Abstract:
Disclosed herein are conferencing systems that include a conferencing device and a head-processing system, both including selectively enabled speakers, the conferencing device including an acoustic echo canceler that remains operable in the system regardless of whether its internal speaker is selected to be enabled. Detailed information on various example embodiments of the inventions are provided in the Detailed Description below, and the inventions are defined by the appended claims.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This Application claims the benefit of U.S. Provisional Application No. 60/987,754 filed Nov. 13, 2007 and U.S. Provisional Application No. 60/987,360 filed Nov. 12, 2007, each of which is incorporated by reference in the entirety. In addition, this application is related to U.S. application Ser. No. 11/963,809 filed Dec. 22, 2007 and U.S. application Ser. No. 11/963,810 filed Dec. 22, 2007. 
    
    
     BACKGROUND 
     The claimed systems and methods relate generally to conferencing products that implement acoustic echo cancellation and connect to an external head-processing device that is capable of injecting sound of a conference into the audible vicinity of a product, and more particularly to conferencing systems that include a portable portion including a speaker and microphone and a connectible head-processing portion that can connect to both distant parties in a conference and the portable portion, the system having at least one speaker controllable by each portion and providing a distant-party signal to an acoustic echo canceler incorporated in the portable portion. 
     BRIEF SUMMARY 
     Disclosed herein are conferencing systems that include a conferencing device and a head-processing system, both including selectively enabled speakers, the conferencing device including an acoustic echo canceler that remains operable in the system regardless of whether its internal speaker is selected to be enabled. Detailed information on various example embodiments of the inventions are provided in the Detailed Description below, and the inventions are defined by the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows the conceptual elements of a basic portable conferencing device connectible to a computer. 
         FIG. 2  depicts the connection of an exemplary portable conferencing device to a computer. 
         FIG. 3  illustrates the elements of an acoustic echo canceler. 
         FIG. 4  shows the elements of a system including a computer with a monodirectional speaker path, an external speaker and a connected conferencing device. 
         FIG. 5  shows the elements of an exemplary conferencing device that includes an incoming audio path and a switch for controlling the production of audio through its internal speaker. 
         FIG. 6  shows the elements of an exemplary conferencing system including a head-processing device having a bifurcated incoming audio path and a conferencing device with a switch for controlling the production of audio through its internal speaker and a switch control path. 
         FIG. 7  shows an exemplary audioconferencing architecture using a computer communicating with a conferencing device using a digital communications port. 
     
    
    
     Reference will now be made in detail to particular implementations of the various inventions described herein in their various aspects, examples of which are illustrated in the accompanying drawings and in the detailed description below. 
     DETAILED DESCRIPTION 
     Conferencing devices are used by many whom wish to avoid the constraints imposed by an ordinary telephone. A telephone includes a handset that is placed to a person&#39;s face providing for a conversation with a distant party. A telephone handset is generally not usable by more than one person because the earpiece is configured for sound production to an ear in close proximity, and a microphone may also be configured for local sound pickup. A conferencing device, in contrast, permits a conversation with a distant party through open-air communication, i.e., without a handset. Open-air communications are desirable in many situations, for example, where there is more than one local participant to be engaged in a conversation, or where a single person wishes to maintain mobility and the use of both of his hands. 
     Some conferencing devices are of the installation-type, meaning that they are intended to be installed into a room and are not mobile. Portable conference devices, in contrast, are portable and relocatable by a user, permitting her to attain the advantages of a conferencing device in virtually any location where a connection to a distant party may be made. Now referring to  FIG. 1 , one exemplary conferencing device  1  includes a speaker  4  and a microphone  5  for producing and receiving sounds with a participant  6  in an open-air conversation. Speaker  4  and microphone  5  are ordinarily incorporated in the physical product of device  1  for portability, although the speaker and microphone could also be provided as attachables. Hereinafter it is understood that one speaker or microphone may be replaced with a plurality or an array as will be understood by one of ordinary skill, and that reference to a single speaker or microphone is merely for convenience and simplicity of the discussion proceeding below. 
     The exemplary conferencing device of  FIG. 1  is attachable to a computer, which provides for a connection with a distant party through software  3  and for control of conferencing product  1 . Although conferencing device  1  includes manual controls, a conferencing device controlled by software need not include any controls or a display if they are provided in software. Software  3  may create a suitable connection with a distant participant by way of a protocol, for example through VoIP or instant messaging protocols. A portable conferencing device such as  1   a  may also have a stand-alone configuration or other configurations, as desired, in which case controls for establishing and disengaging a connection, such as a numeric keypad, volume controls, on/off hook controls, etc., may be incorporated therein. 
