Abstract:
The present invention is a method and apparatus in a data processing system that includes a Voice over Internet Protocol (VoIP) communication system for improving transmit and receive data paths. The communication system includes a digital signal processing unit. The digital signal processing unit includes a mandatory coder/decoder (codec) that does not include an internal packet loss concealment (PLC) function, an internal voice activity detection (VAD) function, an internal comfort noise generation (CNG) function, or an internal discontinuous transmission generation (DTX) function. The digital signal processing unit also includes an enhanced codec that includes any combination of the following modules all internal to the enhanced codec: internal packet loss concealment (PLC) function, a voice activity detection (VAD) function, a comfort noise generation (CNG) function, and a discontinuous transmission generation (DTX) function. The digital signal processing unit does not include a separate packet loss concealment (PLC) module, a separate voice activity detection (VAD) module, a separate comfort noise generation (CNG) module, or a separate discontinuous transmission generation (DTX) module. An input signal is received within the digital processing unit. A determination is made regarding whether the input signal includes voice data. If the input signal does include voice data, the input signal is processed utilizing the mandatory codec. If the input signal does not include voice data, the input signal is processed utilizing the enhanced codec.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Technical Field  
         [0002]     The present invention is directed generally toward voice processing systems. More particularly, the present invention relates to a method and apparatus in a Voice over Internet Protocol (VoIP) communication system for improving transmit and receive data paths.  
         [0003]     2. Description of the Related Art  
         [0004]     There is an increasing demand for Voice over Internet Protocol (VoIP) solutions for use in home and office. VoIP systems transmit voice communications between two computer systems using a data network using the Internet Protocol instead of via a traditional telecommunications network such as the Public Switched Telephone Network (PSTN) or Private Branch Exchange (PBX). A VoIP system receives voice and fax signals, converts them into digital data, and transmits the digital data over a computer network using the IP standard.  
         [0005]     Typically, a transmitting VoIP system receives digital voice input within a digital signal processor (DSP) which encodes the digital voice to produce compressed data and outputs the compressed data. Conversely, a receiving VoIP system also includes a digital signal processor (DSP) which receives the compressed data, converts it back to digital voice, and then outputs the digital voice.  
         [0006]     A coder/decoder (codec) is a module that converts linear voice data to produce compressed data and converts compressed data to produce linear voice. Most VoIP systems have a list of codecs that can be used. This is primarily due to the different quality and bit-rate tradeoffs among the different codecs. A codec includes both an encoder and a decoder.  
         [0007]     However, the G.711 codec is mandatory for all VoIP systems. The G.711 codec lacks any packet loss concealment (PLC), voice activity detection (VAD), discontinuous transmission (DTX), and comfort noise generation (CNG) functionality.  
         [0008]     Many VoIP applications require these PLC, VAD, DTX, and CNG functions. When an application requires these functions, an additional stand-alone module must be provided in the DSP to provide each PLC, VAD, DTX, and CNG function. The additional modules take up valuable hardware real estate within the system.  
         [0009]      FIG. 1  is a block diagram of a transmit data path included within a digital signal processor (DSP) in a Voice over Internet Protocol (VoIP) system in accordance with the prior art. A DSP device  100  includes a transmit data path  101 . DSP  100  is included within a VoIP system. Data path  101  includes a mandatory codec  102 , such as a G.711 encoder, a separate module that provides a discontinuous transmission generator function DTX  104 , a separate module that provides a voice activity detector function VAD  106 , and an enhanced codec, such as enhanced encoder  108  that adheres to the ITU G.729AB standard. Enhanced encoder  108  includes within it an internal DTX and an internal VAD. According to the prior art, a voice signal is received within either enhanced encoder  108  or VAD  106  as selected by a codec select switch  110 . If the mandatory codec is selected by switch  110 , VAD  106  receives the input signal and determines whether voice is present in the received signal. If voice is detected in the signal, VAD  106  selects mandatory encoder  102  which encodes the voice signal to produce an output data signal. The output of encoder  102  is then the output of DSP  100 . If voice is not detected in the signal, VAD  106  selects DTX  104  which produces silence description frames as the output data signal. The output of DTX  104  is then the output of DSP  100 . VAD  106  continues to select either encoder  102  or DTX  104  as the continuous input signal is received depending on whether voice is detected or not currently in the input stream in order to product a continuous stream of digital data output.  
