1. Technical Field
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.
2. Description of the Related Art
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.
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.
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.
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.
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.
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
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.
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.
The above as well as additional objectives, features, and advantages of the present invention will become apparent in the following detailed written description.
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:
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.
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.
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
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.
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.
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.
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.
As depicted by
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
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.
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.
Next, block 514 illustrates the enhanced encoder'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.
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's internal states are updated. The output of the enhanced decoder is then discarded. The process passes back to block 602.
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.
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's internal comfort noise generator (CNG) generating comfort noise. The process then passes to block 630.
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'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's output being used as the output of the receive path. The process then passes back to block 602.
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.
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.
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.
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
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.
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.
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.
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.
Number | Name | Date | Kind |
---|---|---|---|
5689615 | Benyassine et al. | Nov 1997 | A |
6240383 | Tanaka | May 2001 | B1 |
6374211 | Stegmann et al. | Apr 2002 | B2 |
20050055116 | Isaka et al. | Mar 2005 | A1 |
Number | Date | Country | |
---|---|---|---|
20060106598 A1 | May 2006 | US |