JP5370125B2 - Audio signal processing apparatus and audio reproduction apparatus - Google Patents

Description

  The present invention relates to an audio signal processing apparatus that processes and outputs an input audio signal, and an audio reproduction apparatus that reproduces an audio signal output from the audio signal processing apparatus.

  2. Description of the Related Art An audio signal processing apparatus that processes an input audio signal and outputs it as a format that can be reproduced by a subsequent speaker is widely known. Some of these audio signal processing devices perform some operation when they are in a no-signal state (a state in which a certain signal level becomes substantially constant).

  For example, in Patent Document 1, it is determined that there is no signal when a period in which the signal level is equal to or less than a threshold value continues for a predetermined time, and power saving is achieved by reducing the frequency of the drive pulse supplied to the switching element. An audio signal processing apparatus has been proposed.

JP 2004-72707 A

  However, the audio signal processing device of Patent Document 1 has a problem that the power saving effect is low because power is supplied to each unit and the operation is continued even after the audio signal is no longer input and the operation is continued. It becomes. Further, since a change in signal level due to noise or the like is recognized as a signal, it is difficult to accurately determine the no-input state.

  Therefore, an object of the present invention is to provide an audio signal processing device and an audio reproduction device that can accurately determine the no-input state and have a high power saving effect.

  In order to achieve the above object, an audio signal processing device according to the present invention includes a signal processing unit for confirming a state of the audio signal in the audio signal processing device that processes and outputs an input audio signal, and the signal When the processing unit confirms that the period during which the signal level of the audio signal is equal to or lower than the first threshold and is equal to or higher than the second threshold equal to or lower than the first threshold is greater than or equal to a predetermined ratio, It is characterized by.

  Further, in the audio signal processing device having the above configuration, the audio signal is sampled and quantized, and the signal processing unit has a signal level of the audio signal equal to or higher than the first threshold value within a predetermined time or The operation may be stopped when it is confirmed that the number of times equal to or less than the second threshold is equal to or less than a predetermined number.

  If comprised in this way, the state of the sampled and quantized digital audio | voice signal will be confirmed, and it will be determined whether operation | movement is stopped. For this reason, it is possible to perform the determination more easily and accurately than by acquiring and determining an analog audio signal. Furthermore, the state of the audio signal can be confirmed by the signal processing unit without requiring an additional configuration such as an audio signal detection circuit.

  Further, in the audio signal processing device having the above configuration, the number of times that the signal processing unit has the signal level of the audio signal equal to or higher than the first threshold or equal to or lower than the second threshold within a first time is equal to or lower than the first number. Confirm that the number of times that the signal level of the audio signal is greater than or equal to the first threshold or less than or equal to the second threshold within a second time longer than the first time is less than or equal to the second number. In such a case, the operation may be stopped.

  If comprised in this way, it will be determined whether it is a no-input state in each time of 1st short time and 2nd long time. Therefore, it is possible to execute a determination method corresponding to each time. Therefore, it becomes possible to determine the non-input state with higher accuracy.

  Further, an audio reproduction device of the present invention includes the above-described audio signal processing device, and is set to reproduce an audio signal input from the outside of the own device, and the signal processing unit includes the signal of the audio signal. The operation is stopped when it is confirmed that the period during which the level is equal to or lower than the first threshold and equal to or higher than the second threshold is equal to or higher than a predetermined ratio.

  With this configuration, it is difficult to determine whether or not an audio signal is input depending on, for example, a physical connection. When an audio signal is input from the outside of the own device, there is no input state. It is possible to determine whether or not to stop the operation.

  According to the present invention, it is possible to stop the operation of the audio signal processing device and the audio reproduction device when it is determined that the audio signal is not input from the outside in a non-input state. Therefore, it is possible to enhance the power saving effect.

  Furthermore, when the period during which the signal level of the audio signal is within a predetermined range is equal to or greater than a predetermined ratio, it is determined that there is no input. Therefore, even when the signal level suddenly changes due to noise or the like, it can be determined that there is no input state. Therefore, it is possible to determine the non-input state with high accuracy.

These are block diagrams which show an example of a structure of the audio | voice reproduction apparatus concerning embodiment of this invention. FIG. 4 is a diagram illustrating an example of a PCM signal. These are flowcharts which show an example of the stop operation | movement which the audio | voice reproduction apparatus concerning embodiment of this invention performs. These are figures which show the example of a judgment of the necessity of execution of stop operation based on a PCM signal.

