[mythtv-users] PCI-E ATSC (US) Card Recommendation
devin.heitmueller at gmail.com
Tue Dec 1 18:32:11 UTC 2009
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:
Devin J. Heitmueller
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