JPS59223033A - Digital signal transmitting method - Google Patents

Abstract

PURPOSE:To improve the extending effect of a dynamic range, and also to obtain a high correcting capability with a simple code structure, by suppressing an error propagating phenomenon in a short time, enlarging the coefficient for attenuating an error propagation, and also enlarging an adaptive type processing. CONSTITUTION:In this system, a differential PCM data, etc. are converted to a block in prescribed plural word unit, and an error propagating phenomenon is suppressed in a short time. In an in-block maximum value detecting and comparing circuit 34, the maximum value of absolute value of each data in one block is detected and compared, respectively, and that of a mode in which the maximum value is smaller is decided to be high in its compression efficiency, and a mode selection is executed. This mode information and the maximum absolute value of the mode are sent to a mode selecting adaptive information calculating circuit 41. Thereafter, the processing is executed continuously, and a large adaptive operation can be executed, therefore, a dynamic range can be taken widely, and also a small bit rate will do since it is enough if an adaptive information is transmitted in the ratio of one word per one block, and an error correcting capacity can be raised without increasing extremely the redundancy.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a digital signal transmission method for transmitting digital signals such as PCM signals, and in particular, the present invention relates to a digital signal transmission method for transmitting digital signals such as PCM signals, and in particular, the present invention relates to a digital signal transmission method for transmitting digital signals such as PCM signals, and in particular, bit-efficiently detects errors in differential or summation PCM signals that have been subjected to adaptive processing. The present invention relates to a digital signal transmission method that allows transmission while suppressing propagation phenomena.

[Background technology and its problems]

In recent years, with the advancement of digital technology, analog signals such as audio signals and video signals are sampled, quantized and encoded, and the so-called PCM (PCM)
It is increasingly being transmitted (including recording and playback) as a pulse code modulation signal.

In this way, when converting an analog signal into a PCM digital signal and transmitting it, generally speaking, the higher the sampling frequency, the wider the analog signal band that can be transmitted, and the higher the number of quantization bits, the wider the dynamic range. known to be widespread. Therefore, if you try to digitally transmit the original analog signal with high fidelity, that is, over a wide band and a large dynamic range, you will need a high sampling frequency and a large number of quantization bits. rate will be higher.

However, transmission media (including recording media) (7) 4
9 (The above bit rate is limited by 'l, and
The bit rate is limited by the digital signal processing speed on the transmitting/receiving side (recording/playback side), and as a practical matter, economic efficiency and cost performance when supplying products such as PCM signal recording/playback devices. Considering these factors, it is important to perform high-quality signal transmission or recording/reproduction at as low a bit rate as possible.

By the way, differential PC is a technology for transmitting signals with a large dynamic range at a relatively low bit rate.
M method and adaptive differential PCM method are known,
These methods are less susceptible to the negative effects of error propagation phenomena, and if you try to secure a certain degree of robust error correction ability, redundancy increases, and pit-ray 1-[area effect cannot be effectively obtained. do not have.

[Purpose of the invention]

In view of the above-mentioned points, the present invention makes it possible to suppress error propagation phenomena in a short period of time, increase the coefficient for error propagation attenuation, and increase the adaptive processing, thereby increasing the dynamic range. The purpose of the present invention is to provide a digital signal transmission method which can greatly improve the expansion effect of the data, keep redundancy low by using a simple code structure, and obtain high correction ability in the trench.

[Summary of the invention]

That is, the characteristics of the digital signal transmission method according to the present invention are as follows.
The characteristic is that in a digital signal transmission method that digitizes and transmits the difference value or sum value of adjacent sampling values on the time axis, multiple pieces of digital data obtained by adaptively processing the above difference value or sum value. A word is defined as one block, and at least a 1-h information word of the above-mentioned adaptive processing and a word of digital data indicating the above-mentioned sampling are arranged and transmitted within this one block.

〔Example〕

Prior to explaining the embodiment of this invention, the differences between general PCM, differential PCM, and sum PCM, and adaptive processing will be explained.