         [0010]      FIG. 2  is a block diagram of a receive data path included within a digital signal processor (DSP) in a Voice over Internet Protocol system in accordance with the prior art. A DSP device  200  includes a receive data path  201 . DSP  200  is included within a VoIP system. Data path  201  includes a mandatory codec  202 , such as an decoder G.711, a separate module that provides a comfort noise generator function CNG  204 , a separate module that provides a packet loss concealment function PLC  206 , and an enhanced codec, such as enhanced decoder  208  that adheres to the G.729AB standard. Enhanced decoder  208  includes within it an internal PLC and an internal CNG. According to the prior art, a data signal is received within either enhanced encoder  208  or both mandatory decoder  202  and CNG  204  as selected by a codec select switch  210 . If the mandatory codec and CNG path is selected by switch  210 , mandatory decoder  202  and CNG  204  receive the input signal. If the input data signal is transmitted silence, CNG  204  inserts comfort noise. If the input data signal includes a voice frame, mandatory decoder  202  decodes the voice frame to produce a voice output signal. In the case of data packet loss where no voice data is present and the input data signal is neither transmitted nor untransmitted silence, PLC  206  attempts to extrapolate voice data to fill in the gap when the voice output signal is produced.  
         [0011]     Modem DSP devices sometimes include codecs in addition to the mandatory G.711 codec. For example, an enhanced codec, e.g. codec G.729AB, was provided in the DSP in both  FIGS. 1 and 2 . These other non-mandatory codecs often include the PLC, VAD, DTX, and CNG functions within the codec itself. The G.729AB codec includes within it an internal PLC, VAD, DTX, and CNG. Therefore, these DSP devices include a G.711 codec, a separate PLC module, a separate VAD module, a separate DTX module, a separate CNG module, and a non-mandatory codec that includes within it internal PLC, VAD, DTX, and CNG functions.  
         [0012]     Therefore, a need exists for a method and apparatus for improving transmit and receive data paths in a Voice over Internet Protocol communication system by removing duplicated functional modules from a digital signal processing unit that includes a mandatory codec as well as an enhanced codec that includes these functions internally.  
       SUMMARY OF THE INVENTION  
       [0013]     The present invention is a method and apparatus in a data processing system that includes a Voice over Internet Protocol (VoIP) communication system for improving transmit and receive data paths. The communication system includes a digital signal processing unit. The digital signal processing unit includes a mandatory coder/decoder (codec) that does not include an internal packet loss concealment (PLC) function, an internal voice activity detection (VAD) function, an internal comfort noise generation (CNG) function, or an internal discontinuous transmission generation (DTX) function. The digital signal processing unit also includes an enhanced codec that includes any combination of the following modules all internal to the enhanced codec: internal packet loss concealment (PLC) function, a voice activity detection (VAD) function, a comfort noise generation (CNG) function, and a discontinuous transmission generation (DTX) function. The digital signal processing unit does not include a separate packet loss concealment (PLC) module, a separate voice activity detection (VAD) module, a separate comfort noise generation (CNG) module, or a separate discontinuous transmission generation (DTX) module. An input signal is received within the digital processing unit. A determination is made regarding whether the input signal includes voice data. If the input signal does include voice data, the input signal is processed utilizing the mandatory codec. If the input signal does not include voice data, the input signal is processed utilizing the enhanced codec.  
