Adjustment device and program

Abstract

To provide a technology of automatic adjustment of a signal level advantageous for reducing labor of manual adjustment by a user.SOLUTION: An adjustment device adjusts the signal level of an audio signal consisting of two or more frames recorded on a file, at discrete adjustment points corresponding to an envelope of the audio signal. The adjustment device comprises: acquisition means which acquires the envelope of the audio signal; and adjustment means which adjusts the envelope. The adjustment means: detects a peak value of the envelope for each frame; calculates a first average value which is an average value of the detected peak values in the two or more frames; calculates a second average value which is the average value of the peak values higher than the first average value; and adjusts the envelope so that at least a part among the peak values higher than the second average value is suppressed.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to an adjustment device and a program. [Background technology]

[0002] The dynamic range of an audio signal may be wider than the dynamic range of an output device such as a speaker. In this case, the low signal level of the audio signal may be inaudible, and the high signal level may be clipped. Therefore, it is necessary to appropriately compress the dynamic range of the audio signal. The process of compressing such a dynamic range is called dynamic range compression (or simply compression), and the adjustment device that performs compression is called a compressor.

[0003] Patent Document 1 discloses a technique for automatically adjusting a signal level by using an average power level and a maximum power level of an audio signal. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2001-103593 A Summary of the Invention [Problem to be solved by the invention]

[0005] Currently, automatic signal level adjustment is performed uniformly on a track-by-track basis, and not on a waveform-by-waveform basis. Therefore, the results of automatic signal level adjustment are not always satisfactory, and ultimately, manual adjustment by the user on a waveform-by-waveform basis is essential, which requires a great deal of effort. Improvements in automatic signal level adjustment are desired.

[0006] An object of the present invention is to provide a technique for automatically adjusting a signal level, which is advantageous for reducing the effort required for manual adjustment by a user. [Means for solving the problem]

[0007] According to one aspect of the present invention, there is provided an adjustment device that adjusts the signal level of an audio signal consisting of multiple frames recorded in a file at discrete adjustment points corresponding to the envelope of the audio signal, the adjustment device having an acquisition means for acquiring the envelope of the audio signal and an adjustment means for adjusting the envelope, wherein the adjustment means detects peak values ​​of the envelope for each frame, calculates a first average value which is the average value of the detected peak values ​​in the multiple frames, calculates a second average value which is the average value of peak values ​​higher than the first average value, and adjusts the envelope so that at least a portion of the peak values ​​higher than the second average value are suppressed. Effect of the Invention

[0008] According to the present invention, it is possible to provide a technique for automatically adjusting a signal level, which is advantageous for reducing the effort required for manual adjustment by a user. [Brief description of the drawings]

[0009] [Figure 1] FIG. 2 is a block diagram showing the configuration of an adjustment device according to the embodiment. [Diagram 2] FIG. 2 is a diagram illustrating an example of a waveform of an audio signal. [Diagram 3] 4A and 4B are diagrams illustrating an example of an audio signal waveform and adjustment points. [Figure 4] 5 is a flowchart of a process for adjusting the signal level of an audio signal. [Diagram 5] 5 is a flowchart of a process for adjusting the signal level of an audio signal. [Figure 6] 5 is a flowchart of a process for adjusting the signal level of an audio signal. [Figure 7]11A and 11B are diagrams illustrating waveforms and adjustment points after automatic adjustment of a signal level is performed. [Figure 8] 1 is a diagram illustrating waveforms and adjustment points of audio signals of multiple files. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, the embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the invention according to the claims, and not all combinations of features described in the embodiments are essential to the invention. Two or more features among the multiple features described in the embodiments may be arbitrarily combined. In addition, the same reference numbers are used for the same or similar configurations, and duplicated descriptions are omitted.

[0011] 1 shows a block diagram illustrating a configuration of an adjustment device C according to an embodiment. The adjustment device C is a device that adjusts the signal level of an audio signal consisting of multiple frames recorded in a file at discrete adjustment points corresponding to the envelope of the audio signal.

