Patent Publication Number: US-2003224778-A1

Title: Method and apparatus for audio data communication with non-audio area detection

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001] This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2002-157740, filed May 30, 2002, the entire contents of which are incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002] 1. Field of the Invention  
       [0003] The present invention generally relates to audio data communication apparatuses, and more particularly pertains to a communication control method for controlling transmission of audio data in a non-audio data area.  
       [0004] 2. Description of the Related Art  
       [0005] In recent years, portable or simplified systems for wireless audio communication have been realized using a radio communication technique based on short-range radio communication standards such as Bluetooth (registered trademark). Specifically, according to the systems, wireless audio communication is provided between, for example, a mobile phone or a mobile audio gateway device (hereinafter referred to as an AG device) and a headset device (hereinafter referred to as an HS device).  
       [0006] For communication connecting systems based on the Bluetooth standards, communication connection methods called an asynchronous connection-less (ACL) link and a synchronous connection-oriented (SCO) link are provided.  
       [0007] The ACL link is an asynchronous connection method without previously selecting a radio band. According to the ACL link, if data includes an error, retransmission is carried out to ensure data integrity. The SCO link is a synchronous connection method for previously selecting a predetermined radio band and conducting communication at predetermined intervals. The SCO link is particularly used for communication such as real-time audio data communication. The foregoing wireless audio communication can be realized using the SCO link.  
       [0008] When audio data communication is performed by the radio communication system using the SCO link, audio data is transferred from, for example, an AG device to an HS device at predetermined intervals. If communication with the SCO link is established, audio data is successively transferred.  
       [0009] However, in the audio data communication, a state without any sound of a predetermined level or higher (non-audio state, silent State, or no-audible state) often occurs. In the normal radio communication method, if data includes audio data in a non-audio area (non-audio data area), the data transfer operation is continued as it is. When such useless data transfer frequently occurs, power consumption of the useless data transfer operation is not negligible.  
       [0010] In order to solve the above problem, according to a related art (refer to, for example, Jpn. Pat. Appln. KOKAI Publication No. 7-22994), a non-audio period (non-audio data area) is detected from audio data and the level of radio transmission power in non-audio data transmission is lower than that in audio data transmission. However, the power consumption cannot always be reduced effectively by merely reducing the radio transmission power level in response to the detection of the non-audio period. Particularly, if a short non-audio period often occurs, the frequency of switching control of the power level is high, resulting in a deterioration in the efficiency of communication.  
       BRIEF SUMMARY OF THE INVENTION  
       [0011] In accordance with one embodiment of the present invention, there is provided an audio data communication apparatus and method for disconnecting a communication connection to interrupt transmission of audio data when a non-audio area is generated for a predetermined time during audio data communication.  
       [0012] The audio data communication apparatus includes: a data communication unit which transmits data including audio data and non-audio data to a receiver, with which a communication connection is established; a non-audio detection unit which detects a non-audio data area in the data; and a communication control unit which effects such control that, when the non-audio detection unit detects a non-audio data area having a predetermined amount of data, the communication connection with the receiver is disconnected for a period corresponding to the transmission period of the non-audio data area. 
     
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
     [0013] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention.  
     [0014]FIG. 1 is a block diagram showing an essential part of an audio data communication system according to an embodiment of the present invention;  
     [0015]FIGS. 2 and 3 are timing charts for explaining a radio communication connection procedure according to the present embodiment;  
     [0016]FIG. 4 is a timing chart for explaining a communication connection procedure concerned with a non-audio detection processing according to the present embodiment;  
     [0017]FIG. 5 is a diagram for explaining a state of a buffer concerned with the non-audio detection processing; and  
     [0018]FIG. 6 is a flowchart for explaining the audio data communication operation according to the present embodiment. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0019] An embodiment of the present invention will now be described with reference to the drawings.  
     [0020] (Structure of Audio Data Communication System)  
     [0021]FIG. 1 is a block diagram showing an essential part of an audio data communication system according to the present embodiment.  
     [0022] According to the invention, a short-range radio data communication system (based on, for example, the Bluetooth standard) comprises an audio gateway (AG) device  1  and a headset (HS) device  2 . Audio data communication is performed between the AG device  1  and the HS device  2 .  
