screencast instructions

Christian Lohmaier lohmaier+libreoffice at
Fri Nov 30 07:28:59 PST 2012

Hi Noel, *,

On Fri, Nov 30, 2012 at 3:28 PM, Noel Power <nopower at> wrote:
> Christian
> On 30/11/12 13:16, Christian Lohmaier wrote:
> doh!! but obviously I copied the wrong link
> is what I meant

Ah :-)

>> for me the high bit rate "--v_bitrate  2000000" was necessary to smoothly
>> capture mouse movements,
>> Strange that the bitrate has impact - should have been the framerate..
>> But with low bitrate the image gets "muddy", so maybe that's what you
>> meant.
> no really for me the main problem was it seemed not to pick up fast
> movements I can't recall exactly now whether it was additionally 'muddy',
> don't think it was but...

Hmm. Maybe it couldn't keep up with encoding so it was dropping
frames, and  higher bitrate=less work to squeeze bits, so that did

>>> [...]
> unfortunately aegisub really just didn't work, complained about no video
> provider ( or some error that sounded vaguely like that ). From looking
> around it appeared it should use ffmpeg [...]

aegisub uses ffms2 AKA ffmpegsource - so close enough, but not quite
the same thing :-)

> [...]
>> My key point is to not use a chain of lossless conversions, but only
>> to do the lossless one as last step.
> as interesting as the arcade of options to the various tools above is (
> thanks for posting them :-),

:-) they look much, but really they aren't that obscure...

> sometime I will find the time to look at them
> more closely ) what I really was after was a way to go from ogv video
> file ( or .ass if you prefer ) -> ogv file with re-encoded subtitles ideally
> *without* the need to download restricted formats [*]

Oh, x264 just has a nice lossless format, but of course no need to use
it if you don't want to.. ffmpeg has the ffv1 format that is also
lossless, although not quite as efficient.

ffmpeg -f x11grab -r 15 -s ${WIDTH}x$HEIGHT -i :0.0+$POS_Y,$POS_Y
-vcodec ffv1 -threads 0 -sameq output.mkv

will capture the selected area and use the ffv1 codec.

> not sure if the info
> above tells me that,

No, definitely doesn't tell you that you have to use specific formats,
it just shows that you can use virtually any encoder with both mplayer
as well as ffmpeg (in case the desired output is not supported
directly or option-handling is much easier when running the tools
separately) by using yuv4mpeg streams.


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