JPH0199307A - audio processing device - 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 [Industrial Field of Application] The present invention relates to an audio processing device, and particularly aims at improving mute processing for noise removal.

[Prior Art] Conventionally, in an audio recording and reproducing device, noise is generated due to transient phenomena in an audio amplifying circuit when power is turned on/off or when audio reproduction ends. This noise is emitted as a loud sound from the speaker. Therefore, in order to eliminate noise when the power is turned on/off or when audio reproduction ends, an electrical connection is installed between the audio amplification circuit 8 and the speaker 10 or in front of the audio amplification circuit 8, as shown in FIG. By providing the switch 9, a so-called mute process is performed in which the circuit is cut off only when the power is turned on/off.

[Problems to be Solved by the Invention] However, in the conventional example described above, the process is performed on an analog signal, and the mute process only cuts off the audio output, so it is limited to the function of removing noise.

SUMMARY OF THE INVENTION Therefore, the purpose of the present invention is to solve the above-mentioned conventional problems, and instead of performing mute processing by interrupting the circuit,
An object of the present invention is to provide an audio processing device which is configured to attenuate the audio output level using a conversion table and is capable of removing noise and controlling the audio output level.

[Means for Solving the Problem] To this end, the present invention provides a table storage means that stores a plurality of amplitude conversion tables having different attenuation amounts, and an amplitude level that converts the amplitude level of audio data based on the amplitude conversion table. A conversion means, a counting means for counting the number of audio data manually input to the amplitude level conversion means, and a table selection means for changing the selection of the amplitude conversion table in the table storage means every time the counting means counts a predetermined number of counts. It is characterized by the following.

[Operation] According to the above configuration, the audio amplitude level is converted according to the selected amplitude conversion table.

[Example] Hereinafter, the present invention will be described in detail based on the example shown in the drawings.

FIG. 1 shows a part of a circuit block diagram of an image recording/reproducing apparatus which is an embodiment of the present invention. 1 is an audio memory for storing audio data to be output as audio, and 2 is a mute processing unit that stores a table in which a muting curve described later is written and performs mute processing by conversion using this table. , 3 is a 0/8 converter, 4 is an audio amplification circuit, 5 is an address counter that indicates the address to be accessed in the audio memory 1, 6 is a select counter that selects the table of the mute processing section 2, and 7 is shown in FIG. This is a control circuit for controlling the entire system shown in , and is mainly composed of a CPU.

FIGS. 2A and 2B are a diagram and a block diagram, respectively, for explaining mute processing.

As shown in FIG. 2(B), the mute processing section 2 receives 4-bit data for instructing the conversion table number from the select counter 6 and 8-bit audio data from the audio memory 1, and inputs the mute processing section 2 manually. The audio output level is converted according to the conversion table and output as 8-bit audio data.

As shown in FIG. 2(A), the conversion table of the mute processing unit 2 is composed of a conversion table of 18 levels of output levels indicated by table numbers 0 to 15, and these output level conversions are performed according to the table numbers. Attenuation curve defined by the Hanning function f(x)=0.5+〇, 5 cos The table values are created according to the following.

That is, for input levels OFl to FFH, for example, in table 0, output levels OH to FFH, in table 8, output levels 40H to BFH, and in table 15, output levels 80H are the ranges that can be taken depending on the input level, and the input level A table of values proportionally distributed within each output level range is created so as to correspond to each value in the range of 0H-FFH.

Next, details of the mute process will be explained with reference to the flowchart shown in FIG. In steps S31 and S32, the address counter 5 and the select counter 6 are initialized, and then the number of audio data to be read from the audio memory 1 is set in the loop counter. Audio digital data input from the audio input circuit or data recording medium is stored in the audio memory 1, and these audio data are indicated by the address counter 5 in accordance with the read/write timing pulses of the control circuit 7 in step S34. The data at the address set is read from the audio memory 1, and the address counter 5 is sequentially incremented in step S35, thereby sending the data to the mute processing section 2 by the number of data set by the loop counter.