     [0023] The AG device  1  comprises a radio communication unit  10 , an audio input unit  11 , a communication control unit  12 , and a non-audio detection unit  13 .  
     [0024] The radio communication unit  10  and the communication control unit  12  operate as a radio data communication function. The audio input unit  11  is connected to a recording medium  3  such as an IC memory or a disk recording medium. The audio input unit  11  receives audio signals (including music data comprising PCM signals) from the medium  3 . The audio input unit  11  has a function of converting the audio signal into audio data in a predetermined digital format. Further, the audio input unit  11  includes a buffer  50  which temporarily stores the converted audio data in the digital format (refer to FIG. 5).  
     [0025] The radio communication unit  10  transmits the audio data (including a non-audio data area serving as a non-audio interval, which will be described later) stored in the buffer  50  of the audio input unit  11  to the HS device  2  serving as a communication destination under control through the communication control unit  12 .  
     [0026] The non-audio detection unit  13  detects a non-audio data area from the audio data stored in the buffer  50  of the audio input unit  11 . The non-audio detection unit  13  notifies the communication control unit  12  of the detection result. In other words, the non-audio detection unit  13  has a function of discriminating between an audio data area and the non-audio data area on the basis of an audio signal level of audio data. Specifically, the non-audio detection unit  13  includes a microprocessor (CPU) which allows software to execute a process of, for example, discriminating between the audio data area and the non-audio area.  
     [0027] The audio input unit  11  can be connected to not only the recording medium  3  but also an audio output device such as a mobile phone. The audio input unit  11  can also receive an audio signal and a music signal from the audio output device.  
     [0028] In the system according to the present embodiment, the AG device  1  serves as a transmitter and the HS device  2  functions as a receiver. The HS device  2  comprises a radio communication unit  20  for communicating with the radio communication unit  10  of the AG device  1  by radio, an audio output unit  21 , and a communication control unit  22 .  
     [0029] The audio output unit  21  converts audio data received by the radio communication unit  20  into an analog audio signal and generally generates the signal to a speaker. The radio communication unit  20  and the communication control unit  22  operate as a radio data communication function based on the same radio communication standards (for instance, the Bluetooth standard) as that of the AG device  1 .  
     [0030] (Communication Connection Procedure)  
     [0031] A communication connection procedure in a case where the present system uses a communication connection method based on the Bluetooth standard will now be described with reference to FIGS. 2 and 3.  
     [0032] Referring to FIG. 2, the AG device  1  transmits an ACL link establishment request to the HS device  2 . In response to the request, an ACL link is established between the AG device  1  and the HS device  2 .  
     [0033] Further, the AG device  1  transmits a call command to the HS device  2  through the ACL link. The HS device  2  transmits an acknowledgement (ACK) in response to the command. When receiving the acknowledgement, the AG device  1  generates an SCO link establishment request to the HS device  2 . Consequently, the SCO link is established, thus starting to transfer audio data from the AG device  1  to the HS device  2 .  
     [0034] Referring to FIG. 3, when receiving a disconnection request from the HS device  2 , the AG device  1  generates an SCO link disconnection request. Consequently, the SCO link is disconnected, thus interrupting the communication of audio data between the AG device  1  and the HS device  2 .  
     [0035] (Communication Control Operation of Audio Data)  
     [0036] The communication control operation of the present system will now be described with reference to FIGS. 4, 5, and  6 .  
     [0037] In accordance with the foregoing procedure shown in FIG. 2, a communication connection processing of establishing the ACL link and the SCO link between the AG device  1  and the HS device  2  is executed (step S 1 ). The AG device  1  converts an audio signal supplied from the recording medium  3  into audio data and then starts communication with the HS device  2 , the communication including transfer of the audio data (step S 2 ).  
     [0038] Referring to FIG. 5, in the AG device  1 , the audio input unit  11  stores the audio data converted in the predetermined digital data format into the FIFO buffer  50 . The audio input unit  11  sequentially transfers data from the buffer  50  to the radio communication unit  10 .  