First, we will explain general PCM and differential PCM.
A general PC is a computer that quantizes and encodes each sampled peak value of an input signal as shown in Figure 1.
In contrast to the M data, the difference PCM data is obtained by quantizing and encoding the IW tangent value difference numerator ad. When the input waveform changes relatively slowly, that is, when the input signal frequency is lower than the sampling frequency, the gloss difference value is smaller than the sampling peak value, and the condition of the same quantization bit number is So, the difference P
The power of CM can provide a greater dynamic range than that of general PCM.

Here, constant frequency fi (angular frequency ω□=2πfi
) is sampled at a constant sampling frequency f8, and a difference value between adjacent sampling values is taken will be considered.

First, the function f (t) of time t as an input signal is expressed as f
(t)=sinωit 11...1
1 (1), the sampling period Ts(-1/
The difference value d(t) when fS) is d(t),”= f(t) −f Ct−Ts )=
sinωit sinω1Ct--) -----(
2) 8 In order to find the maximum value of this d (t), we differentiate equation (2) and get d' (t) 2 ω + (leos' 2) sin ωits, ω1 + 51n-cos ωtt ” (3) s Therefore, From equation (5), the maximum value dmax of d(t) is: Here, the maximum value of data in the case of general PCM is the amplitude value that is the maximum sampling value, !p, the amplitude l of equation (1)
Therefore, if the input frequency f11 at which the maximum value of the differential PCM is equal to the maximum value of the general PCM is d+ in the above equation (6),
As y+ax = 1, ω11 2 cos −= 1 Ts ω11 −1 π fs 2 3 ,・,fl,−2π ”” fs cos−1−2π
2 “fs L, 0°167 fs” (7) In other words, input frequency f1 is 1 of sampling frequency fs
/6, the maximum value of the differential PCM data is the same, and the dynamic range is the same.

Next, summation PCM data is obtained by quantizing and encoding the summation value of adjacent sampling values, and the summation value a (t) when the sinusoidal input signal f (t) is
is a(t)-f(t)+fCt-Ts). The maximum value a max of this sum value a (t) can be calculated in the same way as in the case of the difference value, and therefore, the input frequency fi2 at which the maximum value of sum I) CM and the maximum value of general PCM become curved is is '= 0.33
3 fs ” Cl0).In other words, the input frequency f1 is the sampling frequency fs
When the value becomes 173, the maximum value of the summed PCM data (the direct value and the maximum value of the general PCM data become equal).

Therefore, when the input signal is sampled at a constant sampling frequency and the peak value, difference value, and sum value are each quantized with the same number of bits, the resulting dynamic range is, for example, as shown in Figure 2. Become. This second
In the figure, the vertical axis shows the dB value of the dynamic range.
The horizontal axis represents the input signal frequency f, and the sampling frequency fs and the number of quantization bits are, for example, 32 KHz and 8 bits, respectively, for a general PC.
A characteristic curve A1 in the M mode, a characteristic curve B1 in the differential PCM mode, and a characteristic curve C in the summation PCM mode are shown, respectively. As is clear from FIG. 2, when the human input signal frequency 11 is in the low range fs/6i, the dynamic range of the differential PCM mode is large and the compression efficiency is relatively the highest.

Similarly, when the input signal frequency f□ is in the range from fs/6 to fs/3, the general PCM mode is activated, and when the input signal frequency f''r is greater than or equal to fs/3, the summation PCM mode is activated. can be increased, resulting in high compression efficiency.

By the way, when transmitting (including recording and reproducing) digital data such as differential PCM data as described above, adaptive processing that transmits a part of the focus without using all bits of the data is necessary. generally known.