     Now referring to  FIG. 2 , a portable conferencing device  1  may connect to a computer  2  through a cable  7 , which in this example connects through a USB connection. A USB port, even if low-speed, provides suitable bandwidth for an audio channel between device  1  and computer  2 . Other connection methods may be used, such as analog audio in/outs (perhaps provided by speaker and microphone jacks), IEEE 1394, infrared, or other connections, and no particular connection is required so long as requirements of desired use for bandwidth, noise-immunity, etc. are met. As it is used, a portable conferencing device  1  is ordinarily placed on a tabletop or near tabletop height, such as by placing on a seat or a shelf if a table is not available. A portable conferencing device may be made in many sizes, from a device that is small enough to slip into a briefcase or a pocket to a more substantial size that can be carried from room to room. Device  1  is approximately four inches on a side and less than two inches high. A computer  2  is typically be placed nearby at about the same height. Although a laptop is shown, any type of computer may be used within range of cable  7 . Furthermore, in the concepts described below a computer  2  is not required, but rather a head device of any kind may be used that incorporates a mode of connecting to a distant party and is capable of supporting a connection to a portable conferencing device. 
     A portable conferencing device such as  1  may incorporate acoustic echo cancellation, which is now described with reference to  FIG. 3 , simplified for this discussion. A conferencing device  200  is connected to a far-side participant through a carrier medium  212 , which might be a telephonic channel, for example. Near-side audio is received at microphone  204  and delivered to the far side device at times through medium  212 . As far-side audio is received, device  200  produces audio at speaker  202 . The sound produced at speaker  202  is picked up by microphone  204  through a feedback path  214 . Thus, the far-side participant will hear an acoustic echo of himself with approximately two-times the carrier medium latency plus path latency  214 , if production of sound received from path  214  is not controlled or cancelled. 
     Device  200  may include an echo controller  216  for reducing acoustic echo. Standard methods of control include operation at half-duplex, and operation at full-duplex with echo cancellation. Half-duplex operation simply cuts off the sound received at microphone  204  when the audible volume at speaker  202  exceeds a pre-selected threshold. Many conferencing products implement half-duplex operation, however that operation carries a disadvantage that participants at only one side of the conference can be heard at any time, and neither side can interrupt or acknowledge the other. 
     When possible, it is therefore preferable to apply echo cancellation to achieve full-duplex operation. In digital audio systems, echo cancellation can be performed by subtracting off, at controller  216 , a modified version of the signal produced at speaker  202 , leaving only near-side audio. A conceptual method of cancellation merely applies an attenuation and a delay to the outgoing audio, accounting for the delay and attenuation of feedback path  214 . However, in the real world path  214  is complex, including dispersed components from reflections off the several surfaces and persons in proximity to the speaker and microphone. 
     To deal with that complexity, controller  216  ordinarily implements echo cancellation through use of a finite impulse response (FIR) filter, with the received far-side audio signal as input. The FIR filter utilizes a finite number of coefficients of a length sufficient to cover the longest path  214  of significance expected in operation. The reader should recognize that acoustic echoes will be, in general, of longer duration and greater complexity than line echoes. An acoustic echo canceller therefore requires a much larger number of coefficients to provide echo cancellation, which might cover a number of seconds in a device designed for operation in high-echo rooms (rooms with parallel walls and no carpeting.) These coefficients are applied to a copy of the incoming audio, providing the predicted echo component received at the microphone. The determination of these coefficients is by an iterative method, generally understood by those skilled in the art, and will not be further described here for the sake of brevity. In theory, the FIR coefficients could be determined by the application of a step function to the speaker and a recording of the received audio (in reverse) received at the microphone. 
     As discussed above, a portable conferencing device may include one or more speakers for producing the far-side audio of a conference. To make the device more portable and/or affordable, it may be that the speakers incorporated into the product are inferior in some way, for example it may be that a pocket device includes a single small form-factor speaker with a limited frequency range. However, even if a portable conferencing device produces adequate sound, it may be that a computer includes a better sound system than the device i.e., better frequency range, directivity, volume or is preferable in some other way. 
     Now referring to  FIG. 4 , a conferencing system similar to that of  FIG. 1  is shown, but here computer  2  is directing far-side audio to speaker  4   c  rather than the conferencing device&#39;s internal speaker  4   i . Participant  6  can conduct a conversation into microphone  5  and listen by speaker  4   c . Here, however, no far-side audio reaches conferencing device  1  from computer  2 , because it is desired to have that audio produced at external speaker  4   c . Although conferencing device  1  might include an acoustic echo canceler, it is not operable in this configuration because device  1  is starved of far-side audio. 
