System and process for muting audio transmission during a computer network-based, multi-party teleconferencing session

A system and process for muting the audio transmission from a location of a participant engaged in a multi-party, computer network-based teleconference when that participant is working on a keyboard, is presented. The audio is muted as it is assumed the participant is doing something other than actively participation in the meeting when typing on the keyboard. If left un-muted the sound of typing would distract the other participant in the teleconference.

BACKGROUND

1. Technical Field

The invention is related to multi-party, computer network-based teleconferencing, and more particularly to a system and process for muting the audio transmission of a participant using a keyboard during such a conference to prevent the other participants from hearing keyboard typing noise.

2. Background Art

Meetings are an important part of everyday life for businesses large and small. However, it is often inconvenient for meeting participants to be at the same location at the same time. When these distributed team members are not co-located, meetings are typically conducted using computer network-based teleconferences. A variety of live teleconferencing systems are available commercially to facilitate these meetings.

During these teleconferences, the participants tend to multi-task. For example, a participant may check or edit email, surf the web, and so on, while “attending” the meeting. In some situations, this multi-tasking is actually more efficient than attending the meeting all the time. The participant will only need to be attentive to the meeting when the discussion is relevant to the participant.

However, it has been observed that this multi-tasking typically involves the use of a computer keyboard, and conversely when the participant is actively participating in the meeting he or she is typically talking and not typing on their keyboard.

This keyboard activity by a multi-tasking meeting participant presents a problem. When a participant is typing on a keyboard, the typing sound will be captured by either a microphone associated with the participant's computer (if the teleconference audio is being handled via VoIP), or the participant's telephone (if the teleconference audio is being captured via a conventional telephone, and if a) the telephone PBX exposes APIs to control the phone or there is a dangle between the PC and phone so that the two can communicate). This is socially unacceptable, because other meeting participants will know that the participant is multi-tasking and not paying attention to the meeting, and the typing noise may be distracting to the other participants.

One solution can be for the multi-tasking participant to manually turn the audio transmission on and off. However, this is an impractical imposition on the participant and would restrict the participant's ability to spontaneously move between typing on the keyboard and talking with the other participants. The present invention resolves this dilemma, while still allowing a meeting participant to type on a keyboard and spontaneously participate in the meeting without having to manually turn the audio transmission on and off.

SUMMARY

The present invention is directed toward a system and process for muting the audio transmission from a location of a participant engaged in a multi-party, computer network-based teleconference when that participant is using a keyboard. The audio is muted as it is assumed the participant is doing something other than actively participating in the meeting when typing on the keyboard. If left un-muted the sound of typing would distract the other participant in the teleconference. The system and process generally involves first monitoring keyboard activity to determine when the participant is using his or her keyboard during the conference. More particularly, one way to accomplish this task is to monitor keyboard activity to determine when the participant strikes a key of the keyboard for the first time during the time audio is being transmitted from the participant's location to other participants in the teleconference. The first time the participant strikes the key, he or she is deemed to be using the keyboard. The key struck can be any key of the keyboard, or limited to any one of a group of prescribed keys of the keyboard, or even a single prescribed key.

In one embodiment of the present system and process, when it is found that the participant is using the keyboard, audio transmissions from the participant's location to other participants in the teleconference are suspended. However, in another embodiment, the audio transmissions are gradually muted. This prevents transient or inadvertent keystrokes from causing a full muting of the audio. One way of gradually muting the audio transmissions is to first establish the number of keystrokes typically occurring during a typing session involving the participant, or the duration of a typical typing session. In this case, a typing session is defined as the period of time a participant types before a keystroke threshold period is exceeded, where the keystroke threshold period represents a period of time which if exceeded without a keystroke occurring indicates the participant has stopped using the keyboard. Once the number of keystrokes or duration of a typical session has been established, the audio transmissions are gradually muted based on the number or duration, and a prescribed decreasing function such as a linearly decreasing function or an exponentially decreasing function.

