Keith C. Perry on 20 Nov 2014 14:00:50 -0800

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Re: [PLUG] AWS Presentation at PLUG Central

ffmpeg runs on OS-X so here is an example of my record command...

ffmpeg -f alsa -ac 2 -ar 44100 -i hw:2,0 -f x11grab -r 15 -s 1920x1080 -i :0.0 -f mp4 -c:a libmp3lame -c:v libx264 -preset veryfast -vf "scale=1024:576" screencast_raw.mp4

The critical items are in bold.  "alsa" is the audio driver so you'll need to use what's appropriate for OS-X.  "hw:2,0"  is my audio interface which would be different (and based on your audio driver).  "x11grab" is the screen capture driver- I'm not sure if that's the same for OS-X.  "1920x1080" is my screen size, which I then scale down to 1024x576 so that its a reasonable size when posted.  You don't have to scale down while you are recording if your system is fast enough.  I needed that when I was on a slower system to maintain the 15fps rate but the quality is just fine if you do.  This will yield you a decent mp4 file accept that youtube won't like it so I convert it with...

ffmpeg -y -i screencast_raw.mp4 -ar 48000 -vcodec libx264 -pix_fmt yuv420p -profile:v baseline -preset veryfast -f mp4 -q:v 1 -crf 17 -qp 0 -threads 0 screencast.mp4 create something proper.  Again, if your machine is fast enough, you could probably do this combine the options here with the ones during recording.  The critical parameter is the including the baseline profile.

Finally, I index the file ever 500ms so that its streams properly...

MP4Box -inter 500 $2

In my case, I publish to G+  and my web server and the flash player (jwplayer) needed this to work properly.  I'm not sure its need for G+/YouTube publishing.

YMMV   :)

~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
Keith C. Perry, MS E.E.
Owner, DAO Technologies LLC
(O) +1.215.525.4165 x2033
(M) +1.215.432.5167

From: "David Colon" <>
To: "Philadelphia Linux User's Group Discussion List" <>
Sent: Thursday, November 20, 2014 4:28:22 PM
Subject: [PLUG] AWS Presentation at PLUG Central

Since there is interest, I can do my AWS presentation titled "To the Cloud" at PLUG Central on January 7th. There is currently nobody on the calendar so let me know if someone has already committed to that date.
In the other thread people are talking about different methods to stream/record presentations. For my presentation I can record the audio with my cell phone or laptop and use some kind of screencasting software to record as I switch between my slides and the CLI for the demo. I'll figure out how to synchronize the audio and video and then upload to Youtube. Can someone recommend a solution that works under OSX and is preferably FOSS?



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