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To: Randall Hopper <rhh@ct.picker.com>
cc: multimedia@freebsd.org
Subject: Re: [video] fxtv feedback 
In-reply-to: Your message of "Sat, 13 Sep 1997 18:53:48 EDT."
             <19970913185348.15487@ct.picker.com> 
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Date: Sat, 13 Sep 1997 16:37:17 -0700
From: Amancio Hasty <hasty@rah.star-gate.com>
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yuv at least the yuv format that the mpeg encoder takes as a frame:

X*Y + 2( X/2 * Y/2)

So yes in yuv 4:2:2 every pixel gets two bytes : 
YU YV where U and V are chrominance values and Y is the gray component.

The RGB 16 format is very straight forward:

X*Y*2

------

example for 640x480:
yuv 422

460800 = 640*480 + 2 ( 320 * 240)
614400 = 640*480*2



The Bt848 databook has the format for various flavors of yuv so
just read up on the mpeg encoder which clearly states its
supported format for yuv.

If you are interested in yuv 422 like for the mpeg encoder, check out
this site which has a good explanation on yuv as well as other
video formats:

http://www.flash.net/~dawilson/fourcc/

----
Yes, I know about the problem with FPS and I am working on it.


	Cheers,
	Amancio
		
>From The Desk Of Randall Hopper :
> Amancio Hasty:
>  |Randall Hopper:
>  |> Amancio Hasty:
>  |>  |1. Try to use yuv for mpeg encoding it should speed up video capture an
d
>  |>  |   mpeg encoding also it should not be hard to implement given
>  |>  |   all the work that has gone into fxtv to support video capture.
>  |> 
>  |> Had this on the list from your previous request.  Don't have it very high
>  |> though since RGB does everything I need.  Wouldn't really save capture
>  |> bandwidth since, if you're running in 15- or 16-bit, RGB16 capture is bei
ng
>  |> used.  Probably would speed up image save and encoding though; don't have
 a
>  |> feel for how much since I've never tried it.  It's on the list.
>  |
>  |You save about 1/3 in bandwith and I have on my list of things
>  |to do to have the X server support yuv directly which will be
>  |nice for scaling to 1024x768.
> 
> Really?  Ok.  Guess I need to read up on YUV somewhere.  From scanning the
> driver source, I got the impression that the supported YUV fmts were 2
> bytes per pixel, inferring from that that it would occupy the same raw
> capture bandwidth as RGB16.  Guess I misinterpreted.
> 
> Say, on your list of things to do, (it may be there already, but if not),
> can you put FPS fix for the driver up above YUV X server extensions.  Then
> I can move fxtv up from my tweaked 4/97 rev to the latest version.  Just
> can't give up that video capture, even if it does only work for
> single-field. :-)
> 
>  |I like the contents of your desktop it gives me the feeling of 
>  |serious programming going on over there 8)
> 
> OH yeah.  ;)  
> 
> Later--
> 
> Randall