[0012] The adjustment device C may be a computer device such as a personal computer or a workstation. The adjustment device C includes a CPU (Central Processing Unit) 101 that controls the entire device, a RAM 102 that functions as a main storage device and provides a work area for the CPU 101, and a ROM 103 that stores fixed data and programs. The adjustment device C also includes an audio interface (I / F) 104. A microphone M and a speaker S may be connected to the audio interface 104. An external storage device 110 is connected to the adjustment device C via an interface (I / F) 105. The external storage device 110 may be, for example, a hard disk drive (HDD), a solid state drive (SSD), or a combination thereof. The external storage device 110 may be configured inside the adjustment device C as a secondary storage device. The network interface 106 is connected to a network N to perform communication. The adjustment device C may be connected to a server A via the network N so as to be able to communicate with the server A.

[0013] An input device such as a keyboard or a mouse can be connected to the adjustment device C via an interface 107. An external media device F such as a CD-ROM drive or a DVD drive can be connected to the adjustment device C via an interface 108. The adjustment device C further includes a video controller 109. The video controller 109 controls image display by the display device D.

[0014] A boot program for starting up the adjustment device C is stored in the ROM 103. As shown in Fig. 1, an operating system (OS) 111, a signal processing program 112 for performing audio signal processing, and one or more audio files 113 may be installed in the external storage device 110. The audio file 113 may be supplied from an external device such as a server A via a network N, or may be supplied from a medium contained in an external media device F. Alternatively, the audio file 113 may be created from sound picked up by a microphone M.

[0015] In one example, the file format of the audio file 113 may be a WAVE file format that is commonly used in personal computers. A WAVE file may include a header including information such as monaural / stereo type, sampling frequency, quantization bit rate, etc., and audio signal data. Note that the file format of the audio file 113 is not limited to the WAVE file format. The file format of the audio file 113 may be a format other than the WAVE file format, such as AIFF, MP3, AAC, etc.

[0016] 2 shows an example of a waveform W of an entire section of an audio signal displayed on the display device D when the signal processing program 112 is executed by the CPU 101 and an audio file 113 to be processed is loaded. The displayed waveform W is a time domain waveform, with the horizontal axis representing time and the vertical axis representing signal level.

[0017] In one example, when compressing an audio signal, an envelope indicating an outline of a waveform W of the audio signal may be obtained. An adjustment device C serving as an adjustment device may set adjustment points at a plurality of discrete positions corresponding to the envelope.

[0018] FIG. 3 shows an example of a waveform W and an adjustment point P for its envelope. When the user clicks the envelope button 32 with the mouse, an envelope generation process for the waveform W is executed. The envelope shows the outline of the waveform, and is obtained by connecting the peaks of the waveform. The audio signal may be full-wave rectified to obtain the envelope of the full-wave rectified audio signal. Then, an envelope curve representing the envelope generated by the envelope generation process is displayed. The user can adjust the envelope curve by adding or moving an adjustment point P corresponding to the envelope curve. For example, the user can adjust the signal level of an arbitrary adjustment point P by dragging it with the mouse. The waveform W may be re-rendered according to the adjusted signal level. In addition, when the user clicks the autocomp button 33, the signal level is automatically adjusted (autocomp) (auto-adjustment mode). In the example of FIG. 3, a GUI having the envelope button 32 and the autocomp button 33 is provided, but instead of that, a pull-down menu may be provided, from which the envelope or autocomp function can be selected.

[0019] 4 shows a flowchart of an adjustment process for adjusting the signal level of an audio signal by the adjustment device C. A program corresponding to this flowchart is included in the signal processing program 112 and is executed by the CPU 101.

[0020] In step S100, the CPU 101 acquires an envelope of the entirety (entire section) of an audio signal consisting of multiple frames contained in the audio file loaded as the processing target. This process may be performed automatically in response to clicking the autocomp button 33, or in response to clicking the envelope button 32. In this embodiment, the subsequent processes are performed on this acquired envelope.

[0021] In step S200, CPU 101 detects the peak value of the envelope for each frame. Here, a frame refers to a waveform unit obtained by dividing the waveform of an audio signal (envelope) into segments of a predetermined time length. The time length of one frame may be, for example, 10 ms. CPU 101 then calculates an average value (first average value) of the detected peak values ​​in the entire audio signal (i.e., all frames). Next, CPU 101 calculates an average value (second average value) of peak values ​​higher than the first average value.

