Abstract:
A method and device are disclosed which receives packets streamed over a packet network, decodes the packets received to generate a decoded signal stream and filters the decoded signal stream to generate a pulse code modulated (PCM) signal stream. The PCM signal stream may be tailored to conform to the target destination transport requirements, including call channels established over circuit-switched networks, whether wired or wireless, without modifying the capabilities associated with the network infrastructure or the client phone.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 60/180,245, filed on Feb. 4, 2000. The application is related to another U.S. patent application, having a filing date of Mar. 14, 2000, and Ser. No. 09/525,595 entitled “Media Gateway Appliance,”(Kalavade 5). 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to the processing of a streamed media source, especially applicable for audio signal streaming over a circuit-switched service connection. 
     BACKGROUND OF THE INVENTION 
     Streaming is a technique for breaking up a media file into packets and sending those packets to the user in sequence, via a packet network such as the Internet or intranet. A receiving computer is able to play the data when it arrives, instead of waiting for the entire file to download. Audio streaming is an extremely popular application on the Internet today, as evidenced by the immense popularity of music and other audio content in the MP3, RealAudio, and Microsoft Media formats. With the increasing proliferation of cellular users, and the trend towards ubiquitous services, it is believed that there could also be an enormous demand for similar streaming applications to cellular phone users, should such capability be developed. A recent study by Arbitron found that over 75% of polled web users expressed interest in portable streaming services, saying they would increase their tuning into streaming programs if these services were available on portable devices. 
     Audio streaming over the Internet uses a packet-based approach, where the audio source is broken down into packets, each packet is encoded, and sent to the receiving client in sequence. The client receives the packets, decodes them, and plays them out on the receiving terminal. Unfortunately, cellular systems today cannot offer such Internet-style packet-based audio streaming due to limitations at the terminal (client cell phone) and due to limitations of the infrastructure. For example, cellular phones can not support streaming since they do not have decoders (e.g. mp3 decoder) or streaming controls (skip, pause, etc.). Additionally, data rates over the cellular networks today are quite limited and are insufficient to transport encoded streaming packets. 
     SUMMARY OF THE INVENTION 
     These and other limitations associated with the prior art are overcome by the present invention which receives packets streamed over a packet network, decodes the packets received to generate a decoded signal stream and filters the decoded signal stream to generate a pulse code modulated (PCM) signal stream. The PCM signal stream may be tailored to conform to the target destination transport requirements, including call channels established over circuit-switched networks, whether wired or wireless, without requiring modification of the capabilities associated with the network infrastructure or the client phone. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete understanding of the present invention may be obtained from consideration of the following description in conjunction with the drawings in which: 
         FIG. 1  illustrates an exemplary application of a Media Gateway Appliance (MGA) used to generate a Pulse Code Modulated (PCM) audio signal stream for delivery to a client cellular phone via a wireless network, in accordance with the principles of the present invention; 
         FIG. 2  is a high-level flow diagram illustrating the MGA&#39;s function as a gateway between the Internet and the cellular network of  FIG. 1 , in accordance with the principles of the present invention; 
         FIG. 3  is a high-level, functional block diagram of one embodiment of the MGA, in accordance with the principles of the present invention; 
         FIG. 4  is a block diagram of the architecture of one embodiment of the MGA, in accordance with the principles of the present invention; 
         FIG. 5  is a flow diagram illustrating one embodiment of a user interface process, in accordance with the principles of the present invention; 
         FIG. 6  is a functional block diagram of one embodiment of the MGA, in accordance with the principles of the present invention; 
         FIG. 7  is a flow diagram illustrating one embodiment of a Service Control is Module&#39;s processes, in accordance with the principles of the present invention; 
         FIG. 8  is a flow diagram illustrating one embodiment of a Session Control Module&#39;s processes, in accordance with the principles of the present invention; 
         FIG. 9  is an illustration of an exemplary embodiment of the mapping of the Audio Session Gateway Protocol (ASGP), in accordance with the principles of the present invention; 
         FIG. 10  is a flow diagram illustrating the cell casting processes for one exemplary embodiment of the present invention; 
         FIG. 11  is a block diagram of one-embodiment of a Media Translation Module, in accordance with the principles of the present invention; 
         FIG. 12  illustrates an exemplary application of the MGA used in conjunction with Wireless Application Protocol (WAP) functionality, in accordance with the principles of the present invention; and 
         FIG. 13  is a flow diagram illustrating the MGA&#39;s function as a gateway between the Internet and the WAP cellular network of  FIG. 12 , in accordance with the principles of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Although an embodiment of the present invention is illustrated and described herein as a method and device for accessing Internet audio content provider sources and for converting packet-based streamed audio to a Pulse Code Modulated (PCM) audio signal stream for delivery to a cellular network service provider&#39;s client cell phone over a circuit-switched connection, the embodiment is merely illustrative for the purposes of teaching and describing the principles of the present invention and should not be construed as being so limited. The present invention is equally applicable to any device and method for conversion of packet streamed media to a PCM signal stream, regardless of the source packet network type and regardless of the source media file and transport format, and irrespective as to whether the PCM signal stream is delivered to a wireless client&#39;s cell phone, a wire-line phone, or via any circuit-switched connection whatsoever. 
