Description Advanced Multi-Band Excitation (AMBE) Complete Definition Advanced Multi-Band Excitation (AMBE) is a very powerful proprietary speech  coding standard developed by Digital Voice Systems, Inc.. AMBE operates at very low bitrates of between 2000 and 9600 bit/s. The audio  data is usually combined with up to 7 bit/s of forward error correction data to  produce a total RF bandwidth of approximately 2250 Hz (compared to 2700–3000 Hz  for an analog single sideband transmission). This has the effect of increasing  sound quality and removing static from HF communications. Lost frames can be  masked by using the parameters of the previous frame to fill in the gap. AMBE has a low complexity, lower than CELP format. Wikipedia AMBE Definition Also See IMBE ... View more

Description Improved Multi-Band Excitation (IMBE) Complete Definition Improved Multi-Band Excitation (IMBE) is a proprietary vocoder developed by  Digital Voice Systems, Inc. (DVSI). It is the predecessor of their Advanced  Multi-Band Excitation (AMBE). Wikipedia IMBE  Definition Also See AMBE ... View more

Description Vector Sum Excited Linear Prediction (VSELP) Complete Definition Vector Sum Excited Linear Prediction (VSELP) is a speech coding method used  in the IS-54 standard. This codec was used in early TDMA cell phones in the  United States. It was also used in the first version of RealAudio for audio over  the Internet. The IS-54 VSELP standard was published by the Telecommunications  Industry Association in 1989. IS-54 VSELP specifies an encoding of each 20 ms of speech into 159-bit  frames, thus achieving a raw data rate of 7.95 kbps . In an actual TDMA cell phone, the  vocoder output is packaged with error correction and signaling information,  resulting in an over-the-air data rate of 16.2 kbps . For internet audio, each 159-bit frame  is stored in 20 bytes, leaving 1 bit unused. The resulting file thus has a data  rate of exactly 8 kbps . A major drawback of VSELP is its limited ability to encode non-speech sounds,  so that it performs poorly when encoding speech in the presence of background  noise. For this reason, use of VSELP has been gradually phased out in favor of  newer codecs. VSELP is also the encoding method used in some early Motorola Type II  trunking systems. It was phased out in favor of the newer IMBE method. Wikipedia CELP  Definition Also See CELP RELP LPC ACELP RCELP LD-CELP ... View more

Description Low Delay Code Excited Linear Prediction (LD-CELP) Complete Definition Low Delay Code Excited Linear Prediction (LD-CELP), Delay of the codec is  only 5 samples (0.625 ms). The linear prediction is calculated backwards with a  50th order LPC filter. The excitation is generated with gain scaled VQ. The  standard was finished in 1992 in the form of algorithm exact floating point  code. LD-CELP is based on CELP Wikipedia LD-CELP  Definition (part of G.728) Also See CELP RELP LPC ACELP RCELP VSELP G.728 ... View more

Description Relaxed Code Excited Linear Prediction (RCELP) Complete Definition Relaxed Code Excited Linear Prediction (RCELP) is a method used in some  advanced speech codecs. The RCELP algorithm does not attempt to match the  original signal exactly. Instead, it matches a time-warped version of this  original signal that conforms to a simplified pitch contour. RCLEP is based on CELP. Wikipedia RCELP  Definition Also See CELP RELP LPC ACELP LD-CELP VSELP ... View more

Description Linear Predictive Coding (LPC) Complete Definition Linear Predictive Coding (LPC) is a tool used mostly in audio signal  processing and speech processing for representing the spectral envelope of a  digital signal of speech in compressed form, using the information of a linear  predictive model. It is one of the most powerful speech analysis techniques, and  one of the most useful methods for encoding good quality speech at a low bit  rate and provides extremely accurate estimates of speech parameters. Wikipedia LPC Definition Also See CELP RELP ACELP RCELP LD-CELP VSELP ... View more

Description Residual Excited Linear Prediction (RELP) Complete Definition Residual Excited Linear Prediction (RELP) is an obsolete speech coding  algorithm. It was originally proposed in the 1970s and can be seen as an  ancestor of Code Excited Linear Prediction (CELP). Unlike CELP however, RELP directly transmits the  residual signal. To achieve lower rates, that residual signal is usually  down-sampled (e.g. to 1-2 kHz). The algorithm is hardly used anymore. Wikipedia RELP  Definition Also See CELP LPC ACELP RCELP LD-CELP VSELP ... View more

Description G.723.1 is an audio codec for voice audio. Complete Definition G.723.1 is an audio codec for voice that compresses voice audio in 30 ms  frames. An algorithmic look-ahead of 7.5 ms duration means that total  algorithmic delay is 37.5 ms. ITU G.723.1 Status Wikipedia Definition  for G.723.1 Also See G.703/G.704 G.711 G.726 G.728 G.729 ... View more

  Definition X.509 Digital Certificates   Complete Definition X.509 is an ITU-T standard for a public key infrastructure (PKI) and Privilege Management Infrastructure (PMI). X.509 specifies, amongst other things, standard formats for public key Digital Certificates, certificate revocation lists, attribute certificates, and a certification path validation algorithm.   In the X.509 system, a CA issues a certificate binding a public key to a particular Distinguished Name in the X.500 tradition, or to an Alternative Name such as an e-mail address or a DNS-entry.   An organization's trusted root certificates can be distributed to all employees so that they can use the company PKI system. X.509 also includes standards for certificate revocation list (CRL) implementations, an often neglected aspect of PKIsystems. The IETF-approved way of checking a certificate's validity is the Online Certificate Status Protocol (WebVPN/SSL VPN does not work with Public Key Infrastructure (PKI) and Online Certificate Status Protocol (OCSP) on the Cisco Adaptive Security Appliance (ASA)/PIX 7.2(1) and above). Popular browsers like Internet Explorer and Firefox don't check for certificate revocation by default. The time lag for performing the checking could be one of the reasons.   X.509 Wikipedia Definition   RFCs: PKIX for Public Key Infrastructure (X.509) - RFC 3280   Also See: Encryption Decryption VPN DMVPN GETVPN TLS IPSec ... View more