The present system and process also includes a provision for re-establishing audio transmissions when a participant stops using his or her keyboard, based on the assumption that they are ready to actively participant in the teleconference. This involves first determining when a participant has stopped using the keyboard. If it is determined that the participant has stopped using the keyboard at a time when the audio transmissions from the participant's location is muted (or partially muted), then the transmissions are restored. It is noted that the actual audio connection between a muted participant and the other participants in the teleconference need not be terminated. Rather, just the audio gain is lowered to an inaudible level. One way of determining if a participant has stopped using their keyboard is to ascertain whether the participant has struck any key on the keyboard within a prescribed period of time. If not, it is deemed that the participant has stopped using the keyboard.

Another way to determining if a participant has stopped using their keyboard, involves recording the time each keystroke occurs after the audio transmission from the participant's location is suspended (or begun to be suspended). A keystroke threshold period is then established using the keystroke time data. This threshold represents the period of time, which if exceeded without a keystroke, indicates the participant has stopped using the keyboard. Thus, determining if a participant has stopped using their keyboard entails, for each keystroke made after the audio transmission from the participant's location is suspended (or begun to be suspended), first ascertaining if a new keystroke occurs within the keystroke threshold period. If no new keystroke occurs within the keystroke threshold period, the participant is deemed to have stopped using the keyboard.

In one embodiment of the present system and process, establishing the aforementioned keystroke threshold period involves assuming that the times between keystrokes follow a Gaussian or Poisson distribution. This being the case, the keystroke threshold period can be established by first computing the average time between keystrokes using the recorded keystroke times. Then, the standard deviation of the actual times between the keystrokes is computed. The keystroke threshold period is designated as being the average time plus a prescribed multiple of the standard deviation (e.g., 0-3 times). The keystroke threshold period can also be periodically updated.

The present system and process can further include a provision for allowing a participant to manually override the muting. More particularly, upon the receipt of a manual override command from the participant, the audio transmissions are prevented from being muted even if the participant starts using his or her keyboard. In addition, if the transmissions are already muted (or partially muted), the manual override will re-establishing the audio transmission to other participants in the teleconference.

Still further, the present system and process can include a provision for playing locally-generated audio when transmissions from a participant lacks audio data. When another participant in the teleconference starts using his or her keyboard and audio transmissions from that participant are muted as a result, the abrupt absence of an audio input from that participant may be noticeable to the other participants. Typically, the other participants would expect to hear so-called background noise from another participant's location even if that participant is not speaking. One way of preventing this situation is for the receiving participant to generate the missing background noise associated with another participant that is no longer transmitting audio. More particularly, incoming audio transmissions are monitored from each participant in the teleconference, and any participant who is no longer transmitting audio data is identified. Audio simulating background noise typical of previously transmitted audio data received from an identified participant is then generated and played for as long as the participant is not transmitting audio data.

It is also noted that detecting the absence of audio data transmissions can be a difficult task. This difficulty can be overcome by having a participant who is no longer transmitting audio data, instead transmit message frames indicating the audio from that participant is currently muted. The receiving participant would then be able to determine if a message frame is received from the participant in lieu of audio data, and if so deem the participant to be no longer transmitting audio data for purposes of generating the aforementioned background noise replacement.

In addition to the just described benefits, other advantages of the present invention will become apparent from the detailed description which follows hereinafter when taken in conjunction with the drawing figures which accompany it.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

1.0 The Computing Environment

Before providing a description of the preferred embodiments of the present invention, a brief, general description of a suitable computing environment in which portions of the invention may be implemented will be described.FIG. 1illustrates an example of a suitable computing system environment100. The computing system environment100is only one example of a suitable computing environment and is not intended to suggest any limitation as to the scope of use or functionality of the invention. Neither should the computing environment100be interpreted as having any dependency or requirement relating to any one or combination of components illustrated in the exemplary operating environment100.

