TY - GEN
T1 - Towards iLBC speech coding at lower rates through a new formulation of the start state search
AU - Garrido, Christopher M.
AU - Murthi, Manohar N.
AU - Andersen, Søren Vang
PY - 2005/1/1
Y1 - 2005/1/1
N2 - The Internet Low Bit-rate Coder (iLBC) has emerged as a candidate for Voice over Internet Protocol (VoIP) applications. By avoiding the inter-frame coding dependencies endemic to many speech coders such as those based on Code Excited Linear Prediction, iLBC is able to achieve superior robustness to packet loss. In addition to robustness to packet loss, a VoIP codec should possess the agility to adjust its source coding rate in order to react to network congestion and to be amenable to joint source channel coding for wireless channels. Towards this end, we develop a new formulation of the iLBC encoding process that allows for a variable rate iLBC. In particular, we demonstrate how the LP excitation signal is constructed from a much shorter vector of 'start state' samples through a non-square synthesis matrix that captures the effects of the Adaptive Codebook operations. With this new framework, the search and quantization of the start state is re-formulated as an Analysis by Synthesis matching problem. We demonstrate how a Multi-Pulse (MP) approach can be utilized to effect a variable rate coding solution for this new framework. A variable rate coder with the MP start state achieves better performance than the Adaptive Multi-Rate (AMR) coder at 12.2 and 10.2 kbps for packet loss rates greater than 4 %.
AB - The Internet Low Bit-rate Coder (iLBC) has emerged as a candidate for Voice over Internet Protocol (VoIP) applications. By avoiding the inter-frame coding dependencies endemic to many speech coders such as those based on Code Excited Linear Prediction, iLBC is able to achieve superior robustness to packet loss. In addition to robustness to packet loss, a VoIP codec should possess the agility to adjust its source coding rate in order to react to network congestion and to be amenable to joint source channel coding for wireless channels. Towards this end, we develop a new formulation of the iLBC encoding process that allows for a variable rate iLBC. In particular, we demonstrate how the LP excitation signal is constructed from a much shorter vector of 'start state' samples through a non-square synthesis matrix that captures the effects of the Adaptive Codebook operations. With this new framework, the search and quantization of the start state is re-formulated as an Analysis by Synthesis matching problem. We demonstrate how a Multi-Pulse (MP) approach can be utilized to effect a variable rate coding solution for this new framework. A variable rate coder with the MP start state achieves better performance than the Adaptive Multi-Rate (AMR) coder at 12.2 and 10.2 kbps for packet loss rates greater than 4 %.
UR - http://www.scopus.com/inward/record.url?scp=33646764229&partnerID=8YFLogxK
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U2 - 10.1109/ICASSP.2005.1415227
DO - 10.1109/ICASSP.2005.1415227
M3 - Conference contribution
AN - SCOPUS:33646764229
SN - 0780388747
SN - 9780780388741
T3 - ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings
SP - I769-I772
BT - 2005 IEEE International Conference on Acoustics, Speech, and Signal Processing, ICASSP '05 - Proceedings - Image and Multidimensional Signal Processing Multimedia Signal Processing
PB - Institute of Electrical and Electronics Engineers Inc.
T2 - 2005 IEEE International Conference on Acoustics, Speech, and Signal Processing, ICASSP '05
Y2 - 18 March 2005 through 23 March 2005
ER -