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• Fast movie creation using MATLAB and ffmpeg

  24 février 2018, par hyiltiz

  I have some time series data that I would like to create into movies. The data could be 2D (about 500x10000) or 3D (500x500x10000). For 2D data, the movie frames are simply line plot using plot, and for 3D data, we can use surf, imagesc, contour etc. Then we create a video file using these frames in MATLAB, then compress the video file using ffmpeg.

  To do it fast, one would try not to render all the images to display, nor save the data to disk then read it back again during the process. Usually, one would use getframe or VideoWriter to create movie in MATLAB, but they seem to easily get tricky if one tries not to display the figures to screen. Some even suggest plotting in hidden figures, then saving them as images to disk as .png files, then compress them using ffmpeg (e.g. with x265 encoder into .mp4). However, saving the output of imagesc in my iMac took 3.5s the first time, then 0.5s after. I also find it not fast enough to save so many files to disk only to ask ffmpeg to read them again. One could hardcopy the data as this suggests, but I am not sure whether it works regardless of the plotting method (e.g. plot, surf etc.), and how one would transfer data over to ffmpeg with minimal disk access.

  This is similiar to this, but immovie is too slow. This post 3 is similar, but advocates writing images to disk then reading them (slow IO).

• avfilter/vf_ciescope : fix black-point position

  17 janvier 2023, par Paul B Mahol

  avfilter/vf_ciescope : fix black-point position
  

  • [DH] libavfilter/vf_ciescope.c

• How to automatically remove black bars using ffmpeg and powershell ?

  7 avril 2020, par timlwsk

  Thanks to the help of the user mklement0 I got this script to automatically convert all files in the folder "video_old" and move them into "video_new", all while keeping the original filename. Original Post.

  



  Now I want to remove the black bars in the container. I know that there is "cropdetect" but AFAIK you have to manually parse the the value into the script manually. How can I automate this process using PowerShell ?

  



  Get-ChildItem .\video_old -Filter *.mkv | ForEach-Object {
  .\ffmpeg.exe -i $_.FullName -c:v libx265 -crf 18 ".\video_new\$($_.Name)"
}