Making movies

using recordmydesktop

A video tutorial can be produced in the following way:

  • change the screen resolution to 1280x1024,

  • record the movie of the screen (without sound) using recordmydesktop (gtk-recordMyDesktop),

  • convert the resulting ogv into avi using mencoder:

    mencoder video.ogv -o video.avi -oac copy -ovc lavc
  • record and edit the sound track using audacity:

    • use 44100 Hz for recording and save the final file as sound.wav,
    • make sure not to keep the microphone to close to avoid signal peaks,
    • cut microphone signal peaks, insert silences, …
  • edit the movie using avidemux (to match the sound track):

    • load the video.avi: File ‣ Open, make sure to use the following options when editing and saving: Video ‣ Copy, Audio ‣ Copy, Format ‣ AVI,

    • add the sound.avi: Audio ‣ Main Track ‣ Audio Source ‣ External WAV,

    • cut video frames (or copy and insert still frames to extend the video) to match the sound track. Set beginning mark and end mark - the cut or copy/paste operation applies to the selected region,

    • make sure to save intermediate stages when working on the video File ‣ Save ‣ Save Video (as AVI):

      • avidemux caches the audio track so to match the audio to a freshly cut video you can copy the audio file into another name, and add the sound track from that name,
      • sometimes when cutting frames avidemux does not allow to set the markers correctly, and there is no undo the last step in avidemux!
    • save the video_final.avi (that matches the sound track), and encode it into mpeg4 format using mencoder, using two passes:

      opt="vbitrate=550:mbd=2:dc=10 -vf unsharp=l:0.4:c:0.0:hqdn3d"
      mencoder -ovc lavc -lavcopts vcodec=msmpeg4v2:vpass=1 -nosound -o /dev/null video_final.avi
      mencoder video_final.avi -oac mp3lame -af resample=32000:0:2 -lameopts vbr=3:br=80:mode=3 \
              -ovc lavc -lavcopts acodec=mp3lame:vcodec=msmpeg4v2:vpass=2:$opt \
              -info name="Overview and installation of ASE":artist=CAMd:copyright="CAMd 2009" -o video_final_mpeg4.avi
    • convert video_final.avi into a 800x600 swf file for streaming:

      ffmpeg -i video_final.avi -pass 1 -s 800x600 -b:a 256k -ar 44100 -ac 1 \
             -vcodec flv -b:v 1200k -g 160 -mbd 2 oi_en_800x600.swf
      ffmpeg -i video_final.avi -pass 2 -s 800x600 -b:a 256k -ar 44100 -ac 1 \
             -vcodec flv -b:v 1200k -g 160 -mbd 2 -y oi_en_800x600.swf

using avconf to collect png files

Load the trajectory and write the images out as single png files, e. g.:

from ase import io

t ='mytrajectory.traj')

for i, s in enumerate(t):
    # rotate to the desired direction
    s.rotate('z', 'x', rotate_cell=True)

    # repeat with keeping old cell
    cell = s.get_cell()
    s = s.repeat((1, 3, 3))

    ofname = str(i) + '.png'
    print('writing', ofname)
    io.write(ofname, s,
             bbox=[-3, -5, 50, 22])  # set bbox by hand, try and error

In case you do not have avconv, install it (ubuntu):

sudo apt-get install libav-tools libavcodec-extra-53 libavdevice-extra-53 libavformat-extra-53 libavutil-extra-51 libpostproc-extra-52 libswscale-extra-2

Convert the png files to a movie (

avconv -i "%d.png" -r 25 -c:v libx264 -crf 20  -pix_fmt yuv420p

the options are:

-i “img%d.png” uses these files as the input, %d is a placeholder for the number

-r 25 the desired frame rate, 25 FPS in this case

-c:v libx264 use the h264 codec x264

-crf 20 the video quality, 20 is pretty high, the default is 23

-pix_fmt yuv420p a compatible pixel format