[M4IF Technotes] What is the type of dc_scaler for intraDC?

Herbert Thoma tma iis.fhg.de
Wed Apr 16 12:11:26 EDT 2003


Á¶ÁøÇö schrieb:
> 
> Hi!
> 
> In intraDC quantization, dc_scaler is derived to minimize the visibility of artifacts.
> Using piecewise liniar function, dc_scaler has several break-point. (Qp:1~4,5~8,9~24,25~31)
> In luminance case, dc_scaler type is integer in all Qp range. (Refer to attatched file.)
> On the other hand, in chrominance case, dc_scaler has floating point number.(x.0 or x.5 in range Qp 5~24)
> If dc_scaler type is integer, under point will be truncated. In this case, Qp 5 and 6 has same value(9).
> other 7 and 8, 9 and 10,... are same! That is, more break-points are added to chrominance linear equation
> between Qp 5 and Qp 24!
> because IntraDC value is commonly large number, this truncation error will become serious!
> So, I think, dc_scaler type must be float-type. Do you agree?

Well, in the reference software dc_scaler is an integer.
So we have to live with the break-points.
Regards,
 Herbert.
> Regards,
> Jin.H Cho
> 
> 
> 
> 
> 
> 
>   ------------------------------------------------------------------------------------------------------------------------------------------------
>                                      Name: intra_DC_dc_scaler_diagram.xls
>    intra_DC_dc_scaler_diagram.xls    Type: Microsoft Excel Worksheet (application/vnd.ms-excel)
>                                  Encoding: base64

-- 
Herbert Thoma
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Phone: +49-9131-776-323
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