         [0014]     The above as well as additional objectives, features, and advantages of the present invention will become apparent in the following detailed written description.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]     The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself however, as well as a preferred mode of use, further objects and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein:  
         [0016]      FIG. 1  is a block diagram of a transmit data path included within a digital signal processor (DSP) in a Voice over Internet Protocol system in accordance with the prior art;  
         [0017]      FIG. 2  is a block diagram of a receive data path included within a digital signal processor (DSP) in a Voice over Internet Protocol system in accordance with the prior art;  
         [0018]      FIG. 3  is a block diagram of an improved transmit data path included within a digital signal processor (DSP) in a Voice over Internet Protocol system in accordance with the present invention;  
         [0019]      FIG. 4  is a block diagram of an improved receive data path included within a digital signal processor (DSP) in a Voice over Internet Protocol system in accordance with the present invention;  
         [0020]      FIG. 5  depicts a high level flow chart that illustrates receiving a linear digital voice signal and transmitting a compressed digital data signal utilizing the improved transmit data path of  FIG. 3  in accordance with the present invention;  
         [0021]      FIG. 6  depicts a high level flow chart that illustrates receiving a compressed digital data signal and transmitting a linear voice signal utilizing the improved receive data path of  FIG. 4  in accordance with the present invention;  
         [0022]      FIG. 7  depicts a network of computer systems that implements the present invention in accordance with the present invention; and  
         [0023]      FIG. 8  is a block diagram that illustrates a host computer system that includes the present invention in accordance with the present invention.  
     
    
     DETAILED DESCRIPTION  
       [0024]     The description of the preferred embodiment of the present invention has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art. The embodiment was chosen and described in order to best explain the principles of the invention to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated.  
         [0025]      FIG. 3  is a block diagram of an improved transmit data path included within a digital signal processor (DSP) in a Voice over Internet Protocol system in accordance with the present invention. A DSP device  300  includes a transmit data path  301 . DSP  300  is included within a VoIP system. Data path  301  includes a mandatory codec  302 , such as an encoder G.711, and an enhanced codec, such as enhanced encoder  304  that adheres to the G.729AB standard. Although the enhanced codec includes both an enhanced encoder and an enhanced decoder, only the enhanced encoder is described herein as the enhanced decoder&#39;s functions are not utilized in the transmit data path. Data path  301  also includes a silence description frame generator SID  306 , a switch  308 , and control logic  310 . Enhanced encoder  304  includes within it an internal DTX, an internal VAD, an internal DTX, and an internal CNG.  
         [0026]     According to the present invention, linear voice data is received within both mandatory encoder  302  and enhanced encoder  304 . Both mandatory encoder  302  and enhanced encoder  304  attempt to encode the received voice data. If the VAD that is internal to the enhanced encoder  304  detects voice in the input data, control logic  310  outputs a control signal  312  that causes switch  308  to close to select the path of the mandatory encoder  302 . The control logic is enhanced codec dependent and is used to determine if the voice data received is coded voice or silence. This is typically done by analyzing the output of the enhanced codec. If the VAD that is internal to the enhanced encoder  304  detects silence in the input signal, control logic  310  outputs a control signal  312  that causes switch  308  to close to select the path of the enhanced encoder  304 . The DTX that is internal to the enhanced encoder  304  then generates a silence description frame that conforms to the G.729AB standards. This frame is then output from enhanced encoder  304  and received within SID  306 . SID  306  performs the necessary conversion from the enhanced codec SID frame to the format required for the VoIP system. For example, a format often required in VoIP is described in IETF RFC 3389, “Real-time Transport Protocol (RTP) for Comfort Noise (CN)”. This silence frame is then transmitted as digital data out of the DSP  300 .  
         [0027]     Those skilled in the art will recognize that an additional transmit data path exists within DSP  300 . In this additional transmit data path, enhanced encoder  304  receives the linear digital voice input. Enhanced encoder  304  then generates a compressed data output. This compressed data output is then made available to be selected by switch  308 . This additional transmit data path is known in the art and is not depicted by  FIG. 3  or described below.  