  Hereinafter, an audio reproducing apparatus according to an embodiment of the present invention will be described with reference to the drawings. First, an example of the configuration of the audio playback device will be described. FIG. 1 is a block diagram showing an example of the configuration of an audio playback device according to an embodiment of the present invention.

  As shown in FIG. 1, an audio reproduction device 1 of this example is an ADC (Analog to Digital Converter) that digitizes and outputs an input signal, which is an analog audio signal input via, for example, an AUX (Auxiliary) terminal. 10, a decoder 11 that performs a predetermined process on the digital audio signal output from the ADC 10, and an output based on a gain (amplification degree) that is obtained by acquiring the audio signal output from the decoder 11 A digital signal processor (DSP) 12 that performs various processing such as sound field processing and outputs, and a PWM (Pulse Width Modulation) process on the audio signal output from the DSP 12 to generate and output a PWM signal The PWM processing unit 13, the amplifier 14 that amplifies and outputs the PWM signal output from the PWM processing unit 13, and the PWM signal output from the amplifier 14 is reproduced. And a speaker 15 to be provided.

  The decoder 11 performs decoding by a decoding method corresponding to the encoding method when a compression-coded signal is input, but performs decoding when an uncoded signal is input. Absent. Note that the decoder 11 may perform predetermined processing (for example, surround processing) as necessary, or the audio signal output from the ADC 10 without passing through the decoder 11 may be input to the DSP 12. .

  Further, at least the audio signal input to the DSP 12 is preferably a sampled (sampled) and quantized signal such as a PCM (Pulse Code Modulation) signal. In the following, it is assumed that the ADC 10 generates a PCM signal for the sake of concrete description. The PCM signal will be described with reference to FIG. FIG. 2 is a diagram illustrating an example of a PCM signal.

  The thick curve shown in FIG. 2 indicates an (analog) audio signal that can take a continuous signal level, and the corresponding PCM signal is indicated by a white circle. The PCM signal is obtained by sampling an analog audio signal at a certain time interval (vertical thin solid line shown in FIG. 2) and quantizing (in FIG. 2, only an integer value of quantization levels 0 to 15 can be obtained, that is, In this example, the quantization bit number is 4 bits). The example shown in FIG. 2 is merely an example, and any sampling frequency, number of quantization bits, and the like may be used.

The transmission format of the PCM signal may be an I ² S (Inter-IC Sound) format. As the I ² S format, serial data, a sampling clock indicating the acquisition timing of the serial data, a word clock indicating the channel to which the acquired serial data belongs, and a master clock indicating the operation timing of the entire apparatus are provided. You may include the format.

  Next, an example of the sound reproduction operation of the sound reproduction device 1 will be described with reference to FIG. The audio reproduction device 1 first acquires an analog audio signal input via an AUX terminal or the like. The analog audio signal acquired by the ADC 10 is sampled and quantized to generate and output a PCM signal.

  The PCM signal output from the ADC 10 is subjected to audio processing as necessary by the decoder 11 and then input to the DSP 12. The DSP 12 outputs the input PCM signal after performing amplification processing based on the set gain or various processing such as sound field processing. Further, the DSP 12 confirms the state of the input PCM signal and determines whether or not to perform a stop operation. The stop operation is an operation for stopping at least a part of the operation (for example, signal processing operation) of the audio reproduction device 1, and may include stopping power supply.

  The PCM signal output from the DSP 12 is input to the PWM processing unit 13. The PWM processing unit 13 performs PWM processing on the input PCM signal to generate and output a PWM signal. The PWM signal output from the PWM processing unit 13 is input to the amplifier 14. The amplifier 14 amplifies and outputs the input PWM signal.

  The PWM signal output from the amplifier 14 is converted into an analog audio signal that can be reproduced by the speaker 15 by being passed through, for example, an LPF (Low Pass Filter, not shown). Then, the speaker 15 reproduces this analog audio signal. For example, a voice coil (not shown) provided in the speaker 15 is driven according to an audio signal, and the vibration plate vibrates accordingly, thereby reproducing the audio.

  The stop operation performed by the DSP 12 during the above sound reproduction operation will be described with reference to the drawings. FIG. 3 is a flowchart showing an example of a stop operation performed by the audio reproduction device according to the embodiment of the present invention. FIG. 3 particularly shows a method for determining whether or not the stop operation is required by the DSP 12.

