Ffmpeg¶

FFmpeg is a command line utility to do video/audio/image processing. It is commonly used to generate video from image frames.

Installation on Windows¶

Recent versions of M-Star CFD come with ffmpeg. You can add M-Star install directory to your PATH environment variable.

You can also install ffmpeg yourself from https://ffmpeg.org/

Whenever possible, always use your package manager to install ffmpeg. Some platforms such as Redhat might require additional setup steps.

Redhat

Enable RPM Fusion repo (as recommended by ffmpeg ) – https://rpmfusion.org/Configuration
In M-Star Post, be sure to specify the full path ffmpeg “/usr/bin/ffmpeg” and click the Save button in the lower left corner of the form

The below command is used to animate a set of frames. The output produces an mp4 file called “top.mp4”

A quick explanation of each argument:

-r 1 : This is the rate of image frames in units (1/s). A value of 1 means 1 frame is used every second in the video. If your output interval was 0.1s, your image frame rate would be 10.
-i "ScalardyeVolumeFraction(-)_top_%05d.png" : The image filename patterm of the frames being used. Note the %05d will be used by ffmpeg to zero pad an integer with up to 5 zeros.
-vcodec libx264 : Selects the libx264 codec. A highly efficient video compression technology.
-vf "pad=ceil(iw/2)*2:ceil(ih/2)*2" : ffmpeg requires that each side of the frame is divisible by 2. Sometimes the frames coming out of paraview/post/vtk or whatever will not satisfy this requirement. You can use this argument to pad the images the necessary amount (single row or column of blank pixels).
-crf 20 : Video quality, lower is better. 15-25 is a good range.
-pix_fmt yuv420p : Color/picture format. This makes the video highly compatible across an array of video players.
top.mp4 : the last argument is simply the output filename you want.

ffmpeg -r 1 -i "ScalardyeVolumeFraction(-)_top_%05d.png" -vcodec libx264 -vf "pad=ceil(iw/2)*2:ceil(ih/2)*2" -crf 20 -pix_fmt yuv420p top.mp4