[LAU] screencast using jack

Len Ovens len at ovenwerks.net
Tue Mar 19 01:25:38 UTC 2013


On Mon, March 18, 2013 5:44 pm, Federico Bruni wrote:
> Il 18/03/2013 00:10, David Adler ha scritto:
>>>> http://apps.linuxaudio.org/wiki/screencasttutorial
>>>> >>might also be helpful. The ffmpeg command will likely demand some
>>>> love,
>>>> >>for adapting its arguments to what suits your machine.
>>> >
>>> >I had to replace "-vpre lossless_ultrafast" with "-preset ultrafast"
>>> >and "-i 0:0" with "-i :0.0".
>> Thanks for posting, that does it here as well.
>
> I have another issue with the tutorial above.
> It says:
> "Now you have two separate files, an .mkv and a .wav file and because
> jack_capture was started right after ffmpeg audio should be no more out
> of sync then just a few millisecs."
>
> Actually my files are out of sync because they have different durations.
> Video is 5:31 and audio is 9:21.

My first guess is a frame rate issue... like a half frame rate that is
also mistranslated from 25hz to 29.*dropframe (or vise versa). It really
doesn't matter at this point, check two things. Listen to the wave, does
it sound right"? Watch the video stream, does it look really fast? Do they
play back at the listed times?

Are you using spdif for audio in? If so, where is it getting sync from?

These are all shots in the dark. The first thing is to play them back and
see if there is an issue with audio or video or both.

-- 
Len Ovens
www.OvenWerks.net



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