🚀 go-pugleaf

In article <1992Nov6.151148.7943@news2.cis.umn.edu> bedros@loon.cs.umn.edu (Saad Bedros 625 7542) writes:
>
>working in quantization for the DCT coefficients, I know I can apply
>MAX quantizer for the ac coefficients with a laplacian source,
>But for the DC term, a uniform quantization is best.
>What is the best approach for quantizing the DC term:
> 1- calculate the min and max, then quantizing using 8 bits after
>     normalization. in this case, the min and max should be transmitted.
> 2- find a global max for the DC, normalize then quantize. I know in JPEG
>    they use 16 as a quantization level.

From a hardware implementation point of view, finding a global max may
need quite an amount of memories to accomodate all transformed blocks.
This is the drawback I see in the second method.

>
>What is the advantage to set the range between -128,128 instead 0,255
>before taking the DCT ? ( I think that is what they do in JPEG)
>

The advantage is to simplify H/W implementation.
Hardware implementation usually uses 2's complement representation of 
numbers. That is the cause.

>By the way, I was looking for a DCT in matlab, and I got one, not fast
>but not slow if somebody is intersted.
>
>Saad Bedros
>U of Minnesota