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• avfilter/palettegen : use AV_QSORT()

  25 février 2015, par Clément Bœsch

  avfilter/palettegen : use AV_QSORT()
  This makes the sorting of the colors along an axis (r, g or b)
  
  predictible, and thus testable under FATE. The performance is not really
  
  an issue here since the function is called only once at the end and will
  
  need to sort very small number of entries, so an alternative would be to
  
  make the sorting functions (see DECLARE_CMP_FUNC()) fallback on another
  
  axis in case of equality. This approach was actually simpler.
  I don’t know if there is any advantage in using a multidimensional sort,
  
  but it will affect the final palette one way or another.
  

  • [DH] libavfilter/vf_palettegen.c

• Transparent PNG created in Imagemagick drawn as opaque in FFMPEG

  23 février 2015, par user2711915

  I am trying to script the creation of videos using ImageMagick to create some overlays which are then placed on top of a video.

  If I try to use the image created by ImageMagick directly the transparency is drawn as opaque.

  I have created a transparent PNG using ImageMagick draw commands. When loaded into GIMP and examined, the PNG has an alpha channel and each transparent pixel appears to have transparency : RGBA = 0,0,0,0

  This image when then used as an overlay in ffmpeg just has an opaque black background in the video.

  If I export the image again from GIMP then the file looks identical, but in the video just appears as a solid blue (the colour of the drawings in the overlay image).

  I can fix this by taking the overlay image, loading it in GIMP and then selecting all and creating a new image from the clipboard and exporting that (using exactly the same settings as when I re-exported before without creating a new file) and it will then work exactly as desired, showing the non-transparent portions of the overlay and not showing transparent parts.

  KEY QUESTION :

  How can I either script the conversion that somehow occurs when creating a new file in GIMP, or (much better) not have it go wrong in the first place ?

  Here are the two files :

  BROKEN :
  
  WORKS :
  
  What is the difference ?

• avformat/mov : Add simple ACLR atom reading to set the color range of the incomming...

  19 février 2015, par Kevin Wheatley

  avformat/mov : Add simple ACLR atom reading to set the color range of the incomming track for codec’s like DNxHD that utilise AVID’s proprietary atom.
  On input ACLR will be used to set colour range no matter which codec
  
  it is associated with.
  
  No change for when it will be output.
  Rework mov_read_extradata function to allow detection of truncated
  
  atom reads by callers.
  Signed-off-by : Michael Niedermayer <michaelni@gmx.at>
  

  • [DH] libavformat/mov.c