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• Creating a transparent color mask that covers half of every frame in a video with opencv/moviepy/ffmpeg

  24 octobre 2019, par Nyktofob

  I’m doing a pose estimation in rats separated into two compartments of a cage. To make my tracking better I want to put a transparent color mask that covers half of every frame so that one of the rats will appear to the neural net as being of different color, thus making it easier for the net to differentiate those rats. My question is : Is there any easy way to do this using python (moviepy/opencv/ffmpeg) ?

  Bare in mind, I’m completely new to python, so I’d appreciate any recommendation of a tutorial or detailed answer.

  I tried using blender to do this, but failed miserably.

  I expect to be able to modify the video, so that there will be a rectangular transparent mask in some color that covers certain part of every frame (Let’s say video is 1920x1080 pixels, so from pixel 960 on x axis everything to the right is transparently green)

• ffmpeg - color-grading video material AND display original source as picture-in-picture, using -filter_complex

  5 octobre 2019, par raven

  this is my first post on this forum, so please be gentle in case I accidentally do trip over any forum rules that I would not know of yet :).

  I would like to apply some color-grading to underwater GoPro footage. To quicker gauge the effect of my color settings (trial-and-error, as of yet), would like to see the original input video stream as a PIP (e.g., scaled down to 50% or even 30%), in the bottom-right corner of the converted output movie.

  I have one input movie that is going to be color graded. The PIP should use the original as an input, just a scaled-down version of it.

  I would like to use ffmpeg’s "-filter_complex" option to do the PIP, but all examples I can find on "-filter_complex" would use two already existing movies. Instead, I would like to make the color-corrected stream an on-the-fly input to "-filter_complex", which then renders the PIP.

  Is that doable, all in one go ?

  Both the individual snippets below work fine, I now would like to combine these and skip the creation of an intermediate color-graded TMP output which then gets combined, with the original, in a final PIP creation process.
  Your help combining these two separate steps into one single "-filter_complex" action is greatly appreciated !

  Thanks in advance,
  raven.

  [existing code snippets (M$ batch files)]
  
  
  
  ::declarations/defines::
  
  set "INPUT="
  
  set "TMP="
  
  set "OUTPUT="
  
  set "FFMPG="
  
  set "QU=9" :: quality settings
  
  
  
  set "CONV='"0 -1 0 -1 5 -1 0 -1 0:0 -1 0 -1 5 -1 0 -1 0:0 -1 0 -1 5 -1 
  
  0 -1 0:0 -1 0 -1 5 -1 0 -1 0'"" :: sharpening convolution filter
  
  
  
  ::color-grading part::
  
  %FFMPG% -i %INPUT% -vf convolution=%CONV%,colorbalance=rs=%rs%:gs=%gs%:bs=%bs%:rm=%rm%:gm=%gm%:bm=%bm%:rh=%rh%:gh=%gh%:bh=%bh% -q:v %QU% -codec:v mpeg4 %TMP%
  
  
  
  ::PIP part::
  
  %FFMPG% -i %TMP% -i %INPUT% -filter_complex "[1]scale=iw/3:ih/3 
  
  [pip]; [0][pip] overlay=main_w-overlay_w-10:main_h-overlay_h-10" -q:v 
  
  %QU% -codec:v mpeg4 %OUTPUT%
  
  
  
  [/existing code]

• `sage -pip install —user ffmpeg` did not make the "`OSError : Error : ffmpeg does not appear to be installed.`" message go away

  2 septembre 2019, par SomeoneElse

  I am running a Docker instance of Cocalc on a Ubuntu 16 server. Everything seems to be working but I am trying to debug why sage -pip install --user ffmpeg did not make the "OSError: Error: ffmpeg does not appear to be installed." message go away, even though it said it had been installed. Here is the full message.

  Error in lines 9-9
  
  Traceback (most recent call last):
  
    File "/usr/local/sage/local/lib/python2.7/site-packages/smc_sagews/sage_server.py", line 1188, in execute
  
      flags=compile_flags) in namespace, locals
  
    File "", line 1, in <module>
  
    File "/usr/local/sage/local/lib/python2.7/site-packages/smc_sagews/sage_salvus.py", line 2944, in show
  
      s = show0(objs, combine_all=True)
  
    File "/usr/local/sage/local/lib/python2.7/site-packages/smc_sagews/sage_salvus.py", line 2903, in show0
  
      b = show0(a)
  
    File "/usr/local/sage/local/lib/python2.7/site-packages/smc_sagews/sage_salvus.py", line 2868, in show0
  
      show_animation(obj, **kwds)
  
    File "/usr/local/sage/local/lib/python2.7/site-packages/smc_sagews/sage_salvus.py", line 2642, in show_animation
  
      obj.ffmpeg(t, delay=delay, **kwds)
  
    File "/usr/local/sage/local/lib/python2.7/site-packages/sage/plot/animate.py", line 885, in ffmpeg
  
      raise OSError(msg)
  
  OSError: Error: ffmpeg does not appear to be installed. Saving an animation to
  
  a movie file in any format other than GIF requires this software, so
  
  please install it and try again.
  
  </module>

  For reference, here is the code that gives the error :

  n = var("n")
  
  frames = []
  
  xr = (x, 0, 1)
  
  for k in srange(1, 50):
  
      g = plot((sum((-1)^(n-1)*sin(n*x)/n,n,1,k)), xr, color="blue", legend_label='k = %d' % k)
  
      g += plot(x/2, xr, color="green", legend_label="x/2")
  
      frames.append(g)
  
  
  
  a = animate(frames, ymin=0.0, ymax=1.0, legend_loc=(0.2,0.8))
  
  a.show()