         [0028]      FIG. 4  is a block diagram of an improved receive data path included within a digital signal processor (DSP) in a Voice over Internet Protocol system in accordance with the present invention. A DSP device  400  includes a receive data path  401 . DSP  400  is included within a VoIP system. Data path  401  includes a mandatory codec  402 , such as a decoder G.711, an enhanced encoder  406  and an enhanced decoder  404  that both adhere to the G.729AB standard, a silence description frame generator  408 , frame control logic  410 , an input switch  412 , and an output switch  414 . Enhanced encoder  404  includes an internal DTX and an internal VAD. Enhanced decoder  406  includes an internal PLC and an internal CNG.  
         [0029]     Those skilled in the art will recognize that a single enhanced codec, that includes both an enhanced encoder and enhanced decoder, may be utilized to provide the functionality described herein of the enhanced encoder  404  and the enhanced decoder  406 .  
         [0030]     According to the present invention, compressed data is received within frame control logic  410  and at input switch  412 . If frame control logic  410  detects that the input data signal includes a voice frame, frame control logic  410  outputs control signal  416  to cause switch  412  and switch  414  to both select the path that includes the mandatory decoder  402 . Mandatory decoder  402  then receives the compressed data, decodes the received compressed data, and outputs a linear digital voice signal. This linear digital voice signal is then used as the output of receive path  401 .  
         [0031]     In addition, the voice signal is then input into enhanced encoder  404  which encodes the linear digital voice signal to produce compressed data. The compressed data is then received in enhanced decoder  406 . Enhanced decoder  406  receives and decodes the compressed data. The output of enhanced decoder  406  is then discarded. This step of having the enhanced decoder  406  decode the compressed data causes the internal states of the enhance decoder to be updated properly. The internal state updates are needed for proper PLC functionality.  
         [0032]     If frame control logic  410  detects that the input data signal does not include a voice frame, frame control logic  410  outputs control signal  416  to cause switch  412  and switch  414  to both select the path that includes the enhanced decoder  406 . The input compressed data is received by SID  408  which converts the silence data frame that is compatible with the standard of the G.711 to a silence data frame that is compatible with the standard of the G.729AB. SID  408  then outputs a silence data frame that is compatible with the standard of the G.729AB. This silence frame signal is received within enhanced decoder  406  which uses its internal PLC to determine if any packet loss occurred. If any packet loss did occur, the PLC internal to enhanced decoder  406  then attempts to generate the missing voice signal. If no packet loss is detected, the CNG that is internal to enhanced decoder  406  then inserts comfort noise. The output of enhanced decoder  406  is then used as the output of receive path  401 .  
         [0033]     As depicted by  FIGS. 3 and 4 , separate PLC, VAD, DTX, and/or CNG modules are not included in DSP  300  or DSP  400 .  
         [0034]     Those skilled in the art will recognize that an additional receive data path exists within DSP  400 . This additional receive data path may be selected utilizing switch  412 . In this additional receive data path, the compressed data input signal is received within enhanced decoder  406 . Enhanced decoder  406  then generates a linear digital voice output signal. This linear voice output signal is then made available to be selected by switch  414 . This additional receive data path is known in the art and is not depicted by  FIG. 4  or described below.  
         [0035]      FIG. 5  depicts a high level flow chart that illustrates receiving a linear digital voice signal and transmitting compressed data utilizing the improved transmit data path of  FIG. 3  in accordance with the present invention. The process starts as depicted by block  500  and thereafter passes to block  502  which illustrates receiving a signal in both the mandatory encoder and in the enhanced encoder. Next, block  504  depicts the mandatory encoder encoding the signal. Block  506 , then, illustrates the Voice Activity Detector (VAD) that is included in the enhanced encoder analyzing the input signal to determine if voice is present in the signal.  
         [0036]     The process then passes to block  508  which depicts a determination of whether or not voice is detected in the signal. If a determination is made that voice is detected, the process passes to block  510  which illustrates the enhanced encoder transmitting a signal to the switch to select the output of the mandatory encoder as the signal output for the transmit data path. The process then passes back to block  502 .  
         [0037]     Referring again to block  508 , if a determination is made that voice is not detected in the signal, the process passes to block  512  which depicts the enhanced encoder sending a signal to the switch to select the output from the enhanced encoder path as the output of the transmit path.  