     [0039] In this instance, the non-audio detection unit  13  detects the non-audio data area (non-audio data  500 ) in the audio data input to the buffer  50  (step S 3 ). In other words, the non-audio detection unit  13  discriminates between the audio data area and the non-audio data area of the audio data to be stored in the buffer  50 .  
     [0040] The communication control unit  12  controls the radio communication unit  10  to transmit useful audio data, transferred from the audio input unit  11 , to the HS device  2  (step S 9 , if NO in step S 3 ). When the transmission operation of all audio data is completed, the communication control unit  12  terminates the communication operation (step S 10 ).  
     [0041] On the other hand, when the non-audio detection unit  13  detects the non-audio data area from the audio data at predetermined timing (NT) and the non-audio data area continues for a predetermined period, the non-audio detection unit  13  notifies the communication control unit  12  of the detection (YES in step S 4 ). As shown in FIG. 5, the predetermined period corresponds to a predetermined proportion of the amount of non-audio data  500  to the capacity (BT) of the buffer  50 . Referring to FIG. 5, a data area  501  is shown subsequent to the non-audio data area  500 .  
     [0042] In response to the information from the non-audio detection unit  13 , the communication control unit  12  allows the radio communication unit  10  to disconnect the SCO link in accordance with the procedure shown in FIG. 3 (step S 5 ). Thus, the transfer of audio data from the AG device  1  to the HS device  2  is interrupted. As a matter of course, while the SCO link is being disconnected, audio reproduction is suspended in the HS device  2 .  
     [0043] Subsequently, when detecting the audio data area ( 501 ) subsequent to the non-audio data area ( 500 ), the non-audio detection unit  13  notifies the communication control unit  12  that the non-audio data disappears (YES in steps S 6  and S 7 ). Consequently, as shown in FIG. 4, the communication control unit  12  re-establishes the SCO link between the AG device  1  and the HS device  2  (step S 8 ). Therefore, the transfer of audio data from the AG device  1  to the HS device  2  is restarted. Thus, audio reproduction is restarted in the HS device  2 .  
     [0044] As mentioned above, in the present system, during the transfer of audio data from the AG device  1  (transmitter) to the HS device  2  (receiver) with radio communication, if a non-audio data area is generated in audio data, a communication connection corresponding to, for example, the establishment of the SCO link is disconnected. Therefore, since the transfer of the non-audio data area is stopped for a non-audio period in the audio data communication, useless data transfer can be avoided. Thus, the power consumption of the useless data transfer can be cut.  
     [0045] In the present system, when the non-audio data area continues for a predetermined period (the predetermined amount of data), the communication connection is disconnected. Accordingly, if a relatively short-time non-audio data area is often generated, the communication connection is held as it is. Therefore, it is possible to avoid a case where the disconnection of the communication connection and the establishment thereof are frequently performed, resulting in deterioration of the communication efficiency.  
     [0046] Accordingly, the present invention is effectively used for audio communication in an audio gateway device or a mobile phone using a battery having a limited capacity. Since the deterioration of the communication efficiency can be minimized, the present invention can be effectively used for real-time audio communication.  
     [0047] The communication control unit  12  of the AG device  1  controls to switch the disconnection and the establishment of the SCO link in accordance with the detection result supplied from the non-audio detection unit  13 . When the disconnected SCO link is changed into the establishment state, the communication control unit  12  controls so that the head of a restarted audio output is not cut or the audio reproduction is not delayed.  
     [0048] According to the present embodiment, the audio data communication between the AG device  1  and the HS device  2  has been described. The present invention is not limited to the case. The present invention can also be applied to audio communication between personal computers and mobile phones. For the communication connection method, the application of the radio communication standards based on the Bluetooth standard have been described. The present invention is not limited to the case. Other communication standards can be used.  
     [0049] As mentioned above, according to the present embodiment, if a predetermined non-audio period continues in audio data communication, a communication connection is disconnected to interrupt the audio data communication operation. Consequently, power consumption in the communication operation for the non-audio period can be cut. In this instance, if a short non-audio period occurs very often, the communication connection is maintained, thus preventing deterioration of the communication efficiency. Therefore, in the audio data communication, useless data transfer for the non-audio period can be avoided, deterioration of the communication efficiency can be prevented, and power consumption can be effectively reduced in the communication operation.  
     [0050] Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.