I have written a LPC10 encoder which produces the reflection cofficients,gain, pitch parameters etc using a 6711. These values are in floating point notation. What I want to know is how are these values are converted to a integer representation, for transmission, considering that for LPC10,these parameters are represented as anything from 3 to 7 bits depending on the parameter (eg. gain is 7 bits, refection coefficients 3 to 4 bits). Is it a simple scaling of the integer range for each parameter? Maurizio Gencarelli Electronics Engineer Royal Australian Air Force 

SCALING OF LPC COEFFICIENTS
Started by ●September 30, 2002
Reply by ●September 30, 200220020930
Maurizio > I have written a LPC10 encoder which produces the reflection > cofficients,gain, pitch parameters etc using a 6711. These values are > in floating point notation. What I want to know is how are these > values are converted to a integer representation, for transmission, > considering that for LPC10,these parameters are represented as > anything from 3 to 7 bits depending on the parameter (eg. gain is 7 > bits, refection coefficients 3 to 4 bits). Is it a simple scaling of > the integer range for each parameter? For LPC10 I'm not sure, but for newer coders it's normally a combination of linear or log quantization followed by additional coding, such as vectorquantization. For example, log10 of pitch might be quantized to 0127 (7 bits), or LP coefficients might be quantized to 32768 to 32767 (Q15) then combined into a vector to access codebook indexes. Reflection coefficients are 34 bits linearquantized in LPC10? Yikes, no wonder it sounds so bad. Jeff Brower DSP sw/hw engineer Signalogic 