     Referring to  FIG. 1 , a Media Gateway Appliance (MGA)  120  is shown interposed between a mobile switching center (MSC)  150  of a cellular network  170  and a content provider server  140 . Internet Protocol (IP) sessions between the MGA  120  and the content provider server  140  are accomplished over the Internet  160 . A cellular network&#39;s client cell phone  130  is shown accessing the MSC  150  via the cellular network  170  to establish a wireless circuit-switched connection with the MGA  120 . The present invention is agnostic with respect to the various cellular modes and standards, and is compatible with all cellular air interfaces, including, but not limited to Groupe Speciale Mobile (GSM), Time Division Multiple Access (TDMA), Code Division Multiple Access (CDMA), and Advanced Mobile Phone Service (AMPS). 
     Furthermore, the instant embodiment illustrates the MGA  120  as interfacing the Internet  160  and the cellular network  170 , but the MGA  120  is not shown as included within either network. Those skilled in the art would appreciate that the MGA  120  may be implemented in either network while still adhering to the principles of the present invention. In fact, special value may be extracted by incorporating the MGA  120  within either network. For example, incorporating the MGA  120  within the cellular network  170  adds value inuring to the wireless service provider since the provider may: (i) choose to charge additional subscriber fees for client&#39;s use of wireless audio (or other media) streaming services, (ii) choose to offer the additional streaming services to entice prospective subscribers away from competitor providers, or both. Alternatively, value may be extracted from MGA  120  services if the MGA is implemented within an Internet domain server as well, whether in conjunction with the content provider server  140  or in conjunction with a third-party server (not shown). Including wireless media streaming services is of value to web-sites, since it will result in more site hits and attract greater numbers of visitors and clients. 
     The MGA  120  acts as a gateway between the cellular network  170  and the Internet  160 . In an exemplary embodiment of the present invention, a client cellular user requests MGA  120  media streaming services by initiating a call to an MGA  120  service telephone number. The MGA  120  is responsible for: (a) establishing a session on the Internet  160  in response to the call request, (b) retrieving packet-based streaming audio content from the content provider server  140 , (c) decoding the packet-based streaming audio content, and (d) translating it to a 64 kbps PCM signal stream. The decoded and translated PCM signal stream is then delivered to the client cell phone  130  over a standard speech channel using the underlying services in the cellular network. Therefore, the MGA  120  leverages the circuit-switched (“speech”) channel in the cellular network  170  to deliver streaming audio from the MSC  150  to the client cell phone  130 . Streaming session control and decoding is performed at the MGA  120 . Thus, audio and other media content can be played out utilizing existing cell phones, phones which don&#39;t include decoders or streaming audio players. Second, the content is played out over a speech channel. Therefore, special high-bandwidth circuit-switched connections to the cellular network  170  are not required. Since the cellular network  170  receives the audio content from the MGA  120  via a circuit-switched connection, mobility, transport and delivery issues are not encountered. In addition, because the MGA&#39;s  120  output signal stream is typically 64kbps PCM, it can be connected directly to the MSC  150 , either by co-locating the MGA  120  within the cellular service provider premises, or alternatively, via a direct digital connection into the MSC  150 . Such a configuration makes the MGA  120  simple to deploy since changes are not required in the cellular service provider&#39;s infrastructure. Thus service providers may use the MGA to deploy audio signal streaming, a next-generation wireless service, while still leveraging their infrastructure. 
     A high-level description of one embodiment describing the MGA&#39;s  120  function as a gateway between the Internet  160  and the cellular network  170  may be had by referring to FIG.  2 . The client user initiates a media streaming session by requesting service ( 210 ). The user begins this process by dialing a phone number from the client cell phone  130  corresponding to the MGA  120 . The servicing MSC  150  establishes a connection between the client cell phone  130  and the MGA  120  ( 220 ). Once the incoming call is received, the MGA  130  forwards options to the user and solicits a response ( 230 ), typically via voice announcement indicating a choice of selections with a request that the user select and press a digit corresponding to her desired selection. Other options for information exchange between the MGA  120  and the user are also well-known and would be apparent to those skilled in the art, two such examples being solicitation and/or response via text or voice messages. The request to the user for option selections is presented within an MGA  120  service presentation layer. 
