# How to show quantisation error for frequency coefficient

I have the following question from an exam which reads:

For the second question my answer is:

24 5 2 3
9 2 1 3
2 3 2 2
1 1 1 0


I am unsure of what formula to apply to each value to get the quantisation error. Can anybody tell me??

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When the data is reconstructed from the quantized coefficients, the resulting coefficients will be

240 100  60 120
180  60  40 210
60 120 140 200
40  70 100   0


Thus the (signed) quantization errors are

 -3   2  -3  -3
-7  -5   8  32
-8  -1   9   2
-14 -23  38 -81

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Ah brilliant, thank you! – Tom celic May 7 '13 at 21:19