Capture Card Resolution -- was: Re: [mythtv-users] 2 Capturecard questions

Ken VanDine ken at
Sun Mar 23 15:28:09 UTC 2003

Thanks, adding gbuffers=16 helps considerably.  But, gbuffers=32 just hangs
mythfrontend.  It still appears as if it is dropping frames in both rtjpeg and
mpeg4, but it is much better than before.  If the height for capture is set to
240 it doesn't appear to drop any frames.  CPU load is fine, always at least 25%
idle.  I am using DMA for hd access and get ~30MB/s.  I did find some references
to gbuffers=32 on the web and people seem to have success.  Not me.  Any other
ideas?  Would it help to go to the v4l2 stuff and the lastest bttv driver?  I am
willing to try anything.  One thing I have observed is the CPU usage of X.  If I
capture at 720x240 X uses about 6-8% cpu.  Capturing at 352x480 X uses about 22%
cpu.  I don't think this is the issue, but might be something wrong.  I am
pretty sure the dropped frames are on the capture side, I always of idle % of 10+.

The NVidia card was no problem.  I found someones example XF86config that just
worked for me.  Very little tweaking.  I am attaching mine, it does seem to
work.  I would recommend using the older drivers, 3123.  The latest have some
performance problems.     


Quoting Edward Wildgoose <edward.wildgoose at>:

> > Well, I have some interesting (yet frustrating) results.  It seems the
> problem
> > for me is the height.  I can record at 720x240 using mpeg4 at only like
> 33% cpu,
> > rtjpeg works great too.  However, if I select 480 for the height, the
> quality is
> > terrible no matter what the width is and the cpu usuage is very high.  I
> have a
> > P4 1.5Ghz using a WinTV Go for capture and NVidia 440MX for TV out (3123
> drivers).
> Define "quality is terrible"?  Do you mean lost frames, ie jerky video or
> that the picture is grainy and horrible?
> Lost frames would seem to imply a performance problem.  Check for DMA on
> the
> hard disk (hdparm /dev/hda) first.  Does switching to rtjpeg help?
> The other thing that I have found is that adding a "gbuffers=lots" option
> to
> the bttv module options helps quite a bit, although this seems to be
> against
> the general advice that I have seen elsewhere (this file is usually
> /etc/modules.conf - google on gbuffers= for more documentation)
> Did you find it fairly easy getting tv out on your NVidia?  Is the 440MX
> fast enough for myth game and general video duties?  I am assuming that it
> runs cool enough to air cool?  I am thinking about getting a cheap one to
> replace my ATI Radeon which I have so far failed to get TVout working...
> _______________________________________________
> mythtv-users mailing list
> mythtv-users at
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