     One embodiment of the present invention solicits user response regarding web-site content provider, type and/or genre of music, etc. The MGA  120  provides three types of media streaming services, including: (i) web-casted live content, for example, Internet radio provided by content providers such as SHOUTcast.com or Broadcast.com, (ii) on-demand content providers such as RealNetworks, MP 3 .com or any of a myriad of web-sites which maintain archived media files at their servers, and (iii) profile playback, which allows users to maintain a user profile database at the MGA  120  server, the profile being used to select content for playback to the client cell phone  130 . 
     The user selects her desired options using the client cell phone  130  ( 240 ). Once the user selected options are received at the MGA, the MGA establishes a session with the content provider server  140  ( 250 ), and the content provider server  140  begins streaming packets to the MGA  120  ( 260 ). The MGA  120  decodes the received packet-based streamed audio and translates to a PCM signal format ( 270 ). The MGA  120  then delivers the PCM audio signal stream to the client cell phone  130  via the established circuit-switched connection ( 280 ). 
       FIG. 3  is an exemplary illustration of the function and interrelationship of the main functional components of the MGA  120  on a per call connection basis. In one illustrative embodiment of the present invention, the MGA  120  is comprised of three functional components: (i) the service control function  310 , (ii) the session control function  320 , and (iii) the media translation function  330 . The service control function is used as an interface with the call connection established over the circuit-switched cellular network  170 . The service control function  310  presents the various service control options to the client cell phone  130 , processes requests for service, and processes playback commands. The service control function  310  information exchange with the user may be presented in several formats, including, but not limited to, such illustrative examples as standard interactive voice response (IVR), wireless application protocol (WAP) interface, or VoiceXML (VXML). The session control function  320  is used to interface the MGA  120  with the Internet  160 . The session control function  320  establishes and controls sessions with the content provider server  140 . The session control function  320  also implements a protocol for converting the client cell phone  130  into a virtual personalized player by translating playback control requests from the client into session commands routed to the content provider server  140 . This protocol is called an Audio Session Gateway Protocol (ASGP), and will be described in more detail later in conjunction with FIG.  9 . The media translation function  330  receives packet-based streamed audio files over the Internet  160 , and decodes and converts the packet-based streamed audio files into a PCM audio signal stream compatible for delivery over a circuit-switched voice channel to the client cell phone  130 . 
     As shown in  FIG. 4 , the MGA  120  includes a central processor (CPU)  405 , random access memory (RAM)  410 , read only memory (ROM)  420 , clock  425 , packet network interface  430 , circuit-switched line interface  435 , and data storage device  440 . A conventional personal computer or computer workstation with sufficient memory and processing capability may be used as the MGA  120 . Data storage device  440  may include hard disk magnetic or optical storage units, as well as CD-ROM drives or flash memory. Data storage device  440  contains applications and databases used for the implementation of the present invention, including: MGA application software  450 , WAP server application software  455 , web server application software  460 , content caching software  465 , user profile database  470 , recorded audio database  480 , and live channel directory database  490 . WAP server application software  455  is optionally included for use in delivery of web page content from the content provider server  140  to the client cell phone  130 . Content caching software  465  is implemented optionally for local storage content at the MGA  120  for repeatedly accessed Internet  160  media files, so that content that is repeatedly accessed does not require repeated downloads from the Internet  160 . 
     The user profile database  470  includes information associated with a client, including, for example, user preferences and/or client cell phone number. In one embodiment of the present invention, user data may be entered in the user profile database  470  utilizing the keypad on the client cell phone. In another embodiment of the present invention, user data may be entered in the user profile database  470  from a personal computer or other information appliance accessing the web (not shown) to use the optional web server application software  460  at the MGA  120 . Thus user profile database  470  entries may be created or edited without the benefit of an established connection between the client cell phone  130  and the MGA  120 . Recorded audio database  480  is a portion of the data storage device  440  in which the user may store audio files which the user has selected. The live channel directory database  490  is a portion of the data storage device  440  in which information pertaining to available live content channels is maintained at the MGA  120 . 
     Packet network interface  430  is utilized as an interface to the Internet  160 . Any appropriate interface may be used, such as an Ethernet interface, as would be known to those skilled in the art. Circuit-switched line interface  435  is utilized as the interface to the cellular network  170 . Similarly, such interfaces are also well-known to those skilled in the art. 
