[mythtv-users] Tuner cards that do HD?

Rod Smith mythtv at rodsbooks.com
Mon Apr 16 17:30:24 UTC 2007


On Monday 16 April 2007 13:00, Geoff Mishkin wrote:
> Rod Smith wrote:
> > On Monday 16 April 2007 02:02, Geoff Mishkin wrote:
> >> I use the pcHDTV HD-3000 which I highly recommend.
> >
> > I couldn't disagree more, particularly for digital cable use. I've got
> > two pcHDTV 3000s, and neither can reliably tune a digital cable (QAM)
> > signal.> My anecdotal evidence is better than your anecdotal evidence :-)
>
> No, this does have all the signs of a problem with interacting with
> other hardware.  But, I've had my HD-3000 in two different computers,
> and connected to four different cable systems plus OTA systems in two
> different regions.  No problems.  So the OP shouldn't count it out just
> yet.

It's not just me who's had problems; lots of others have reported difficulties 
here, on the pcHDTV forums, and elsewhere. Note that this is a QAM issue (for 
cable TV reception); AFAIK, OTA users are unaffected by this issue. My point 
is this: Even though the device works fine for some people, it's not worth 
the risk for the average buyer; other devices do *NOT* have this problem, and 
the only real advantage of the pcHDTV 3000 over them is its analog tuner, 
which is a minor advantage, IMHO. I'll also say that I don't know if the 
current model (the pcHDTV 5500) suffers from this problem.

> > For the OP's purposes, too, the pcHDTV 3000 (and I believe the 5500) use
> > framegrabber analog tuners, which increases the CPU load when recording
> > analog signals. IMHO, it's better to go with two tuner cards, one analog
> > and one digital (or more if you want more than that).

> My CPU load when recording analog is between 5% and 7%, which hardly
> seems exceptional.  It still records fine even if the rest of the system
> is under load.  The biggest disadvantage in my opinion is the fact that
> recordings are larger.  But, disk space is cheap, and there's always
> transcoding.

The exact CPU load will vary depending on the CPU speed and encoding format. 
Given your "recordings are larger" comment, I suspect you're using RTJpeg, 
which uses less CPU than MPEG-4 but produces bigger files. Certainly a 5-7% 
CPU load isn't likely to cause serious problems, but if somebody's using a 
less capable CPU than yours and/or wants to encode using more CPU-intensive 
options, this could become an issue. Also, no matter what the CPU load, it 
will be lower if a hardware-encoding card is swapped in. This might or might 
not be important for any given configuration, but I think it's important to 
mention it so that the reader can judge the matter him/herself.

FWIW, on my system with a 3.06GHz Celeron-D 347, framegrabber cards such as 
the pcHDTV 3000's analog tuner consume about 20-40% CPU time when recording, 
depending on the encoding options used. (The true range might be greater than 
that; I haven't tried every single option.) This is a big enough load to be 
important, particularly when using two tuners and/or when playing back HD 
content (which consumes 70-100% of CPU time, depending on the content and 
settings) while recording analog content.

-- 
Rod Smith
http://www.rodsbooks.com


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