On 9/26/05, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote:
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.
Hope that helps.
Another gentleman by the name of Brian Steele responded to my post, also. He noted:
<snip>
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.
<snip>
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.
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.
Hope that helps.
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