Hi,
Please keep the ML in the CC and do not do full quotes.
Thanks
On Wed, 24 Jan 2007 16:42:06 +0100
"Nicolas Boulay" <[EMAIL PROTECTED]> wrote:
> 2007/1/24, Attila Kinali <[EMAIL PROTECTED]>:
> > For further reference in the field of video (de)coding, please
> > have a look at the thread i started a few months ago, about
> > subsampling/upsampling (sorry, i'm too lazy to look up the subject atm).
>
> It was "RGB/YUV converstion... importance?" But nothing is said about
> coeffiscient to use.
Yes, especially the mail [EMAIL PROTECTED]
Date: Tue, 12 Sep 2006 22:04:36 +0200
From: Attila Kinali <[EMAIL PROTECTED]>
And those following this mail.
> > As Timothy already said, for OGP it is of no matter whether the
> > the colour values are in YUV or RGB. There will be a conversion
> > to RGB at some point which can be easily pipelined and thus does
> > not impose any speed los. The real problem with YUV comes from the
> > subsampling impossed. Ie for the up sampling we need to perform
> > some form of interpolation and filtering on the image in either only
> > vertical direction (4:2:2 -> 4:4:4) or both horizontal and vertical
> > (4:2:0 -> 4:4:4). And also the UV samples may be half a pixel off
> > from the Y samples, depending on the used video codec.
> >
>
> Does it means that the value in the convertion matrix is not fixed ?
> In that case, the problem is gone.
I didn't say anything about this. I just said that the YUV->RGB
conversion is easy compared to up sampling.
Whether we use fixed or variable coefficients is not decided yet.
Fixed coeficients are faster and allow for a smaller unit while
variable coeficients allow flexibility. And IMHO, the decision
whether we use fixed or variable is not so important and should
be done somewhen late in the project when we know how much
space we have left.
> An other point : if you mix yuv image and rgb image and do some
> filtering, must you convert the different images in the same format
> (rgb or yuv... or hsl or what ever color system with good color
> linearity)?
Yes, it'll be most likely in RGBA.
Attila Kinali
--
Praised are the Fountains of Shelieth, the silver harp of the waters,
But blest in my name forever this stream that stanched my thirst!
-- Deed of Morred
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