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Dear all, In GSM-EFR, the mean of the innovation energy is needed for the quantization of the fixed codebook gain. The standard mentions that this energy is 36 dB. Could somebody tell me how this value was computed ? Thanks in advance, Giusy |
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mean of the innovation energy in GSM-EFR
Started by ●March 30, 2000
Reply by ●March 30, 20002000-03-30
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Hello folks, We can start to examine the question by introducing a few symbols. So, let us denote the subframe length by N, and the ideal unquantized gain of the fixed-codebook excitation at subframe n by g(n). Using this notation, the innovation energy E(n) [dB] at subframe n becomes E(n) = 10*log10(e(n)), in which N-1 e(n) = (1/N) g(n)^2 sum c(i)^2. (1) i=0 Here {c(i)} is the excitation sequence generated by the fixed- codebook. Obviously its mean value is constant for ACELP-coders like GSM EFR. The mean of the innovation energy E(n) can now be estimated by encoding a long speech database and computing all quantities needed in (1) at every subframe. Please see [1] for a more thorough explanation. Hope this helps. Vesa Ruoppila University of Sherbrooke Department of Electrical Engineering Sherbrooke, QC, J1K 2R1, Canada [1] R. Salami, C. Laflamme, J-P. Adoul, D. Massaloux, "A toll- quality 8 kb/s speech codec for personal communications system (PCS)," IEEE Trans on Vehicular Technology, Vol.43, No.3, pp. 808-815, August 1994. ---------- From: [mailto:] Sent: Thursday, March 30, 2000 07:19 To: Subject: [speechcoding] mean of the innovation energy in GSM-EFR Dear all, In GSM-EFR, the mean of the innovation energy is needed for the quantization of the fixed codebook gain. The standard mentions that this energy is 36 dB. Could somebody tell me how this value was computed ? Thanks in advance, Giusy |