The drives and their associated computer storage media discussed above and illustrated inFIG. 1, provide storage of computer readable instructions, data structures, program modules and other data for the computer110. InFIG. 1, for example, hard disk drive141is illustrated as storing operating system144, application programs145, other program modules146, and program data147. Note that these components can either be the same as or different from operating system134, application programs135, other program modules136, and program data137. Operating system144, application programs145, other program modules146, and program data147are given different numbers here to illustrate that, at a minimum, they are different copies. A user may enter commands and information into the computer110through input devices such as a keyboard162and pointing device161, commonly referred to as a mouse, trackball or touch pad. Other input devices (not shown) may include a microphone, joystick, game pad, satellite dish, scanner, or the like. These and other input devices are often connected to the processing unit120through a user input interface160that is coupled to the system bus121, but may be connected by other interface and bus structures, such as a parallel port, game port or a universal serial bus (USB). A monitor191or other type of display device is also connected to the system bus121via an interface, such as a video interface190. In addition to the monitor, computers may also include other peripheral output devices such as speakers197and printer196, which may be connected through an output peripheral interface195. A camera192(such as a digital/electronic still or video camera, or film/photographic scanner) capable of capturing a sequence of images193can also be included as an input device to the personal computer110. Further, while just one camera is depicted, multiple cameras could be included as input devices to the personal computer110. The images193from the one or more cameras are input into the computer110via an appropriate camera interface194. This interface194is connected to the system bus121, thereby allowing the images to be routed to and stored in the RAM132, or one of the other data storage devices associated with the computer110. However, it is noted that image data can be input into the computer110from any of the aforementioned computer-readable media as well, without requiring the use of the camera192.

The exemplary operating environment having now been discussed, the remaining parts of this description section will be devoted to a description of the program modules embodying the invention.

2.0 Muting System and Process

The present invention is embodied in a system and process for muting the audio transmission of a participant in a multi-party teleconference during times he or she is using a computer keyboard. In general, referring toFIG. 2, this involves the participant's computer continuously monitoring keyboard activity during the teleconference (process action200), and determining when the participant is using the keyboard (process action202). Whenever it is determined the participant is using the keyboard, in process action204the audio is muted (i.e., by suspending or gradually decreasing the “volume” of audio signal transmissions from the participant's location to the other participants). In addition, it is determined if a participant has finished using the keyboard (process action206) after the audio has been muted. Whenever it is determined the participant has stopped, the audio transmission is restored (process action208). This is done under an assumption that when the participant is not working on the keyboard, he or she wishes to participate in the meeting. Once the audio is restored, the procedure is repeated for as long as the teleconference is ongoing.

One way of determining when a participant has started or stopped using a keyboard is to monitor and analyze keystroke activity. For example, anytime a key on the keyboard is pressed for the first time, this can be used as a signal that the participant has begun to use the keyboard. The particular key that needs to be pressed can be a prescribed key, or one of a group of prescribed keys, or any key. Determining when the participant has finished using the keyboard can be done in several ways. For example, a prescribed time period between keystrokes could be established. The program would then monitor the participant's keyboard activity after the audio has been muted during a teleconference, and restore the audio transmission if there is no new keystroke within the prescribed time period from the last keystroke. Another way to determine if keyboard use has ceased is to record the time of each keystroke once the audio has been muted and perform a statistical analysis on the recorded data to establish a keystroke duration threshold and to deem the keyboard activity to have stopped if the time since the last keystroke exceeds the threshold. This has the advantage of accommodating various participants that may type at widely disparate rates, because a set time period may not accurately reflect when an extremely fast or extremely slow typist has ceased using the keyboard.

More particularly, referring toFIG. 3, one embodiment the process for muting the audio transmission of a participant in a multi-party teleconference that employs the aforementioned keystroke duration threshold approach, begins by continuously monitoring keyboard activity (process action300). While this monitoring is going on, it is determined if a key of the keyboard has been pressed (process action302). If a key is pressed, it is next determined if the participant is currently in a typing session (process action304). If not, the audio transmission for the participant is muted (process action306) and process actions300through304are repeated. Thus, a typing session is entered. The muting can take on several forms as will be described shortly. Whenever it is determined that the participant is already in a typing session when a keystroke is detected, the time elapsed since the last keystroke is computed (process action308). This elapsed time is then compared to the keystroke duration threshold to determine if it exceeds the threshold (process action310). If not, then the foregoing process is repeated starting with process action300. However, if the threshold is exceeded, then it is deemed in process action312that the current typing session has ended (i.e., the participant has stopped using his or her keyboard), and the audio is restored. The entire process is then repeated, starting with process action300, for as long as the teleconference is ongoing.

