[mythtv-users] *Performance* of LiveTV auto recording?

[Pekka Savola]

On Tue, 18 Apr 2006, Steve Daniels wrote:
>> I don't care about disk space.  My reason is performance.  I don't have
>> too
>> fast a system (P3/800), and watching LiveTV already gulps about 180 MB of
>> memory and about 30-50% of CPU.  I have done no measurements, but I
>> suspect a
>> non-trivial part of that is due to disk-I/O (yes, DMA is enabled).
>
> A *doubt* that the high percentages come from writing and reading to and
> from the disk respectively. Although you are using a lot of resources to
> watch LiveTV, do you need these resources for anything else? What graphics
> are you using? Try XVMC?

XvMC is not an option as the hardware (old Riva TNT2 card) doesn't 
support that.

This is an example with MythTV:

25602 psavola   15   0  276m 101m  33m S 49.6 26.8   2:20.26 mythfrontend
25674 root      15   0  270m  29m 9784 S 17.4  7.8   0:15.42 mythbackend

Or two alternatives:
25390 psavola   15   0  223m  46m  27m S 43.6 12.4   2:01.05 kaffeine

25521 root      15   0  266m  37m  16m S 35.8 10.0   0:18.92 xine

(Without deinterlace, CPU is 10-15% lower, but that'd probably apply 
to all of these.)

While I don't usually need most resources at the same time (though 
it's not atypical to have a dozen or two Firefox windows open, which 
take quite a bit of memory :-), this is causing some jumpiness in 
MythTV.  I haven't traced the roots of that jumpiness yet, though my 
suspicion is lack of memory (I only have 384MB) when multiple other 
windows are open, leading to swapping, which isn't good especially 
when LiveTV is already engaged in heavy disk I/O.

> Try using a program that allows you to watch the stream directly such as
> mplayer, of kaffiene (spelling?) See what percentages you get.

See above.

> The thing about the way MythTV works, is there are A LOT of very good
> reasons for it to work this way. For it NOT to write the stream to disk
> first, which I believe it has done for quite a few versions, (it was called
> a ring buffer in previous incarnations) would require extra coding, and you
> would lose the PVR functions of Myth. So then people would ask why you are
> using the MythTV PVR when you don't want to use the PVR functionality?

Maybe some folks don't need PVR functionality all the time.  Maybe 
they don't need to be able to rewind a random recording, but rather 
just perform "time shifting", where starting to record when you pause 
the liveTV would be enough.

> If you want to launch mplayer of kaffiene or tvtime or some other linux tv
> program, look for the exectv function and build your own menu entry for it.
> http://www.google.co.uk/search?hs=hUt&hl=en&safe=off&c2coff=1&client=firefox
> -a&rls=org.mozilla%3Aen-US%3Aofficial&q=exectv+mythtv&btnG=Search&meta=

I'll look at this, thanks.  The problem here is that I'd like to be 
able to launch mythtv with the same/similar options (e.g., the same 
deinterlace methods etc.) as MythTV is configured.  Running xine, 
mplayer etc. directly would require configuring these at two different 
places.  Is it possible to do something in between these extremes?

Another problem might be that I couldn't run mplayer etc. at least on 
command line while mythbackend is running as it's reserving the DVB 
card.  But I'd suspect when I look at exectv, there's going to be a 
solution for this..

-- 
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings