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Re: [Discuss-gnuradio] USRP for YPbPr ADC?

From: Dave Emery
Subject: Re: [Discuss-gnuradio] USRP for YPbPr ADC?
Date: Fri, 24 Dec 2004 17:27:34 -0500
User-agent: Mutt/1.4.1i

On Fri, Dec 24, 2004 at 01:57:48PM -0800, Steve Schear wrote:
> At 01:19 PM 12/24/2004, Seth David Schoen wrote:
> >Does anyone have any information that would tend to indicate how useful
> >the USRP would be for digitizing a YPbPr component video signal?
> I have an active and funded project going that is designed to digitize a 
> YPbPr component video signal at 80 MSPS and 8/10-bits.  One option provides 
> a lossless compressed output (between 4- 4.5-to-1) onto either USB 2.0 and 
> Firewire, which may be sufficient for at least 720p resolution.  No current 
> plans for GNURadio use.

        There is a professional interface standard in wide use for HDTV
component video called HDSDI.    There is an equivalent standard for
regular NTSC type video called SDI (601)  which is universally used in
professional digital broadcast plant these days.    Both Sample the luma
at twice the highest expected frequency (13.5 mhz for NTSC)  with 10 bit
samples and sample the two chroma components every other pixel (6.25
mhz)  for 4:2:2 video.

        Regular NTSC SDI is encoded into a 270 mbs ECL level serial
stream with some other added optional data (including audio and vertical
interval information stuffed into the blanking intervals).     This
interface is what most contemporary broadcast equipment uses to
interchange video (there is also a less used parallel version of the
same interface) with other gear such as switchers, MPEG encoders and
decoders, satellite receivers, special effects boxes, and disk and tape
based storage systems.

        HDSDI is basically the same thing as SDI in the same format, but
at HDTV rates and image formats - on a 1.5 gbs ECL stream.   There is a
version that uses two coaxes and 4:4:4 sampling as well.

        Relevant to the present discussion, encoders and decoders for
SDI to and from composite or component NTSC are a standard off the shelf
item in the professional broadcast market and are even available on
occasion on Ebay.  They are available as small 4 by 6 by 1 inch boxes
one can hang behind an item of analog gear that needs its output
converted to SDI... or visa versa.

        PCI interface boards capable of outputting and accepting SDI are
also a standard product as are boxes that will shovel SDI over Fireware.
These are universal components of computer based production editing

        HDSDI encoders and decoders are being introduced and becoming
available - there very well may be a version made by one of the video
equipment companies that will do precisely what Steve describes minus
the compression.  And there are PCI boards available for HDSDI for video
editing and production naturally... (these are currently pretty pricey).

        There are even boxes available that will take HDSDI and spit out
DVI-D format... a company called AJA and another called Miranda make
        Of course Steve's contraption ought to grown a HDSDI in,
firewire at 800 mbs out version - and visa versa - this would be QUITE a
useful product... as the 4.5 to 1 compression would allow firewire
hardware to handle HDSDI data...

   Dave Emery N1PRE,  address@hidden  DIE Consulting, Weston, Mass 02493

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