[mythtv-users] Frames per second?
Ray Olszewski
ray at comarre.com
Mon Apr 21 19:58:19 UTC 2003
At 03:32 PM 4/21/2003 -0400, jeff at burstable.net wrote:
>It doesnt appear to be 'torn'. The best I can describe it would be if
>playing a PC game on a underpowered pc and the FPS drop under 20 fps or
>so. Typical CPU usage is about 60% - 70% when watching live tv. Oh and
>the deinterlace filter is one.
It is always hard to be certain from these sorts of descriptions (the one
above and your earlier one), but what you describe sounds like the capture
process is dropping frames for some reason. The usual one is that the image
is sufficiently rich in complexity that the encoder can't work fast enough
on one frame before it has to get the next one, so some are lost. In this
context, "complexity" is anything that makes encoding harder to do,
including simple noise (I get a 50% drop rate in frames when there is
nothing connected to the Television input, for example).
Panning motion is a good way to introduce this sort of complexity ... I
don't tape sporting events, but I've seen similar sorts of problems in The
Simpsons, at the beginning where the "camera" (the animation PoV) pans over
the field full of supporting characters, or a bit earlier where sometimes
it pans and zooms to the school for a Bart Blackboard Quote.
If I'm right, I think your only options are (A) get a faster computer or
(B) reduce the pixel size of the capture.
Oh, one thing you should check: when you load the bttv module, are you
including a suitable gbuffers= argument? (I usually use gbuffers=32 with my
non-Myth systems, and I expect I'll do the same when I finally get Myth
running here. If MythTV doesn't work the way I'm assuming here, I hope
someone will correct me.) This can help buffer against brief bursts of
complexity in the frame sequence.
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