[0022] In step S300, CPU 101 adjusts the envelope so that at least a portion of the peak values ​​higher than the second average value is suppressed.

[0023] The detailed flow of steps S200 and S300 will be described with reference to FIGS.

[0024] Step S200 includes the following steps S201 to S203. In step S201, CPU 101 detects the peak value of the envelope for each frame. As described above, a frame is a waveform unit obtained by dividing the waveform of an audio signal (envelope) into segments of a predetermined time length, and the length of one frame can be, for example, 10 ms. In one example, one frame may be further divided into subframes of a predetermined time length (for example, 1 ms), and a peak value may be detected for each subframe and the maximum peak value within one frame may be found, thereby detecting the peak value of one frame.

[0025] In step S202, CPU 101 calculates an average value (first average value) of the detected peak values ​​in the entire audio signal (envelope) (i.e., all frames). This first average value may represent the dominant volume in the audio signal. Peaks that exceed this first average value tend to widen the dynamic range. Peaks that exceed the first average value may also include sudden peaks that unnecessarily widen the dynamic range. In the following process, such sudden peaks are detected and their signal levels are suppressed. In step S203, CPU 101 detects peak values ​​higher than the first average value and calculates their average value (second average value).

[0026] Step S300 includes the following steps S204 to S205. In step S204, CPU 101 detects peak values ​​higher than the second average value and calculates their average value (third average value). Here, a peak exceeding the third average value is determined to be an unexpected peak that makes the dynamic range excessive. Therefore, in step S205, CPU 101 adjusts the peak values ​​higher than the third average value so as to approach the third average value. In one example, CPU 101 adjusts the peak values ​​higher than the third average value to the third average value. In another example, CPU 101 can also adjust the peak values ​​higher than the third average value to an adjustment value set in advance by a user. For example, CPU 101 detects peak values ​​higher than the third average value and calculates their average value (fourth average value). Then, the adjustment value may be set to a value between the third average value and the fourth average value. In that case, the adjustment value set in advance by the user may be displayed in percentage, for example, with the third average value being 0% and the fourth average value being 100%.

[0027] In the following, a process is performed to make low signal level parts easier to hear. In particular, there is a strong tendency for the audible sound to be low in the section immediately after the start of the audio signal. Therefore, in step S206, CPU 101 searches for the presence of an envelope peak value that is lower than the first average value and higher than the first threshold value in a first period (e.g., 0.1 seconds) from the start of the audio signal. Here, the first threshold value is a value that is predetermined as being equivalent to, for example, a noise level. If such a peak value is present, in step S207, CPU 101 increases the signal level of the peak value up to a first adjustment amount (e.g., 7 dB). Note that the first threshold value and the first adjustment amount can be arbitrarily set by the user in advance.

[0028] Next, in step S208, CPU 101 searches for the presence of an envelope peak value that is lower than the first average value and higher than a second threshold value that is higher than the first threshold value, during a second period (e.g., 0.2 seconds) longer than the first period from the start of the audio signal. If such a peak value is present, in step S209 CPU 101 increases the signal level of the peak value up to a second adjustment amount (e.g., 4 dB) that is smaller than the first adjustment amount. The second threshold value and the second adjustment amount can be arbitrarily set by the user in advance.

[0029] Next, in step S210, CPU 101 searches for the presence of an envelope peak value that is lower than the first average value and higher than a third threshold value that is higher than the second threshold value after the second period. If such a peak value is present, in step S211 CPU 101 increases the signal level of the peak value up to a third adjustment amount (e.g., 2 dB) that is smaller than the second adjustment amount. The third threshold value and the third adjustment amount can be arbitrarily set by the user in advance.

[0030] The above processing results in appropriate dynamic range compression that sounds superior to the ear.

[0031] Through the above process, CPU 101 can adjust the signal level of the audio signal. CPU 101 re-renders the waveform of the audio signal according to the adjusted signal level. In step S212, CPU 101 sets a volume curve corresponding to the envelope of the audio signal whose signal level has been adjusted, and sets a predetermined position of each frame on the volume curve as an adjustment point. The predetermined position of the frame can be set to, for example, the center of the frame. Alternatively, the predetermined position of the frame may be set to the start or end of the frame.

