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• af_hdcd : Add analyze mode

  7 août 2016, par Burt P

  af_hdcd : Add analyze mode
  A new mode, selected by filter option, to aid in analysis of HDCD
  
  encoded audio. In this mode the audio is replaced by a solid tone and
  
  the amplitude is adjusted to signal some specified aspect of the process.
  
  The output file can be loaded in an audio editor alongside the original,
  
  where the user can see where different features or states are present.
  Signed-off-by : Burt P <pburt0@gmail.com>
  

  • [DH] doc/filters.texi
  • [DH] libavfilter/af_hdcd.c

• lavu/channel_layout : change av_get_channel_layout() behavior at the next bump

  4 octobre 2013, par Stefano Sabatini

  lavu/channel_layout : change av_get_channel_layout() behavior at the next bump
  The new syntax is preferred since it allows backward syntax compatibility
  
  with libswr when switching to the new option handling code with
  
  AV_OPT_TYPE_CHANNEL_LAYOUT.
  With the new parser the string :
  
  1234
  is interpreted as a channel layout mask, rather than as a number of
  
  channels, and thus it’s compatible with the current way to set a channel
  
  layout as an integer (e.g. for the icl and ocl options) making use of
  
  integer option values.
  ff_get_channel_layout() with compat=0 will be used in the
  
  AV_OPT_TYPE_CHANNEL handler code.
  The user is encouraged to switch to the new forward compatible syntax,
  
  which requires to put a trailing "c" when specifying a layout as a number
  
  of channels.
  

  • [DH] libavutil/channel_layout.c
  • [DH] libavutil/channel_layout.h
  • [DH] libavutil/internal.h
  • [DH] libavutil/version.h

• ffmpeg : Create a fake shadow below alpha channel webm/png sequence

  6 mai 2021, par Beneos Battlemaps

  Purpose : I'd like to render out animated 3D meshes as png sequence to use them as animated tokens for virtual tabletop games. To make the mesh looks more natural I'd like to create a fake show beneath the actual token.

  


  Problem : I have a png sequence 1 (as well as a webm file created with ffmpet out of this png sequence if it makes it easier) with alpha channel. To create the webm I use :
ffmpeg -framerate 24 -f image2 -i Idle_Top.%04d.png -c:v libvpx-vp9 -crf 25 -pix_fmt yuva420p Idle_Top.webm (If its relevant). I'd like to render out the png sequence to a webm file that have the current images as well as the transparent shadow beneath the token combined.

  


  Possible workflow : I think a good way to achieve the wanted shadow effect is to use the alpha channel image as a mask on a black picture with the same resolution as the source image 2. Then you have a complete black version of the image. Then you need to place this image beneath the colored image and make a offset of 10px left and 10px down to create the ilusion of perspective 3. At the end the black image below the colored image must have a transparency as well ( 30% visibility should be enough) 4.

  


  Workflow overview

  


  Assets : I've put the webm file and the png files on my gDrive https://drive.google.com/drive/folders/1wznGaPwhKc2UyPpSZBSISa1gs3oixsHR?usp=sharing

  


  Though I work with ffmpeg on a regular basis I have no clue where to start. Can you please help me out with this interesting problem ?

  


  Best regards
Ben