Method of passing signal events through a voice over ip audio mixer device

Abstract

In Voice-over-IP or like systems, audio mixers are used for implanting conferencing applications for IP networks. In such systems, a problem exists as how to pass through user signal events, such a DTMF digits, in-band as well as out-of-band telephony events (RFC 2833/4733) because they are not handled well in such systems. In accordance with certain embodiments, a signalling event in incoming audio packets or user signalling event received out-of-band is detected at one of the inputs. A meta-data representation of the signal event is attached to the audio and passed through the mixer for regeneration, as in-band or out-of-band telephony events, on the other side of the mixer.

1 . A method of passing user signal events through a packet-based audio mixer device implementing a conference application and having a plurality of user inputs and a plurality of user outputs, said method comprising:
 decoding and detecting a signal event in incoming audio packets at one or more of said user inputs;   placing a meta data representation of said signal event in an audio buffer associated with the user input at which the event was detected;   passing said meta-data representation through said audio mixer with the user's audio data to a user output with a packet audio stream; and
 regenerating said signal event at a user output. 
   
     
     
         2 . The method of  claim 1 , wherein said meta-data representations are placed in buffers associated with the user's audio stream. 
     
     
         3 . The method of  claim 1 , wherein the meta-data representations comprise codes representing the information content of said signal events. 
     
     
         4 . The method of  claim 3 , wherein said codes are alphanumeric codes. 
     
     
         5 . The method of  claim 1 , wherein the signalling events are carried by out-of-band packets. 
     
     
         6 . The method of  claim 5 , wherein during periods of packet loss or silence, the meta-data representations are placed in empty audio buffers. 
     
     
         7 . The method of  claim 1 , wherein the signalling events are in-band audio events, an decoder decodes audio streams at a user input, and said in-band audio events are detected by an audio event detector and converted to the meta-data representations for placement in the audio buffers. 
     
     
         8 . The method of  claim 7 , wherein said audio events are DTMF events, which are decoded and converted to said meta-data representation. 
     
     
         9 . The method of  claim 7 , wherein the audio event detector overwrites any meta-data in the audio buffer of the corresponding user. 
     
     
         10 . The method of  claim 7 , wherein said signal events include end events, and the an audio signal event is regenerated at a user output until an end event is received. 
     
     
         11 . The method of  claim 7 , wherein a predetermined minimum gap is placed between successive signalling events passed through said audio mixer. 
     
     
         12 . The method of  claim 1 , further comprising recording audio passing through said audio mixer, wherein said signal events are recorded as said meta-data representations associated with said audio so that said signal events are recorded without interfering with the audio record. 
     
     
         13 . The method as claimed in  claim 1 , wherein the signal event regenerator terminates signal events after a predetermined period of time if no internal end event signal is received. 
     
     
         14 . A system for passing audio signals between a plurality of users during a conference call, comprising:
 a packet-based audio mixer for passing packet-based audio signals between a plurality of user inputs and a plurality of user outputs in a conference application; a detector for detecting an audio signalling event at each user input in incoming audio packets, creating a meta-data representation of the signalling event, and placing said meta-data representation in an audio buffer associated with a user's audio stream of input to said audio mixer; and   a regenerator for regenerating a said audio signalling event at a user output after said meta-data representation has passed through said audio mixer.   
     
     
         15 . The system of  claim 14 , wherein said packet-based audio signals are Voice over IP (VoIP) packets, and said system further comprising a decoder for decoding a VoIP audio stream at one of said inputs, and wherein said detector is configured to detect said audio signalling events as in-band signals in said decoded VoIP audio stream and create said meta-data. 
     
     
         16 . The system of  claim 15 , wherein said audio signalling events are DTMF signals, and said detector includes a DTMF detector. 
     
     
         17 . The system of  claim 16 , further comprising a DTMF generator at said user outputs for regenerating DTMF input signalling events. 
     
     
         18 . The system of  claim 14 , comprising a packet media interface for receiving packet media, said packet media interface serving as said detector for detecting said audio signalling events as out-of-band signals. 
     
     
         19 . The system of  claim 18 , further comprising an encoder at said user outputs for regenerating said signalling events as out-of-band packets. 
     
     
         20 . The system of  claim 14 , wherein said audio mixer comprises a plurality of processors for processing said audio signals, and in inter-processing sub-system for transferring audio buffers containing said meta-data representations between said processors.