  As shown in FIG. 3, the DSP 12 confirms whether or not it is set to reproduce an audio signal input from the outside via, for example, an AUX terminal (STEP 1). If the audio signal input from the outside is not set to be reproduced (STEP 1, NO), the setting confirmation (STEP 1) is continued.

  When reproducing an audio signal input from the outside of the audio reproduction device 1 (for example, another device that is not controlled by the audio reproduction device 1) (STEP 1, YES), it is determined whether or not the audio signal is input. Difficult to do. For example, when a plug or the like is connected to an AUX terminal or the like (even if it is physically connected) and no audio signal is input, even if plug detection or the like is performed, the presence or absence of an audio signal is detected. I can't. Therefore, in the audio reproduction device 1 according to the embodiment of the present invention, the presence or absence of the audio signal is determined by checking the state of the PCM signal to which the DSP 12 is input, and it is determined whether or not the stop operation should be performed. .

  A specific example of this determination will be described below with reference to FIG. FIG. 4 is a diagram illustrating an example of determining whether or not the stop operation needs to be performed based on the PCM signal. Note that the PCM signal illustrated in FIG. 4 has the same format (sampling and quantization) as the PCM signal shown in FIG.

  The DSP 12 determines whether or not the signal level (quantization level) of the PCM signal is within a predetermined range that is interpreted as a signal level when no audio signal is input from the outside (no input state) (first threshold value). (8) Whether or not it is equal to or less than or equal to or greater than the second threshold (7) equal to or less than the first threshold (STEP 2). If the signal level of the PCM signal is not within this range (STEP2, NO), the process returns to STEP1 and the confirmation of the setting and the confirmation of the signal level of the PCM signal are continued.

  On the other hand, when the signal level of the PCM signal falls within the predetermined range (STEP 2, YES), counting of the number of times that the signal level is outside the predetermined range is started (STEP 3). Then, the number of times that the signal level of the PCM signal is out of the range within the first time (for example, 2 seconds) is confirmed (STEP 4). That is, it is confirmed whether or not the period during which the signal level of the audio signal is within a predetermined range is a predetermined ratio or more (no input state).

  In the example shown in FIG. 4A, it is counted that 8 is out of range in the signal level (white circle in the drawing) 20 of the PCM signal acquired by the DSP 12. On the other hand, in the example shown in FIG. 4B, 1 is counted as out of range in the signal level 20 of the PCM signal acquired by the DSP 12. Therefore, for example, in the case of FIG. 4A, it is determined that there is no input state, and in the case of FIG. 4B, it is determined that there is no input state.

  If the number of times that the signal level of the PCM signal is out of range within the first time (count number) is greater than or equal to the first number (STEP 4, YES), the DSP 12 determines that there is no input and resets the count. (STEP 5) Returning to STEP 1, confirmation of settings and confirmation of the signal level of the PCM signal are continued.

  On the other hand, when the number of times that the signal level of the PCM signal is out of the range within the first time (count number) is smaller than the first number (STEP 4, NO), the second time longer than the first time (for example, 30) Minutes), the number of times the signal level of the PCM signal is out of the range is confirmed (STEP 6). That is, it is confirmed whether or not the period during which the signal level of the audio signal is within a predetermined range is a predetermined ratio or more (no input state). In addition, the confirmation of the count number in the second time is performed in the same manner as the confirmation of the count number in the first time (see FIG. 4).

  If the number of times the signal level of the PCM signal falls outside the range (count number) within the second time is equal to or greater than the second number (STEP 6, YES), the DSP 12 determines that there is no input and resets the count. (STEP 5) Returning to STEP 1, confirmation of settings and confirmation of the signal level of the PCM signal are continued.

  On the other hand, when the number of times that the signal level of the PCM signal is out of the range during the second time is smaller than the second number (STEP 6, NO), it is confirmed whether or not the second time has passed (STEP 7). If the second time has not elapsed (STEP 7, NO) and the first time has not elapsed (STEP 8, NO), the process returns to STEP 4 and continues counting and confirmation. If the second time has not elapsed (STEP 7, NO) and the first time has elapsed (STEP 8, YES), after resetting only the count of the first time (STEP 9), the process returns to STEP 4 Continue checking.

