On Sat, Mar 05, 2005 at 01:05:19AM -0500, Jonathan M. Cooper wrote: > I've been reading that HDTV decoding takes a substantial amount of > processing power. I was wondering if anyone has gotten 2 or more HDTV > tuner cards working with myth, and, if so, what the CPU and memory > requirements would be. I'm considering replacing 2 UltimateTV boxes > with myth. The UltimateTVs each have 2 tuners, so I'd want a setup > where I could record 4 shows at once (ideally). That could be 2 boxes > with 2 tuners or 1 backend with 4 tuners.
While Jarod answered your rought question, your wording belies the common misconception about what the hdtv tuner cards do. They do almost nothing (they are only expensive because they are small volume.) They just receive a digital bitstream off the air, and your PC does nothing but write it to disk. It takes effectively zero CPU to do this, you could fill your machine with cards and barely notice it as it recorded 5 shows at once. While the pchdtv-3000 also has a raw NTSC capture component (not yet fully supported in myth) the ATSC tuner does nothing else. It can't take HDTV from a cable box or satellite box. It can't encode mpegs or decode them. It can (just recently) receive non-encrypted digital cable (a tiny fraction of the cable channels, but often including the local HD ones.) It's just a radio receiver and demodulator of a pre-compressed, pre-encoded bitstream. The UTV, like other boxes, has NTSC tuner cards including an mpeg encoder for each tuner. Your HD tuner card won't do this. In the future, proper support for the raw NTSC capture will be in place and you could record NTSC -- but that will take CPU, a fair chunk of it, to record to mp4, and so you probably would not be able to record 2 mp4s, for example, and also watch hdtv, though right now I have not heard anybody benchmark what it takes to do this.
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