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Accepted
josinalvo
Asked: 2012-06-17 18:04:06 +0800 CST

Create a screencast in a low end PC, but fast (maybe by sacrificing compression ?)

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As the title suggests, I am asking a lot.

We've been trying to generate some screencasts on my eeepc. recordmydesktop is doing the job decently, but only if allowed time to "compile" the video afterwards. If we ask it to do "on the fly", video and audio get out of sync.

Now, we are creating many screencasts as practice (and like to watch them after, to criticize). Reducing quality is undesirable, because eventually a good practice run becomes the one we'll release.

So we'd like a way to do screencasts "on the fly", with decent quality, on the low end machine. As nothing is ever free, we are willing to sacrifice: we don't care too much about compression: 20GB for a 15min video is acceptable

screencast

3 Answers

  1. Best Answer

    I've found a satisfatory way:

    It seems that mkv(**) allows for many levels of compression. By using a low compression for video, I am able to record in real time and with quality on my lowly eeepc.

    To achieve that, I had to use ffmpeg. It is available in Ubuntu, but I used a version from a ppa(*):

    To install:

    sudo add-apt-repository ppa:jon-severinsson/ffmpeg
sudo apt-get update
sudo apt-get install ffmpeg

    To record: 

    ffmpeg -f x11grab -r 25 -s 800x450 -i :0.0+0,60 -f alsa  -i plughw:1,0 -vcodec libx264 -crf 0 -preset ultrafast -acodec pcm_s16le file.mkv

    The important part is this "preset ultrafast" that tells the encoder not to compress the video too much.

    (*) apparently, Ubuntu is using a fork of ffmpeg that is not the most common in use. I tried that line with Ubuntu's ffmpeg and it did not work. However, one should note that I am still using 11.10

    (**) probably mkv is a container, and this libx264 is the codec that allows different compressions ...

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  2. I've had only great experiences with Kazam Screencaster so far. I don't know how it would behave on a low end PC, but on mine it produces high quality recordings that can be saved instantly after the recording is stopped.

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  3. Here's how I solved the issues

    http://www.meta64.com/?id=13404

    but I need to try Kazam now!

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