Abstract: A network audio system allows AV files existing in a PC to be readily registered and music to be reproduced using a client machine. The client machine is connected to the PC and a server application and a controller application are installed in the PC. Music is reproduced using the client machine based on an AV file existing in a user folder, when the user drags and drops an icon for the AV folder to an icon for the client machine. In response to the operation, the controller application produces music piece information including the artist name and the like based the tag information of the AV file. When the music piece information is not yet registered, the server application provides the music piece information with a music piece ID for registration in the content information database. The controller application transmits a command including the ID to the client machine.

Abstract: A client repeatedly transmits a firmware request including an obtaining start address and an obtaining data length. The obtaining start address indicates the first address of firmware data to be obtained from the server by the client. The obtaining data length indicates the length of the firmware data to be obtained from the server by the client with respect to each firmware request. The server receives the firmware request from the client repeatedly and returns the firmware data for the obtaining data length from the obtaining start address with respect to each firmware request. The client further obtains the firmware data returned from the server repeatedly and updates the firmware by using the firmware data obtained from the server.

Abstract: A network AV system comprises a controller, a client connectable to the controller via a network, and an AV equipment connectable to the client. The controller includes a first transmitting unit transmitting a command for controlling a controlled element of the AV equipment to the client. The client includes a first receiving unit receiving the command from the controller, and a second transmitting unit transmitting the command to the AV equipment. The AV equipment includes the controlled element, a second receiving unit receiving the command from the client, and a controlling unit controlling the controlled element according to the received command.

Abstract: A client repeatedly transmits a firmware request including an obtaining start address and an obtaining data length. The obtaining start address indicates the first address of firmware data to be obtained from the server by the client. The obtaining data length indicates the length of the firmware data to be obtained from the server by the client with respect to each firmware request. The server receives the firmware request from the client repeatedly and returns the firmware data for the obtaining data length from the obtaining start address with respect to each firmware request. The client further obtains the firmware data returned from the server repeatedly and updates the firmware by using the firmware data obtained from the server.

Abstract: A network AV system comprises a controller, a client connectable to the controller via a network, and an AV equipment connectable to the client. The controller includes a first transmitting unit transmitting a command for controlling a controlled element of the AV equipment to the client. The client includes a first receiving unit receiving the command from the controller, and a second transmitting unit transmitting the command to the AV equipment. The AV equipment includes the controlled element, a second receiving unit receiving the command from the client, and a controlling unit controlling the controlled element according to the received command.

Abstract: The network type audio system includes a content server storing a large number of music data pieces, an audio client reproducing music, and a controller monitoring and controlling the audio client through the content server. The audio client requests the server to provide the music data of a music piece selected in response to the user's operation. The content server returns the music data of the selected music piece in response to the request from the audio client. The music data is distributed from the content server to the audio client on the basis of a specified amount. The audio client notifies the content server of its status. The content server notifies the controller of the status of the audio client. The controller displays the status. The controller also instructs the audio client to reproduce the music piece selected in response to the user's operation through the content server.

Abstract: The network type audio system includes a content server storing a large number of music data pieces, an audio client reproducing music, and a controller monitoring and controlling the audio client through the content server. The audio client requests the server to provide the music data of a music piece selected in response to the user's operation. The content server returns the music data of the selected music piece in response to the request from the audio client. The music data is distributed from the content server to the audio client on the basis of a specified amount. The audio client notifies the content server of its status. The content server notifies the controller of the status of the audio client. The controller displays the status. The controller also instructs the audio client to reproduce the music piece selected in response to the user's operation through the content server.

Abstract: The network type audio system includes a content server storing a large number of music data pieces, an audio client reproducing music, and a controller monitoring and controlling the audio client through the content server. The audio client requests the server to provide the music data of a music piece selected in response to the user's operation. The content server returns the music data of the selected music piece in response to the request from the audio client. The music data is distributed from the content server to the audio client on the basis of a specified amount. The audio client notifies the content server of its status. The content server notifies the controller of the status of the audio client. The controller displays the status. The controller also instructs the audio client to reproduce the music piece selected in response to the user's operation through the content server.

Abstract: The network type audio system includes a content server storing a large number of music data pieces, an audio client reproducing music, and a controller monitoring and controlling the audio client through the content server. The audio client requests the server to provide the music data of a music piece selected in response to the user's operation. The content server returns the music data of the selected music piece in response to the request from the audio client. The music data is distributed from the content server to the audio client on the basis of a specified amount. The audio client notifies the content server of its status. The content server notifies the controller of the status of the audio client. The controller displays the status. The controller also instructs the audio client to reproduce the music piece selected in response to the user's operation through the content server.

Abstract: The network type audio system includes a content server storing a large number of music data pieces, an audio client reproducing music, and a controller monitoring and controlling the audio client through the content server. The audio client requests the server to provide the music data of a music piece selected in response to the user's operation. The content server returns the music data of the selected music piece in response to the request from the audio client. The music data is distributed from the content server to the audio client on the basis of a specified amount. The audio client notifies the content server of its status. The content server notifies the controller of the status of the audio client. The controller displays the status. The controller also instructs the audio client to reproduce the music piece selected in response to the user's operation through the content server.

