Abstract:
A method and apparatus for improving the mute function of an IP telephone is disclosed, where the method comprises determining, by a transmitting IP telephone, whether the mute function has been activated; and if the mute function has been activated, then providing, a predetermined output. Various aspects of the method are disclosed, including: an aspect where the predetermined output is characterized by the absence of silence as detected by an RX unit when the mute function of a TX unit is activated; an aspect where the predetermined output comprises a signal in which voice information has been removed; and an aspect where the removing of voice information is performed by an audio filter disposed within the TX unit of an IP telephone.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to telephony. In particular, the present invention relates to concealing the mute function in an IP-based telephony system. 
     2. The Prior Art 
     BACKGROUND. 
     The widespread acceptance and use of the Internet has generated much excitement, particularly among those who see the Internet as a possible substitute for the traditional telephone system. As the backbone of the Internet continues to be upgraded and expanded, the promise of a low-cost substitute to the traditional PBX system may now be realized. 
     One type of Internet-based telephony system that is gaining acceptance is IP telephony, which transfers voice information over the Internet Protocol (IP) of the TCP/IP protocol suite. While many standards exist, such as Voice over Packet (VOP) for Frame Relay and ATM networks, as used herein the term “IP telephony” will be used to designate voice over any packet-based network. In IP telephony, a user wishing to communicate uses an IP telephone, which is a device which transports voice over a network using data packets instead of the traditional switched circuits of a voice only network. 
     FIG. 1 shows an IP telephony system  100  of the prior art. System  100  includes a business system  102  configured to provide IP telephony in an enterprise environment. Business system  102  may include a network  104 , such as a corporate Ethernet LAN, to which a plurality of IP telephones  106  may be operatively coupled to network  104  using hardware and software standard in the art. To couple the business system  102  to the outside world, typically a gateway  108  standard in the art is provided and operatively coupled between network  104  and backbone network  110 . 
     Backbone network  110  may be any packet-based network standard in the art, such as IP, Frame Relay, or ATM. To provide voice communications to legacy POTS phones, typically a gateway  112  is provided, which may be a VoP gateway. Gateway  112  provides access to the Public Switched Telephone Network (PSTN)  114 . Through PSTN  114 , voice-only communications may be provided to legacy POTS phones  116 . 
     The system  100  of FIG. 1 also includes an example of a broadband residential system  118 . To reach individual residences, typically local ISP providers provide a cable or DSL head end  120  standard in the art. An individual wishing to utilize the ISP&#39;s service may then employ a cable modem or DSL modem  122  coupled to the user&#39;s home LAN  124 . The user&#39;s home LAN may be provided by a home PC  126  configured to run software standard in the art such Microsoft Windows®. The user may then operatively couple an IP telephone  128  to the LAN  124 . 
     Thus, in the system  100  of FIG. 1, IP telephones  106  in business system  102  may communicate by voice with other similar business systems similarly configured with IP telephones. For a business enterprise, communication by IP telephony may be advantageous because the need for a traditional PBX system can be eliminated. Furthermore, an IP telephony system is scalable and may be upgraded along with the enterprise&#39;s network system. 
     Likewise, the residence of system  118  may communicate by voice to a POTS phone  116  using IP telephone  128 . From the view of the home user, the communication of FIG. 1 is advantageous because the communication operates over the backbone network  110  without accessing traditional long-distance service providers. 
     FIG. 2 is conceptual block diagram of a prior art IP telephone system  200  including a TX unit  202  of a transmitting IP telephone standard in the art and a RX unit  204  of a receiving IP telephone standard in the art. TX unit  202  and RX unit  204  are shown operatively coupled to each other through a network cloud  216 . For the sake of clarity, elements of a typical IP telephone not essential to the explanation of the present invention are not shown in the disclosure. 
     TX unit  202  includes a microphone  206  coupled to a mute switch  207 . The mute switch is toggled by a mute user input  227  which may consist of a physical button or softkey on the IP telephone. Mute switch  207  couples the input audio stream to a Voice Activity Detector (VAD)  208 , a silence indication packet generator  212  and an encoder  214 . VAD  208 , encoder  214 , and silence indication packet source  212  are operatively coupled to each other to provide an output for transmission over network  216 . 
     In a typical operation, voice information is received on microphone  206  and presented to mute switch  207 . If the mute function of the IP telephone is not engaged through the mute user input  227  (i.e., the mute is off) the mute switch  207  will be closed, and the voice information will be presented to the VAD  208 , the encoder and the silence indication packet source  212 . 
     Using methods known in the art, the VAD  208  will determine whether there is voice activity present in the signal coming from microphone  206 . If there is voice activity in the signal, the switching logic will pass the output of the encoder (i.e., a packet stream) for transmission to network cloud  216  using methods standard in the art. 