For example, FIG. 3 shows an example of an adaptive differential PCM encoder. In FIG. 3, a digital signal obtained by quantizing (and encoding) the above-mentioned sampling values is connected to the input terminal 1. This input digital signal is sent to an adder 2, and the difference between it and the output from the local decoder 10, that is, the error amount, is taken, and the error signal from the adder 2 is requantized by a quantizer 3. Then, so-called pin reduction is performed to shorten the bit length of the l word, and the resultant signal is sent to the output terminal 5. Here, the adaptive algorithm block 4 adaptively changes the characteristics of the quantizer 3 and the multiplier 6 that performs complementary operation to the quantizer characteristics, and there are various algorithms. As a typical example, the quantization step width of the quantizer 3 is set to be larger as the output signal level becomes larger. Local decoder 1
o decodes the output signal from the quantizer 3 and sends the local decoder output as a predicted output to the adder 2;
The purpose of subtraction from the input signal is to obtain the difference between the input signal and the predicted signal, that is, the error signal. This local decoder 1o includes a multiplier 6 that performs a complementary operation to the quantizer 3, an adder 7 that adds the output of this multiplier 6 and the output of the local decoder, and a It consists of a delay circuit 8 that delays the output by one sampling period, and a coefficient multiplier 9 that multiplies the output of the delay circuit 8 by an attenuation coefficient k to perform error attenuation.

In the above-described adaptive differential PcM encoder, the adaptive operation by the adaptive algorithm block 4 is performed by the quantizer 3 and the multiplier 6. The larger the encoded output of the output terminal 5 is, the larger the quantization step is given to the quantization step. This adaptive operation makes it possible to process high-frequency, large dynamic range signals with a limited word bit length.

However, such adaptive operation significantly impairs tranquillity between the encoder and decoder when an error occurs, and is adversely affected by error propagation, which is a weak point of differential PCM, and may become unbearable in use. .

(7) Error propagation will be explained below.

FIG. 4 is a block circuit diagram showing an example of the basic configuration of an encoder for obtaining the differential PCM decoder, and the sampling peak value data input to the input terminal 11 is
The signal is supplied to an adder 12 and a delay circuit 14. The delay circuit 14 delays input data by an esampling period Ts, and this delayed data is sent as a subtraction input to the adder 12 via a coefficient multiplier 15 for multiplying by an attenuation coefficient k. The output from the adder 12 is sent to the output terminal 13 as the differential PCM data.

The peak value data sequentially input to the input terminal 11 in FIG.
2. ..., then the difference value data D, , D2 .・
... is D1=W, -kw.

D2=W2　k”W.

becomes. This attenuation coefficient must be 0<k<1 and is used to reduce the influence of past data so that the influence of error occurrence does not continue for an infinite time.

However, although it is possible to shorten the error propagation time by choosing k to be small, it is not preferable to make k too small because this reduces the effect of expanding the dynamic range.

Therefore, in order to investigate the influence of the attenuation coefficient on the dynamic range, looking at the relationship between the output VCnT) and the input xc'nT) in Figure 4, -y(nT)=x(
nT)- to -x(nT-T)" (11) where T is the sampling period. Now taking e as the input, equation (11) becomes
y(n'I")=x(nT)-'ke-ko"TxcnT
)=(1-ke-j(T)x(nT)...(12
) and the transfer function H(e'°T) is H(ekoQ7T) = 1-k ejlT, and the magnitude of the transfer function IH(e)l is +Hcej
``T) + = + 1- ke3('TI'' l C
1-kcosωT)+jksinωT1= ((1-k
cos(tJT)2+(ksinωT)2)1/2
= (2-2kcosωT to 1+)P2-(13)
.

Here, let the input frequency be flc= ), and
If the π ringing frequency is fs C-1/'I's ), then ω
t'rs = 2πftTs =2π-...(14) fs Above, IH(e)17', = (2-2kcos2π to 1+
C)"S...(15) When this equation (15) is normalized by the size of the transfer function at fl=0 (DC), the relationship between G and :h/fs can be expressed by When displayed as a parameter, it will look like the one shown in Figure 5.

As is clear from FIG. 5, as the value of k decreases, the low frequency cant-off frequency increases, expanding the dynamic range of the low frequency range relative to the high frequency range.

Mizuki is becoming less and less. Therefore, it is desirable to select k above 0.85, for example, and there is a need for a technique that can suppress error propagation in a short time even with a value of k of this order.

