Re: [video] Re: question

[Richard Herveille <richard@asics.ws>]

> Hi Richard,
>
> Really thanks for your reply,
>
> For RGB converted into YUV,I see following equation,
>     Y = 0.2999R + 0.587G + 0.114B
>     U = 0.492(B-Y)
>     V = 0.877(R-Y)
> I am not sure you implement the design by this formula or anything else ?

YUV is the term used for analog signals, YCrCb is the term for the digital 
color space. They are not the same!!!

>
> For Y/C generation,I think it need first create YCbCr format color
> space,

YCrCb to YUV:
Y=0.591(Y-64)
U=0.504(Cb-512)
V=0.711(Cr-512)

RGB to YUV
Y=0.151R + 0.297G + 0.058B
U=-0.074R - 0.147G + 0.221B
V=0.312R - 0.261G - 0.051B

>and also there is some formula as the above one could create YCbCr
> signals,

Just use the block available from the video_systems directory. It's in the 
common subdirectory.

>but how YCrCb convert into composite signal is still unclear for
> me,could you tell me how/where I can get the reference/document for this
> algorithm,

The colors are qam modulated, so you need to generate this modulation scheme. 
You need a sine/cosine translation to do this, I would suggest using the 
cordic algorithm (also available from OpenCores) to do this.
Besides the colors you need to generate sync and blanking signals.

I would suggest buying a good book (e.g. Video Demystified), or outsourcing 
this project (I can help you with this).

Richard



>
> Best Regards,
> Andrew
>
> ----- Original Message -----
> From: "Richard Herveille" <richard@asics.ws>
> To: <video@opencores.org>
> Sent: Monday, October 21, 2002 3:12 PM
> Subject: Re: [video] Re: question
>
> > In fact, I do.
> > Your problem isn't easy to explain; you need to do a number of things.
> > From top to bottom (e.g composite video relies on Y/C):
> >
> > - Create composite video signal (i.e. TV signal)
> > - Create Y/C signals
> > - Create YUV (or YCrCb for digital signals)
> >
> > Converting the UV (or CrCb) signals into the Chroma ("C") signal is the
> > not easy part. You need to use sine/cosine translations (probably using a
> > cordic algorithm, available from opencores) to translate them.
> >
> > Please be more specific about your problem and I can give some more
> > detailed information.
> >
> > Richard
> >
> > > Hi Richard,
> > >
> > > So this mail list is for image IP developer discussion ? I want to ask
> > > a question,is there anyone have experience in TV interface design like
> > > TV encoder,my question is how the digital image signal(RGB pixel) be
> > > modulated into composite/component signal,
> > >
> > > Best Regards,
> > > Andrew
> > >
> > > ----- Original Message -----
> > > From: "Richard Herveille" <richard@asics.ws>
> > > To: "andrewxue" <andrewxue@vimicro.com>; <video@opencores.org>
> > > Sent: Thursday, October 17, 2002 6:01 PM
> > > Subject: Re: question
> > >
> > >
> > >
> > > Hi Andrew,
> > >
> > > This mailing list is dedicated to video systems in general, and digital
> > > video systems/image processing in particular. Anything you want to
> > > discuss can be discussed.
> > >
> > > Currently this list is kinda quite, mostly because there's not a lot of
> > > activity in developing imaging cores. But it is supposed to change.
> > >
> > > Richard
> > >
> > > > Dear,
> > > >
> > > > I am a newcomer for this mail list.I am really interested in video &
> > > > image processor design and also want to learn from expert guys and
> > > > also share my experience with others.But as fresh guy,I am not sure
> > > > the vidoe aspect you are discussing and  interested in.So could you
> > > > update me some reference or hot topic of this mail list,
> > > > Best Regards,
> > > > Andrew
> >
> > --
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