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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 vector-quantization. For example, log10 of pitch might be quantized to 0-127 (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 3-4 bits linear-quantized in LPC10? Yikes, no wonder it sounds so bad. Jeff Brower DSP sw/hw engineer Signalogic |