Therefore, in the embodiment of the present invention, the differential PCM data and the like are divided into blocks in units of a certain plurality of words to suppress the error propagation phenomenon described above in a short time.

That is, in FIG. 6, data D, , D2 . ...Dn-1 is one block, and within this one block, the above-mentioned peak value data (general PCM
data) Ad and at least one word each indicating the information data Ad of the above-mentioned aggressive (adaptive) processing, and
It consists of +1 word. However, the focus length of these words may be different depending on each data.
For example, the data Ad of the peak value (or instantaneous value) information word should be 14 bits, and each word of the adaptively processed difference data D1 to Dn- and the word of adaptive information Ad should be 7 bits per word. good. In addition, general PCM mode, differential PCM mode,
When transmitting by selecting the summation PCM mode as appropriate, place a general PCM data (peak value data) word, difference data word, or summation data word in the position of each word of the difference data D1 to Dn-, respectively. Furthermore, the mode selection information word may be included in one block.

The data Ad of the adaptive information word in the case of blocking in this way is common to all the words of the adaptively processed data included in the block, for example, the differential PCM data D1 to Dn, -, in FIG. It is used for. This is because adaptive information is included in each word when transmitting adaptively processed data in the past, but since the adaptive tii fl exists in a separate form, the entire bit The number can be reduced, and even if only this adaptive information is configured as a code with high error correction ability, the increase in overall redundancy can be small. An example of such a code structure is shown in FIG. In this FIG. 7, parity data P
1 performs a parity check on only the adaptive information Ad, and the parity data P2 is the adaptive information Ad,
A parity check is performed on the instantaneous peak value data d and on all of the differential PCM data D1 to Dn, -, for one block. Furthermore, as described above, when including a mode selection information word for selecting and transmitting any one of the general PCM mode, differential PCM mode, and summation PCM mode, three modes are included. The number of focus points required to select one of the modes is 2 bits, so the total number of bits is 6 bits, including not only the mode selection information for the block in question, but also the mode selection information for the previous and subsequent blocks. do it.

By blocking multiple words in this way,
Even if k is increased, the error propagation time can be kept short, but here, when transmitting differential PCM data, 1-bit error occurs when the above-mentioned blocking is not performed and when blocking is performed. Compare the error propagation time when this occurs. Now, the sampling frequency fs
When = 32KHz and the damping coefficient = 0.99,
In conventional differential PCM data transmission that does not perform blocking, in order to attenuate errors to 1% of the time when they occur, 0.99''≦0.01 is required, even if the effects of errors in adaptive operation are ignored. (It is necessary to pass the time of n?sampling period, which is added to 1.) In this case, n is 459 or more, and the error propagation time nTs (Ts = 1/fs = Q.315 m
5), nTs: 14.3 ms. On the other hand, when one block is made up of 32 words, for example, the error propagation is completed within the block (1), so the influence of the error disappears in a short time of about 1 mS. Therefore, there is no need to make the attenuation constant k particularly small, and as is clear from FIG. 5, the dynamic range in the low frequency range can be widened, and the aggressive operation can also be made large.

By the way, in the case of 1) performing such blocks, the maximum absolute value of each word in one block in each of the general PCM mode, differential PCM mode, and summation PCM mode is the same as that of the above three modes. Depending on which mode has the smallest value, it is possible to know in which frequency region the main part of the signal spectrum within the block exists, and also to examine the conditions that enable the determination of the mode with the highest compression ratio. .

Now, when the input signal is a sine wave signal of frequency f, the number of words in one block is N1, and the block period is TB, as shown in FIG. 8, the block period TB is the period of the input signal T1C=1/ ft), the maximum absolute fr within one block in the general PCM mode becomes approximately equal to the amplitude value (zero-beak value) of the input signal. Since the number of words N in one block is given by TB/Ts (where Ts is the sampling period), if the number of words N that satisfies the following conditions is taken in one block, then the number of words N in one block in general PCM mode is The maximum absolute value is close to the amplitude value of the above input signal, and within one block,
The maximum absolute value is smaller in the differential PCM mode than in the general PCM mode. On the other hand, the number of words N for which the condition of equation (17) above is not satisfied
When , the maximum absolute value within the pronk of the general PCM mode decreases, and the maximum absolute value within the pronk of the differential PCM mode may also become smaller, but the value of N must be smaller than 3. is shown as follows.

