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• Writing linear float range to openEXR turns out non linear

  3 avril 2022, par Chryfi

  I am writing the linearized depth buffer of a game to openEXR using FFmpeg. Unfortunately, FFmpeg does not adhere to the openEXR file specification fully (like allowing unsigned integer for one channel) so I am writing one float channel to openEXR, which is put into the green channel with this command -f rawvideo -pix_fmt grayf32be -s %WIDTH%x%HEIGHT% -r %FPS% -i - -vf %DEFVF% -preset ultrafast -tune zerolatency -qp 6 -compression zip1 -pix_fmt gbrpf32le %NAME%_depth_%d.exr.

  


  The float range is from 0F to 1F and it is linear. I can confirm that the calculation and linearization is correct by testing 16 bit integer (per pixel component) PNG in Blender compositor. The 16 bit integer data is written like this short s = (short) (linearzieDepth(depth) * (Math.pow(2,16) - 1)) whereas for float the linearized value is directly written to OpenEXR without multiplying with a value.

  


  However, when viewing the openEXR file it doesn't have the same "gradient" as the 16 bit png... when viewing them side by side, it appears as if the values near 0 are not linear, and they are not as dark as they should be like in the 16 bit png.
(And yes, I set the image node to linear), and comparing it with 3d tracking data from the game I cant reproduce the depth and cant mask things using the depth buffer where as with the png I can.

  


  How is it possible for a linear float range to turn out so different to a linear integer range in an image ?

  


• (ffmpeg) : Failed to read frame size : Could not seek to 1026

  24 mai 2021, par UserUNP

  I was trying to convert Midi files to Mp3 files using timidity and ffmpeg
using this command

  


  python -m timidity play.mid -Ow -o - | ffmpeg -i - -acodec libmp3lame -ab 64k play.mp3


  


  so I can use it in my Discord bot, but whenever I execute the command, it always returns this error that I couldn't understand

  


  [mp3 @ 0x56226d7e0440] Format mp3 detected only with low score of 1, misdetection possible!
[mp3 @ 0x56226d7e0440] Failed to read frame size: Could not seek to 1026.
play.mp3: Invalid argument


  


  If you have any idea to what this means or how can I fix it then please give me an Answer, thanks !

  


• vulkan_shaderc : fix error reporting for certain errors

  23 juillet 2024, par Lynne

  vulkan_shaderc : fix error reporting for certain errors
  The issue is that shaderc_result_get_num_errors may sometime
  
  return 0 even when shaderc_result_get_compilation_status returns
  
  a non-zero error code.
  
  Since we use the result from the former, override the status
  
  if it returned 0.
  

  • [DH] libavfilter/vulkan_shaderc.c