     If the VAD  208  determines that there is no voice activity present on the signal coming from microphone  206 , then the switching logic  210  will send one or more silence indications packets to network cloud  116 . The silence indication packets contain at least a background noise level so that the comfort noise generator  218  on the receive side can generate noise similar in level and character to the actual background noise on the transmit side. 
     As is known by those skilled in the art, in some IP telephony systems, a user may disable the VAD of their IP telephone. In such a situation, only background noise can be sent, since silence indication packets can no longer be sent. As used herein, background noise will be used to designate either real background noise, or comfort noise, depending on how the IP telephone is configured. 
     Comfort noise is a prior art solution to save network bandwidth. The prior art methods determined that if there is no voice activity present, then no voice packets should be sent over the network. However, this results in a unnatural silence appearing on the receiving unit, since no packets are being sent. As a result, the prior art methods developed the concept of comfort noise, which presents the listener with generated noise designed to mimic the line noise of traditional legacy telephones when there is no voice activity present. The comfort noise reassures listeners that their connection is still active. 
     Referring still to FIG. 2, RX unit  204  includes a comfort noise generator  218  operatively coupled to a decoder  220 . The comfort noise generator  218  and decoder  220  are both operatively coupled to switching logic  224 . When the output of TX unit  202  has been transmitted over network  216 , it will be received by RX unit  204 , and presented to a decoder  220  and a comfort noise generator  218  using methods standard in the art. 
     If the switching logic receives an encoded voice packet it routes it to the decoder which then outputs the decoded audio signal tot the speaker  226 . If the switching logic receives a silence indication packet it routes it the comfort noise generator  218  which then generates comfort noise to the speaker  226  until further voice packets are received. Typically, the CF comprises white or pink noise. 
     While the systems of FIGS. 1 and 2 perform well for there intended purpose, some disadvantages have been encountered when compared to legacy phone systems. For example, some users of IP telephones have reported inconveniences when using the mute function of an IP telephone. 
     Referring back to FIG. 2, when the mute function is engaged (i.e., the mute is turned on), mute switch  207  will be open. In prior art systems, the switching logic  210  will sense the opening of mute switch  207 , and cease to send voice packets or CF packets over the network. Thus, no information will be transmitted over the network, resulting in silence appearing on the receiving unit. Switching logic  210  may also send CF packets which contain pure silence indication due to the opening of switch  207 . Since this silence does not have any voice information or CF noise present, listeners may perceive that the line has gone dead or that they have been disconnected. 
     FIG. 3 is a prior art conceptual diagram showing IP telephony data flow received by a receiving unit when the mute function is engaged on a transmitting unit. The blocks of FIG. 3 represents the information present during time intervals T 1  through T 5 . 
     In time interval T 1 , the receiving unit may be receiving voice information while engaging in a conversation. When the conversation quiets down, the receiving unit may then receive background noise in time interval T 2 . If the transmitting parties engage the mute function of the transmitting unit, the receiving unit will then hear the background noise disappear and be replaced by silence during time interval T 3 . After the transmitting party disengages the mute function of the transmitting unit in time interval T 4 , background noise will reappear. Finally, the conversation may resume in time interval  5 , and the receiving unit will again hear voice information. Thus, the listening parties utilizing IP telephones of the prior art will perceive silence when the transmitting parties engage the mute function of their IP telephones. This interval of silence has certain disadvantages, including the perception by the receiving party that the connection has been lost, as well as the uncomfortable feeling the results from knowing the other party is censoring the conversation. 
     Hence there is a need for a method and apparatus to eliminate the silence that occurs when the mute function of an IP telephone is engaged. 
     BRIEF DESCRIPTION OF THE INVENTION 
     The invention satisfies the above needs. The present invention relates to telephony. In particular, the present invention relates to concealing the mute function in an IP-based telephony system. 
     A method and apparatus for improving the mute function of an IP telephone is disclosed, where the method comprises determining, by a transmitting IP telephone, whether the mute function has been activated; and if the mute function has been activated, then providing, a predetermined output. 
     Various aspects of the method are disclosed, including: an aspect where the predetermined output is characterized by the absence of silence as detected by an RX unit when the mute function of a TX unit is activated; an aspect where the predetermined output comprises a signal in which voice information has been removed; and an aspect where the removing of voice information is performed by an audio filter disposed within the TX unit of an IP telephone. 
     Additional aspects of the present invention is disclosed where the predetermined output is comfort noise, and where the act of providing comfort noise is performed by a mute switch disposed within the switching logic of a TX unit of an IP telephone. 
     By using IP telephones configured according to the present invention, listeners will not experience the silence which is heard in IP telephones of the prior art when the mute function is activated. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING FIGURES 
     FIG. 1 is a prior art diagram of an IP telephone communications system. 