In other words, as shown in Figure 9, the sample points of the input sine wave are a, b, c, etc., and points a and b are located at the zero cross of the input sine wave so that the difference value between them is maximized. If it is placed equidistant from the point on the time axis, then
The difference value (absolute value) D a b between t and b is, Next, if one block includes N sample points from point a, the maximum value C in the block (absolute value) L is N= 2.5, N must be an integer, but if N is 3 or more, the maximum absolute value of 2 in the block can be made smaller than in the general PCM mode, and in each of the above modes, for example, in the general PCM mode, P
By comparing the maximum absolute value within the block (1) between the CM mode and the differential PCM mode, it is possible to determine whether the signal frequency is high or low.

Next, as a preferred embodiment of the present invention, a specific configuration example for realizing each of the technical ideas described above will be described with reference to the drawings.

FIG. 10 is a block circuit diagram showing an example of a PCM encoder used for PCM signal transmission.

In FIG. 10, an input terminal 31 of the encoder is supplied with, for example, a 14-bit digital data signal (sampled peak value data signal). The noise emphasis circuit 32 connected to this input terminal 31 is used to improve the signal-to-noise ratio by particularly emphasizing high-frequency signals, and has a time constant of, for example, 50 μs. For example, 14 from this pre-emphasis circuit 32.
The bit outputs are sent to a multiplexer 33, an intra-block maximum value detection comparison circuit 34, a difference processing circuit 35, and a summation processing circuit 36, respectively. In addition to the 14-bit sampling data signal from the pre-emphasis circuit 32, the intra-block maximum value detection and comparison circuit 34 receives, for example, a 15-bit difference data signal from the difference processing circuit 35 and the summation processing circuit 3G. A 15-pinto sum data signal is supplied. This in-bronc maximum direct detection comparison circuit 34 detects and compares the maximum absolute value of each of the data in one block (multiple words), and assumes that the mode with the smaller maximum value has higher compression efficiency. Make mode selection. The difference processing circuit 35 has a basic configuration as shown in FIG. 4, for example, and sequentially extracts the difference data of the next i times adjacent words of the hum pull data from the pre-emphasis circuit 32.

That is, n words W of the sample wave height value data correspond to one block of -l. ,Wl,...Wn.

is input, the difference processing circuit 35 outputs D,=
Wo-ni-Wl D2. = Wt- to -W2 Dn, -1 = Wn-, - to -Wn- where k is the attenuation coefficient, 0 (k (1 n = 1 word difference PCM data D11D2.am
...Dn+t is output. Each of the differential PCM data D1 to Dn, -1 for one block is stored in the block memory 37.
sent to and stored. The summation processing circuit 36 is for calculating the sum of the input peak value data and the coefficient multiplication value of the input data one sampling period before, and calculates the sum of the input peak value data and the coefficient multiplication value of the input data one sampling period before. The n, -1 words A□ to A n-1 of the summation data for -Wn, - are A, = W, + -WO A2 = W2+ -W.

An-r-Wn-1+k''Wn-t.

Then, in the intra-block maximum value detection and comparison circuit 34, (1) the maximum absolute value of the word data in each mode in the block, that is, the data (peak value data) in the general PCIVf mode (peak value data) Wl to Wn-; ,
The maximum absolute value of the difference data D1 to I) n− in the difference PCM mode.

and the maximum absolute value of the summation data A□ to An-1 in the summation PCM mode are respectively detected, and the maximum absolute value of each of these three modes is compared to find the most It is determined that the mode with a small maximum absolute value is a mode with high compression efficiency that can widen the dynamic range with the same number of focus points, and this mode information and the maximum absolute value of this mode are used for mode selection and adaptive information calculation. The signal is sent to circuit 41. Here, in order to select the mode with the highest compression ratio, in addition to comparing the maximum values of each mode in the block, the average energy of each mode is also compared. The compression ratio of these modes may be evaluated.
.

