[mythtv-users] Dual processors -- better than single fastprocessor?

Jonathan Wiebe jwiebe at intermaptechnologies.com
Fri Jul 16 13:40:39 EDT 2004


Thanks for the response.

I guess that Mythtv doesn't split the encoding across processors .... Or
may be this simply isn't possible with the way mpeg4 encoding is done;
i.e. can't spawn a process for top half of frame and spawn a another
process for the bottom half.  I don't know the first thing about video
encoding.

I guess if you watch tv from a remote front end this must be essentially
using dual processors ... The backend encodes and ships packets to the
remote and the remote decodes.  If you don't watch tv at the backend the
remote can handle the decoding and displaying load ... Is that true?

Jonathan

-----Original Message-----
From: mythtv-users-bounces at mythtv.org
[mailto:mythtv-users-bounces at mythtv.org] On Behalf Of Cory Papenfuss
Sent: Friday, July 16, 2004 11:09 AM
To: Discussion about mythtv
Subject: Re: [mythtv-users] Dual processors -- better than single
fastprocessor?

 	I have used mythtv on both a dual celeron 300->450, and a duall
PIII 
750->1GHz (see a pattern here?... :)  No single process of mythtv can 
750->utilize
more than one cpu at present, but the nature of what mythtv does lends
itself to multiple processes to some degree.  A 1GHz PIII is pushing it
for both encoding (MPEG4) and playing at the same time.  The dual worked
will in that situation (mythbackend took 90% cpu, mythfrontend + X
approx 60-80% of the other).  If you were trying to do something fancy
with the encode or really high resolution, you'd be bumping up against a
single 1GHz PIII encoding.  I did on mine, and ended up with a 480x480
IIRC.  If you wanted full-tilt 720x480 with deinterlacers, denoisers,
etc, the 1GHz won't do.

 	Even with the dual, it tends to boil down to how fast the rest
of the system is as well.  There's lots of data flying around (raw YUV
over PCI bus being a huge one), so if you don't have things tweaked and
good vid card, it's pushing it.  I've since gotten rid of the bttv card
from my system (crappy hardware), so I only use the pvr-250.  I highly
recommend the MPEG2 card, as it gave me better quality in addition to
the reduced CPU load.

YMMV
-Cory

************************************************************************
*
* The prime directive of Linux:
*
* 	- learn what you don't know,
*
* 	- teach what you do.
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* 						(Just my 20 USm$)
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On Fri, 16 Jul 2004, Jonathan Wiebe wrote:

>
> I'm curious what are your experiences?
>
>> From the documentation I've read a single PIII 1Ghz processor is able
to
> encode mpeg4 and allow tv watching (live tv - encoding and decoding,
> with no encoding done in hardware).  If for example I wanted to build
a
> backend server is it better to look at a dual PIII 1Ghz motherboard or
a
> single processor board with a higher powered processor, say 2.6GHz?
>
> How mutltithread friendly is MythTv?
>
> Jonathan
>
>
>
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