JPS60167166A - Modulation system for pcm sound recording and reproducing - Google Patents

Abstract

PURPOSE:To make high-density recording possible with small bound length LC and to reduce error transmission even when there is code errors by dividing 1 word at every 4 bits, converting each division into a channel bit of 8 bits and adding a combined bit of 1 bit to the channel bit in order of division of an original signal and combining both bits. CONSTITUTION:A combined bit is enclosed by a square, and 4 data bits correspond to 9 bits including the combined bit. Accordingly, as TMIN is a channel bit and generated by ''1001'', it is a 3-channel bit and becomes (4/9T)X3, and corresponds to 1.3T. TMAX is a 9-channel bit when regarding the combined bit as a channel bit of ''0'' block and considering ''00000010'' in which ''1'' is only in LSB+1, and corresponds to (4/9T)X9 i.e. 4T as a data bit. The minimum inversion interval TMIN is slightly smaller than other systems. However, it is sufficiently larger in comparison with NRZI and its recording density can be heightened. The maximum inversion interval TMAX is minimum, and is most advantageous in bit synchronism. Further, its bound length LC is shortest and errorneous transmission is few.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field PCM signal modulation method in PCM recorder The PCM method is not limited to communication methods, but has come to be widely used in consumer equipment. Such consumer devices, for example, digital audio.

Compact discs do not transmit data using carriers like communication systems do, but use baseband transmission, so modulation methods suitable for each have been developed based on the characteristics of the transmission medium or recording medium. In general, the numerical characteristic parameters used to evaluate the modulation method are detection window 11@T11+minimum inversion interval Txw.

Maximum reversal interval TMA! , the constraint length is 1,0. All values are expressed numerically based on the data bit interval p#iT'. The detection window Ill Tw is set when the playback signal is affected by jitter, etc. 1441+a margin that does not cause sign s4 when fluctuation is rare, and minimum inversion interval TMXM+maximum inversion interval TMAx indicate the minimum and maximum of the intervals between two adjacent inversion points of the modulated waveform. The constraint length La completely indicates how many bits preceding a certain bit have an influence on determining the modulation waveform of that bit.

The minimum reversal interval T MXN corresponds to the resolution capability of the recording mechanism. In other words, since there is a limit to the recording frequency depending on the properties of the recording medium and the recording method, in order to effectively utilize the recording capacity and record high-density sound, the minimum reversal interval Tur is necessary.
It is necessary to increase g′. Maximum reversal interval T MAN
Since the jitter of the caterpillar signal is corrected every time fcJ6° is inverted to follow the bit clock, the smaller the maximum inversion interval T MAN is, the higher the reliability of the device is.

The constraint 13cLa is a measure of I5T simple error propagation, and the smaller it is, the more advantageous it is.

The modulation method differs depending on which of the above characteristic parameters rC is prioritized. The modulation method of the present invention is primarily used for recording. Comparison methods include 5PM, which is applied to magnetic disks for computers, and HDM, which was devised for magnetic tapes and disks for digital audio. In both cases, the minimum reversal interval T
A high density Q has been achieved in which the MIN is 1.5T to 2T compared to the T of NRZI, which is a standard modulation method. In addition, the maximum inversion interval TM is such that the bit clock can easily follow even if there is jitter, as in the case of NRZI, and it can cope with frequent dropouts such as in audio recording media. However, the constraint length Lo is 3PM. is 9T
, HDMid 5.5T to 12T, all of which have the disadvantage of being significantly longer than the NRZI T. Disclosure of the Invention The purpose of the present invention is density recording, and the constraint length Lo
It is an object of the present invention to provide a modulation method that can reduce error transmission even if there is a small code error.

The PCM*t sound/reproduction modulation method of the present invention is a modulation method for a digital signal in which one word has 4N (N: an integer) bits, and each word is divided into four bits. The channel bits are converted into 8-bit channel bits and combined by adding a 1-bit combination bit in the order of the original signal classification of the channel bits. bit(
C) Two or more II Q between two N I 11 pits
II bit: If the two bits before and after the combined bit are both "o" pits, the combined bit shall be set as a '1' bit, and in other cases, it shall be set as an 'o'bit.'?% It is a sign.

The specific mm using the tISlli method by Yuaki Moto will be explained in the example, but the minimum inversion interval TMXN is 1.3T (
5X4/T), maximum inversion 1uJ m T MAR is 4.
4i T・(1'o y7, ・r)〜4T(9
X I) T jM bay window 11111rll is 0.4 T
(4iT) and the detection window 'I'M Two M small inversion interval m TMIN lti, 5PM.

