Re: [Pfspd-users@sf.net] PV rgb conversion

[Harold S. <har...@ph...>]

Hi Bram,

I was aware that the current code may overflow with 16 bit data,
and had already converted the code to 12 bit after the dot (but not 
committed yet).
I'll modify the precision to be a compile-time constant, and commit to 
cvs.

On a related note:
I intend to optimize the convert_line_3x3 functions with SSE2 
instructions,
but this is not compatible with the precompiled wxWindows library in 
/home/sofftv/
I guess wxWindows needs to be recompiled ?

Regards,
Harold
___________________________________
Ing. H.A.W. Schmeitz
Video Processing Systems, Philips Research Laboratories

High Tech Campus 36, 5656 AE Eindhoven, The Netherlands
Tel. +31 (0)40 27 46489
har...@ph...








Bram Riemens 
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28-09-2006 15:01

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Subject
[Pfs...@sf...] PV rgb conversion
Classification








Hi Harold, 

Recently, you changed / generalized the RGB conversion of PV module 
'format_convert'. 

Currently, only 8 bits input data is handled; however, we plan for the 
near future to handle up to 16 bit files wherein the 16 bits are retained 
in all calculations. 
Calculation is done in fixed point. 
Matrixes are specified in floating point. 
In the conversion from float to fixed point, 16 bits after the "dot" are 
used. 

This means for 16 bit data: 16 data + 16 after-dot = 32 bits 
Thus, 32 bits are really required, there is no headroom. 
Therefore, clipping will not work, as the to-be clipped data is wrapped 
around by the 32 bit C arithmetic. 

Proposal: change the calculations to 8 bits after-dot precision to prepare 
for 16 bits input data. 

Regards, Bram. 

--
A.K. (Bram) Riemens
Principal Scientist, Systems & Algorithms, NXP Corporate Research
Office: WDC 3.41, Postbox WDC-03    <--- New address
High Tech Campus 31 (WDC), 5656 AE Eindhoven, The Netherlands
Tel: +31 40 27 43833, Fax: +31 40 27 44639
E-mail: bra...@ph...
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