[0032] An adjustment point is a position where the user can drag it with the mouse to perform manual adjustment as desired. It is meaningless to present adjacent adjustment points with almost no level difference. Also, when the user listens to the output sound after automatic adjustment and performs fine adjustment, if there are too many adjustment points, fine adjustment becomes difficult. Therefore, in step S213, CPU 101 searches for a pair of adjacent adjustment points whose signal level difference is equal to or less than a predetermined threshold value (for example, 0.5 dB or less) among the multiple adjustment points set on the volume curve of the audio signal after the signal level is adjusted based on the generated parameters. If such a pair is found, in step S214, CPU 101 deletes one of the pairs.

[0033] 7 shows an example of a waveform W and an adjustment point P after automatic adjustment of the signal level. The appropriate automatic adjustment of the signal level according to this embodiment reduces the effort of manual adjustment by the user.

[0034] In the examples of Figures 3 and 7, audio signals recorded in one file loaded as a processing target are displayed, but multiple files may be loaded in advance as processing targets. Figure 8 shows examples of waveforms and adjustment points of audio signals T1, T2, and T3 of multiple files loaded in advance. The user can specify any one of the audio signals T1, T2, and T3 to cause the adjustment device C to execute the above-mentioned signal level adjustment process.

[0035] The present invention can also be implemented by causing a computer to execute a program for implementing the functions of the adjustment device described in the above embodiment.

[0036] The invention is not limited to the above-described embodiment, and various modifications and variations are possible within the scope of the gist of the invention. [Explanation of symbols]

[0037] A: server, C: adjustment device, D: display device, K: input device, 101: CPU, 112: signal processing program

Claims

1. 1. An adjustment device for adjusting a signal level of an audio signal consisting of a plurality of frames recorded in a file at discrete adjustment points corresponding to an envelope of the audio signal, comprising: an acquisition means for acquiring an envelope of the audio signal; an adjusting means for adjusting the envelope; having The adjustment means is Detecting a peak value of the envelope for each frame; calculating a first average value which is an average value of the detected peak values ​​in the plurality of frames; Calculating a second average value which is an average value of peak values ​​higher than the first average value; adjusting the envelope such that at least some of the peak values ​​higher than the second average value are suppressed; An adjustment device characterized by:

2. The adjustment means further comprises: calculating a third average value which is an average value of the peak values ​​detected that are higher than the second average value; adjusting the envelope so that a signal level of a peak value higher than the third average value approaches the third average value; 2. The adjustment device according to claim 1 .

3. The adjustment means further comprises: calculating a third average value which is an average value of the peak values ​​detected that are higher than the second average value; Calculating a fourth average value which is an average value of peak values ​​higher than the third average value; adjusting the envelope so that a signal level of a peak value higher than the third average value becomes a value between the third average value and the fourth average value; 2. The adjustment device according to claim 1 .

4. The adjustment means further comprises: if there is a peak value of the envelope that is lower than the first average value and higher than a first threshold value during a first period from the start of the audio signal, increasing the signal level of the peak value up to a maximum of a first adjustment amount; 2. The adjustment device according to claim 1 .

5. 5. The adjustment device according to claim 4, wherein the first threshold value is a value that is predetermined as corresponding to a noise level.

6. The adjustment means further comprises: if there is a peak value of the envelope that is lower than the first average value and higher than a second threshold value that is higher than the first threshold value during a second period from a start of the audio signal that is longer than the first period, increasing the signal level of the peak value up to a second adjustment amount that is smaller than the first adjustment amount; 5. The adjustment device according to claim 4.

7. The adjustment means further comprises: if there is a peak value of the envelope that is lower than the first average value and higher than a third threshold value that is higher than the second threshold value after the second period, increasing the signal level of the peak value up to a third adjustment amount that is smaller than the second adjustment amount; 7. Adjusting device according to claim 6.

8. 2. The adjustment device according to claim 1, wherein said adjustment means further sets a predetermined position of each frame as an adjustment point.

9. 9. The adjustment device according to claim 8, wherein the adjustment means deletes one of the two adjustment points when a signal level difference between two adjacent adjustment points of the audio signal after the signal level has been adjusted by the adjustment means is equal to or less than a predetermined threshold value.

10. A program causing a computer to function as each of the means of the adjustment device according to any one of claims 1 to 9.

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