     Referring now to  FIG. 5 , there is shown a flow diagram illustrating an exemplary embodiment of the service control function  310  interfacing sequence with the client cell phone  130  user. The client user initiates a media streaming session by requesting service ( 510 ). The user begins this process by dialing a phone number from the client cell phone  130  corresponding to the MGA  120 . The service control function  310  for the assigned call connection attempts to identify the client cell phone  130  or a user registration and dips the user profile database  470  to determine if a user profile exists ( 515 ). If a user profile does exist, the user profile is then read to return user-selected channel, category, or genre preferences ( 520 ). An Internet session with the user-selected content provider server is established and the appropriate content packets are streamed to the MGA  120 . The MGA  120  decodes the selected content and translates it to a PCM audio signal stream, which is then launched over the established circuit-switched connection to the client cell phone  130  ( 525 ). 
     If however, a user profile does not exist, then the service control function  310  queries the user regarding her desired session preferences ( 530 ). The user selects her desired options using the client cell phone  130  in response to the query ( 535 ). The MGA  120  then determines if the user has requested delivery of live content ( 540 ). 
     If the user desires to listen to live content channels, then the user is presented with a set of scan-mode channels and queried for a selection from the available scan-mode channels ( 555 ). Scan-mode channels are identified by a cell cast scan channel module of the MGA  120 , described in greater detail in conjunction with FIG.  6 . The available scan-mode (or cell cast) channels may be presented to the user in several formats, as would be apparent to skilled in the art. In one embodiment of the present invention, audio samples from each of the available scan-mode channels are multiplexed in short audio segments, so that a user can listen to sequential segments of available audio content. One alternative method for scan-mode channel presentation to the user is to forward content playlist or genre text to the user. Once available scan-mode channels are presented, the user responds by selecting a scan-mode channel ( 560 ). The user&#39;s response is collected via the service control function  310  by any number of well-known alternative collection means, including by way of example, but not limitation, dual tone multi-frequency (DTMF) digit collection, text message recognition, or voice recognition. Once the user has selected a scan-mode channel, the content of the selected scan-mode channel is launched over the established circuit-switched connection to the client cell phone  130  ( 525 ). 
     If however, the user does not desire to listen to live content channels, but rather wishes to invoke on-demand mode channels, then the user is presented with options, typically via voice announcement ( 545 ). In one embodiment of the present invention, the options presented may be as to type or genre of audio content desired; such as “Press  1  for classical,” Press  2  for jazz,” etc. The client cell phone  130  user then selects the desired option ( 550 ). The user&#39;s response is collected via the service control function  310  by any number of well-known alternative collection means, including by way of example, but not limitation, dual tone multi-frequency (DTMF) digit collection, text message recognition, or voice recognition. Once the user has selected a content option, the selected content is fetched, decoded, translated, and launched over the established circuit-switched connection to the client cell phone  130  ( 525 ). 
     Playback controls are asynchronously enabled ( 565 ). Playback controls are available to the client cell phone  130  user to perform various playback and control functions. These are functions typically associated with any audio playback device. Such controls include, by way of example and not limitation, fast forward, reverse, play, record, pause, resume, stop, skip, channel select, mute, etc. Playback control commands are divided into two general types: content altering commands and non-content altering commands ( 570 ). Non-content altering commands include those commands in which the content provided to the MGA  120  from the content provider server  140  is to remain unchanged; that is, the user has not selected an alternate media channel for the MGA  120  to stream. Content altering commands include those in which the content provided to the MGA  120  from the content provider server  140  is to be changed; that is, the user has selected an alternate media channel for the MGA  120  to stream. 
     Referring now to  FIG. 6 , a functional block diagram of one embodiment of the MGA  120  is presented. Functionally, the MGA  120  includes packet interface  430 , circuit-switched line interface  435 , call processing interface  610 , call channels  620  (a total of k+n call channels shown), cell cast channels  640  (a total of j+n cell cast channels shown), cell casting control module  650 , and cell cast scan channel module  660 . Greater detail of the functional architecture of an individual call channel  620  may be had by referring to call channel k  620   k , which includes a service control module  622   k , a session control  624   k , media translation module  626   k , and a line driver  628   k . Greater detail of the functional architecture of an individual cell cast channel  640  may be had by referring to cell cast channel j  640   j , which includes a cell cast session control module  642   j  and a cell cast media translation module  644   j . 
