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• avformat : add vapoursynth wrapper

  27 avril 2018, par wm4

  avformat : add vapoursynth wrapper
  This can "demux" .vpy files. Autodetection of .vpy scripts is
  
  intentionally not done, because it would be a major security issue. You
  
  need to force the format, for example with "-f vapoursynth" for the
  
  FFmpeg CLI tools.
  Some minor code copied from other LGPL parts of FFmpeg.
  I did not find a good way to test a few of the more obscure VS features,
  
  like VFR nodes, compat pixel formats, or nodes with dynamic size/format
  
  changes. These can be easily implemented on demand.
  

  • [DH] configure
  • [DH] libavformat/Makefile
  • [DH] libavformat/allformats.c
  • [DH] libavformat/vapoursynth.c
  • [DH] libavformat/version.h

• fftools/cmdutils : split stream specifier parsing and matching

  7 août 2024, par Anton Khirnov

  fftools/cmdutils : split stream specifier parsing and matching
  This approach has the major advantage that only parsing can fail (due to
  
  a malformed specifier or memory allocation failure). Since parsing is
  
  done generically, while matching is per-option, this will allow to
  
  remove substantial amounts of error checking code in following commits.
  The new code also explicitly allows stream specifiers to be followed by
  
  additional characters, which should allow cleaner handling of optional
  
  maps, i.e. -map <stream_specifier> ?, which is currently implemented in a
  
  hacky way that breaks when the stream specifier itself contains the ' ?'
  
  character (this can happen when matching metadata). It will also allow
  
  further extending the syntax, which will be useful in following commits.
  This introduces some minor behaviour changes :
  
  * Matching metadata tags now requires the ' :' character in keys or
  
    values to be escaped. Previously it could not be present in keys, and
  
    would be used verbatim in values. The change is required in order to
  
    know where the value terminates.
  
  * Multiple stream types in a single specifier are now rejected - such a
  
    specifier makes no sense.
  
  * Non-existent stream group ID or index is now ignored with a warning
  
    rather than causing a failure. This is consistent with program
  
    handling and is required to make matching fail-free.
  

  • [DH] fftools/cmdutils.c
  • [DH] fftools/cmdutils.h

• How to put a png onto an mp4/gif using imagemagick ?

  24 juillet 2022, par Harrison

  TLDR : How do I convert an MP4 to GIF without sacrificing quality ? How can I lay a PNG on a GIF without sacrificing quality ? And how to get rid of the flicker from combining them ?

  


  So I have an MP4 that is 3000x3000 and a PNG that is 1000x1000.

  


  The end result that I want is a GIF that is 1000x1000 where the PNG is layered on top of the MP4 as a background.

  


  These are the step I tried and the issues I am running into. Mainly the issues I am running into are a loss in quality.

  


  MP4 to GIF :

  


  


  1. I have converted the MP4 to a gif with ffmpeg -i background.mp4 background.gif. Result : A major loss of quality in the gif.

     


  


  2. Instead of that - I tried an online converter. Works better but would like to do it on my own. But I will use this GIF from the online converter in the next examples. Still a slight loss of quality but not near as bad.

     


  


  3. I have sized down my gif using convert temporary.gif -coalesce -resize 1000x1000 smaller.gif. (Have also tried with specifying the -size 3000x3000 but no difference really.) Another minor loss of quality there.

     


  


  


  PNG ontop of GIF - Trial 1

  


  

  1. I have converted my PNG to a single page GIF with convert front.png front.gif (Along with some other options). Loses quality, anything that fades or is semi see through gets turned into a solid pixel.

  


  2. Duplicated this page a bunch of times to match number of pages in my background gif using convert front.gif front.gif front.gif multiple times.

  


  3. Merged background and front together with convert background.gif -coalesce null: front.gif -layers composite both.gif. Little more lose of quality and some flickering on the foreground..? Tried some other variations but thats the best I got.

  


  


  PNG on GIF - Trial 2

  


  

  1. Instead of making a GIF of the PNG, I am just using the original PNG with the background.gif like this convert smaller.gif -coalesce null: front.png -layers composite -layers optimize both.gif. This one comes out weird. The from image is very different looking in color and flickery. Not gonna work.

  


  2. Tried without optimization. convert smaller.gif -coalesce null: front.png -layers composite test.gif. This on is closer. The foreground looks great, but is just flickery still ! Again the background is not great but it doesn't seem to have much more impact from after the original mp4 conversion. Did this without -coalesce and still get the same output.

  


  


  The best I can get is a decent front image with details preserved - but flickery. On top of a lossy background.

  


  How can I go about doing this with imagemagick or some other library ?