Re: [LAD] Screencasting with JACK [SOLVED!]

Le Thu, 8 Aug 2013 18:54:29 -0700,
"J. Liles" <malnourite@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/d02509d04d396a98646ca81e9ba327a501486130.patch
>
> 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."
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