, from time _{t 1} to time _{t 2 in FIG .}
are sequentially read out and set as the first comb-shaped data block. Also, odd-numbered data A ₁ , A ₃ , A ₅ , ...A ₁₂₅ , between time t ₂ and time t ₃ in FIG.
A ₁₂₇ is sequentially read out and used as the second comb-shaped data block.

If the first comb-shaped data block and the second comb-shaped data block are read out, all of _A0 to _A127 will be read out. In this embodiment, as shown in FIG. 3D, the data _A0 has a structure of 1 word of 13 bits including the parity check bit, and the parallel-to-serial converter 6 outputs each bit in the arrangement shown in FIG. 3D. The signals are sent out sequentially.

Further, as is clear from FIG. 3C, a composite PCM signal in which two pieces of data are arranged between the frame synchronization signals 15 is formed, and the magnetic data 20 is also recorded in this state.

Further, in this embodiment, as shown in FIG. 3B, data blocks A to F are generated between the vertical synchronizing signal 14 generated at time _t1 and the vertical synchronizing signal 14 generated at time _t2 .
are arranged so as not to perform double recording over another vertical synchronizing signal section. As a result, even if the tape is edited and data is replaced in the vertical synchronization signal 14 portion, the double recording data A' to F' will not disappear.

In the reproducing apparatus shown in FIG.
magnetic tape 2 with the same or different magnetic head 21 as 8.
For example, if a composite PCM signal recorded as FM 0 is played back, 5.4M corresponds to "1" of the PCM signal.
Hz frequency signal is obtained, and “0” of PCM signal is obtained.
A 4.6MHz frequency signal is obtained in response to the synchronization signal, and a 3.8MHz signal is obtained in response to the synchronization signal.
The FM wave detected by the magnetic head 21 is amplified by a regenerative amplifier circuit 22 and then demodulated by an FM demodulation circuit 23 to become, for example, a ternary composite PCM signal. The dropout detection circuit 24 is connected before the FM demodulation circuit 23, and detects a drop in the level of the reproduced signal, that is, the reproduced FM wave, as a dropout. The data separated by a signal separation circuit 25 connected to the FM demodulation circuit 23 is sent to a scratchpad memory 26. Further, the vertical synchronization signal and frame synchronization signal separated by the synchronization signal separation circuit 27 connected to the FM demodulation circuit 23 are sent to the write address circuit 28 and used to control writing of data to the memory 26. The PCM signal output from the signal separation circuit 25 is also applied to a parity check circuit 29, where a parity check is performed.
Then, only when a parity error occurs, an output is generated from the check circuit 29, and this is output from the OR circuit 3.
0 to memory 26 and it is stored in memory 26 that the address is in error.
Since the output of the dropout detection circuit 24 is also input to the OR circuit 30, even when a dropout is detected, it is stored in the memory 26 that the address is an error. In this example
The OR circuit 30 has two inputs, a parity error signal and a dropout detection signal.
The discrepancy output of the overlapping record comparison circuit 31 is also input, and 2
An error may occur when the first recorded data and the second recorded data of the overlapping recording do not match. In the double recording comparison circuit 30, for example, the first
The recorded data A ₁ and the second recorded data A' ₁ are compared, and if they match, the first recorded data A ₁ is written into the memory 26. On the other hand, the first recorded data A ₁ and the second recorded data A′ ₁
If they do not match, the data A ₁ or A′ ₁ that does not have parity error or dropout
is written. Therefore, if the first recorded data
If _A1 is found to be in error during parity check or dropout detection, second recorded data _A'1 is written to the memory 26 in place of _A1 ;
It will then be output. Furthermore, the output of the OR circuit 30 indicates that the first recorded data _A1 is also an error.
If it turns out that the second recorded data A′ ₁ is also an error, an output is generated from the error detection circuit 32,
The error compensation circuit 33 compensates for data errors by, for example, linear interpolation based on data before and after the error or by holding the signal before the error.

Data sent sequentially is sequentially written to addresses specified by the write address circuit 28. At this time, from the magnetic tape 20, as shown in FIG.
A signal with the pattern shown in is detected, and the signal separation circuit 25 also outputs data in the arrangement shown in FIG. . That is, data A ₂ is input after writing data A ₀ to a predetermined address, but instead of writing it to the address next to A ₀ , it is written to the address that skips one place, and the address next to A ₀ is written. Write data A ₁ that will be sent after a while. As a result, the data in the memory 26 is arranged in the order of A ₀ , A ₁ , A ₂ , . . . as shown in FIG. 3A.

Reading of data from memory 26 is performed based on address designation by read address circuit 34. Since the data is converted into the original array and written into the memory 26 as described above, the read address circuit 34 reads the data sequentially. That is, A ₀ , A ₁ , as shown in FIG. 3A,
A ₂ , ... are arranged in the order of arrangement. As a result, a PCM signal in which data is arranged corresponding to the analog signal is obtained.

In this embodiment, when writing data to the memory 26, the data array shown in FIG. 3C is returned to the data array shown in FIG. 3A, but when reading data from the memory 36, the data array shown in FIG. may be returned to the arrangement shown in FIG. 3A. In this case, the data
After reading A ₀ , read A ₁ without reading A ₂ , and then read A ₂ . As a result, the data array shown in FIG. 3A can be obtained.

