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• 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

  


• FFMPEG - Output video not playing after effect

  11 mai 2021, par D.B.

  I am using FFMPEG for giving effects to video.

  


  I tried to give effect to video using below commands.

  


  ffmpeg -i Input1.mp4 -i Input2.mp4 -filter_complex xfade=transition=circleopen:duration=5:offset=0 OutPutVideo.mp4


  


  My command runs fine but output video is not running even in VLC media player.

  


  I got these commands from location :
https://ottverse.com/crossfade-between-videos-ffmpeg-xfade-filter/

  


  My videos are at location :
https://drive.google.com/drive/folders/1SLsrRUjyGH3eM7Oe3cptU_YPkga7EoCO?usp=sharing

  


  Please advise what is the issue ?

  


  Kind Regards,

  


• How to debayer bmp image with FFMpeg ? (.exe file)

  19 mai 2021, par Aleksey Timoshchenko

  I have an bayer image .bmp I would like to debayer with FFMpeg, I thought that possibly FFMpeg knows to debayer it by default so I tried to use such a very simple query

  


  ffmpeg -i input.bmp output.png


  


  but output.png looks gray, so ffmpeg doesn't apply debayer automatically. I tried to figure out if is it possible with ffmpeg, but there is almost nothing about it on google.

  


  Image example (it is too large to upload it here) : https://drive.google.com/file/d/1V8HwOuIo9PBX3ix0eKFQFGimskU_H0mN/view?usp=sharing

  


  How to do it ?

  


  UPD

  


  this is what I tried to do

  


  ffmpeg -y -i D:\Buffer\Bayer\Time0000000_img.bmp -pix_fmt gray D:\Buffer\Bayer\bmp\test11.y -hide_banner
ffmpeg -y -pixel_format bayer_rggb8 -video_size 4104x3006 -i D:\Buffer\Bayer\bmp\test11.y D:\Buffer\Bayer\bmp\result1.png -hide_banner


  


  and there is an error I get

  


  Input #0, image2, from 'D:\Buffer\Bayer\bmp\test11.y':
  Duration: 00:00:00.04, start: 0.000000, bitrate: 1013196 kb/s
    Stream #0:0: Video: rawvideo ([186]RG[8] / 0x84752BA), bayer_rggb8, 4104x3006, 25 tbr, 25 tbn, 25 tbc
Stream mapping:
  Stream #0:0 -> #0:0 (rawvideo (native) -> png (native))
Press [q] to stop, [?] for help
[rawvideo @ 0000027da39d3f80] Invalid buffer size, packet size 5065984 < expected frame_size 12336624
Error while decoding stream #0:0: Invalid argument
Output #0, image2, to 'D:\Buffer\Bayer\bmp\result1.png':
  Metadata:
    encoder         : Lavf58.29.100
    Stream #0:0: Video: png, rgb24, 4104x3006, q=2-31, 200 kb/s, 25 fps, 25 tbn, 25 tbc
    Metadata:
      encoder         : Lavc58.54.100 png
frame=    0 fps=0.0 q=0.0 Lsize=N/A time=00:00:00.00 bitrate=N/A speed=   0x
video:0kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown
Output file is empty, nothing was encoded (check -ss / -t / -frames parameters if used)
Conversion failed!


  


  if I change the resolution to 1920x1080 like this

  


  ffmpeg -y -pixel_format bayer_rggb8 -video_size 1920x1080 -i D:\Buffer\Bayer\bmp\test11.y D:\Buffer\Bayer\bmp\result1.png -hide_banner


  


  I don't get an error, but the output is wrong