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• Correcting color cast with ffmpeg

  16 mai 2018, par Henry H

  I have two videos that have a pretty significant blue cast to them. I took some stills at the same time and I’m happy enough with the colors on those and I’d like to re-encode the videos, adjusting the colors to something similar to the stills.

  • A frame from the original video can be seen here : http://www.dotrose.com/temp/img_20180513_153484_original.png
  • An attempt at correcting the color, which would be acceptable : http://www.dotrose.com/temp/img_20180513_153484_corrected.png
  • A still image taken at the same time (but with some help from a flash) : http://www.dotrose.com/temp/img_20180513_153476.jpg

  I understand I could either create a large collection of jpg images from the video and color correct them before reassembling them into a new video or I could use ffmpeg’s color level’s filter to do it directly. What I don’t know is how to get the numbers to pass to the filter. I’m assuming I want to do something like this :

  ffmpeg -i video.mov -vf "colorlevels=rimin=##/255:gimin=##/255:bimin=#/255:rimax=###/255:gimax=###/255:bimax=###/255, eq=gamma=#.##" -y out.mov

  How do I get the values to use for each of the r, g, and b min and max settings and gamma to use in place of the ###s ? Assuming this is the right approach, of course.

  Update : Perhaps this question would be better asked in a forum for gimp or photoshop. But I know how to adjust the color in those. What I need to know is how I translate those changes to what ffmpeg is expecting.

• Washed colors with ffmpeg in macOs

  18 décembre 2020, par Gabrielle

  I am having problems regarding the colors of a screen recorded video generated by ffmpeg on mac.

  


  

  


  I am using the following command to generate the video :

  


  ffmpeg -f avfoundation -video_size 1980x1140 -framerate 30 -capture_cursor 1 -capture_mouse_clicks 1 -i '1' -preset ultrafast -an -qp 0 -crf 22 -pix_fmt yuv420p  -y -c:v libx264 -c:a libfaac -vf eq=brightness=0.00:contrast=1:saturation=1 video_test.mkv


  


  I tried to change qp to 1 and 2, to change the crf to 0 and 2 (let it higher and lower than qp), tried to use pix_fmt yuv444p and bgr0 and 0rgb, tried to change c:v to libx64rgb, tried to not use vf but the result is the same.

  


  The only real difference I've noticed is when I put a really high crf that makes the image very pixelated...

  


  I've tried different numbers for brightness, contrast and saturation but I couldn't find a good combination.

  


  Any idea how to make the video look more as the original ?

  


  Full log :

  


  

  


  About the red message in the middle of the image, this is always printed even when I use yuv444p (the red message prints yuv420p)

  


• ImageJ / Fiji shows wrong number of frames in video (FFMPEG import)

  28 avril 2023, par locoric_polska

  I am counting the number of animals in a an area using Fiji. I import the video through the FFMPEG plug-in (videos are mp4 with mpeg-4 codec). However, I noticed that when I import the videos Fiji uploads the wrong number of frames, and I cannot understand why and how.

  


  An example. I have a video shot at 25fps which is 1582s long. If I do the calculations the video should have 39550 frames in total (1582*25). When I open it through a Computer vision package in R, I see that the video correctly contains 39550 frames. However, when loaded in Fiji, the shown number of frames is 49511. So Fiji is adding 9961 frames to the video. This is consistent across all videos that are recorded in 25fps, while it does not appear in videos shot at 24fps.

  


  Curiously, I found that the ratio between the number of frames read by Fiji and the 'real' number of frames is consistent between 0.79 and 0.80. This makes me think that Fiji is expecting the video to be 30fps and (possibly) duplicating frames to adjust the video to this assumption.

  


  Unfortunately, I discovered all this after finishing my analysis and while trying to merge this dataset with another obtained through CV. The number of frame does not match between datasets and I am not sure how to solve this.

  


  Any help would be greatly appreciated !!

  


  An idea is to multiply all the frame numbers by 0.8 to adjust them to the old assumption. This solution assumes that Fiji is duplicating frames throughout the video in a consistent way