view matlab/bmm/carfac/CARFAC_CAR_Step.m @ 648:1c2a5868f23a

Fix memory leak in CARFAC.

Also get rid of most uses of auto, which tend to hurt readability
unless the type name is particularly long, especially when it masks
pointers.

% Copyright 2012, Google, Inc.
% Author: Richard F. Lyon
%
% This Matlab file is part of an implementation of Lyon's cochlear model:
% "Cascade of Asymmetric Resonators with Fast-Acting Compression"
% to supplement Lyon's upcoming book "Human and Machine Hearing"
%
% Licensed under the Apache License, Version 2.0 (the "License");
% you may not use this file except in compliance with the License.
% You may obtain a copy of the License at
%
%     http://www.apache.org/licenses/LICENSE-2.0
%
% Unless required by applicable law or agreed to in writing, software
% distributed under the License is distributed on an "AS IS" BASIS,
% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
% See the License for the specific language governing permissions and
% limitations under the License.

function [car_out, state] = CARFAC_CAR_Step(x_in, CAR_coeffs, state)
% function [zY, state] = CARFAC_CAR_Step(x_in, CAR_coeffs, state)
%
% One sample-time update step for the filter part of the CARFAC.

% Most of the update is parallel; finally we ripple inputs at the end.


% do the DOHC stuff:

g = state.g_memory + state.dg_memory;  % interp g
zB = state.zB_memory + state.dzB_memory; % AGC interpolation state
% update the nonlinear function of "velocity", and zA (delay of z2):
zA = state.zA_memory;
v = state.z2_memory - zA;
% nlf = CARFAC_OHC_NLF(v .* widen, CAR_coeffs);  % widen v with feedback
nlf = CARFAC_OHC_NLF(v, CAR_coeffs);
% zB * nfl is "undamping" delta r:
r = CAR_coeffs.r1_coeffs + zB .* nlf; 
zA = state.z2_memory;


% now reduce state by r and rotate with the fixed cos/sin coeffs:
z1 = r .* (CAR_coeffs.a0_coeffs .* state.z1_memory - ...
  CAR_coeffs.c0_coeffs .* state.z2_memory);
% z1 = z1 + inputs;
z2 = r .* (CAR_coeffs.c0_coeffs .* state.z1_memory + ...
  CAR_coeffs.a0_coeffs .* state.z2_memory);

zY = CAR_coeffs.h_coeffs .* z2;  % partial output

% Ripple input-output path, instead of parallel, to avoid delay...
% this is the only part that doesn't get computed "in parallel":
in_out = x_in;
for ch = 1:length(zY)
  % could do this here, or later in parallel:
  z1(ch) = z1(ch) + in_out;
  % ripple, saving final channel outputs in zY
  in_out = g(ch) * (in_out + zY(ch));
  zY(ch) = in_out;
end

% put new state back in place of old
% (z1 is a genuine temp; the others can update by reference in C)
state.z1_memory = z1;
state.z2_memory = z2;
state.zA_memory = zA;
state.zB_memory = zB;
state.zY_memory = zY;
state.g_memory = g;

car_out = zY;