In the error compensation circuit 33, when there is only one data error, compensation is performed by interpolation, and when two or more data errors occur consecutively, compensation is performed by holding the data before the error. Compensate. By the way, in this method, two or more consecutive data errors almost never occur. This is because the data is recorded divided into even numbers and odd numbers, so for example, in Figure 3C
Even if data A ₀ A ₂ A ₄ A ₆ is dropped out and an error occurs, the data recorded in a different location
The probability that A ₁ A ₃ A ₅ A ₇ will result in a dropout error is extremely low. Therefore, if part of one comb-shaped data block drops out, but the other comb-shaped data block remains, the data remains in a comb-shaped data block. If the data remains in a comb-like shape as described above, it is possible to obtain compensation data extremely close to correct data by interpolation calculation. Furthermore, since the number of data errors is constant, interpolation calculations are extremely easy. In addition, in this embodiment, interpolation compensation is performed in the case of one data error, but even when compensation is performed by holding the data before the error, errors do not occur continuously, so a signal close to the original signal is You can get it.

The PCM signal obtained from the memory 26 or the error compensated PCM signal is converted into an analog signal by the DA converter 33. As a result, an analog signal substantially equal to the analog signal applied to the input terminal 1 of FIG. 1 is obtained at the output terminal 36.

As is clear from the above, in this embodiment, a memory is used to divide a large number of continuous data into data blocks, which are further divided into comb-shaped blocks and recorded at different locations. Even if a dropout occurs in the comb-shaped data block, the possibility of dropout occurring in the second comb-shaped data block is extremely low, and an analog signal close to the original analog signal is generated based on the second comb-shaped data block. It becomes possible to reproduce it easily.

Further, in the above-described embodiment, since two blocks are recorded and the data is arranged in a comb-like shape, the probability that one of the comb-like data blocks will result in a data error is extremely low. Therefore, PCM recording and playback can be performed with fewer problems caused by signal dropouts.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-mentioned embodiments, and can be further modified. For example, instead of changing the arrangement of data in units of words to form a comb-like shape, the arrangement may be changed in units of multiple words. That is, _the data _block as _{shown in FIG .}
a first comb-shaped data block such as;
It may be recorded separately with a second comb-shaped data block such as A ₂ A ₃ A 6 A _{7 A 10 A 11} . Also, Figure 3A
A first comb-shaped data block of A ₀ , A ₃ , A ₆ . . . , a second comb-shaped data block of A ₁ , A ₄ , A _{7 . 5} 、 _A8 ...
It may also be a third comb-shaped data block. Furthermore, it may be divided into even more comb-like data blocks.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a recording section of a PCM recording and reproducing apparatus according to an embodiment of the present invention, FIG. 2 is a block diagram showing a reproducing section, and FIG. 3 is a waveform diagram illustrating a data arrangement. In the figure, A shows the original data arrangement, B shows the double recording arrangement, C shows the comb-like recording arrangement, and D shows the bit arrangement. In addition, in the symbols used in the drawings, 1 is the input terminal, 2 is the sample hold circuit, and 4 is A-D.
Converter, 5 is a data memory, 6 is a parallel-to-serial converter, 8 is a write address circuit, 9 is a read address circuit, 18 is a magnetic head, 19 is a VTR,
20 is a magnetic tape.

Claims (1)

[Claims] 1. Data obtained by sampling an analog signal at a constant period and sequentially converting it into a digital signal is not arranged in the order of sampling, but the data obtained sequentially is The information is obtained by dividing the data into data blocks, and sequentially recording the data in the data blocks on a recording medium as an array of at least first and second comb-shaped information data blocks including the data intermittently in the order of sampling. In a method for reproducing a PCM signal using a recorded recording medium, the first and second comb-shaped information data blocks are sequentially reproduced from the recording medium, and the reproduced first and second comb-shaped information data blocks are Instead of directly writing the tooth information data block to the memory, the data is returned to the same arrangement as the data obtained by sampling the analog signal at a constant period and converting it into a digital signal, and writing the data from the memory. A method for reproducing a PCM signal, characterized in that the data is read out in the order of arrangement, and the data read out from the memory is converted into an analog signal. 2 Data obtained by sampling an analog signal at a fixed period and converting it into a digital signal sequentially is not arranged in the order of sampling, but the data obtained sequentially is formed into a data block consisting of a plurality of data. and using a recorded recording medium obtained by sequentially recording on a recording medium an array of at least first and second comb-shaped information data blocks including data in the data blocks intermittently in sampling order. In the method for reproducing a PCM signal, the first and second comb-shaped information data blocks are sequentially reproduced from the recording medium, and the reproduced first and second comb-shaped information data blocks are reproduced. The data obtained by sampling the analog signal at a constant period and converting it into a digital signal without writing it into the memory as it is and reading out the first and second comb-shaped information data blocks from the memory as they are. A method for reproducing a PCM signal, comprising: returning the data to the same arrangement as the arrangement, reading the data, and converting the data read from the memory into an analog signal.