[MPlayer-users] Jumpy capturing from tv with mencoder

Giles RC Morant giles.morant at durham.ac.uk
Sat Feb 22 16:37:29 CET 2003

On Fri, 2003-02-21 at 14:18, Jukka Kajava wrote:
> [Automatic answer: RTFM (read DOCS, FAQ), also read DOCS/bugreports.html]
> I started getting problems with mencoder and tv input
> after I upgraded my kernel to 2.4.21-pre4 from 2.4.19.
> The picture is jumpy and every 5 seconds or so I get a
> line

Could this be to do with the default 5 seconds for ext3 syncing to
disk?  Try running vmstat and see if any processes are blocked/waiting
when disk writes occur.  I often have to run "watch sync" to enable
smooth progress.  Mencoder doesn't do any work when it needs to write to
disk -- something to do with the thread-free architecture?
You can also edit the bdflush parameters to have a similar effect if
watch sync helps.

> video capture thread: frame delta ~ n fps
> where n is a number between 1 and 15.  My tv card is
> Hauppauge bt878. 
> What makes me curious is that the picture is not jumpy
> with mplayer or any other TV software, it is only when
> encoding with mencoder. I have tried also with kernel
> 2.4.20 and the same thing happened.
> This is not a CPU limitation because I grabbed
> perfectly good picture with the same options before
> upgrading the kernel and now I get the jumpy picture
> even if I use very small image size and bitrate (CPU
> usage less than 10%). It is not a sound problem either
> because it appears with the nosound flag.
> Same phenomenon happens with both rc3 and rc4 (haven't
> tested others). I have also tried almost every bttv
> version between 0.7.96 and 0.7.104 and played with
> almost all options. I do not know whether this is a
> mencoder or kernel problem but I am totally puzzled.
> Any ideas?
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Giles RC Morant <giles.morant at dur.ac.uk>

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