     When used within the context of the instant description, the word “coupled” is meant to describe the capability of the functional components and modules so coupled to exchange, relay, correlate, impart, and/or otherwise share various messages, data, communications, signaling, media, and signals, regardless of whether the functional components and modules exist as physical devices or as functional constructs of the MGA&#39;s  120  software architecture, and regardless of whether the MGA  120  is implemented in a single computer, distributed over a plurality of computers, or distributed over a plurality of processors and a plurality of data storage devices. Packet network interface  430  is utilized as an interface to the Internet  160 . Circuit-switched line interface  435  is utilized as the interface to the cellular network  170 . Call processing interface  610  is coupled to: (i) the circuit-switched line interface  435 , and (ii) the service control modules  622  and line drivers  628  of respective individual call channels  620 . Service control modules  622  are coupled to respective session control modules  624  and line drivers  628 . Session control modules  624  are coupled to the packet interface  430  and the cell casting control module  650 . Media translation modules  626  are coupled to the packet interface  430  and respective line drivers  628 . The cell casting control module  650  is coupled to the cell cast scan channel module  660  and cell cast session control modules  642 . Cell cast session control modules  642  are coupled to the packet interface  430 , which is in turn coupled to the cell cast media translation modules  644 . Cell cast media translation modules are coupled to the cell cast scan channel module  660 , which is in turn coupled to the line drivers  628 . 
     The call processing interface  610  performs the function of receiving and terminating client cell phone  130  call connections and assigning client cell phone  130  call connections to call channels  620 . Individual call channels  620  are assigned to each call and are comprised of a service control module  622 , session control module  624 , media translation module  626 , and line driver  628 . 
     The service control module  622  performs the service control function  310 , which in the instant embodiment of the invention encompasses the illustrative tasks of presenting various service control options to the client cell phone  130 , processing requests for service, and processing playback commands. The service control function  310  may utilize any of a number of well-known user interface means, formats, and protocols including, but not limited to, such illustrative examples as standard interactive voice response (IVR), DTMF digit detection and collection, voice recognition, text messaging, wireless application protocol (WAP) interface, or VoiceXML (VXML). The session control module  624  performs the session control function  320 , which in the instant embodiment of the invention encompasses the illustrative tasks of maintaining an Internet  160  interface, establishing and controlling Internet sessions with the content provider server  140 , implementing the AGSP for converting the client cell phone into a virtual personalized player by translating playback control requests from the client into session commands routed to the content provider server  140 . The media translation module  626  performs the media translation function  330 , which in the instant embodiment of the invention encompasses the illustrative tasks of receiving packet-based streamed audio files over the Internet  160 , and decoding and converting the packet-based streamed audio files into a PCM audio signal stream compatible for delivery over a circuit-switched voice channel to the client cell phone  130 . In accordance with the instant embodiment of the invention, the line driver module  628  receives the PCM audio signal stream from the media translation module  626  and launches the audio content for the respective call channel to the client cell phone  130 . The line driver module  628  also receives inputs from various processes, including playback options from the session control module  622 , on-demand data from the media translation module  626 , and live content, scan-mode channels and live channel directory information associated with cell cast channels  640 . 
     In the case of live content, the MGA  120  is designed to support the multi-casting of a single PCM audio signal stream to a plurality of users, that is to one or more client cell phones  130 , without requiring the replication of resources on a per call channel  620  basis for each call connection to each client cell phone  130 . I call this mode of multi-casting “cell casting.” Cell Casting reduces the bandwidth and processing overhead when a plurality of clients want to listen to the same content. In accordance with the instant illustrative embodiment of the invention, cell casting is supported by the MGA  120  in the following manner. The cell casting control module  650  establishes content sessions with one or more Internet broadcast channels over the packet interface  430 . The cell casting control module  650  maintains a list of each of the sessions established and the cell cast channels  640  through which corresponding session data is processed, the content provider server address  140 , and the group of client users currently subscribing to each of the cell cast channels  640 . Each cell cast channel  640  is comprised of a cell cast session control module  642  and a cell cast media translation module  644 , with functionality replicating the functionality of individual call channel&#39;s similarly-named session control modules  624  and media translation module  626 . The cell cast scan channel module  660  provides the previously described scan-mode channel presentation for a client cell phone  130  user. That is, if a user desires to listen to live content channels, then the user is presented with a set of scan-mode (or cell cast) channels and queried for a selection from the available scan-mode channels. Scan-mode channels are identified by the cell cast channel module and presented to the user in any of several formats, as would be apparent to those skilled in the art. In one embodiment of the present invention a scan-mode channel presentation format which is thought to be especially useful, in the context of delivery of PCM audio signal stream to a client cell phone  130 , is to provide audio samples from each of the available cell cast channels  640  which are multiplexed in short audio segments, so that a user can listen to sequential segments of available audio content. Upon hearing a short audio segment which the user desires to have delivered, the user selects the desired audio content and the MGA  120  delivers a PCM audio signal stream corresponding to the selected cell cast channel  640  content. As previously described, it would be apparent to those skilled in the art to provide other well-known alternative presentation types and methods representing the available cell cast channels  640 . Once available cell cast channels  640  are presented, the user may respond by selecting a particular cell cast channel. The user&#39;s response is collected via the service control function  310  by any one of a number of well-known alternative collection means, including by way of example, but not limitation, dual tone multi-frequency (DTMF) digit collection, text message recognition, or voice recognition. Once the user has selected a cell cast channel  640 , the content of the selected cell cast channel  640  is launched over the established circuit-switched connection to the client cell phone  130 . 
