pencode.m

FS1016源代码

% MATLAB SIMULATION OF NSA FS-1016 CELP v3.2
% COPYRIGHT (C) 1995-99 ANDREAS SPANIAS AND TED PAINTER
%
% This Copyright applies only to this particular MATLAB implementation
% of the FS-1016 CELP coder.  The MATLAB software is intended only for educational
% purposes.  No other use is intended or authorized.  This is not a public
% domain program and distribution to individuals or networks is strictly
% prohibited.  Be aware that use of the standard in any form is goverened
% by rules of the US DoD.  Therefore patents and royalties may apply to
% authors, companies, or committees associated with this standard, FS-1016.  For
% questions regarding the MATLAB implementation please contact Andreas
% Spanias at  [phone].  For questions on rules,
% royalties, or patents associated with the standard, please contact the DoD.
%
% ALL DERIVATIVE WORKS MUST INCLUDE THIS COPYRIGHT NOTICE.
%
% ******************************************************************
% PENCODE
%
% PORTED TO MATLAB FROM CELP 3.2a C RELEASE
% 7-7-94
%
% ******************************************************************
%
% DESCRIPTION
%
% Encode and quantize pitch gain for various quantizer types
%
% DESIGN NOTES
%
% This funtion uses output level data obtained by Max's minimum
% distortion quantization priciples and quantizes to the nearest
% level (L1 norm).  (Using level data only was found superior to
% using both of Max's level and boundry data.)
%
% VARIABLES
%
% INPUTS
%   input      -     Pitch gain input (unquantized or true value)
%
% OUTPUTS
%   index      -     Quantized pitch gain index
%   qpgain     -     Quantized pitch gain value
%
% GLOBALS
%   pitch2max5 -     Quantization table
%
% REFERENCES
%
% 1. Quantizing for Minimum Distorion
%    J. Max, IRE Trans. Inform. Theory, vol. IT-6, pp.7-12, Mar. 1960
%
% 2. Data used in the quantizer table generation is from file 3m3f.spd,
%    a standard speech data file distributed by NSA with CELP 3.2a.
%
% ******************************************************************
%
% NOTE WELL
%
% While the author(s) of the original pitchencode() function (C language)
% indicate the source of the data used to generate this Lloyd-Max quantizer,
% they fail to indicate what set of assumptions were applied to the data
% set. What type of pdf has been assumed? Gaussian, Laplacian, Rayleigh, etc.
% As shown in [1] above, pdf assumptions are built in to the quantizer/
% quantization levels.  More information would be helpful.
%
% The quantizer table used below has been blindly copied from the C
% implementation without knowledge of the governing assumptions.
%
% See init.m for the table pitch2max5.
%
% ******************************************************************

function [ index, qpgain ] = pencode( input )

% DECLARE GLOBALS
global pitch2max5

% QUANTIZE INPUT TO NEAREST VALUE IN PITCH2MAX5 TABLE
[ qpgain, index ] = min( abs( input - pitch2max5 ) );

% RETURN QUANTIZED VALUE TO CALLER
qpgain = pitch2max5( index );

% CORRECT INDICIES TO MATCH C LANGUAGE RESULTS FOR EASE OF TEST/VERIFICATION
index = index - 1;