JPS6314428B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an apparatus for converting an analog signal into a digital signal and recording the same, and more particularly to the structure of the signal. A device that converts analog audio signals into digital codes and records them is well known as a PCM recorder. In a PCM recorder, information is composed of code words. This code word is a representation of the amplitude value of an analog signal at a predetermined time, usually as a binary digital quantity of "1" or "0". Here, since the time series of information consists of only "1" and "0", it is necessary to specify the starting position of the code word. This is called word synchronization, and for this purpose a certain number of code words constitute a group called a frame, and a specific signal (frame synchronization signal) to identify the group is inserted at the beginning or end of this group. be done. Additionally, in PCM recorders, code errors occur due to dropouts that occur during recording and playback. Since this code error becomes noise unrelated to the original information, it must be detected and processed reliably. Generally, a method of performing a parity check on a word-by-word basis is used to detect errors in digital signals, but recently codes called cyclic codes, which have a high error detection probability, have come into widespread use. This is to add an error detection code to each frame. As mentioned above, the contents to be recorded with a PCM recorder are basically code words, frame synchronization signals,
and an error detection code; however, from a practical standpoint, it is required to add a code called a control signal in addition to these. The control signal has no direct relation to the reproduced audio information, and is a signal for controlling the system to improve usability during reproduction. This includes, for example, specifying absolute addresses by inserting numbers at regular intervals to facilitate editing or indicate the beginning of the music, specifying recording conditions such as whether or not to use emphasis, and even the recording content. Examples include records of Conventionally, for this purpose, these signals were recorded frame by frame, or the video signal was used to convert PCM.
When recording, a method has been adopted in which these control signals are inserted all at once for each vertical synchronization signal of the composite synchronization signal of the television. This control signal requires several tens of bits or more in order to record the absolute address and recording contents, and on the other hand, the number of bits in a frame is often about 100 bits in PCM recording. Therefore, a space is required that allows one frame to be composed only of control signals. Furthermore, considering the purpose of the control signal, it is not necessary to insert a large number of control signals; rather, it is preferable to insert the control signal less frequently, since this can reduce the required bandwidth during recording. In this way, when inserting a control signal portion into each of a plurality of frames, it is necessary to distinguish between the information frame portion and the control signal portion. For this reason, in PCM recording, for example, as described above, a method is used in which a control signal is inserted into one horizontal scanning section immediately after the vertical synchronization signal of the composite synchronization signal. , a method of recording at a pre-designated position with respect to a reference position, etc. are known. But it doesn't use video signal
In a PCM recorder, it is necessary to specify a data start position (BOD) and a data end position (EOD), like a computer storage device. This results in increased redundancy during recording, and frequent determination of EOD and BOD complicates processing in hardware, which is not desirable. An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and provide a PCM recording/playback device that can discriminate and play back digital signals with different contents without increasing redundancy and without increasing the hardware scale. It is in. In the present invention, for the purpose of simplifying the hardware, the same frame synchronization signal pattern is used for both the information frame part and the control signal part, and in order to suppress the increase in redundancy, the control signal is differentiated. Instead, different polynomials are used for generating polynomials of cyclic codes, which are error detection codes, for the information frame portion and the control signal portion. Further, in the present invention, the same generating polynomial may be used for both the information frame portion and the control signal portion, and polynomials with different configurations may be used as the polynomials representing the original data when generating the cyclic code. Hereinafter, the present invention will be explained in detail with reference to Examples.
In PCM recorders that record and reproduce code words in batches for each frame, cyclic codes with high detection efficiency have recently been frequently used to detect code errors. Now, the frame structure is shown in Figure 1, where the number of bits of the information part A consisting of code words is k,
If the number of bits in the entire frame is n, then (n-k) bits are used for the inspection part B, that is, the code for detecting code errors. In a cyclic code,
In order to generate the code of the test portion B, a specific code string called a (nk)-order generator polynomial is used. Here, the polynomial is one in which each bit of the information part A is expressed by a polynomial of the variable x. The degree of the generating polynomial is determined by the (n-k) bits in FIG. 1, and has a form determined by the system to which it is applied. Polynomial M corresponding to information part A in Figure 1
From (x), the polynomial of the test portion B is obtained by the following procedure. That is, the polynomial M of the information part A
(x) is multiplied by x ^nk , which is the degree of the generator polynomial G(x), and divided by the generator polynomial G(x). If the quotient at this time is Q(x) and the remainder is R(x), then x ^nk M(x) = Q(x) G(x) + R(x)
It is expressed as …………(1). The code structure in Figure 1 is the polynomial P of the sum of x ^nk M(x) and R(x) in equation (1).
It is given by (x). This polynomial P(x) is recorded, but since it contains an error part of the code on the reproduction side, the polynomial S(x) of the reproduced signal can be expressed as S(x) if the error part is expressed as a polynomial E(x). )=P(x)+E(x) …………(2) Here, the code string recorded from equation (1) is P(x)=x ^nk M(x)+R(x)=Q(x)・G(
x)
......(3) Therefore, if the reproduced code S(x) is divisible by the generator polynomial G(x), E(x)=0 and there is no error. In this way, in a cyclic code, the generator polynomial G(x) is the same on the recording side and the reproduction side.
will be processed. FIG. 2 shows a configuration in which a control signal frame is inserted every predetermined number of frames in the configuration shown in FIG. In Figure 2, Pi(x),
Pi'(x), Pi''(x)...... are frames containing information, and each frame has the configuration shown in Figure 1. Uj(x) is a frame of the control signal section; Like the information frame, the frame also includes a control signal, a frame synchronization signal, and a code for detecting code errors within the frame.Here, both the P(x) part and the U(x) part are "0". , is a binary code sequence of "1", so processing is required to clearly distinguish between the two. In the present invention, an error detection code is added to each frame using a cyclic code. Focusing on the fact that In the code sequence, P(x)=Q(x)・G(x) ……(4) U(x)=Q′(x)・G′(x) …………(5) There are two groups of code sequences.For example, if the bit configuration of polynomial U(x) is the same as P(x), the degree of generator polynomial G'(x) is also the same as generator polynomial G(x). They have the same degree. Therefore, if G(x)=x ¹⁶ +x ¹² +x ⁵ +1 ......(6), then G'(x) is a polynomial of the same degree but different form G'(x)= x ¹⁶ + x ¹² + x ³ + Therefore, it is desirable that the signal be a polynomial. Fig. 3 shows the signal processing system of the reproduction system in the present invention. The reproduction signal applied to terminal 1 is subjected to bit synchronization and waveform shaping in waveform shaping circuit 2. This waveform-shaped signal is stored in temporary storage circuits 3 and 4, and at the same time, division processing is performed in G(x) division circuit 5 and G'(x) division circuit 6. Depending on the result, it is determined whether it is an information frame or a control signal frame, and gate 7 or 8
is opened and closed, and either information or control signals are sent to the processing system. Table 1 shows the algorithm for this judgment.
Shown below.

