10 Aug
2013
10 Aug
'13
7:22 p.m.
Le Thu, 8 Aug 2013 18:54:29 -0700,
"J. Liles" <malnourite(a)gmail.com> a écrit :
As some of you may recall, every time I've posted
a demo video to
LAD, I've had to include a disclaimer excusing the poor quality due
to a lack of functional screencasting tools.
Well, it took a couple of weeks of hair pulling and many, many hours
of testing, but I finally arrived at a solution.
Anyone who wants to create a screencast and record audio via JACK *in
perfect sync* must do the following:
Get ffmpeg. Apply this patch to it:
https://github.com/original-male/FFmpeg/commit/d02509d04d396a98646ca81e9ba3…
Build it with vorbis and h264 support.
Then, start your favorite desktop environment. I use Xephyr for this.
Have jack running (at -r 48000)
Then run the following command:
ffmpeg -fflags +genpts+igndts -f x11grab -vsync 0 -r 30 -s 1920x1080
-i :${DISPLAY}.+0,0 -vcodec h264 -f jack -ac 2 -r:a 48000 -i
screencast -acodec pcm_s16le -r:v 30 -vsync 2 -async 1 -map 0:0,1,0
-map 1:0 -preset ultrafast -qp 0 "$FILE"
Where DISPLAY is the number of your X11 display and FILE is the
filename for the screencast. I use a .mkv extension for the matroska
container.
Remember to connect the streams you want recorded to the 'screencast'
JACK inputs!
With this setup I'm able to record a full 30 FPS @ 1080P with audio in
perfect sync. Please share your results too. With some more evidence I
might have a good case to get ffmpeg to accept my patch.
It work fine, thank you.
My screen is 1280 by 1024 on a phenom amd64 system.
When searching for an explanation for the -i display parameter, I find
screecastor. You may be interested by it:
http://www.hecticgeek.com/2012/12/screencastor-screen-recorder-ubuntu/
http://hizo.fr/linux/screencastor/
To make it work with jack, you can edit directly the ffmpeg command, or
change 2 of screencaptor's files:
In go_screencastor.sh:
–combobox=’@@_audio_provenance@@col
pulse
/dev/dsp1
ffmpegjack
hw:0,0
hw:1,0′ \
and
–combobox=’@@_audio_serveur@@col
alsa
jack
oss’ \
In screencastor.sh:
case « ${G2S_audio_provenance} » in
0) G2S_audio_provenance=pulse ;;
1) G2S_audio_provenance=/dev/dsp1 ;;
2) G2S_audio_provenance=ffmpegjack ;;
3) G2S_audio_provenance=hw:0,0 ;;
4) G2S_audio_provenance=hw:1,0 ;;
esac
case « ${G2S_audio_serveur} » in
0) G2S_audio_serveur=alsa ;;
1) G2S_audio_serveur=jack ;;
2) G2S_audio_serveur=oss ;;
esac
Dominique
Enjoy!
--
"We have the heroes we deserve."