Abstract: The network type audio system includes a content server storing a large number of music data pieces, an audio client reproducing music, and a controller monitoring and controlling the audio client through the content server. The audio client requests the server to provide the music data of a music piece selected in response to the user's operation. The content server returns the music data of the selected music piece in response to the request from the audio client. The music data is distributed from the content server to the audio client on the basis of a specified amount. The audio client notifies the content server of its status. The content server notifies the controller of the status of the audio client. The controller displays the status. The controller also instructs the audio client to reproduce the music piece selected in response to the user's operation through the content server.

Abstract: The network type audio system includes a content server storing a large number of music data pieces, an audio client reproducing music, and a controller monitoring and controlling the audio client through the content server. The audio client requests the server to provide the music data of a music piece selected in response to the user's operation. The content server returns the music data of the selected music piece in response to the request from the audio client. The music data is distributed from the content server to the audio client on the basis of a specified amount. The audio client notifies the content server of its status. The content server notifies the controller of the status of the audio client. The controller displays the status. The controller also instructs the audio client to reproduce the music piece selected in response to the user's operation through the content server.

Abstract: The network type audio system includes a content server storing a large number of music data pieces, an audio client reproducing music, and a controller monitoring and controlling the audio client through the content server. The audio client requests the server to provide the music data of a music piece selected in response to the user's operation. The content server returns the music data of the selected music piece in response to the request from the audio client. The music data is distributed from the content server to the audio client on the basis of a specified amount. The audio client notifies the content server of its status. The content server notifies the controller of the status of the audio client. The controller displays the status. The controller also instructs the audio client to reproduce the music piece selected in response to the user's operation through the content server.

Abstract: A network audio system allows AV files existing in a PC to be readily registered and music to be reproduced using a client machine. The client machine is connected to the PC and a server application and a controller application are installed in the PC. Music is reproduced using the client machine based on an AV file existing in a user folder, when the user drags and drops an icon for the AV folder to an icon for the client machine. In response to the operation, the controller application produces music piece information including the artist name and the like based the tag information of the AV file. When the music piece information is not yet registered, the server application provides the music piece information with a music piece ID for registration in the content information database. The controller application transmits a command including the ID to the client machine.

Abstract: An AV system that permits only a single copy of an AV content without encryption and prevents the copy from being further duplicated in order to protect the copyright is provided. The hard disk of a home server is divided into a secure system region and a non-secure user region. A PC searches for the home server to establish a connection for authentication. The PC includes a ripping unit and a reproducing unit. The network type audio apparatus also includes a reproducing unit and is authenticated. The ripping unit rips music data from a music CD after the authentication and duplicates the data in the system region. The reproducing unit reads out music data from the system region after the authentication and reproduces the music data by a streaming method.

Abstract: A low-pass filter (700) includes a differential operation circuit (2), a voltage-current conversion circuit (3), and a capacitor (C1). The voltage-current conversion circuit (3) and the capacitor (C1) form a filter circuit (700), and therefore the low-pass filter can remove a high frequency component. The differential operation circuit (2) outputs a differential signal (&phgr;C) for the difference between an analog signal (&phgr;A) and an output signal (&phgr;B). Therefore, with the differential operation circuit (2), a necessary frequency band is not attenuated. The phase level of the output signal (&phgr;B) output from the low-pass filter (700) can be substantially equal to that of the analog signal (&phgr;A) by the differential operation circuit (2). Therefore, the low-pass filter have a higher attenuation ratio for a high frequency component.

Abstract: A low-pass filter (700) includes a differential operation circuit (2), a voltage-current conversion circuit (3), and a capacitor (C1). The voltage-current conversion circuit (3) and the capacitor (C1) form a filter circuit (700), and therefore the low-pass filter can remove a high frequency component. The differential operation circuit (2) outputs a differential signal (&phgr;C) for the difference between an analog signal (&phgr;A) and an output signal (&phgr;B). Therefore, with the differential operation circuit (2), a necessary frequency band is not attenuated. The phase level of the output signal (&phgr;B) output from the low-pass filter (700) can be substantially equal to that of the analog signal (&phgr;A) by the differential operation circuit (2). Therefore, the low-pass filter have a higher attenuation ratio for a high frequency component.

Abstract: A digital-to-analog (D/A) converter used for a digital audio equipment, comprises a binary D/A converting circuit and a calculation processing circuit for receiving an analog signal derived from the binary D/A converting circuit. This D/A converter is capable of considerably reducing a load given to an LPF (low-pass filter) or, of omitting such an LPF. The binary D/A converting circuit outputs an analog signal value corresponding to each sampling point of a digital signal as a first analog output value, and also outputs an analog output signal value delayed by only 1 sampling period as a second analog output value. A difference calculating unit of the calculation processing circuit calculates a difference value between the first analog output value as a first analog input value, and the second analog output value as a second analog input value.