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• FFmpeg parameters for Fisheye image correction

  19 janvier 2023, par Julio Cesar

  I am trying to achieve two things (any of them will work for my solution) :

  


  

  1. Fisheye video to equirectangular (and view it in 360 view)

  


  2. Fisheye video to flat (if I understood correctly, it will be just like the fisheye image (maybe I will lose some FoV ?) but without distortions. Of course in this case I will not use 360 view).

  


  


  Camera specs : https://documentation.meraki.com/MV/Viewing_Video/Understanding_Image_Quality_on_the_MV32

  


  For test purposes I am using an image as input :

  


  For 1), I am using ffmpeg -i input_file -vf v360=fisheye:e:ih_fov=180:iv_fov=180:pitch=90 output_file. This command gives me a rectangular image where the half upper is black, and when testing in https://renderstuff.com/tools/360-panorama-web-viewer/ the user can navigate through this black space (I would like to limit user view, so he could not get to the black part). If I crop and remove the black part, the image in the 360 view becomes distorted (loses the aspect ratio).

  


  For 2), I tried ffmpeg -i input_file -vf v360=fisheye:flat:ih_fov=180:iv_fov=180 output_file but it doesn't seem to correct the distortions properly.

  


  FYI this video will be published in AntMedia server to be used as an iframe in web applications. I'll try to use 1) in AntMedia since it supports 360 view (https://antmedia.io/play-live-360-degree-video/).

  


  Since I am new to this, please ask for more information if needed.
  
Thanks in advance.

  


• ffmpeg crop and watermark in a single step

  11 juin 2018, par rbarab

  We are processing short videos. Most of them are 640x480, recorded by mobile. Many of them have a black frame on left and right.
  I would like to watermark the videos and currently using this command.

  ffmpeg -i IN.mp4 -i WATERMARK.png -filter_complex "overlay=main_w-overlay_w-10:main_h-overlay_h-10" OUT.mp4

  The problem is that if there is a frame, part of the watermark goes on the frame and only a part is on the actual content. Would like to place the watermark on the bottom right of the actual content.

  Are any of these possible, or any other ideas ?

  a, Dynamically detect the black frames and adjust the watermark position accordingly.

  b, Crop the black frame and watermark the content correctly in the same step.

  Thanks a lot for your help !

  EDIT :

  I have found that it won’t be possible in one step.

  1, I can get the crop size

  ffmpeg -i INPUT.mp4 -t 2 -vf cropdetect -f null - 2>&1 | awk '/crop/ { print $NF }' | tail -1

  2, Then crop the video

  ffmpeg -i INPUT.mp4 -filter:v "crop=352:480:144:0" -c:a copy OUTPUT.mp4

  3, Then watermark it

  ffmpeg -i INPUT VIDEO.mp4 -i INPUT IMAGE.png -filter_complex "overlay=main_w-overlay_w-10:main_h-overlay_h-10" OUTPUT VIDEO.mp4

  Is there a way to merge 2, and 3, into a single step ?

• FFmpeg concatenation, no Audio in Final Output

  12 septembre 2016, par user4889724

  I have the following command working in ffmpeg, which adds 1 second of a black frame to the beginning of the video. However, I lose the audio from the original video in the output video. How can I adjust the command to make sure the original audio stays with the final output, or better yet, there is 1 second of "blank" audio at the beginning so it matches the new output video.

  ffmpeg -i originalvideo -f lavfi -i color=c=black:s=1920x1080:r=25:sar=1/1 -filter_complex "[0:v] setpts=PTS-STARTPTS [main]; [1:v] trim=end=1,setpts=PTS-STARTPTS [pre]; [pre][main] concat=n=2:v=1:a=0 [out]" -map "[out]" finaloutputvideo.mp4