SU1767698A1 - Sonic signal frequency coder - Google Patents

Abstract

The invention relates to computing and communication technology. Its use in digital audio broadcasting systems improves the accuracy of encoding audio signals. The device comprises an analog-to-digital converter 1, a Fourier converter 2, a converter 3 rectangular coordinates to polar. By introducing delay unit 4, subtractor 5, adaptive differential converter 6, elements OR 7, 8, parallel register 9, switch 10, and buffer accumulator 11, differential coding methods are applied. 2 Il.

Description

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The invention relates to computing and communication technology and can be used in digital audio broadcasting systems.

The purpose of the invention is to improve the accuracy of encoding audio signals.

Figure 1 shows the block diagram of the device; figure 2 shows the location of information in a parallel register.

The device contains analog-to-digital converter 1, Fourier converter 2, converter 3 rectangular coordinates to polar, block 4 delay, subtractor 5, adaptive differential converter 6, first 7 and second 8 elements OR, parallel register 9, switch 10 and buffer storage 11.

Adaptive differential converter 6 is used to combine several bits of the incoming code in accordance with the chosen adaptation law of the increment step of the delta code depending on the value displayed by it. (The standard is the adaptation of the step with a transition function, described by a sequence of Fibonacci numbers).

The device works as follows. -. .,

The audio signal in analog form is fed to the input of the analog-digital converter 1, where it is digitized and fed to the input of the Fourier converter 2, in which it is converted into a series of Fourier coefficients, represented as complex numbers. In converter 3, the coefficients are converted from a rectangular coordinate system to a polar system, where the number is represented in the form of amplitude and angle (phase). Since the human ear is less sensitive to the phase of the signal, fewer bits of information are used (four is enough).

The amplitude information from the first outputs of the converter 3 is fed to the first input of the subtractor 5, and the second - after a delay of one cycle in block 4 delays. At the same time, the output of the first multi-input element OR 7 produces a logical 1 signal in the case of at least one T in the code combination and a logical O signal in the absence of them. From the output of the subtractor 5, the difference between the two subsequent values of the coefficients is fed to the adaptive differential converter 6, where it is displayed as a limited number of bits, for example, three. At the same time, information about the difference between the two coefficients is fed to the input of the second multi-input

logical element OR 8, the output of which generates a logical 1n signal in the case of at least one 1 in the code combination and a logical O signal in the absence. Further, information on the presence of a signal from the output of the first element OR 7, on the presence of a change in the signal from the output of the second multi-input element OR 8, on the magnitude of the change in the signal from the outputs of the adaptive differential converter 6 and on the phase from the second outputs of the converter 3 goes to the first, second, third and the fourth inputs of the parallel register 9 (figure 2).

Information is read from parallel register 9 using switch 10, which is controlled by the first two bits recorded in parallel register 9. Switch 10 connects information to the inputs of buffer storage 11 as follows: only the first two bits in the absence of a signal, only the first five bits in case of no change in the amplitude of the signal change; all nine bits in the case of a signal and a change in its amplitude.

Thus, code words of different duration are recorded in the buffer memory 11, which allows reducing the clock frequency when selecting information.

The principle of operation of the device is based on the physics of the sound formation and auditory perception of the sound image, in which the harmonic components of the sound amplitude vary long enough, which increases the efficiency of using difference coding methods that require less information to be transmitted. The additional statistical reduction in the digital stream produced in the buffer memory based on the same regularities, makes it possible to further reduce the amount of information transmitted without changing the objective signal quality.

The advantage of the device in comparison with the prototype and the analogs is an increase in the accuracy of the sound transmission during the transmission of musical signals due to the transmission of all the spectral components included in it.

Claims (1)

Invention Formula A device for encoding audio signals in the frequency domain, containing a series-connected analog-to-digital converter, a Fourier transducer, and a rectangular coordinate converter polar, the input of the analog-to-digital converter is an input Devices, characterized in that, in order to improve the accuracy of coding audio signals, a delay block, a subtractor, an adaptive differential code converter, OR elements, a parallel register, a switch and a buffer store are inserted into the device, the first outputs of the rectangular-to-polar converter are connected to the first inputs of the subtractor and the inputs of the delay unit, the outputs of which are connected to the inputs of the first OR element and the second inputs of the subtractor, whose outputs are 0h O. GO X CL Fgg. 2 0 the keys to the inputs of the second OR element and the adaptive differential code converter, the outputs of the first and second OR elements, the outputs of the adaptive differential code converter, and the second outputs of the rectangular-to-polar converter are connected to the first, second, third, and fourth inputs of the parallel register, the outputs of which through the switch, they are connected to the inputs of the buffer accumulator, the output of which is the output of the device. I - presence, C - no signal I is nadgchie, 0 is the absence of change. signal UTL Cr Crc ::. About change h z S2.