[MPlayer-users] FPS or resolution?

[D Richard Felker III]

On Sat, Jul 05, 2003 at 11:32:20PM +0200, Nikolaus Rath wrote:
> [Automatic answer: RTFM (read DOCS, FAQ), also read DOCS/bugreports.html]
> Hello,
> 
> First a big thank you to the developers: mplayer is really a great
> program. I just discovered this when comparing capturing speed.
> 
> Now my question: My computer is too slow for realtime PAL grabbing
> (768x576 with 25 fps). I have to decrease either resolution or fps. A
> value of 21 fps or a resolution of 640x480 would be sufficient. Now
> which value should I decrease? Which affects quality lesser?

Lowering framerate is absolutely not an option. TV signals (PAL) are a
fixed 50 fields per second (typically captured as 25 pseudo-frames),
so encoding at "21 fps" does not mean getting 21 evenly spaced frames
per second, but rather dropping 4 pairs of consecutive fields out of
every 5 -- giving you horrible choppiness!!

> And another issue: Grabbing 688x525 seems to be much slower than
> 768x576. Is this a bug, incorrect measurement or absolutely normal?

Not sure, but the vertical size you capture MUST be 288 or 576 if you
don't want horrible artifacts...

On the other hand, you can change horizontal resolution freely without
damaging the video. 640 is a plenty horizontal resolution; 480 is
probably even enough.

BTW, if you're capturing 576 lines, video will be interlaced, meaning
you'll have to deinterlace to watch it on anything but a PAL TV. So
you might consider capturing at 768x288 or something, to get
progressive frames instead of interlaced.

Rich