Here, if the input signal is a sine wave, the mode may be selected in accordance with the frequency characteristics shown in FIG. 2 described above so as to switch to the mode with the widest dynamic range.

Next, the mode selection/adaptive information calculation circuit 41
A circuit that outputs information for selecting the mode with the smaller maximum value, that is, a mode with a higher compression rate, and adaptive information indicating the size of the quantization step.The mode selection information is sent to the mode switching processing circuit 42 and the multiplexer 33. Then, one block of differential processing data D, ~Dn-, stored in the block memory 37 is sent to the shunted 42, and one block of differential processing data D, ~Dn-, stored in the block memory 37 is sent to the shunt 42. The data of all words, that is, the data of W to Wn-□ when the general PCM mode is selected, the data of -Dn- when the differential PCM mode is selected, and the data of A1 to An-1 when the summation PCM mode is selected. It is output and sent to the adaptive processing circuit 43. Here, as a specific operation of the mode switching processing circuit 42, one block of differential data D□ to I)n-
, and the instantaneous wave height direct data Wo from the pre-emphasis circuit 32 to perform processing to obtain the data of the selected mode9. When the differential PCM mode is selected, the input data D1 to I)n'' You just need to output + as is.When you select general PCM mode, you just need to cancel the difference processing by summation operation, specifically, output -W to D1+ to W.

W2 ''= D 2 + k -Wt Wn-1 = D, +k - Wn-2.Similarly, when selecting the summation PCM mode, by performing the summation operation twice, the above Input data D1~
Dn-, and W. Integration data A1 to An-1 can be obtained from A + = Wl + kWo "" D
1+2 kW.

A2 = W2 +kw, = D2 +'21cw2
A n-1= Wn-t + kW n-2= D
n-1+2 kW n-2.

Next, the adaptive processing circuit 43 requantizes the data of the words in the block from the mode switching processing circuit 42 with a quantization step width corresponding to the maximum absolute value.

A specific example of this adaptive operation will be explained.

For example, when the data from the mode switching processing circuit 42 is expressed in two's complement with 15 bits of word, the most significant bit, so-called MSB, indicates a positive or negative sign, and when it is "0" it is positive data and when it is "1" it is negative data. means. On the contrary,
The intra-block maximum value of the selected mode obtained by the intra-block maximum value detection and comparison circuit 34 is an absolute value; if the original data is positive, it is left unchanged; if it is negative, a two's complement is taken. Therefore, it is always a positive 15-bit value.

The MSB of this maximum absolute value is always "0", and depending on the size of that value (especially the actual number of digits when expressed in binary),
As shown in FIG. 11, m+
One "0" is placed. That is, the actual number of digits of the maximum absolute value in FIG. 11 is 14-m, which corresponds to the exponent value when expressed as a floating point number. Mode selection/
The adaptive information calculation circuit 41 calculates the number m+1 of consecutive "0"s from the MSB of the maximum absolute value,
Adaptive processing circuit 43 using m as adaptive information
send to The aggressive processing circuit 43 shifts the input 15-bit data to the left by m bits, extracts, for example, 7 bits from the MSB of the shifted data as the number of effective digits, and sends it to the multiplexer 33. The output data from this adaptive processing circuit 43 is data of n-1 words input into the apron, for example, 15 bits, that is, when the general PCM mode is selected, the data is W1.
~Wn-1, data D□ when selecting differential PCM mode ~
Dn-□, data A1 to A when summation PCM mode is selected
Adaptive processing is performed on each of n-1,
■Word data X of n-1 words, for example 7 bits
□~Xn-, if the original 15-bit input data is a positive number, as shown in FIG.
The MSB of the 7-bit output data shifted to the left is also "
0'' to represent a positive number, and when the original 15-bit person data is a negative number, the MSB is
If there are at least m+1 consecutive bits of 1, M of the 7-bit output data shifted left by m bits.
SB also becomes "1", representing a negative number.

