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Discussion Groups | Speech Coding | Urgent Help Needed on CELP

Technical discussions related to Speech Coding (all itu and other vocoders, ACELP, CELP, AMR, etc)

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Quantization performance of LSFs in G.723.1 - koro - May 5 3:40:00 2004

Hi everyone: I am working on the quantization of LSFs in G.723.1. I found that sometimes G.723.1 introduces a quite large percentage of outliers in the range of 2-4dB, for example, over 10%. So G.723.1 does not satisfy the transparent quantization? Is this correct? Could anyone tell me where can I find the LSFs' quantization performance of G.723.1?

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Urgent Help Needed on CELP - B James - May 10 5:40:00 2004

Hi,
What is diff between CELP ACELP & RCELP?
What is meaning of zero excitation to synthesis filter in case of CELP,
will the output not be zero corresponding to zero excitation( since filter is a linear system)?

thanx in advance,
Mahesh

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Re: Urgent Help Needed on CELP - dai Guangfa - May 11 11:07:00 2004

CELP ACELP & RCELP is all based on LPC.

LPC means Linear Predictive Coding;

CELP means code exited Linear Predition ;

RELP means Residual Excited Linear Prediction;

ACELP means Algebraic Code Excited Linear Prediction,which is a simple version of CELP.

You can get the detailed imformation by using Google searching engine.B James <s...@yahoo.co.in> wrote:

Hi,
What is diff between CELP ACELP & RCELP?
What is meaning of zero excitation to synthesis filter in case of CELP,
will the output not be zero corresponding to zero excitation( since filter is a linear system)?

thanx in advance,
Mahesh

Yahoo! India Matrimony: Find your partner online.

_____________________________________

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RE: Urgent Help Needed on CELP - ied1970r - May 16 6:21:00 2004

(Sorry, this messsage can appear twice in this newsgroup because of Yahoo). CELP is the name for the family of the speech coders based on analysis-by-synthesis (examples - G723 5.3 Kbps and 6.3 Kbps, FS 1016, G729 etc). ACELP - is a coder from CELP-family with algebraic codebook (example - G723 5.3 Kbps). MELP - belongs to the family of parametric coders (STC, WI, MELP, FS 1015), and it is significantly different from CELP although it also uses LPC. About zero excitation. Filter is linear operator WITH HISTORY. The history is what makes the output of filtering zero excitation non-zero. Symbolically it can be presented as follows. Suppose A is the filter with the history, A0 is the same filter with zero history, x is the signal to be filtered and 0 is zero signal. Then you can easily check that the following relation holds: A*x = A*(x+0) = A*0+A0*x Both elements on the right side are generally non-zero! If you understand this formula you have got the key to understanding the analysis-by-synthesis method. Ilya Druker

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