[mythtv-users] PCI-E ATSC (US) Card Recommendation
wpdster at gmail.com
Tue Dec 1 17:19:03 UTC 2009
On Tue, Dec 1, 2009 at 12:11 PM, Brian Wood <beww at beww.org> wrote:
> On Tuesday 01 December 2009 09:52:42 am Devin Heitmueller wrote:
>> Hi Brian,
>> On Tue, Dec 1, 2009 at 11:47 AM, Brian Wood <beww at beww.org> wrote:
>> > I assume you mean "hardware NTSC decoders", unless the unit has
>> > outputs ???
>> I think you just have the terminology backwards. An MPEG encoder
>> converts a raw NTSC signal to MPEG format. An MPEG decoder converts
>> an MPEG file to raw video. James is correct in that the 2250 has dual
>> MPEG encoders.
>> > Do you mean it can receive NTSC analog broadcasts (assuming proper
>> > drivers)?
>> The hardware supports it, but the Linux driver does not.
> OK, makes sense. I thought that your reference to "NTSC encoders" might
> mean that it could receive ATSC signals then output them as analog for use
> by older NTSC TV sets or capture by a PVR-150. If that were the case it
> would have been the first such unit I had heard of. Alas, that's not the case.
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.
It's completely backwards from what I typically think of when I hear
MPEG-2 encoder and MPEG-2 decoder, but that appears to be the
terminology in use.
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