  On the other hand, if the second time has elapsed (STEP 7, YES), the DSP 12 determines that there is no input, performs a stop operation (STEP 10), and ends. In the stop operation, at least a part of the operation of the audio playback device 1 is stopped. Note that the supply of power may be stopped when the operation is stopped.

  If comprised as mentioned above, when it determines with it being a no-input state in which the audio | voice signal is not input from the outside, it will become possible to stop operation | movement of the audio | voice reproduction apparatus 1. Therefore, it is possible to enhance the power saving effect.

  Furthermore, when the period during which the signal level of the audio signal is within a predetermined range is equal to or greater than a predetermined ratio, it is determined that there is no input state. Therefore, even when the signal level suddenly changes due to noise or the like, it can be determined that there is no input state. Therefore, it is possible to determine the non-input state with high accuracy.

  Further, the DSP 12 confirms the state of the sampled and quantized digital audio signal (PCM signal) and determines whether or not there is a no-input state (necessity of the stop operation). Therefore, it is possible to make determination more easily and more accurately than acquiring and determining an analog audio signal (for example, an audio signal input via an AUX terminal or an audio signal reproduced by the speaker 15). It becomes. Furthermore, it is possible to confirm whether or not the DSP 12 is in the no-input state without requiring an additional configuration such as an audio signal detection circuit.

  In addition, the DSP 12 determines whether or not there is a no-input state at each of the short first time and the long second time. Therefore, it is possible to execute a determination method corresponding to each time. Therefore, it becomes possible to determine the non-input state with higher accuracy.

  The first threshold value (8) and the second threshold value (7) described above are merely examples, and may be any value. For example, the first threshold value and the second threshold value may be the same value. Moreover, although the threshold value applied by STEP2 and STEP3 of FIG. 3 was made into the same value, it is good also as a different value. Further, in STEPs 4 and 6 to 8 in FIG. 3, the measurement of the first time and the second time may be performed by counting the sampling timing (vertical line in FIG. 4).

  In STEP 3, the signal level that is equal to or higher than the first threshold value or equal to or lower than the second threshold value is counted. Conversely, a signal level that is smaller than the first threshold value and larger than the second threshold value may be counted. In this case, when the count number is equal to or less than the predetermined number, it is determined that the state is not in the no-input state (STEP 4 and 6, YES), and the count is reset (STEP 5).

  As mentioned above, although embodiment in this invention was described, the range of this invention is not limited to this, It can add and implement various changes in the range which does not deviate from the main point of invention.

  The present invention relates to an audio signal processing apparatus that processes and outputs an input audio signal, and an audio reproduction apparatus that reproduces an audio signal output from the audio signal processing apparatus. In particular, the present invention relates to an audio signal processing apparatus and an audio reproduction apparatus that have a high power saving effect.

1 Audio playback device 10 ADC
11 Decoder 12 DSP
13 PWM processing unit 14 Amplifier 15 Speaker

Claims (3)

An analog-to-digital converter for sampling and quantizing the audio signal;
Having a first threshold and a second threshold less than or equal to the first threshold;
The signal level of the sampled and quantized voice signal and is equal to or less than the first threshold value within a predetermined time, and the time the second threshold value or more Ri der predetermined ratio or more, and,
A signal processing unit for stopping the operation when the number of times that the signal level of the audio signal is equal to or higher than the first threshold value or equal to or lower than the second threshold value within a predetermined time is equal to or less than a predetermined number of times;
The audio signal processing apparatus characterized by comprising a. The predetermined time has a first predetermined time and a second predetermined time longer than the first predetermined time,
The signal processing unit determines that the number of times is less than or equal to the first number of times within the first predetermined time and less than or equal to the second number of times within the second predetermined time. The audio signal processing apparatus according to claim 1. Having a first threshold and a second threshold less than or equal to the first threshold;
A time during which a signal level of the audio signal is equal to or lower than the first threshold value within a predetermined time and is equal to or higher than the second threshold value is equal to or higher than a predetermined ratio; and
The number of times that the signal level of the audio signal is greater than or equal to the first threshold value or less than or equal to the second threshold value is less than or equal to the first number within the first predetermined time and is longer than the first predetermined time. In a predetermined time of 2, the signal processing unit that stops the operation when it is equal to or less than the second number of times,
An audio signal processing apparatus comprising:

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