In regard to the aforementioned statistical analysis of the keystroke time data to determine if keyboard use has ceased, this can be accomplished in one embodiment of the present system and process by assuming a Gaussian or Poisson distribution. For example, a teleconference can be thought of as consisting of multiple sessions, in terms of audio, as shown inFIG. 4. These sessions can be generally classified as keyboard sessions Sk400, silence sessions Sl402and speech sessions Sp404. A keyboard session Sk400is a session in which a participant is typing on a keyboard. A silence session Sl402is a session in which there is no speech or keyboard noise. And finally, a speech session Sp404is a session containing speech. For the purposes of the present system and process only the keyboard sessions Sk500are important, and the other sessions can be collectively categorized as non-keyboard sessions Sn502, as shown inFIG. 5. Each keyboard session600is made up of individual keystrokes602, which are represented by vertical lines in the session timeline shown inFIG. 6. In between each keystroke is a gap604representing the time period between two consecutive keystrokes.

Let the time between two consecutive keystrokes j and j+1 be dkijin keyboard session Skiwhere i denotes the sequential number of the keyboard session within the overall audio timeline (i=0, 1, 2 . . . ) and j denotes the sequential number of the keystrokes within that session (j=0, 1, 2 . . . ) Given this, the keystroke duration threshold Tkdcan be characterized as:
Tkd=μt+mσt,  (1)
where μtis the average duration between consecutive keystrokes, σtis the standard deviation, and m is a multiplier factor. The average duration μtis characterized as,

μt=1L⁢∑l=i-Li⁢(1Nkl⁢∑j=0j=Nkl-1⁢dkij)(2)
where L is a prescribed number (e.g., 5) of the most recent keystroke sessions Ski, and Nkiis total number of keystrokes in keystroke session Ski. The standard deviation σtis characterized as,

σt=1L⁢∑l=i-Li⁢(1Nkl⁢∑j=0j=Nkl-1⁢(dkij-μt)2).(3)
Thus, as can be seen from Eqs. (2) and (3), the average duration between keystrokes and the standard deviation are estimated for the current session Ski, based on previous sessions. The multiplier factor m adjusts the sensitivity of the keystroke duration threshold. In tested embodiments of the present invention, m ranged between 0 and 3.

It is noted that in one embodiment of the foregoing process, the keystroke duration threshold is updated each time a new typing session begins by recomputing the average duration and standard deviation. Additionally, in the case where the sequential number of the keyboard session i is less than the prescribed number of sessions L, a threshold value that was computed during a past teleconference can be employed, or a prescribed default threshold value could be used, until enough typing sessions have occurred to update the threshold value. The threshold value would then be updated with each new typing session thereafter.

As mentioned previously, the muting can take several forms. The simplest of these is that the audio gain is set to zero anytime it is determined a participant is using their keyboard. In this way, the audio is suspended from that participant immediately. However, in order to handle a situation where a participant might use his or her keyboard to type a quick note during a teleconference, or where the participant might inadvertently strike a key—but is still actively participating in the meeting, the program can be configured to gradually mute the audio once a keystroke occurs. In this way, any transient or inadvertent keystrokes would only result in a small reduction in the “volume” of the audio transmission, which would most likely be imperceptible to the other participants. One way to accomplish this gradual muting would be to reduce the volume of the audio transmission at some prescribed rate. However, given the different rates at which different people type, a statistical analysis may be more appropriate. For example, if a set muting rate is applied in the case of an extremely fast typist who is multitasking and not actively participating in the meeting, the rate might be to slow to prevent the typing from distracting the other participants in the teleconference.

Referring toFIG. 7, this second analysis analyzes “global” keyboard activity to establish either the number of keystrokes typically occurring during a typing session associated with the participant under consideration or the typical duration of such a typing session (process action700). Once established, the number of keystrokes per session, or session duration, is used to gradually mute the audio transmission over time based on a prescribed function (process action702). In the case of the second statistical analysis, the typing sessions involved would have occurred in the past, such as during a past teleconference. The number-of-keystrokes-per-session value can be established based on some predefined number of typing sessions, or more preferably, continuously updated each time a new typing session occurs. It is noted that for the purposes of the foregoing analysis a typing session is defined as the period of time a participant types before the previously described keystroke duration threshold is exceeded since the last keystroke.

