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• 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]

• lavfi/color : cache and reuse colored picture in context

  29 juillet 2012, par Stefano Sabatini

  lavfi/color : cache and reuse colored picture in context

• Started Programming Young

  6 septembre 2011, par Multimedia Mike — Programming

  I have some of the strangest memories of my struggles to jump into computer programming.

  Back To BASIC
  I remember doing some Logo programming on Apple II computers at school in 5th grade (1987 timeframe). But that was mostly driving turtle graphics. Then I remember doing some TRS-80 BASIC in 7th grade, circa 1989. Emboldened by what very little I had learned in perhaps the week or 2 we took in a science class to do this, I tried a little GW-BASIC on my family’s “IBM-PC compatible” computer (they were still called that back then). I still remember what my first program consisted of. Even back then I was interested in manipulating graphics and color on a computer screen. Thus :

  10 color 1
  20 print "This is color 1"
  30 color 2
  40 print "This is color 2"
  ...
  

  And so on through 15 colors. Hey, it did the job– it demonstrated the 15 different colors you could set in text mode.

  What’s FOR For ?
  That 7th grade computer unit in science class wasn’t very thick on computer science details. I recall working with a lab partner to transcribe code listings into a computer (and also saving my work to a storage cassette). We also developed form processing programs that would print instructions to input text followed by an “INPUT I$” statement to obtain the user’s output.

  I remember there was some situation where we needed a brief delay between input and printing. The teacher told us to use a construct of the form :

  10 FOR I = 1 TO 20000
  20 NEXT I
  

  We had to calibrate the number based on our empirical assessment of how long it lasted but I recall that the number couldn’t be much higher than about 32000, for reasons that would become clearer much later.

  Imagine my confusion when I would read and try to comprehend BASIC program code I would find in magazines. I would of course see that FOR..NEXT construct all over the place but obviously not in the context of introducing deliberate execution delays. Indeed, my understanding of one of the fundamental building blocks of computer programming — iteration — was completely skewed because of this early lesson.

  Refactoring
  Somewhere along the line, I figured out that the FOR..NEXT could be used to do the same thing a bunch of times, possibly with different values. A few years after I had written that color program, I found it again and realized that I could write it as :

  10 for I = 1 to 15
  20 color I
  30 print I
  40 next I
  

  It still took me a few more years to sort out the meaning of WHILE..WEND, though.