JPS63141100A - Adaptive quantizer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

[Purpose of the invention] (Industrial application field) This invention is a phonetic code

[Adaptive quantizer f used in technology
(Related to prior art) CCITT (International Telegraph and Telephone Consultative Committee) G, 721
The 32 Kbps ADPCM quantizer recommended as FIG. 6 shows the configuration of this quantizer. @6 Figure C, 15 is the input terminal,
A difference signal between the ADPCM input signal and the predicted signal is input. The manually input difference signal is subjected to a normal ratio using a scale factor calculated by a scale factor calculation circuit, and then subjected to a quantization circuit 16. The scale factor is adaptively and sequentially corrected according to the quantized output so that the quantization error becomes small. Further, the adaptation speed changes depending on the degree of level fluctuation of the quantum 1' output, and is adapted to both an audio signal with a large level, lc@, and a modem signal with a small level fluctuation. This operation will be explained in a little more detail. aI speed control μ
What is the degree of level fluctuation of the 1st child fhi output for s rotation 19? Adaptation speed + 111511 parameter α
is output to the scale factor calculation circuit 18. α approaches 1 when the level fluctuation rate is large. Conversely, if it is small, it approaches 0. The scale factor calculation circuit 18 first inputs the quantum 1 output. A fast adaptive scale factor for signals with large level fluctuations and a slow adaptive scale factor for signals with gradual level fluctuations? calculate. next. A fast adaptive scale 7 actor and a slow adaptive scale factor are combined with the distribution determined by the adaptive speed control parameter,
Find the scale 7 actor r. Assuming that the fast adaptive scale 7 actor tynm is the slow j adaptive scale factor tyt, the scale factor Y is calculated by the following equation. Y-ayn+(1-α)yl...fl)
(Temporary point before the invention is approved) ee%TTG, 32Kbps A recommended in 721
The DPCM system has a problem in that it cannot be transmitted with a 9600bpS modem signal. One of the reasons is that G
, 721 quantum] adaptive speed control of the device is 9600bps
Since it does not function properly for modem signals, the one-off error increases. i.e. 9600 bps
Since the modem signal level is almost constant with little fluctuation. Although it is desirable that the scale factor does not change, in the case of a sG*721 quantizer and a quantum signal manually operated, the adaptive speed-specific (to) parameter that should be set to zero is originally 0 and l. Since 1iJ1 fluctuates, the scale factor fluctuates excessively and the quantization error increases. This is 0
．． In the 721 quantizer, the degree of level fluctuation from the quantum output? Because we are calculating. This is the ninth case in which the level change aS of the modem signal cannot be determined at dawn. FIGS. 7 and 8 show the behavior of the scale factor and adaptive speed control parameters of the G, 721 converter, respectively, with respect to the modem signal input. From these figures, it is clear that the above behavior is
T'i'0.7211? Recommendation f'l 32KbpsA
With the DPCM method, the 9600BL) S modem signal could not be transmitted. Is this invention a drawback between the above? To solve the rL order, even for 9600 bps modem signal +
'Di is adapted, and the child fhi error is not 173 mouth a response G quantum (to device 1: To provide? Purpose. [Beak of invention α] (Means for solving the gap point) The present invention is characterized in that the voice signal and modem signal are detected from the local decoded signal to the voice/modem detection circuit.The 11 response speed control parameter is locked to zero only when the modem signal fe is detected. In this case, the adaptation speed of the scale factor will be very fast, adapting to the level fluctuations of the modem signal, and an increase in quantization error will be prevented. (Operation) The voice/modem detection circuit will be inverted. Input the station number 561 signal obtained by adding the difference signal and the fl111S number, determine whether the ADPCM input signal is a voice signal or a modem signal, and output the WP word and modem signal. 1
Another Zago? represents the signal and outputs it. The 1IFa rate limit parameter lock circuit is input with the output of the voice/modem detection circuit and the output of the adaptive rate limiter circuit;
The platform whose output from the a voice/modem production circuit is a signal indicating the mill outputs the output of the adaptive speed control circuit as it is to the scale factor calculation circuit. On the other hand, if the output of the voice/modem detector is a signal indicating a modem signal, it outputs zero. Is the voice/modem hawk circuit abbreviated as 1 local post-signal? Because it is human-powered, it is difficult to accept errors and line miscellaneous errors.
Ha effect? have (Embodiment) Figure 1 shows one embodiment of the present invention. Also. Figure 2 shows eight examples of the longevity of this invention (+JI configuration of the voice/modem detection circuit); The configuration shown in Figure 1 is the same as the configuration shown in Figure 6, with the addition of a voice/modem detection circuit 6 and a J speed limiter parameter lock circuit 7.
In tII Ebisu, bru. The voice/modem detection circuit shown in Figure 2 performs detection based on the fact that the time fluctuation rate of the signal power level is large and consistent between the voice signal and the modem signal. The hawks are as follows. First, the locally decoded signal inputted from the input terminal 8 is passed through the band-pass digital filter 9, and then the absolute value is taken by the absolute one circuit 10. Next, the output of the absolute power circuit is passed through a short-time averaging circuit 11 and a long-term averaging circuit 12 to sequentially obtain the short-term average and long-term average of the signal power. wanted t
The short-term average and long-term average are seen in the comparison/judgment circuit 13. Referring to FIG. 2, a band-pass digital filter has a 9-digit pass band near the formant frequency V number to extract the features of the voice signal and modem signal. Namely. The audio signal has level fluctuations of formant @ kosuka ′i
4ζ On the other hand, since the magnitude of level fluctuations in modem signals does not depend on the band, it is necessary to pass them through a band-pass digital filter. As a result, the characteristics of voice signals and modem signals become more pronounced. When the outputs t of the short-time averaging circuit 11 and the long-term averaging circuit 12 are each 8u (!: 81), the fluctuation rate β of the -signal power level is expressed by the approximate S-square equation: β-l 8 u-8/l/Sl-12)
FIGS. 4 and 5 show an example of calculation of the 7-bell fluctuation rate of the 7-bell S modem signal. It can be seen that the level fluctuation rate is significantly different between the voice signal and the modem signal. Ratio/judgment circuit shown in Figure 2 [3 is 8u and 81
? Detection of modem signal when ratio axis and linear formula are established? O is output as the 1M number shown. If this is not the case, then l is output as a signal indicating the detection of the sound row word. 1su-8ol(βt h S t ・----
・−・−f3) However, βthiiy is the threshold value of the Bell change rate. The adaptive vehicle control section parameter lock circuit is composed of a controller 1 shown in FIG. , is input to the second input terminal 15 ]r; 5 speed! 11J-Kaikaku 5
The output is obtained by multiplying the outputs of . In the embodiments described below, when a modem signal is input,
Adaptive speed control (2) Since the parameter α is locked to zero, the scale factor is set to a low speed of 1ll.
iE and the viewing factor f are fixed and do not fluctuate excessively. This will prevent an increase in the difference between births and births. On the other hand, if the audio signal is generated manually, the conventional G
, Similar to 7211 Kohiyo, J is fast due to severe level fluctuations.
respond. [Effects of the Invention] According to the present invention, the problems of the conventional G, 721 terminal, and one terminal can be solved. In other words, it is possible to prevent an increase in quantum error when inputting a modem signal.

