[mythtv] Is there a magic resolution for recording ?

Colin Panisset mythtv-dev@snowman.net
Fri, 13 Dec 2002 18:46:56 -0800

On Friday 13 December 2002 17:25, Christopher Mind spake thus:
> I am trying to tweak mythtv for my P3 1 Ghz machine.  I am using MPEG4 as
> RTjpeg quality was poor on my system.  I have 700 plus MB memory, an ATI
> TV wonder PCI card, Turtle Beach Santa Cruz, 100 Gig Hd, Nvidia Geforce
> Ti200 with TV out running Linux Mandrake 9 via TV out with a resolution
> of 640x480. Also using WindowMaker (which seems to work best the irxevent
> which gets confused with KDE) and Creative Infra Remote.
> So far I found that 640 x 480 is very very choppy at 1800 data rate or
> above.
> 400 x 300 with 2000 data rate seems to be ok for recording only.  When I
> attempt to playback a recording at the same time that the machine is
> encoding, the program that is being encoded gets a little choppy.   352 x
> 300 seems to be fine but is a tad blurry at 2000 data rate.  Does the cpu
> utilization scale with the resolution or data rate or are there optimal
> resolutions which will always result in less cpu utilization.  I am not
> even aware of what other resolutions are possible.   Also does lowering
> the mp3 quality reduce cpu utilization?  I am using Maxquality 2,
> Minquality 15 and 3 for quality difference.  Thanks

Hi Chris,

Similar situation (P3 1GHz, 764MB RAM), except that I can't capture at any 
but an integer multiple of 240 for the y resolution (i.e. 240 or 480). The 
resolution makes the biggest different to performance, and the codec is far 
behind; I use 480x240 for my capture resolution, and speedwise it's just 
fine. Plenty of leftover cycles. I'm using rtjpeg, and it's using an 
NFS-mounted filesystem over a switched 100Mbps network for storage. No 
problems there, either. I'm not currently using any audio compression, 
mainly because I just haven't changed the settings from when I was trying 
to get 640x(anything) working fast enough. 480x240 with a good quality 
input signal looks just fine on my 32" flat-screen Sony TV.

I have recently acquired a Matrox Marvel G200TV, which does hardware MJPEG, 
so we'll see how much of a performance hit is imposed by the network once I 
get that installed and working.

  -- C.