[Table] In other words, if the determination result based on the generator polynomial G(x) is positive and the determination result based on G'(x) is incorrect, the frame is a frame P(x) containing information, and vice versa. is a control signal frame.
Further, if both determination results are correct or incorrect, the frame indicates a frame in which a code error has occurred. The above describes an example in which the generating polynomial of the cyclic code for error detection is different between frames containing information and frames for control signals, but the form of the generating polynomial is the same, and the information polynomial in equation (1) M
A similar effect can be obtained by changing the content of (x). That is, for a frame containing information, a cyclic code is obtained by processing equation (1) using the information polynomial M(x) itself, and for a control signal frame, the control signal part is calculated as the polynomial M(x). A cyclic code is obtained using the polynomial M'(x) including the frame synchronization signal part.
In this case, the calculation of equation (1) is performed using the polynomial M'(x) given by M'(x)=M(x)+D(x)...(8). Here, D(x) is a polynomial representing the frame synchronization signal portion. Therefore,
Since the degree of the polynomial M(x) used to obtain the cyclic code is different between the information-containing frame and the control signal frame, there is no confusion between the two types of frames. The circuit configuration in this case is also the same as that shown in FIG.
The parts of the division circuit 6 by G'(x) are each M
It is simply replaced by an arithmetic processing circuit using (x) and an arithmetic processing circuit using M'(x). Furthermore, the frame containing information is generated by the generator polynomial G
(x), the control signal frame consists of a polynomial M′(x) including the frame synchronization signal part and another generator polynomial.
Similar effects can be obtained by constructing cyclic codes using G'(x). According to the present invention, it is possible to reliably discriminate and reproduce a plurality of types of digitally recorded data having different contents without complicating the hardware configuration or using special dedicated codes.

[Brief explanation of the drawing]

The drawings are all related to the present invention; FIG. 1 is a code configuration diagram of a cyclic code, FIG. 2 is a configuration diagram of an example of frame arrangement in PCM recording, and FIG. 3 is a block diagram of an embodiment of a signal processing system. 1...terminal, 2...waveform shaping circuit, 3...temporary memory circuit, 4...temporary memory circuit, 5...G(x)
Division circuit, 6...G'(x) division circuit, 7...
Gate, 8...gate.

Claims (1)

[Scope of Claims] 1. In an apparatus for digitizing and recording an analog audio signal, an information frame consisting of a digital signal of original audio information, a frame synchronization signal, and a code for detecting a code error in the frame; a control frame consisting of a control signal for controlling the playback operation of the frame, a frame synchronization signal, and a code for detecting code errors in the frame, and a generating polynomial of different forms for the error detection code in both frames. A PCM recording/playback device with a code structure generated using polynomials. 2. In the PCM recording and playback device as set forth in claim 1, the same polynomial is used as the generating polynomial for code error detection codes in two types of frames, and one of the information polynomials used when generating error codes for both frames is used. A PCM recording/playback device having a code structure that uses only information in one frame and uses an information polynomial including a frame synchronization signal in the other frame. 3. Claims 1 and 2
In a PCM recording/playback device, a code error detection code is generated in one of two types of frames using an information polynomial and a first generation polynomial, and in the other frame, a code for detecting a code error is generated using an information polynomial including a frame synchronization part and the above-mentioned A PCM recording/playback device having a code configuration in which a code error detection code is generated using a second generator polynomial different from a first generator polynomial.