     FIG. 2 is a prior art detailed diagram of an IP telephone communications system. 
     FIG. 3 is a prior art diagram of IP telephony data flow received by a receiving unit when the mute function is engaged on a transmitting unit. 
     FIG. 4 is detailed diagram of an IP telephone communications system according to the present invention. 
     FIG. 5 is a flowchart of one aspect of the present invention. 
     FIG. 6 is a diagram of IP telephony data flow received by a receiving unit when the mute function is engaged on a transmitting unit according to the present invention. 
     FIG. 7 is detailed diagram of an IP telephone communications system according to the present invention. 
     FIG. 8 is a flowchart of another aspect of the present invention. 
     FIG. 9 is a diagram of IP telephony data flow received by a receiving unit when the mute function is engaged on a transmitting unit according to another aspect of the present invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Persons of ordinary skill in the art will realize that the following description of the present invention is illustrative only and not in any way limiting. Other embodiments of the invention will readily suggest themselves to such skilled persons having the benefit of this disclosure. 
     It is contemplated that the present invention may be embodied in various computer and machine readable data structures. Furthermore, it is contemplated that data structures embodying the present invention will be transmitted across computer and machine-readable media, and through communications systems by use of standard protocols such as those used to enable the Internet and other computer networking standards. 
     The invention further relates to machine-readable media on which are stored embodiments of the present invention. It is contemplated that any media suitable for storing instructions related to the present invention is within the scope of the present invention. By way of example, such media may take the form of magnetic, optical, or semiconductor media. 
     The present invention may be described through the use of flowcharts. Often, a single instance of an embodiment of the present invention will be shown. As is appreciated by those of ordinary skill in the art, however, the protocols, processes, and procedures described herein may be repeated continuously or as often as necessary to satisfy the needs described herein. Accordingly, the representation of the present invention through the use of flowcharts should not be used to limit the scope of the present invention. 
     FIG. 4 shows a first aspect of an improved mute function according to the present invention. FIG. 4 shows a IP telephony system  400 , further including a TX unit  402  configured according to the present invention and operatively disposed within an IP telephone. Where structure is substantially similar to that of FIG. 2, it has been similarly designated. In the embodiment of FIG. 4, a filter  404  is operatively coupled to mute switching logic  407  and microphone  206 . In an exemplary non-limiting embodiment, filter  404  comprises an audio filter configured to remove voice activity from the signal provided by microphone  206 . 
     It is contemplated that audio filter  404  may comprise a variety of forms. For example, audio filter  404  may comprise one or more filters configured to filter out speech information and let room noise (non-speech information) pass through. The audio filter  404  may also comprise one or more audio filters configured to precisely filter out the active speaker and pass all else. 
     Also, audio filter  404  may comprise a filter which tracks the average background noise level and generates random noise, such as white or pink noise, at a corresponding level. 
     It should be noted that the output generated by audio filter  404  may not represent the final output to the receiver. For example, in one embodiment, audio filter  404  may generate an out-of-band signal encoded to enable the receiving unit to generate a corresponding final output with a particular characteristic. 
     In an exemplary non-limiting embodiment of the present invention, filter  404  comprises a low pass digital filter. Such a filter is configured using methods known in the art to allow audio at frequencies below those encountered in human speech to pass through unaffected while removing or rendering inaudible all audio in the frequencies typically associated with human speech. For example, such a filter might have a stop-band at 60 Hz. The disclosure above regarding filter  404  provides an example of means for removing voice information from a signal. 
     Additionally, mute switching logic  407  is configured to pass the output of microphone  206  or filter  404  depending on the setting of mute user indication  227 . The mute switching logic  407  operatively couples the output of the microphone  206  and the output of the filter block  404  to the input of the VAD  208 , encoder  214  and silence indication packet source  212 . If the mute function is disabled the output of the microphone  206  will be selected by the mute switching logic  407  as the input to the VAD  208 , encoder  214  and silence indication packet source  212 . If the mute function is enabled the output of the filter block  404 , the voiceless signal, will be selected by the mute switching logic  407  as the input to the VAD  208 , encoder  214  and silence indication packet source  212 .In an exemplary non-limiting embodiment of the present invention, mute switching unit is configured to direct the output of either microphone  206  or filter  404  to a particular memory space in the TX unit of an IP telephone. Mute switching logic  407  may comprise hardware and software standard in the art. 
     Referring now to FIG. 5, a flowchart of one preferred method for improving the mute function according to the present invention is shown. The process of FIG. 5 begins with query  500 , where the TX unit determines whether the mute function of the TX unit has been activated. If the mute function is activated or engaged, the present invention will provide a predetermined output. In an exemplary non-limiting embodiment of the present invention, if the mute function has been activated, then the present invention will remove the voice information from the signal in act  502  using the filter  404  of FIG.  4 . 