If it is determined in step 53B that the number set by the loop counter has been completed, the process advances to step S37, where it is determined whether the value of the select counter 6 is fixed, and if the determination is affirmative, the process advances to step 538.

In step 538, the mute processing unit 2 controls the control circuit 7.
The audio data sent from the audio memory 1 is converted into data according to the above-mentioned conversion table selected by the select counter 6 which is counted up based on the control. The converted data is converted into an analog signal by the D/C converter 3, and outputted via the audio amplification circuit 4 to a speaker or the like.

Here, the select counter 6 is fixed until the conversion of a predetermined number of data set by the loop counter is completed, and when the conversion of the predetermined number of data is completed, it is incremented in step 539, and the select counter 6 is incremented in step 539, and the select counter 6 is 80H whose possible range gradually reaches zero level
The process from step S33 onward is repeated until it is determined in step 540 that the mute process has ended, and the audio mute process is performed.

Note that the selection counter 6 is fixed not only in the case described above, but also in the case where no mute processing is performed, and the human output level of the audio is converted using the fixed table.

Furthermore, if the selection counter 6 for table selection in the mute processing unit 2 in FIG. 1 is removed and the conversion table is selected at a predetermined timing directly from the control circuit 7, it becomes possible to convert the attenuation characteristics in various ways. . This can be realized by setting the conversion table selection timing or conversion table selection order in advance.

Furthermore, if the selection counter 6 for selecting a conversion table is changed to a selection circuit, and the conversion table selection signal is output to the mute processing unit 2 in response to a conversion table selection request signal from an external source other than the system as shown in FIG. You can adjust the audio output level from here. By opening this external selection mechanism to the user, the example system can be used to adjust the level of the output.

In the above embodiment, the phoneme data is explained as having 8 bits, but this number of bits is not limited to 8 bits, and the amplitude attenuation function that determines the amount of attenuation in each table of the conversion table written to the mute processing section 2 is as described above. It is not limited to the examples.

[Effects of the Invention] As is clear from the above explanation, when performing mute processing, by converting the output level using a table written in memory, the decay time of the audio output level can be freely set by the control circuit. Furthermore, the attenuation characteristic of the audio output level can be easily changed by changing the contents of the table written in the memory.

Furthermore, by allowing the user to select a table, the user can freely adjust the audio output level.

[Brief explanation of the drawing]

ν1 Fig. 1r is a block diagram of an apparatus according to an embodiment of the present invention, Fig. 2 (A) and (B) are diagrams and block diagrams showing an embodiment of the present invention, respectively, Fig. 3 is a block diagram of an apparatus according to an embodiment of the present invention. Flowchart of processing procedure showing one embodiment. FIG. 4 is a block diagram showing a conventional example. DESCRIPTION OF SYMBOLS 1...Audio memory, 2...Mute processing unit, 3...D/A converter, 4...Audio amplifier circuit, 5...Address counter, 6...Select counter, 7... - Control circuit, 8... Audio amplification circuit, 9... Switch, 10... Speaker. 7 & item Cheal number ('A) * Kameri 111 Hosu figure 2 implementation? 'l+ flowchart 3v4

Claims (1)

[Scope of Claims] 1) table storage means storing a plurality of amplitude conversion tables having different attenuation amounts; amplitude level conversion means for converting the amplitude level of audio data based on the amplitude conversion table; A counting means for counting the number of audio data input to the conversion means; and a table selection means for changing the selection of the amplitude conversion table in the table storage means every time the counting means counts a predetermined number of counts. An audio processing device characterized by: 2) The audio processing device according to claim 1, wherein the table selection means includes means for selecting the amplitude conversion table according to a preset order. 3) The audio processing device according to claim 1, wherein the table selection means includes means for arbitrarily selecting one of the plurality of amplitude conversion tables. .