The HDM K is approximately equal, the maximum inversion interval Tu^1 is the smallest, and p is smaller than 9T of 5PM. Therefore, the reliability of bit clock recovery is high. Also, as a feature of the present invention, it is divided into 4 bits at a time. However, in audio equipment, it is advantageous to have 16 pits in the upper layer of the IP classification, and the constraint length L
Since O is 4T, even if there is a code error, it will be completed within a 4-bit block, so a! ! No v propagation, 1 word v4
It is possible to obtain the result that only the

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, specific embodiments of the 'IJ:g14 system according to the present invention will be described with reference to the drawings.

FIG. 1 is an example of a conversion table in which 4 data bits are assigned to all 8 bits (channels). As shown in the figure, the most significant bit MSNVC++ UI+ is placed, and one or more 1°l is added. Tebru. According to the generation conditions of 8-bit channel bits, there are 181 combinations. In Figure 1, "01000000" and "00000001"
"i Nozoe fc16j is selected and assigned to the data bit. Which data bit is assigned is arbitrary.

Figure 2 shows an example of VC to explain how to decide the connection bits.As seen in this example, there are 11 VCW and 47゜M bits LSB, LSB+1.
MSB, MSB-1 bit °1011. “1゛°
The combined bit can be determined by referring to FIG. 6, which shows a waveform obtained by modulating one word using the modulation method of the present invention, along with NRZI. In the figure, the 4 data bits, including the combined bit, correspond to a 9-bit VC, surrounded by one square (combined pit). Therefore T M
Since XM occurs in channel bits of "'1001", it has 6 channel bits, which is (4/9T)X5, which corresponds to 1.3T.

TMA! The combination bit is II Q ++, and the channel bits of the block are ++ 1 ++ and 1. Only in SB+1" o o.

Considering ``oooio''2, it is a 9-channel pit, and the data bit corresponds to (4/9T)X9, that is, 4T.

Since TI is 1 channel bit, it becomes 4/9T or 0.4T.

As for the performance, since the 8-bit channel is separated from the previous channel bit by the M bit, it is not affected, so one block of 9 channel bits including the combined biller is completed, and it becomes (4/9T)X9, that is, 4T. Become.

By comparing the above characteristic parameters with other modulation methods,
This figure is from ``Digital Audio, published by Radio Gijutsu-sha, written by Doi and Iga.''

This is a reference to the data written in "Sho-Ol March 5.8, 85 Sada".

As shown in the figure, the minimum inversion interval T MXN is sufficiently large compared to NRZI, and the recording density can be increased. The maximum reversal interval T MAN is the minimum, the most advantageous in bit synchronization, and the constraint length is the shortest, resulting in less error propagation◇
Recording density is 3PM.

II D MVC is almost the same, and can be said to be the modulation method with the highest reliability. Note that since 5PM converts every 3 bits, it is inappropriate for 16 bits.

kIMD-5f; l data' is divided into 4-bit units.

The constraint length La is 12T, and there is a large incision point.If you enter the two combinations divided by the conversion table in Figure 1, then T
MAN is (4/9T,)X10 or 4.4TK, Ya\TMA! is larger, other characteristics remain the same.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of a conversion table for converting data bits 11i of a 4-bit block to 8-bit channel bits in the present invention, FIG. 2 is a diagram explaining the channel bit association rule t, Figure 3 is a diagram of the modulation wave board shape, and Figure 4 is a diagram showing the characteristic parameters 1 of each method.Patent applicant Nippon Kouki Home Electronics Co., Ltd. Agent Patent attorney Akihiko Sato Figure 1 Evening and Tsui Ilbit 0000 00000010 0001' 00000100 0010 00001000 0011 00001001 0too 00010000 0101 00010001 0110 00010010 0111 0010 0000 1000 00100001 1001 00100010 IQ to 00100 to. 10 + 1 01000001 1100 01'0OOOI0 1101 01000100 1110 01001000 INI 01001001

Claims (1)

[Claims] A digital signal in which one word has 4N bits (N: an integer) is divided into 4-bit units, each division is converted into 8-bit channel bits, and the channel bits are arranged in the word order 2 of the original signal. Attach the joining bits in the order of classification and join, N
It is a modulation method for recording in RZI, and the channel bits are ((), the most significant bit is ``0°゛ bit (b) 1
1 or more I+ 1 ++ bits Pi 3 conditions are satisfied: 2 or more ``On bits'' between two ``1'' bits, and the above-mentioned combined bit is a HOH bit for each of the 2 bits before and after the combined bit. 11
A PCM recording/playback modulation system characterized by 111 bits and 0° bits for the rest.