Dear Firndz I have one querry regarding the LPC and LSF parameters Why we compute the LSF paramenter when we already had computed the LPC coefficeint. As far as I know all the relevent info is embeded in the LPC coefficent then why we compute the LSF parameters ? Only on thing I can annalyis is that Numbers of LPC coefficent can be represented by the less neumber of LSF parameters.. example 10 LPC coefficent can be represnted with 5 LSF coefficent, So we compute the LSF parameter to avoid the extra mathematical computation ?? One more thing I have seen in most of the case we go for the FIR filters, with cutt off frequency with 1khz .... how we get this magic number ?? why we cant go ahead with the IIR Filters ? what is the diffrence between the FIR filters and the IIR Filters ? Please help me as I am not a DSP GUY but definetly will like to be answered these queries. Thanks for in Advance. Regards don

# LPC and LSF

Started by ●May 24, 2005

Posted by ●May 25, 2005

Don wrote:> Dear Firndz > > I have one querry regarding the LPC and LSF parameters > Why we compute the LSF paramenter when we already had computed the LPC > coefficeint. As far as I know all the relevent info is embeded in the > LPC coefficent then why we compute the LSF parameters ?Is this a homework problem? The LSF parameters are usually easier to quantize and have better error characteristics. (If there's a bit error in the LSFs, it's easier to detect and if you don't it doesn't hurt quality as much. Sort of.)> > Only on thing I can annalyis is that Numbers of LPC coefficent can > be represented by the less neumber of LSF parameters.. > example 10 LPC coefficent can be represnted with 5 LSF coefficent, > > So we compute the LSF parameter to avoid the extra mathematical > computation ?? > > One more thing I have seen in most of the case we go for the FIR > filters, > with cutt off frequency with 1khz .... how we get this magic number ??Probably because most of the information that we want to extract are in this band. But I think the higher frequencies are still needed for intelligibility.> > why we cant go ahead with the IIR Filters ? >Probably could. You don't say what filter you're talking about here. Lots of hand-waving here, but I hope it helps a little. Plus, I don't remember all the details anymore. Ray

Posted by ●May 30, 2005

The LSF are parameters that are equivalent to the LPC. They form an alternative representation for the same information represented by the LPC. The same number of coefficients is used in both representations. But, LSF are more desirable for quantization and interpolation. FIR = Finite Impulse Response IIR = Infinite Impulse Response That's perhaps the most obvious difference between the two. Don wrote:> Dear Firndz > > I have one querry regarding the LPC and LSF parameters > > Why we compute the LSF paramenter when we already had computed the LPC > > coefficeint. As far as I know all the relevent info is embeded in the > LPC coefficent then why we compute the LSF parameters ? > > Only on thing I can annalyis is that Numbers of LPC coefficent can > be represented by the less neumber of LSF parameters.. > example 10 LPC coefficent can be represnted with 5 LSF coefficent, > > So we compute the LSF parameter to avoid the extra mathematical > computation ?? > > One more thing I have seen in most of the case we go for the FIR > filters, > with cutt off frequency with 1khz .... how we get this magic number ?? > > why we cant go ahead with the IIR Filters ? > > what is the diffrence between the FIR filters and the IIR Filters ? > > Please help me as I am not a DSP GUY but definetly will like to be > answered > these queries. > > Thanks for in Advance. > Regards > don >

Posted by ●July 14, 2006

Hi there I read "The LSF parameters are usually easier to quantize and have better error characteristics. (If there's a bit error in the LSFs, it's easier to detect and if you don't it doesn't hurt quality as much. Sort of.)" I want to know is it true " LSF coeffs are more roboust against the channel noise"? can you compare LPC , PARCOR and LSF coeffs and say which one is more roboust against the noise of channel? can you lead me to a paper to get answer for this question? thanks in advance Ramin