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Processor speed question
I'm getting ready to build a dedicated MythTV box for my living room: a
dual-tuner setup with one 120GB Seagate 7200 drive, and the frontend and
backend running on a single machine. I was planning on using an Athlon XP
CPU, maybe a 2200. So, a few questions:

1) How much processor speed will I need to simultaineously record one
channel and time-shift another, both at 400x480?

2) Are there any options for hardware encoding (Matrox Marvel G200, WinTV
PVR-250) that are ready for prime time? I read a lot of threads on
hardware encoding but am not sure where things currently stand. Will
using one of these cards lower my processor requirements, and are there
any tradeoffs?

Thank you for your help!
--
Andre Lewis
andresf@airpost.net

--
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Re: Processor speed question [ In reply to ]
On Thu, 2003-04-17 at 10:14, Andre Lewis wrote:
> I'm getting ready to build a dedicated MythTV box for my living room: a
> dual-tuner setup with one 120GB Seagate 7200 drive, and the frontend and
> backend running on a single machine. I was planning on using an Athlon XP
> CPU, maybe a 2200. So, a few questions:
>
> 1) How much processor speed will I need to simultaineously record one
> channel and time-shift another, both at 400x480?

I've just built up a system similar to the one you have in mind. I
haven't setup a second tuner yet, however my Athlon XP 2200 seems to be
able to capture and playback RTJPEG at 720x480 with about 30-40% CPU
usage on average. I'm planning to put a second tuner in soon, and
possibly a PVR-250 in later on. According to top, the backend typically
consumes 15 - 20% of the CPU, and the frontend typically consumes 10 -
15%. I've seen the backend spike as high as 22%, and the frontend spike
as high as 20%.

I get occasional stutters during livetv playback. I don't think I've
noticed any while playing back a recording. I suspect this might be an
issue with IRQ sharing/prioritization. I haven't had a chance to do much
tuning yet. Obviously there's lots of CPU available.

> 2) Are there any options for hardware encoding (Matrox Marvel G200, WinTV
> PVR-250) that are ready for prime time?

The PVR-250 isn't ready for prime time yet. Maybe soon.

> I read a lot of threads on
> hardware encoding but am not sure where things currently stand. Will
> using one of these cards lower my processor requirements,

Yes.

> and are there
> any tradeoffs?

Flexibility of encoding code comes to mind. Cost, in some cases. Mostly
it seems like hardware encoding support would be a winning scenario
though.

Rick