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Hi Great to have a good follow-up on an interesting topic. It would be great if more who have good exposure to this topic, join in. >All the reasonings given for 10th order LPC is plausible. But i >encountered >50th order filter >in G.728(LD-CELP). what could be the probable reason for having such a >high >order >(computationally intensive) LPC in this codec. > >Note: The codec is a backward adaptive and uses 20 sample frame(2.5msec). The choice of the order of the filter basically depends on the sampling frequency (to bo more precise, half sampling frequency). Its usually taken as follows: A complex pole for every KHZ in half the sampling frequency and 2-4 extra poles. So for CD quality sounds, with 22.1 KHZ we need about 23 cplx poles (46 order) + 4 extra poles = about 50. Any comments? -Hari |
Re: All pole LPC filter again
Started by ●May 6, 2002
Reply by ●May 7, 20022002-05-07
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Here is a document that explains the derivation of no. of segments.... or the no. of LPC coeffs..... -----Original Message----- From: Harikrishna Natarajan [mailto:] Sent: Monday, May 06, 2002 9:07 PM To: Subject: Re: [speechcoding] All pole LPC filter again Hi Great to have a good follow-up on an interesting topic. It would be great if more who have good exposure to this topic, join in. >All the reasonings given for 10th order LPC is plausible. But i >encountered >50th order filter >in G.728(LD-CELP). what could be the probable reason for having such a >high >order >(computationally intensive) LPC in this codec. > >Note: The codec is a backward adaptive and uses 20 sample frame(2.5msec). The choice of the order of the filter basically depends on the sampling frequency (to bo more precise, half sampling frequency). Its usually taken as follows: A complex pole for every KHZ in half the sampling frequency and 2-4 extra poles. So for CD quality sounds, with 22.1 KHZ we need about 23 cplx poles (46 order) + 4 extra poles = about 50. Any comments? -Hari _____________________________________ Note: If you do a simple "reply" with your email client, only the author of this message will receive your answer. You need to do a "reply all" if you want your answer to be distributed to the entire group. _____________________________________ About this discussion group: To Join: To Post: To Leave: Archives: http://www.yahoogroups.com/group/speechcoding Other DSP-Related Groups: http://www.dsprelated.com ">http://docs.yahoo.com/info/terms/ | |||
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Reply by ●May 7, 20022002-05-07
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Hi, I agree with what you said partially. Because, in G.729 Annex E, where the sampling frequency is 8 KHz, the LPC order is 30. Whys so? Harshad. > A complex pole for every KHZ in half the sampling frequency and 2-4 > extra > poles. So for CD quality sounds, with 22.1 KHZ we need about 23 cplx > poles > (46 order) + 4 extra poles = about 50. |