     Now turning to  FIG. 5 , a conferencing device architecture is shown that permits both transmission of far-side audio using external speakers and the application of echo cancellation. In that architecture, a host port  301  is provided for communication with a host computer or head device. Audio data, shown in solid lines, passes to and from port  301  to an audio processing block  302  for buffering, decoding, encoding and other operations that are desired to perform on audio data in proximity to port  301 . Incoming, far-side audio data may pass from processor  302  through a switch  303 , where it is converted into open-air audio through a digital to analog converter  304 , amplifier  305  and speaker  306 . Speech from local participants is received at microphone  311 , and conditioning circuitry  310  may be included to condition the signal for further processing, for example by application of filtering. That analog signal is converted at some point to a digital one by converter  312 , which signal passes through the application portion of the echo canceler, FIR filter  315 , and to a controller  308  by way of an audio level-sensing meter  309 . Echo-canceled audio passes from FIR filter  315  through audio processing block  302  to port  301  for transmission to far-side parties through the computer or head-processing device. The echo canceler includes an adaption engine  313  fed with the incoming audio level and the outgoing audio in this architecture, and may also be fed with the microphone audio if the adaption algorithm so requires. Cancellation coefficients  314 , used by FIR  315 , are adapted by adaption engine  313  to arrive at an echo cancellation solution for particular environment in which the microphone  311  is in operation. Adaption engine  313  is controlled by controller  308  using meters  307  and  309  such that adaption occurs generally only when far-side audio is present and local participants are not speaking. 
     Host port  301  includes an additional control channel  320  communicating commands to controller  308 . One particular command controls the operation of switch  303 , which as described above in one configuration passes incoming audio for production at speaker  306 . In another configuration switch  303  blocks the incoming audio, which is not produced at speaker  306 . This can be accomplished, for example, by passing a zero signal to converter  304  or in the analog domain by feeding a signal tied to an audio AC ground. 
     However, merely blocking the incoming signal from reaching speaker  306  is not sufficient where echo cancellation is to continue. Therefore, after the sending of a command to configure switch  303  to block, a host may continue to send far-side audio to the conferencing device through port  301 . Following a switching command, either to block or unblock at switch  303 , echo cancellation coefficients will no longer be adapted for the speakers producing far-side audio in the environment of microphone  311 . If no action is taken, a period of ineffective echo cancellation may occur which may result in far-side participants hearing some degree of echo, particularly if the system is switched from or to a state where speaker  306  is solely producing far-side audio. If that is not acceptable, a conferencing device may take echo cancellation remedial steps, including accelerated coefficient adaption or operation in half-duplex mode for a period of time or until a recognition that the coefficients have re-adapted. 
     Now turning to  FIG. 6 , another architecture is shown whereby a head-processing device  401  is used in a conferencing system. Device  401  is referred to as a head-processing device because it sits at the head of the communication stream(s) between conferencing device  403  and any far-side parties. Head-processing device incorporates a communication port  410  for establishing one or more audio links with distant parties, which link might be made through an POTS line, VoIP, or other link as desired. A processor  411  may be included to process the several streams passing through head-processing device  401 , providing for encoding, decoding, buffering, sampling, user controls and any other desired processing function. A link to conferencing device  403  is made through conferencing port  412 , which could be an analog or digital link that includes an incoming audio stream  431 , an outgoing audio stream  433  and a control stream  432 . Under a first configuration, the internal speaker  421  of conferencing device  403  is used, and correspondingly echo controller  422  and microphone  423  provide echo cancellation. The echo canceled signal is passed through conferencing port  412 , processor  411  and communication port  410  to far-side parties. 
     Also in head-processing device  401 , and external speaker  402  may be connected thereto and may provide far-side audio to local participants. In its first configuration, conferencing device  403  will apply this additional audio as part of the echo cancellation process, and thus the presence of an external speaker does not generally prevent effective echo cancellation. In a second configuration, conferencing device  403  does not produce audio at internal speaker  421 , which is accomplished by configuring switch  420  to the “off” state by either feeding a DC signal to speaker  421 , turning off its amplifier, or by other means. In that configuration, head-processing device far-side audio through external speaker  402 . In either configuration, head processing device continues stream  431  so that echo cancellation at device  403  can be performed. In the event of a state change at switch  420 , device  403  may take remedial measures to adapt to the new acoustic echo profile in the environment. 