The multiplexer 33 receives instantaneous peak value data Ab from the pre-emphasis circuit 32, adaptive information data Ad and mode selection information data M1 from the mode selection/adaptive information calculation circuit 41, and adaptively processed n-1 from the adaptive processing circuit 43. Word data X□ to xn-+ are rearranged into time-series digital data, and each word data is serially transmitted in the order shown in FIG. 13, for example. The data M-1, Mo 1. of the mode selection information word in FIG. M is the mode selection data M-1 of the previous block, and the mode selection data M of the block to be sent now. , and 3 blocks of mode selection data M1 after 1 block.
This indicates that the mode selection data is transmitted as a word, and one block of mode selection data is transmitted three times, which has a strong effect on transmission errors.

The multiplexer 33 outputs block-by-block serial data including a block synchronization part, a word synchronization part, an error correction part, etc. in the word arrangement order as shown in FIG. Transmitted via transmission lines such as optical fibers, or magnetic tape,
It is recorded on a recording medium such as a magnetic disk or an optical disk.

A decoder for restoring nine sampled peak value signals from digital signals serially transmitted block by block in this manner may be configured as shown in FIG. 14, for example.

In this FIG. 14, the input terminal 51 has a transmission medium (
Also includes recording media. ), a digital signal consisting of one block in the word arrangement as shown in Fig. 13 is input,
This input signal is provided to multiplexer 52. The multiplexer 52 separates the aforementioned various data Ab, , Ad, M, X1 to Xn-1 from each other based on, for example, a block synchronization signal or a word synchronization signal in the input digital signal, and selects one of the adaptively processed data. Adaptive (restoration) processing circuit 5 for mode data X1 to Xn-1
Send to 3. This processing circuit 53 performs an adaptive restoration operation based on the adaptive information data Ad from the multiplexer 52. For example, 7-bit data X1~
The MSB (bit indicating the sign) of xi-+ is sign-extended by the above m bits to make m + 7 bits, and 8-m bits of invalid pin are added following the LSB, resulting in a total of 15 bits. This 1 is converted to the complement display data of
The 5-bit data is mode selection data M. When the general PCM mode is selected, the data W1 to Wn-1 are selected. When the 7-minute difference PCM mode is selected, the data D1 to D n-1 are selected. When the summation PCM mode is selected, the data are Said Dehetam 1-8. -1.

Such data from the adaptive (restoration) processing circuit 53 is sent to the mode switching processing circuit 54. and the above mode selection data M. Processing is performed according to the above-mentioned peak value data W1 to W,1, which is then sent to the multiplexer 5.
Sent to 5. The operation of this mode switching processing circuit 54 is such that input data is general PCM data W1 to wn.
-1, it is output as is, and the input data is the difference PC
When M data D1 to Dn-1, the data W is generated by the above-mentioned summation operation.

~Wn-1, input data is summed PCM data A
1 to An-1, data W1 to W are generated by differential operation.
, convert to i. During these summation and difference operations, instantaneous peak value data A b (=Wo) is also used.

Next, the multiplexer 55 receives the instantaneous peak value data A b C=W from the multiplexer 52 at the input stage.

), and peak value data W from the mode switching processing circuit 54
1 to Wn-1 are output one word at a time, for example, at a sampling period, and n words of data W are output at a block period.

-Wn-1 are output sequentially. The output from the multiplexer 55 is sent to an output terminal 57 via a de-emphasis circuit 56 having characteristics opposite to those of the pre-emphasis circuit 32.
It is taken out.

