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• avformat/matroskadec : Improve invalid length error handling

  17 mai 2019, par Andreas Rheinhardt

  avformat/matroskadec : Improve invalid length error handling
  1. Up until now, the error message for EBML numbers whose length exceeds
  
  the limits imposed upon them because of the element's type did not
  
  distinguish between known-length and unknown-length elements. As a
  
  consequence, the numerical value of the define constant
  
  EBML_UNKNOWN_LENGTH was emitted as part of the error message which is
  
  of course not appropriate. This commit changes this by adding error
  
  messages designed for unknown-length elements.
  2. We impose some (arbitrary) sanity checks on the lengths of certain
  
  element types ; these checks were conducted before the checks depending
  
  on whether the element exceeds its containing master element. Now the
  
  order has been reversed, because a failure at the (formerly) latter
  
  check implies that the file is truly erroneous and not only fails our
  
  arbitrary length limit. Moreover, this increases the informativeness of
  
  the error messages.
  3. Furthermore, the error message in general has been changed by replacing
  
  the type of the element (something internal to this demuxer and
  
  therefore suitable as debug output at best, not as an error message
  
  intended for ordinary users) with the element ID. The element's position
  
  has been added, too.
  4. Finally, the length limit for EBML_NONE elements has been changed so
  
  that all unknown-length elements of EBML_NONE-type trigger an error.
  
  This is done because unknown-length elements can't be skipped and need
  
  to be parsed, but there is no syntax to parse available for EBML_NONE
  
  elements. This is done in preparation for a further patch which allows
  
  more unknown-length elements than just clusters and segments.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavformat/matroskadec.c

• lavu/opt : fix range check logic in set_format()

  16 décembre 2013, par Stefano Sabatini

  lavu/opt : fix range check logic in set_format()
  In particular, allow to reject undefined values. Previously the code
  
  was only accepting values in the range -1 .. NB_FORMATS-1.
  

  • [DH] libavutil/opt.c

• Using ffmpeg to create a video from a sequence of TGA images, with a depth of field blur effect sourced from the TGA's alpha channel

  19 mars 2016, par vpvp

  I’m working on turning a sequence of TGA images into a video using ffmpeg. I want the video to have a depth of field blur effect. The alpha channel of each TGA contains a depth-mask, where black=close and white=far. I want to use this info to add DOF blur to the final output of that frame. After searching, the closest answer I could find was this
  http://superuser.com/questions/916431/ffmpeg-filter-to-boxblur-and-greyscale-a-video-using-alpha-mask, but it is for a static dof-mask. The DOF mask I would be using is obviously changing every frame, and an alpha channel instead of a seperate png.

  Here is my current cmd line

  ffmpeg -framerate 60 -i image.%10d.tga -c:v libx264 -preset slow -crf 0 -c:a copy -pix_fmt yuv420p output0.mp4

  It seems the answer would involve some use of alphamerge/alphaextract/boxblur, but I’m brand new to ffmpeg so I don’t know how to formulate the command.

  Thanks in advance.