function output = adpcm_sgn(x,i)
%
% signum function adpcm_sgn(x,i)
% for adpcm algorithm
% returns +1 if x > 0
% returns -1 if x < 0
% returns +1 if x = 0 and i != 0
% [where x = p(k-i) or x = dq(k-i)]
% returns 0 if x = p(k) = 0 or dq(k) = 0
if (x > 0)
output = 1;
elseif (x < 0)
output = -1;
elseif (x == 0)
if (i ~= 0)
output = 1;
else
output = 0;
end
end