         [0038]     Next, block  514  illustrates the enhanced encoder&#39;s internal discontinuous transmission generator (DTX) generating a silence description frame (SID) or an untransmitted silence frame. The output frame will conform to the standards of the enhanced encoder. Thereafter, block  516  illustrates the enhanced encoder SID frame being converted by a SID generator to a standard SID frame that conforms to the mandatory codec standards. The process then passes back to block  502 .  
         [0039]      FIG. 6  depicts a high level flow chart that illustrates receiving a compressed data signal and transmitting a linear digital voice signal utilizing the improved receive data path of  FIG. 4  in accordance with the present invention. The process starts as depicted by block  600  and thereafter passes to block  602  which illustrates receiving a data frame in the frame control logic (FCL) and also at an input switch. Next, block  604  depicts a determination of whether or not the FCL detects the received data frame being a voice frame. If the FCL does detect the received frame as being a voice frame, the process passes to block  606  which illustrates the FCL signaling the input switch and the output switch to select the path of the mandatory decoder. Block  608 , then, depicts the mandatory decoder receiving the compressed data frame. Thereafter, block  610  illustrates the mandatory decoder decoding the compressed data to produce a digital voice signal.  
         [0040]     The process then passes to block  612  which depicts the decoded data frame being used as the voice output of the receive data path. Next, block  614  illustrates the digital voice signal output from the mandatory decoder being received within the enhanced encoder. Thereafter, block  616  depicts the enhanced encoder encoding the digital voice signal and outputting a compressed data signal, which is the encoded voice signal, to the enhanced encoder. Next, block  618  illustrates the enhanced decoder receiving and decoding the compressed data signal. By receiving and decoding this compressed data signal, the enhanced decoder&#39;s internal states are updated. The output of the enhanced decoder is then discarded. The process passes back to block  602 .  
         [0041]     Referring again to block  604 , if a determination is made that the FCL does not detect the received frame as being a voice frame, the process passes to block  620  which illustrates the FCL signaling the input switch and the output switch to select the path of the enhanced decoder. Next block  621  depicts a determination of whether or not the data is a SID frame. If a determination is made that it is a SID frame, then the process passes to block  622 . Next, block  622  depicts the SID converter converting the standard SID frame that is compatible with the mandatory encoder to an enhanced encoder SID frame that is compatible with the enhanced encoder. The process then passes to block  624  which illustrates the enhanced decoder receiving the enhanced encoder SID frame. Referring again to block  621 , if a determination is made that the data is not a SID frame, the process passes to block  626 .  
         [0042]     Block  626 , then, depicts a determination of whether or not the enhanced decoder detects packet loss in the enhanced encoder SID frame. If a determination is made that the enhanced decoder does not detect packet loss in the enhanced encoder SID frame, the process then passes to block  628  which illustrates the enhanced decoder&#39;s internal comfort noise generator (CNG) generating comfort noise. The process then passes to block  630 .  
         [0043]     Referring again to block  626 , if a determination is made that the enhanced decoder does detect packet loss in the enhanced encoder SID frame, the process passes to block  632  which illustrates the enhanced decoder&#39;s internal Packet Loss Concealment (PLC) device attempting to generate the missing data. The process then passes to block  630  which depicts the enhanced decoder&#39;s output being used as the output of the receive path. The process then passes back to block  602 .  
         [0044]      FIG. 7  depicts a network of computer systems that implement the present invention in accordance with the present invention. Network data processing system  700  is a network of computers in which the present invention may be implemented. Network data processing system  700  contains a network  702 , which is the medium used to provide communications links between various devices and computers connected together within network data processing system  700 . Network  702  may include connections, such as wire, wireless communication links, or fiber optic cables.  