       FIG. 7  is a flow diagram showing the processes performed by a service control module  622  in an illustrative embodiment of the present invention. Although the processes described in conjunction this and subsequent figures are directed towards call channel k  620   k  and cell cast channel j  640   j , the processes are representative of other channels as well, and apply equally to any call channel  620  and any cell cast channel  640 . Upon initiating a call for service to the MGA  120 , service control module  622   k  receives and parses user-identifying information pertaining to the user&#39;s client cell phone  130  via the call processing interface  610  ( 710 ). Such information may be determined through the use of user-supplied per-call information, recalled stored data ascertained by association with Caller-ID data, or any other means selected from a variety of well-known methods for dial-up user account identification. Service control module  622   k  determines whether a user profile exists for the instant caller ( 715 ). If so, the service control module  622   k  dips the user profile database  470  of the data storage device  440  for pertinent profile data associated with the user allocated to call channel module k  622   k  ( 720 ). User requirements, as determined by the user profile database  470 , are then forwarded to the channel k session control module  624   k  ( 720 ). 
     If however, a profile does not exist for the user, then the service control module  622   k  queries the user regarding her desired session preferences ( 730 ). Once the user selects her session preferences, those preferences are forwarded and received by the service control module  622   k  ( 735 ). A determination is made as to whether the user has selected live content as a preference ( 740 ). If the user has requested delivery of live content, then a set of scan-mode channels are presented to the user, via call channel k line driver  628   k , to elicit a user response concerning her desired selection of live content ( 755 ). For example, in an embodiment of the present invention in which options are presented to the user via voice announcement and the user&#39;s response gathered via DTMF digit collection, a presentation script to the user may be as follows: “You are about to listen to audio clips representative of the available live content channels. Each clip is only  5  seconds in length. Please indicate your desired channel by selecting the number ‘1’ on your phone when you hear the content you wish to listen to. The audio clips are looped and will repeat should you miss a selection the first time it is played.” 
     Alternatively, if the user has not requested live content, that is, the user desires content in the on-demand mode, then call channel k line driver  628   k  presents the user with various options for on-demand content ( 745 ). For example, in an embodiment of the present invention in which options are presented to the user via voice announcement and the user&#39;s response gathered via DTMF digit collection, a presentation script to the user may be as follows: “If you wish to listen to news, please push ‘1’ now ... if you wish to listen to classical music, please push ‘2’ now... ” 
     Regardless of whether live content or on-demand content is selected, the user selection is received by the call processing interface ( 750 ) and forwarded to the call channel k session control module  624   k  (( 725 )—go to match point A of FIG.  8 ). 
     Playback controls are asynchronously enabled ( 760 ). Playback controls are available to the client cell phone  130  user to perform various playback and control functions. These are functions typically associated with any audio playback device. Such controls include, by way of example and not limitation, fast forward, reverse, play, record, pause, resume, stop, skip, channel select, mute, etc. Playback control requirements, when selected, are forwarded to the call channel k session control module  624   k  (( 765 )—go to match point B of FIG.  8 ). 
       FIG. 8  is a flow diagram showing the processes performed by a session control module  624  in an illustrative embodiment of the present invention. The processes are described in conjunction with call channel k  620   k , although they apply equally to the session control module  624  of any call channel  620 . Upon receipt of mode requirements from the corresponding service control module  622   k (( 810 )—from matchpoint A of FIG.  7 ), the session control module  624   k  ascertains whether the requested channel is a live content mode or on-demand mode source ( 820 ). If an on-demand mode source is requested, the session control module  624   k  initiates and establishes a HyperText Transfer Protocol (HTTP)/Real Time Streaming Protocol (RTSP) session with the content server to provide the requested media file ( 825 ). If however, a live content mode source is requested, the session control module  624   k  first performs a check to determine whether a cell cast channel  640  is already receiving, decoding and translating the requested source file ( 830 ). This step is performed for purposes of efficiency. That is, it would be unnecessary to replicate the establishment of a session, and the decoding, and translating of a streamed packet audio file, if all of those processes were already performed for a user assigned to another call channel(s). Therefore, should it be determined that the requested content source is already being received and processed via a cell cast channel (say cell cast channel j  640   j , for the purposes of this description), then the cell casting control module adds call channel k  620   k  to the list of channels being provided content from cell cast channel j  640   j , and the PCM audio signal stream generated by cell cast channel j  640   j  is delivered to the line driver  628   k , associated with call channel k  620   k , in addition to the call channels  620  previously assigned ( 835 ). If however, no cell casting channel  640  is processing the requested content, then the session control module  624   k  initiates and establishes an HTTP/RTSP session with the content server to provide the requested media file ( 825 ). 
