[mythtv-users] PCI-E ATSC (US) Card Recommendation

Brian Wood beww at beww.org
Tue Dec 1 18:46:33 UTC 2009


On Tuesday 01 December 2009 11:32:11 am Devin Heitmueller wrote:
> On Tue, Dec 1, 2009 at 12:19 PM, Patrick Doyle <wpdster at gmail.com> 
wrote:
> > I was confused the first time I looked at some data sheets for
> > composite video encoders and decoders.  For whatever reason (and I'm
> > sure there are good hysterical reasons for this), a video "decoder"
> > chip is one that locks onto the composite signal and extracts the Y,
> > Cr, and Cb signals (and, for the ones I looked at for a job I was
> > doing a few years ago) typically outputs a digitized stream to
> > something like a DSP or an ASIC.  The video "encoder" chip would
> > output an NTSC (or PAL) signal from the digital stream.
> 
> To be fair, a video decoder in most cases takes a composite or S-video
> signal as input, and outputs a digital form (typically in ITU-656
> format).  It's an analog demodulator that is responsible for
> converting the IF from the tuner to CVBS or Y/CR/Cb.  In some cases,
> both are done on the same chip.
> 
> I wrote an intro on the topic last month that can be found here, in
> case anyone is interested:
> 
> http://www.kernellabs.com/blog/?p=1045

Nice job and thanks for the link.

To me an "encoder" is something found in a camera or video tape machine 
that converts a component signal to a composite NTSC output, but I'm from 
the "old school" of the analog days.


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