Queries on Quantization input

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Derick Wong
Derick Wong 2013-12-31
编辑： Derick Wong 2014-1-1
Does anyone understand the input of this code ? does the vect represent a matrix and how do i determine the input for bits?
function [levelNumbers,scaling] = quantization(vect,bits)
%...'levelNumbers' contains the index of the quantization value
%...'scaling' contains 2 values, the lowest quant. value and delta
[M,N] = size(vect);
if (M>1)
vect = vect';
end
range = max(vect)-min(vect);
delta = roundVal(range/2^(bits));
levels = 2^bits;
base = roundVal(min(vect));
%quantValues = [base : delta : roundVal(max(vect)-delta)]' + delta/2;
quantValues = [base : delta : roundVal(max(vect)-delta)]';
inputArray = repmat(vect , length(quantValues), 1 );
quantArray = repmat(quantValues, 1 , length(vect));
quantDiff = abs(inputArray-quantArray);
[Y,I] = min(quantDiff);
quantResults=quantArray(I);
for i=1:length(quantResults)
levelNumbers(i) = find(quantResults(i)==quantValues);
end
scaling = [base, delta];
if length(quantResults)==0
levelNumbers=ones(1,length(vect));
end
function newVal = roundVal(num)
num = num*1e4;
num = round(num);
newVal = num*1e-4;

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回答（1 个）

Walter Roberson
Walter Roberson 2013-12-31
The vect must be a vector, but it can be row order or column order.
The number of bits would be as appropriate for your purposes. 1 bit if you want 2 quantization levels, 2 bits if you want 4 levels, 3 bits if you want 8 levels, and so on.
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Walter Roberson
Walter Roberson 2013-12-31
You can reshape() your matrix into a vector before passing it in.
The number of levels you need is not directly related to the matrix; it is based upon your purpose in quantizing. Which you have not happened to mention
Derick Wong
Derick Wong 2014-1-1
编辑：Derick Wong 2014-1-1
My purpose is to do compression. I had to do a compression by going through DCT(discrete cosine transformation) follow by quantization. I have a matrix of
[x1 x2 x3 x4 ... xm
y1 y2 y3 y4 ... ym
z1 z2 z3 z4 ... zm]
In fact there are n rows as well. Initially I used round() as a form of quantization , but now I need to do a inverse quantization which needed me to use this quantization code and another inverse quantization code.

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