The aforementioned function used to compute the rate at which the muting takes place once a key of the keyboard is struck during a teleconference can be any simple linear function or exponential function. For example, one way to gradually reduce the audio gain g from a full audio transmission value of 1 to a fully muted value of 0 using the number of keystrokes in past typing sessions involves employing the linear equation:

g=1-1μkn+m⁢⁢σkn⁢x(4)
where μknis the average number of keystrokes in a Sksession, σknis the standard deviation of the number of keystrokes in the sessions, m is a multiplier factor, and x is the number of keystrokes so far in session Sk. The average number of keystrokes μknis characterized as,

μkn=1L⁢∑l=i-Li⁢Nkl(5)
where L is again a prescribed number (e.g., 5) of the most recent keystroke sessions Ski, and Nkiis total number of keystrokes in keystroke session Ski. The standard deviation σknis characterized as,

Another way to gradually reduce the audio gain g, this time using the duration of past typing sessions, involves employing the linear equation:

g=1-1μkl+m⁢⁢σkl⁢x(7)
where μkiis the average duration of a Sksession, σkiis the standard deviation of the session duration, m is a multiplier factor, and x is the number of seconds so far in session Sk. The average duration μkiis characterized as,

μkl=1L⁢∑l=i-Li⁢Dkl(8)
where L is again a prescribed number (e.g., 5) of the most recent keystroke sessions Ski, and Dkiis the duration of keystroke session Ski. The standard deviation σkiis characterized as,

It is noted that in the foregoing exemplary audio gain computations, the multiplier factor m adjusts the speed of the gradual muting. In tested embodiments of the present invention, m ranged between 0 and 3, however it could be larger if desired. Essentially, the bigger m is, the slower the audio gain is decreased.

It is further noted that in one embodiment of the foregoing processes, μknand σkn, or μkiand σkias the case may be, are recomputed each time a new typing session begins using the last L typing sessions. Additionally, in the case where the prescribed number of sessions L have not yet occurred in the current teleconference (i.e., where the sequential number of the keyboard session i is less than the prescribed number of sessions L), μknand σknvalues (or μkiand σkivalues) that were computed during a past teleconference can be employed, or prescribed default values can be used, until enough typing sessions have occurred to update these values. The μknand σknvalues (or μkiand σkivalues) would then be updated with each new typing session thereafter.

It is also possible to gradually increase the gain of a participant's audio transmission after it is determined he or she has stopped using their keyboard, rather than immediately restoring the full audio. The function used to compute the rate at which the restoring takes place can be any simple linear function or exponential function similar to the previously described decreasing functions. For example, one way to gradually increase the audio gain g is to use the duration of past typing sessions by employing the linear equation:

g=1-1μkl+m⁢⁢σkl⁢x(7)
where μkiis again the average duration of a Sksession and σkiis the standard deviation of the session duration. However, in this case, m is the a multiplier factor that adjusts the speed of the gradual increase in the participant's audio. This value can range between 0 and 3, for example, however it could be larger if desired. Essentially, the bigger m is, the slower the audio gain is increased. In addition, in this case, x now represents the number of seconds so far in the current non-keyboard session Sn.

The present system and process can further include a manual override function so that a participant can either prevent the audio from being muted during a teleconference even if he or she is typing on a keyboard, or re-establish full audio transmission even though the participant continues to type. In operation this feature could be implemented by designating a special override key on the keyboard, or the participant might be required to activate the override via interaction with an appropriate Graphic User Interface (GUI).

It is noted that the present system and process mutes the audio transmission from a participant's location during a teleconference—it does not disable audio capture. In this way, local operations dependent on audio input are not effected.