     If the mute function has not been activated, then the IP telephone will operate normally in query  500 . 
     FIG. 6 is a conceptual diagram showing data flow according to one aspect of the present invention. FIG. 6 represents the scenario shown in FIG. 3, but highlights the results achieved by the present invention. It should be noted that the sequence of events shown in FIG.  6  and other similar figures is but one example and is provided for illustrative purposes only, and many different sequences are possible within the scope of the present invention. 
     The blocks of FIG. 6 represent the information transmitted by a TX unit, and received by a RX unit, during time intervals T 1  through T 5 . 
     In time interval T 1 , the receiving unit may be receiving voice information while engaging in a conversation. When the conversation quiets down, the receiving unit may then receive background noise in time interval T 2 . 
     If the transmitting parties engage the mute function of the transmitting unit, the receiving unit will then hear voiceless information during time interval T 3 , i.e., background noise with the voice information filtered out according to the present invention. 
     After the transmitting party disengages the mute function of the transmitting unit in time interval T 4 , background noise will reappear. Finally, the conversation may resume in time interval  5 , and the receiving unit will again hear voice information. 
     It should be noted that the data transmission according to the present invention may be characterized by the absence of silence during the time interval that the mute function is enabled. 
     Thus, the listening parties utilizing IP telephones according to the present invention will not hear the silence during time interval T 3  which was present in IP telephones of the prior art. 
     FIG. 7 is a block diagram of a second aspect of an improved mute function according to the present invention. FIG. 7 shows a IP telephony system  700 , further including a TX unit  702  configured according to the present invention. Where structure is substantially similar to that of FIG. 2, it has been similarly designated. 
     FIG. 7 incorporates the mute switch into the switching logic  710  by coupling the mute user indication  727  to the switching logic  710 . In an exemplary non-limiting embodiment of the present invention, the mute switching logic  710  is configured to provide comfort noise when the mute user indication  727  is activated. In a presently preferred embodiment, TX unit  702  is configured such that when a user enables the mute feature, switching logic  710  will provide silence indication packets to be transmitted over the network  216 . This will cause comfort noise to be generated by the RX unit  204  when the mute function is engaged, rather than silence as in IP telephones of the prior art. Furthermore, by incorporating the mute switch into the switching logic, it is possible to repeatedly send silence indication packets to the RX unit  204  at regular intervals. By sending silence indication packets at regular intervals to the RX unit  204  the comfort noise generated at the RX unit  204  will more closely follow the background noise at the TX unit  702 . This will ensure that the switch back to comfort/background noise is less noticeable when the mute function is deactivated via the mute user indication  727 . 
     Referring now to FIG. 8, a flowchart of another preferred method for improving the mute function according to the present invention is shown. The process of FIG. 8 begins with query  800 , where the TX unit determines whether the mute function of the TX unit has been activated. In an exemplary non-limiting embodiment of the present invention, if the mute function has been activated, then the present invention will generate comfort noise packets in act  802 . In yet another exemplary non-limiting embodiment of the present invention, the present invention will send silence indication packets at regular intervals in act  802 . 
     If the mute function has not been activated, then the IP telephone will operate normally in query  800 . 
     FIG. 9 is yet another conceptual diagram showing data flow according to a further aspect of the present invention. FIG. 9 also represents the scenario shown in FIG. 3, but highlights the results achieved by the present invention. 
     The blocks of FIG. 9 represent the information transmitted by a TX unit, and received by a RX unit, during time intervals T 1  through T 5 . 
     In time interval T 1 , the receiving unit may be receiving voice information while engaging in a conversation. When the conversation quiets down, the receiving unit may then receive background noise in time interval T 2 . 
     If the transmitting parties engage the mute function of the transmitting unit, the receiving unit will hear comfort noise during time interval T 3 . 
     After the transmitting party disengages the mute function of the transmitting unit in time interval T 4 , background noise will remain. Finally, the conversation may resume in time interval  5 , and the receiving unit will again hear voice information. 
     It should be noted that the data transmission according to the present invention may be characterized by the presence of comfort noise during the time interval that the mute function is enabled. 
     Thus, the listening parties utilizing IP telephones according to the present invention will not hear the silence during time interval T 3  which was present in IP telephones of the prior art. 
     It should be apparent to those skilled in the art that various aspects of the present invention may be combined to provide a less noticeable and more effective mute algorithm. For example, by coupling the filters  404  to the audio signal from the microphone  206  when the mute signal is activated, the silence indication packet source  212  will be able to more accurately measure the background noise levels at the TX unit  702 . 
     While embodiments and applications of this invention have been shown and described, it would be apparent to those skilled in the art that many more modifications than mentioned above are possible without departing from the inventive concepts herein. The invention, therefore, is not to be restricted except in the spirit of the appended claims.