     Upon receipt of a playback control requirement from call channel k service control module  622   k  (( 840 )—from matchpoint B of FIG.  7 ), the session control module  624   k  converts the playback control requirements utilized by the service control module  622   k  into a format appropriate for the packet streaming content server. The conversion is accomplished utilizing the audio session gateway protocol (ASGP) developed in conjunction with the instant invention ( 845 ). In one exemplary embodiment of the present invention, the ASGP converts user selected DTMF digits into command formats appropriate for the content provider server  140  format utilized (i.e.—a command to pause audio playback, although common at the user interface, requires different conversions by the ASGP for different audio content players).  FIG. 9  is representative of an ASGP conversion mapping  900  for an exemplary embodiment of the present invention. 
     The session control module  624   k  ascertains whether the requested channel is a live content mode or on-demand mode source ( 850 ). If the requested channel is an on-demand mode source, then the playback control requirements converted by the ASGP are forwarded to the content provider server  140  or the media translation module  626   k , as appropriate ( 855 ). Differentiation as to whether the ASGP command is forwarded to the content provider server  140  or the media translation module  626   k  is determined by the actual command type. For example, certain playback control commands, such as “skip to the next item” or “rewind,” control the streaming of packets from the content provider server  140  to the MGA  120  and therefore must necessarily be forwarded to the content provider server  140  itself. Other commands, such as volume control changes, are not content or content-delivery altering, and only need to be forwarded to the media translation module  626   k . 
     If the requested channel is a live content mode source, the session control module  624   k  ascertains whether a cell cast channel  640  is already receiving, decoding and translating the requested source channel ( 860 ). As before, this step is performed for purposes of efficiency. If the requested source channel content is already being received, decoded, and translated by a cell casting module, then the ASGP format playback control command is forwarded to the cell casting control module ( 865 ). If not, then the ASGP format playback control command is forwarded to the content provider server  140  or the media translation module  626   k , as appropriate ( 855 ). 
       FIG. 10  is a flow diagram illustrating the cell casting processes in one exemplary embodiment of the present invention. As previously described, cell casting is a form of multi-casting of a single PCM audio signal stream to a plurality of users, that is to one or more client cell phones  130 , without requiring the replication of resources on a per call channel  620  basis for each call connection to each client cell phone  130 . Upon receiving user-selected requirements ( 1010 ), the session control module  624   k  determines whether the user has selected to review the previously described scan-mode channels ( 1020 ). If scan-mode is selected, then audio samples from each of the available cell cast channels  640 , in the form of short audio segments, are multiplexed by cell cast scan channel module  660  into a single audio stream, and delivered to the call channel k line driver  628   k  ( 1040 ). This single audio stream represents the content from all of the live audio streams multiplexed into one stream, allowing the user to select her choice from the available cell cast channels  640 . If scan-mode is not selected, then the selected cell cast channel  640  content (cell cast channel j  640 , in the instant example) is assigned and launched to the call channel k line driver  628   k  ( 1030 ). 
       FIG. 11  is a block diagram of a media translation module  626 , in accordance with an exemplary embodiment of the present invention. The media translation module  626  is comprised of a decoder  1110 , a low pass filter  1120 , and a rate converter  1130 . Content packets streamed from the content provider server  140  to the MGA  120  arrive at the packet interface  430  and are delivered to the decoder  1110 . The decoder  1110  is a matched type, whether proprietary or non-proprietary, for the selected content provider server  140  format type. Therefore, in an exemplary embodiment of the present invention, multiple decoder types are implemented within the media translation module  626  to accommodate selection from any of several content providers. For example, the media translation module may include decoder types to decode MP3, RealAudio, and Microsoft Media formats. Other decoder types may also be added as needed or desired. The decoder  1110  functions to receive a packet stream from the content provider server  140  and generates a decoded bit stream output; for example, a bit stream having a sampled rate of 44.1 or 48 kHz. In an exemplary embodiment of the present invention, the desired PCM signal stream output is 8 kHz. The decoder  1110  output is passed through a low pass filter  1120  to avoid difficulties associated with aliasing. The low pass filter  1120  output is then applied to a rate conversion filter (the rate converter  1130 ) to reduce the sampling rate to the appropriate rate (8 kHz in the instant example). One implementation of the rate converter utilizes a multi-stage filter to reduce filter length. In a practical implementation of the media translation module  626 , the functions of the low pass filter  1120  and the rate converter  1130  may be implemented together as a poly-phase filter. The output of the rate converter  1130  is a PCM signal stream sent to the line driver  628  of the appropriate call channel  620  for delivery to the client cell phone  130 . 