[Brief explanation of the drawing]

Figure 111 shows one of Ichigohiki's works related to Kazutomo Seheishi of this year.
The second factor is the main part of the metering/modem detection circuit shown in Figure 1, and the configuration shown in Figure 3 is the appropriate speed control parameter, which is the main part of Figure 1. FII showing one specific sequence r of the lock circuit! Figures 4 and 5 are examples of the present invention. District shown, 6th
SIG conventional quantum 1 hit device row? Showing only 1. Figure 7 shows the scale factors of the conventional sutures, 1, 5, and 11. Figure 8 shows the conventional quantum [I in Hi4] IF, the time quality of the speed control parameter. FIG. 2.18... Quantum 1 hit generator, 3,19... Inverse quantizer. 4.20...Scale 7 actor calculation times! , 5.21...
- Adaptive speed side - circuit, 6... Voice/modem detection circuit. 7. Adaptive speed control parameter lock circuit, 9. Band pass digital filter, 10. Absolute value circuit. 11...Short time average circuit, 12...Long time average circuit. 13... Comparison/judgment circuit, 16... Multiplier. 4 people Masuakishi Nori Chika i! ! Same as right
Takehana Kikuo No. i F5j Figure 1 Figure 3 To 11 Figure 6 FRACT. FRACT.

Claims (4)

[Claims] (1) In an ADPCM audio encoding device, a first means for detecting an audio signal and a modem signal from a locally decoded signal;
An adaptive quantizer characterized by comprising a second means for changing a quantization parameter at the time of detecting the voice signal detected by the first means and at the time of detecting the modem signal. (2) The first means of detecting voice signals and modem signals is
A digital filter that filters a signal input from an input terminal, a first circuit that takes a short-term average of the power of the output of this digital filter, a second circuit that takes a long-term average, and the short-time average circuit. 2. The adaptive quantizer according to claim 1, further comprising a circuit that compares the output with the output of the long-term average circuit and determines whether the signal is an audio signal or a modem signal. (3) The adaptive quantizer according to claim 1, wherein the second means sets the quantization parameter to zero when a modem signal is detected. (4) The second means for changing the quantization parameter includes an adaptive speed control circuit that takes the quantization output as input and outputs a parameter representing the degree of level fluctuation of the quantization output, and a low-speed adaptive scale from the quantization output. a scale factor arithmetic circuit that calculates a factor and a high-speed adaptive scale factor, and linearly combines and outputs them in a distribution according to the output of the adaptive speed control circuit; and when an audio signal is detected by the first means, the adaptive speed an adaptive speed control parameter lock circuit that supplies the output obtained by the control circuit as is to the scale factor calculation circuit, and supplies zero to the scale factor calculation circuit when a modem signal is detected by the first means; An adaptive quantizer according to claim 1, characterized in that: