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• Record specific window using ffmpeg

  5 décembre 2022, par Ahmed A. Mansour

  I have been trying the below code (which I found on other similiar problem on this site here : How to record a specific window using ffmpeg But it gives me black video and the same video is not playable by windows media player (it works on vlc but with black video..)

  


  ffmpeg -f gdigrab -framerate 30 -i title="german.avi - VLC media player" -b:v 3M  germ.flv


  


  Video example :
Weird thumbnail by WMP which shows it can't play it
Black screen as described, but it opens with black video in VLC

  


  I tried the other suggestions, but this one sometimes (less than 40% of the time) works.
I also noticed it doesn't show the window main title, which is a bit confusing, as it causes the mouse cursor to appear a little down where it should be.

  


• Loop through images, detect if contains color, put in subfolder

  16 avril 2022, par Samo

  I have two kinds of images in my folder : One is all black, the other one is black with yellow (#f8fa27). I am trying to put all the images with yellow colour in a subfolder. But I don't know how this is applicable.

  


  I would like to implement this with ImageMagick or FFMPEG. If possible, shell is redundant and I would like the loop via CMD. If you happen to know of another option that also works, that's no problem either.

  


  I've read about https://imagemagick.org/script/fx.php but I don't know how to apply it with my poor skills.

  


  Edit for now I managed to fix it with python (shitty code but it works)

  


  import cv2
import os
import glob

#check if extension is png
for filename in glob.glob("*.png"):
    #return to folder where all images are saved
    os.chdir('C:/Users/.../.../images')
    #make image black and white
    image = cv2.imread(filename, 0)
    #if image is fully black
    if cv2.countNonZero(image) == 0:
        print ("Black image, skipped")
    else:
        #colored image
        print ("Colored image")
        #restore true colors (rgb in my case, check wiki)
        image = cv2.imread(filename, cv2.COLOR_BGR2RGB)
        #folder to save colored images
        os.chdir(os.getcwd()+"/yellow")
        #save image to subfolder
        cv2.imwrite(filename,image)


  


  Thank you :) !

  


• Replace frames in an AVI with Java

  12 juillet 2018, par webuster

  I’m recording some screencasts and my crap recorder (Camtasia) recorded 2000 videos with a brief black flash (2-3 frames) at, or near the beginning of each.

  I’m looking for a way to automate the replacement of the black frames inside each video with FFmpeg, and I can currently detect which frames are black.

  The problem I have is now : How can I replace frame number X with the content of frame number X-1 in an AVI video ? Not looking to shorten the video, but just to replace a frame in-place.

  Here’s what I have so far :

  FFmpegFrameGrabber g = new FFmpegFrameGrabber("res/video.avi");
  
  g.start();
  
  
  
  FFmpegFrameRecorder recorder = new FFmpegFrameRecorder(new FileOutputStream(new File("res/video_out.avi")), g.getImageWidth(), g.getImageHeight(), 2);
  
  
  
  recorder.setFormat("avi");
  
  recorder.setPixelFormat(AV_PIX_FMT_YUV420P);
  
  recorder.setFrameRate(30);
  
  recorder.setVideoCodec(AV_CODEC_ID_H264);
  
  recorder.setVideoQuality(10);
  
  recorder.setSampleFormat(AV_SAMPLE_FMT_FLTP);
  
  recorder.setSampleRate(48000);
  
  recorder.setAudioCodec(AV_CODEC_ID_AAC);
  
  recorder.setAudioQuality(10);
  
  
  
  g.setFrameNumber(1);
  
  recorder.setFrameNumber(2);
  
  recorder.record(g.grab());
  
  
  
  g.close();
  
  recorder.close();
  
  recorder.release();

  And I’m getting a video back with empty frames (not even black), so I might be messing something here.

  Anyone with experience with FFmpeg ?