According to the embodiment of the present invention described above, by blocking a plurality of words of data to be transmitted, differential PC
Error propagation in M mode or summation PCM mode can be terminated in a short time, the attenuation constant k can be set large, and large adaptive operation can be performed, so adaptive differential (or summation) PCM digital signals with a wide dynamic range can be used. transmission becomes possible. For example, in aggressive differential PCM mode, when the input signal frequency 11 is low, for example fl = IKHz, the response at full focus input (however, the sampling frequency f
s = 32 KHz) appears as shown in Figure 15, and even when transmitting 1 word and 7 bits, the transmission rate is 70 KHz or higher at 2 KHz or higher.
An instantaneous signal-to-noise ratio of more than dB can be obtained, up to 5, and 80 with Eiz.
An instantaneous signal-to-noise ratio of dB or higher can be obtained. Furthermore, because adaptive information only needs to be transmitted at a rate of one word per block, the bit rate is lower than when adaptive information is transmitted for each word of each PCM data, and without significantly increasing redundancy. It becomes possible to significantly improve error correction ability.

Further, according to an embodiment of the present invention, a general PCM mode,
By comparing the maximum values of the words in the above blocks in divine transmission modes such as differential PCM mode and summation PCM mode, a mode that can perform greater compression is selected, and the data of this selected mode is is transmitted in blocks, error propagation, instantaneous S/N ratio deterioration,
It is possible to minimize negative effects such as an increase in distortion rate and to transmit digital signals with high transmission efficiency.

It should be noted that the present invention is not limited to the above embodiments, and it goes without saying that various changes can be made without departing from the gist of the present invention.

〔Effect of the invention〕

According to the digital signal transmission method of the present invention, multiple words such as adaptive differential PCM data are treated as one block, and each block contains an instantaneous peak value data word and an aggressive information word, so error propagation is terminated within the block. Not only can the damping coefficient be increased (close to 1) to suppress the dynamic range reduction effect, but also a large adaptive operation can be performed, so the adaptive difference P with a wide dynamic range can be
CM mode digital signal transmission is possible. moreover,
Since each block (multiple words) has one food instantaneous peak value data word and one adaptive information word, even if a code structure with high correction ability is applied only to the data of these words, the entire bit The rate of increase in number is low, and it is easy to increase error correction capability while keeping redundancy low.

[Brief explanation of the drawing]

Figure 1 is a waveform diagram for explaining the peak value and difference value when sequentially sampling an analog signal waveform, and Figure 2 shows the frequency characteristics of the dynamic range of general PCM mode, differential PGM mode, and summation PCM mode. Figure 3 is a block circuit diagram showing an example of an adaptive differential PCM encoder, Figure 4 is a block circuit diagram showing an example of the basic configuration of a differential PGM encoder, and Figure 5 is a block circuit diagram showing an example of the basic configuration of a differential PGM encoder. A graph showing the PCM transfer function frequency characteristics, Figure 6 is a diagram showing an example of word formation within one block,
FIG. 7 is a diagram showing an example of a code structure for data transmission for one block, and FIGS. 8 and 9 show the magnitude relationship between the maximum value of general PCM data and the maximum value of differential PCM data according to the number of words in one block. FIG. 10 is a block circuit diagram showing an example of the circuit configuration of an encoder used in an embodiment of the present invention, FIG. 11 is a diagram showing an example of a word with the maximum absolute value, and FIG. 12 is a graph for explaining the following. A, B are diagrams for explaining the operation of adaptive processing, FIG. 13 is a diagram showing an example of the word structure within one block, and FIG. FIG. 15 is a block circuit diagram showing an example of a circuit configuration, and is a graph showing frequency characteristics when a low frequency signal is input in the adaptive differential PCM mode. 31...Input terminals 33.52, 55...Multiplexer 34...Intra-block maximum value detection comparison circuit 35...Difference processing circuit 36...Summing processing circuit 37...Block memory 41... Mode selection/adaptive information calculation circuit 42
．． 54...Mode switching processing circuit 43...Adaptive processing circuit 53...Adaptive (restoration) processing circuit Patent applicant
Sony Corporation Representative Patent Attorney Akira Koike

Claims (1)

[Claims] In a digital signal transmission method that digitizes and transmits difference values or sum values of sampling values that match on the time axis, multiple words of digital data obtained by adaptively processing the difference values or sum values are digitized. A method of transmitting a digital signal, characterized in that at least an information word of the adaptive processing and a word of digital data indicating the sampling value are arranged and transmitted in one block.