         [0045]     In the depicted example, a server  704  is connected to network  702  along with storage unit  706 . In addition, clients  708 ,  710 , and  712  also are connected to network  702 . These clients  708 ,  710 , and  712  may be, for example, personal computers, network computers, or other computing devices. In the depicted example, server  704  provides data, such as boot files, operating system images, and applications to clients  708 - 712 . Clients  708 ,  710 , and  712  are clients to server  704 . Network data processing system  700  may include additional servers, clients, and other devices not shown. In the depicted example, network data processing system  700  is the Internet with network  702  representing a worldwide collection of networks and gateways that use the TCP/IP suite of protocols to communicate with one another. At the heart of the Internet is a backbone of high-speed data communication lines between major nodes or host computers, consisting of thousands of commercial, government, educational and other computer systems that route data and messages.  
         [0046]     Of course, network data processing system  700  also may be implemented as a number of different types of networks, such as for example, an intranet, a local area network (LAN), a wide area network (WAN), or a wireless network.  FIG. 7  is intended as an example, and not as an architectural limitation for the present invention.  
         [0047]     Any of these computer systems may be used for VoIP communications. For example, client  708  is used for VoIP communications. Therefore, client  708  may be coupled to a telephone  714  for receiving and outputting an analog voice signal. Client computer system  708  includes a digital signal processing unit  716 . DSP  300  and/or DSP  400  may be included within client  708  as part of digital signal processing unit  716 .  
         [0048]      FIG. 8  is a more detailed illustration of a computer system that may be used to implement any of the computer systems of  FIG. 7  in accordance with the present invention. Data processing system  800  may be a symmetric multiprocessor (SMP) system including a plurality of processors  802  and  804  connected to system bus  806 . Alternatively, a single processor system may be employed. Also connected to system bus  806  is memory controller/cache  808 , which provides an interface to local memory  809 . I/O bus bridge  810  is connected to system bus  806  and provides an interface to I/O bus  812 . Memory controller/cache  808  and I/O bus bridge  810  may be integrated as depicted.  
         [0049]     Peripheral component interconnect (PCI) bus bridge  814  connected to I/O bus  812  provides an interface to PCI local bus  816 . A number of modems may be connected to PCI bus  816 . Communications links to network computers  708 - 712  in  FIG. 7  may be provided through modem  818  and network adapter  820  connected to PCI local bus  816  through add-in boards.  
         [0050]     Network adapter  820  includes a physical layer  882  which conditions analog signals to go out to the network, such as for example an Ethernet network over an R45 connector. A media access controller (MAC)  880  is included within network adapter  820 . Media access controller (MAC)  880  is coupled to bus  816  and processes digital network signals. MAC  880  serves as an interface between bus  816  and physical layer  882 . MAC  880  performs a number of functions involved in the transmission and reception of data packets. For example, during the transmission of data, MAC  880  assembles the data to be transmitted into a packet with address and error detection fields. Conversely, during the reception of a packet, MAC  880  disassembles the packet and performs address checking and error detection. In addition, MAC  880  typically performs encoding/decoding of digital signals transmitted and performs preamble generation/removal as well as bit transmission/reception.  
         [0051]     Additional PCI bus bridges  822  and  824  provide interfaces for additional PCI buses  826  and  828 , from which additional modems or network adapters may be supported. In this manner, data processing system  800  allows connections to multiple network computers. A memory-mapped graphics adapter  830  and hard disk  832  may also be connected to I/O bus  812  as depicted, either directly or indirectly.  
         [0052]     It is important to note that while the present invention has been described in the context of a fully functioning data processing system. Those of ordinary skill in the art will appreciate that the processes of the present invention are capable of being distributed in the form of a computer readable medium of instructions and a variety of forms and that the present invention applies equally regardless of the particular type of signal bearing media actually used to carry out the distribution. Examples of computer readable media include recordable-type media, such as a floppy disk, a hard disk drive, a RAM, CD-ROMs, DVD-ROMs, and transmission-type media, such as digital and analog communications links, wired or wireless communications links using transmission forms, such as, for example, radio frequency and light wave transmissions. The computer readable media may take the form of coded formats that are decoded for actual use in a particular data processing system.  
         [0053]     The description of the present invention has been presented for purposes of illustration and description, and is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art. The embodiment was chosen and described in order to best explain the principles of the invention, the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated.