Re: [video] Re: question

["andrewxue" <andrewxue@vimicro.com>]

----- Original Message ----- 
From: "Richard Herveille" <richard@asics.ws>
To: <video@opencores.org>
Sent: Tuesday, October 22, 2002 6:13 PM
Subject: Re: [video] Re: question


> > 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!!!
> 

I am really confused,in the book of "Video Demystified(2nd edition)" chapter 3 Color spaces, YUV color space,seems similar with the term of YCrCb,it says "YCbCr is a scaled and offset version of the YUV color space.Y is defined to have a nominal 8-bit range of 16-235;Cb and Cr are defined to have a nomainal range of 16-240." Also the above equation is also from that chapter,only RGB has been gamma-corrected.Could you clarify for me ? Thanks,

> >
> > 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).

Really thanks for your help!

> 
> 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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