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• Joining Lots of clips with crossfade filter using FFmpeg

  26 juillet 2020, par Mr. Who

  I have many video-only clips and I would like to join them with crossfade filter using FFmpeg. My Idea was that I join first two then join it with the next and so on. I implemented the loop in the python and run bash commend using os.system(). My code has been demonstrated below :

  


  out_n = '0.mp4' # output of step n (current step)
for i in range(1,10):
    out_np1 = 'mm%d.mp4'%(i)  # output of step n+1 (next step)
    t0 = time.time() 
    o = os.system('ffmpeg  -i %s -i %d.mp4  -f lavfi -i "color=black:s=1920x1080:d=9" -filter_complex "[0:v]format=pix_fmts=yuva420p,fade=t=out:st=4:d=1:alpha=1,setpts=PTS-STARTPTS[va0];[1:v]format=pix_fmts=yuva420p,fade=t=in:st=0:d=1:alpha=1,setpts=PTS-STARTPTS+4/TB[va1];[2:v][va0]overlay[over1];[over1][va1]overlay=format=yuv420[outv]" -vcodec libx264 -map [outv] %s'%(out_n, i, out_np1))
    print('# %d'%i,(time.time() - t0)/60,o)
    os.remove(out_n) 
    out_n = out_np1  


  


  My Problem is that it won't work properly, the very last output does not even contain all of the last clip and there is no trace of previous ones.

  


• avcodec/vc2enc : Simplify writing dirac golomb codes

  8 mars, par Andreas Rheinhardt

  avcodec/vc2enc : Simplify writing dirac golomb codes
  The earlier code used a loop to determine the number of bits used
  
  and called ff_log2() on a power of two (and it would be easy to
  
  keep track of the exponent of said power-of-two) ; neither GCC nor
  
  Clang optimized the loop away or avoided the ff_log2().
  
  This patch replaces the loop and the log2 with a single av_log2().
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
  

  • [DH] libavcodec/vc2enc.c

• How can I simply do color interpolation on this image and then save the image ? With RGBA channels as example

  24 août 2020, par karl-police

  So I got this GIF here :

  


  

  


  As you can see, it has Red, Green and Blue in it. And it also has a full transparency in it. This was composed together with FFMPEG out of images that looked exactly like that.

  


   

  


  Then, with FFMPEG I "decomposed" the RGB and Alpha channels using the filter "extractplanes".

  


  The gallery of that, in correct order starting from up to down, can be found here :

  


  https://imgur.com/a/WN0aGuW

  


  I am not sure if this actually helps me or if I'm supposed to decompose them. Because apperantly now, after decomposing them, I'm supposed to modify them, but I'm not really sure how. It's like how do I modify the red channel that only has black and white, so all at the end, will match to the specified HEX color that I want it to be to.

  


   

  


  Now, my question is. How do I exactly make the color changing happen ? Can I do this simply with JavaScript ? Is it possible to do with FFMPEG, if possible without ImageMagicks ? Maybe a programming language where not much installation is needed to do that ?

  


  What I understood is that. These channels basically contain values from 0 to 255 with black and white. I think the "brightness" is that what 0 and 255. So something inbetween, would be like grey.

  


  So basically, like we do (255,0,0) for red. In these channels, if I want red somewhere I need to put one fully white pixel on the red channel and on all the other channels, there has to be a fully black pixel.

  


  That's the concept. Now is the question, how can I do this ?

  


   

  


  At the end I want to make it look like this one as example :

  


  

  


  This is from a game. So basically that's how it looks like in the game. And the game files only use these RGBA template sprites.

  


   

  


  I asked a similar question here : How to change colors of an image using RGBA and more channels independently of their color

  


  But somehow, I might didn't seem to explain it that well.

  


   

  


  I made a thing here to test around with things. I guess that's nearly close, but the lines are kinda weird. jsfiddle.net/qsgazubk