<br><br><div><span class="gmail_quote">On 9/26/05, <b class="gmail_sendername"><a href="mailto:kteague@speakeasy.net">kteague@speakeasy.net</a></b> <<a href="mailto:kteague@speakeasy.net">kteague@speakeasy.net</a>> wrote:
</span><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><br><br>Another gentleman by the name of Brian Steele responded to my post, also. He noted:
<br><snip><br>You
are correct, they are hardware tuners and they don't perform any
hardware encoding. The reason they don't need to do this is
that ATSC video is already encoded and compressed into MPEG2 before it
is broadcast. The video recorded by the HD-3000 and Air2PC
cards is just streamed over the bus directly to the hard disk with very
little CPU involvement. I have two HD-3000 cards and can
record with both at the same time while using less than 5% of a 3Ghz
Pentium4 CPU. Playback on the other hand, requires quite a
bit of CPU time. I average about 85-90% CPU usage when
playing back 1080i HDTV.<br><snip><br><br>That said, why would
anyone need a hardware encoder if the stream is passed through the PCI
bus and dumped directly to the hard disk as an MPEG2 formatted
file? And where does ATSC come in to play? I
thought the signals we receive in the US are NTSC. Please
forgive my ignorance.</blockquote><div><br>
<br>
Analog signals in the US are broadcast in NTSC format. Digital
signals (SDTV and HDTV) are broadcast in ATSC format. In my area,
the major broadcast networks are broadcasting in both formats
simultaneously using two different channels. ATSC is already
MPEG2 compressed. NTSC is not compressed. You would use a
hardware encoder if you are recording analog signals either from cable
or over the air. Basically, digital broadcasts are just written
to disk because they are already encoded, analog broadcasts have to be
encoded before they are written to disk, either using a hardware
encoder or doing it in software.<br>
<br>
Hope that helps.<br>
</div></div>