When the present system and process is employed to mute the audio of a participant in a multi-party teleconference, the abrupt absence of an audio input from that participant may be noticeable to the other participants. Typically, the other participants would expect to hear so-called background noise from another participant's location even if that participant is not speaking. Like typing noise, the abrupt absence of all audio for a participant can be distracting and indicate to the other participants that a participant is no long paying attention to the meeting. One way of preventing this situation is to include a feature that generates the missing background noise associated with another participant that is no longer transmitting audio. While any existing method of generating this background noise can be adopted for use in the present system and process, in tested embodiments, a new approach was employed that is the subject of a co-pending application entitled “A System And Method For Real-Time Jitter Control And Packet-Loss Concealment In An Audio Signal”, which was assigned to a common assignee. The co-pending application was filed on Sep. 15, 2004 and assigned Ser. No. 10/663,390.

In general, the co-pending application generated background noise, which was referred to as comfort noise, and which was intended to fill in gaps in an incoming audio signal. This is accomplished by simulating a noise level similar to any noise that was present when the audio connection was active, but when there was no speech. Consequently, signal loss is not readily apparent to the listener. The co-pending application described the generation of this comfort noise essentially as follows. Comfort noise is generated by using a running comfort noise buffer containing a number of “silence frames” (where silence frame are previously received audio frames not containing speech). In a tested embodiment, using a comfort noise buffer of about three or so silence frames provided good results. In general, whenever a new frame is received, the overall energy E of the frame is computed and compared to the stored energy of the current silence frames in the comfort noise buffer. If the current frame has lower energy than any of the frames already in the comfort noise buffer, then the frame having the highest energy is replaced with the current frame. Further, in addition to storing the energy of the frame, the magnitude of the FFT coefficients of the frames is also stored for use in synthesizing a “comfort noise frame”. A periodic renewal of the silence frames in the buffer can also be forced through use of a time-out mechanism so as to avoid an atypically low energy silence frame remaining in the buffer forever. For example, if a particular frame is in the buffer for over a predetermined time limit, such as, for example, 15 seconds, the nominal energy Eiof the frame is increased (but not the magnitude of the stored FFT coefficients). This will increase the likelihood that the frame will eventually be replaced with a new frame having lower energy. Assuming a 15 second time limit here, the Eiis doubled every 15 seconds, and a small amount of an arbitrary frame, such as the current frame, for example, is added to handle any cases where Ei=0. When a comfort noise frame is needed, the buffered silence frames are then used to generate one. In particular, the average magnitude of the stored silence frames is computed, and a random phase shift is added to the FFT prior to computing the inverse FFT. This signal is then overlapped/added to the signal in the buffer using a conventional window, such as, for example, a sine window. In particular, comfort noise is created in any desired length by computing the Fourier transform of the average magnitude of the silence frames, introducing a random rotation of the phase into the FFT coefficients, and then simply computing the inverse FFT for each session to create the comfort noise frame. This produces a signal frame having the same spectrum, but no correlation with the original frames, thereby avoiding perceptible artifacts in the signal. In addition, longer signals can be obtained by zero-padding the signal before computing the FFT. These synthesized comfort noise frames are then inserted into the signal playback by using a windowing function to smooth the transition points between the original and subsequent signal frames.

Thus, referring toFIG. 8, the procedure for playing locally-generated audio whenever transmissions from a participant in a multi-party, computer network-based teleconference lacks audio data involves first monitoring incoming audio transmissions from each participant in the teleconference (process action800) and determining if a participant is no longer transmitting audio data (process action802). If so, then audio simulating background noise typical of previously transmitted audio data received from that participant is generated (process action804). The generated audio is then played (process action806) until it is determined that the participant is once again transmitting audio data (process action808). At that point the generation of the simulated background noise ceases (process action810) and the actual audio transmissions are played instead (process action812).

It is noted that the incoming audio signals will have to be audited in order to detect whether the audio transmission for a participant has ceased. There are conventional techniques for doing this, but it can be tricky because, for example, packet losses over the network might cause some audio frames to be dropped, which in turn could appear to be a cessation of the audio from a participant. One way to mitigate this problem of detecting when the audio from a participant has been fully muted is to configure the present system and process so that instead of a participant's computer simply ceasing transmission of audio frames, the frames are replaced with a message frame indicating that the audio is muted. When another participant receives this type of message frame in lieu of an audio frame, the present system and process would generate the aforementioned background or comfort frame to replace it. This message frame could be as simple as an appropriate header followed by a single bit that when present indicates the participant transmitting this frame has fully muted the audio transmission.