     One advantageous feature of the MGA  120  is that it is designed to function with current and emerging technologies (such as WAP compliant networks and cellular phones).  FIG. 12  illustrates an exemplary application of the MGA  120  used in conjunction with a WAP compliant network, in accordance with the principles of the present invention. A brief description of the MGA  120  in this context follows that previously provided in conjunction with  FIG. 1 , with the following exceptions. Typically, for WAP compliant cellular networks, a WAP gateway  1210  is provided as a integral component of the cellular network  170 . When a specified URL is requested by a WAP compliant cell phone  130 , the URL is forwarded to the WAP gateway  1210 , which is translated into an HTTP request. 
       FIG. 13  is a flow diagram illustrating an exemplary embodiment of the present invention in which the MGA  120  functions as a gateway between the Internet and the WAP compliant cellular network of FIG.  12 . The client user initiates a media streaming session by requesting service ( 1310 ). The user begins this process by utilizing a WAP browser to request an audio streaming application. The WAP gateway  1210  translates the request into an HTTP request, delivered to the WAP server associated with the MGA  120  ( 1320 ). The WAP server and the MGA  120  may be implemented on the same computer or server, or alternatively, may exist on separate machines interconnected via an IP link. The MGA  120  returns a script to the client cell phone  130 , the script including user-selectable options ( 1330 ). The user selects her desired options ( 1340 ) and returns the completed script to the MGA  120 . The MGA  120  then instructs WAP client to enter “call accept” mode ( 1350 ). The MGA  120  then initiates a call connection to the client cell phone  130  through the MSC  150  ( 1360 ). The MGA  120  establishes a session with the content provider server  140  ( 1370 ) to initiate streaming audio. The MGA  120  receives packets of streamed audio content launched from the content provider server  140  ( 1380 ). The MGA  120  decodes and translates the streaming packets into a PCM audio signal stream ( 1390 ) and launches the signal stream over the established call connection to the client cell phone  130  ( 1395 ). 
     An exemplary embodiment of the present invention was constructed as an MGA  120  prototype. The MGA prototype is implemented on a standard PC running Windows NT. The PC is equipped with line cards to terminate the circuit-switched call connection (Dialogic D240/PC1-T1 or Natural Microsystems AG4000). As an interface to the Internet, the prototype is connected via an Ethernet high-speed link. 
     The foregoing description merely illustrates the principles of the invention. It will thus be appreciated that those skilled in the art will be able to devise various arrangements which, although not explicitly described or shown herein, embody the principles of the invention and are included within its spirit and scope. Furthermore, all examples and conditional language recited are principally intended expressly to be only for pedagogical purposes to aid the reader in understanding the principles of the invention and the concepts contributed by the inventor(s) to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. Moreover, all statements herein reciting principles, aspects, and embodiments of the invention, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents as well as equivalents developed in the future, i.e., any elements developed that perform the same function, regardless of structure. 
     Thus, for example, it will be appreciated by those skilled in the art that the block diagrams herein represent conceptual views of illustrative circuitry embodying the principles of the invention. Similarly, it will be appreciated that any flow charts, flow diagrams, state transition diagrams, pseudocode, and the like represent various processes which may be substantially represented in computer readable medium and so executed by a computer or processor, whether or not such computer or processor is explicitly shown. 
     The functions of the various illustrated or described elements, including functional blocks labeled as “CPUs” or “processors,” may be provided through the use of dedicated hardware as well as hardware capable of executing software in association with appropriate software. When provided by a processor, the functions may be provided by a single dedicated processor, by a single shared processor, or by a plurality of individual processors, some of which may be shared. Moreover, explicit use of the term “processor” or “controller” should not be construed to refer exclusively to hardware capable of excuting software, and may implicitly include, without limitation, digital signal processor (DSP) hardware, read-only memory (ROM) for storing software, random access memory (RAM), and non-volatile storage. Other hardware, conventional and/or custom, may also be included. 
     In the claims hereof any element expressed as a means for performing a specified function is intended to encompass any way of performing that function including, for example, a) a combination of circuit elements which performs that function or b) software in any form, including, therefore, firmware, microcode or the like, combined with appropriate circuitry for executing that software to perform the function. The invention as defined by such claims resides in the fact that the functionalities provided by the various recited means are combined and brought together in the manner which the claims call for. Applicant thus regards any means which can provide those functionalities as equivalent as those shown herein.