     As to command channel, this may exist as a separate wire or contact in the interface between head processing device and conferencing device  403 . In other cases, it may be desirable to implement streams  431 ,  432  and  433  into a single communications channel, such as in a serial-bus. In that event a protocol may be defined between conferencing port  412  and conferencing device  403  for the communication of bi-directional audio and commands. Commands may also be communicated over an audio channel, either in the audible frequency range or otherwise, for example by the transmission of an ultrasound tone from the head-processing device to the conferencing device. A communication channel may also be omitted, if a user control is provided in a device such as  403 . These methods of communication may be used in any system of the types disclosed herein. 
     In the operation of a system containing a head-processing device  401  and an operational external speaker  402 , consistency between the delivery of audio to the external speaker and the conferencing device over stream  431  is helpful to avoid artifacts in the echo-canceled audio stream. Artifacts may occur where the latency between transmission of audio from processor  411  to speaker  412  and from processor  411  to conferencing device  403  changes over time. In the ideal case, a clock exists between head-processing device  401  and conferencing device  403  by which both are kept in synchronization. Such a clock may be implemented through the scheduled delivery of digital packets from through conferencing port  412 , for example with a fixed-size payload. In that case, conferencing device  403  may adapt its clock rate accordingly. 
     However, it may not be possible to regulate the delivery of a clock signal or packets from head-processing device  401  to conferencing device  403 , or it may be desirable to avoid the expense and complication of synchronization. In that event, where conferencing device  403  includes an adapting echo canceler, a slow drift will not substantially affect echo cancellation. For example, it may be that the audio link to the far-side participants has a sample rate of 16 kHz, or a sample period of 62 μs. A synchronization drift of a few microseconds over a period of about one minute will not substantially affect the echo cancellation, presuming that adaption takes place within about that one minute period of time. Recognize now that the conferencing device need not be synchronized to the far-side equipment; head-processing device  401  may compensate by adding or skipping far-side samples so long as the audio stream produced at speaker  402  and delivered to conferencing device  403  includes the same additions and/or deletions. Even if the accuracy of these clocks is not consistent, some degree of echo cancellation may still be enjoyed, particularly at lower frequencies or where a low-pass filter is used. Digital communication between head-processing device  401  and a conferencing device  403  in a synchronous mode may be used as a countermeasure to drift. 
     Now turning to  FIG. 7 , a more particular embodiment of that shown in  FIG. 6  is now described including a computer  501  and a conferencing device  503  that communicates through a digital computer interface. Computer  501  may be an ordinary personal computer having an audio subsystem  510  controllable through software configuration, which may have a master software audio process that receives audio data from programs that is produced at one or more external speakers  502 . In this example communication with distant parties is accomplished through a computer network and network services  514  implemented for programs. Communication to conferencing device  503  is through peripheral services  515  provided as an operating system service for programs. 
     User-domain software is implemented on computer  501  to enable a conference with a distant party. This software includes an encoder/decoder  513  for communications with conferencing device and general software  511  for implementing user interfaces and for initiating and maintaining a network connection with a distant party. Also in software is a mixer  512  that sends far-side audio data to audio subsystem  510 , conferencing device  503  through encoder/decoder  513 , or both. 
     Conferencing device  503  implements a computer port  524  for communications with computer  501  and encoder/decoder  513  through services  515 , and through encoder/decoder  522  on device  503 . Encoder/decoder processes at least three data streams, which are incoming audio data to switch  520 , outgoing audio data from acoustic echo canceler  525  and command data controller  523 . Controller  523  may control several functions on device  503 , and here those functions include control of switch  520  and AEC  525 . In an alternate configuration, witch  520  is not controlled by controller  523  but by a user-control on the housing of the device. Microphone  526  receives and delivers local audio to AEC  525  which is also fed far-side audio from decoder  522 , and internal speaker  521  may produce far-end audio if switch  520  is so configured. 
     Now although particular systems, functions and methods have been described above, one of ordinary skill in the art will recognize that these are adaptable to related open-air conferencing products and thus the inventions are not limited to the particular implementations described herein. It is to be understood that although the processors and controllers in the various examples herein are shown as individual components for the purposes of discussion, any or all of these can be implemented an a single processor or processing element, or in distributed processing elements as desired and the claimed inventions are not limited to the particular configurations shown. Likewise, although the described functions have been described through the use of block diagrams and in hardware, one of ordinary skill in the art will recognize that most of the functions described herein may be implemented in software as well. Additionally, the exact configurations described herein need not be adhered to, but rather the diagrams and architectures described herein may be varied according to the skill of one of ordinary skill in the art. Moreover, although reference is made to electronics, circuitry and software in the exemplary systems, it is to be recognized that audio functions implemented in electronics/circuitry may often be implemented in software, and vice versa, and thus it is considered within the scope of the inventions that software elements might be implemented in electronics with or without a processor executing software, and electronic aspects can likewise be implemented in software.