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• Can't call FFMPEG from CMD after installing chocolatey+ffmpeg on windows docker container

  19 novembre 2022, par Adil Abdul Rahman

  I have a C# code that is dependent on FFMPEG via CMD/powershell. I am trying to run CLI ffmpeg via a C# code in a windows container with sdk:6.0-windowsservercore-ltsc2022. I found this guide(use 12ft.io to bypass paywall) that says to install chocolatey and then install ffmpeg through that like so :

  


  USER ContainerAdministrator
EXPOSE 3389/tcp


RUN powershell.exe \
  Set-ExecutionPolicy Bypass -Scope Process -Force; \
  iwr -Uri 'https://community.chocolatey.org/install.ps1' -UseBasicParsing -OutFile $home/choco_install.ps1; \
  powershell $home/choco_install.ps1; \
  del $home/choco_install.ps1; \
  choco; \
  exit 0;
  
RUN powershell.exe \
  powershell choco install chocolatey-compatibility.extension -y --force; \
  powershell choco install chocolatey-core.extension -y --force; \
  powershell choco install ffmpeg-full -y --force; \
  ffmpeg; \
  exit 0;


  


  ( I am using this guide for C# dockerfile )

  


  And my C# Code :

  


  string command = $"/C ffmpeg -i \"{VideoUri}\" -vn -ac 1 {outputName}.mp3";
Process.Start("cmd.exe", command).WaitForExit();


  


  But I am running into some trouble. My C# code throws this error :

  


  'ffmpeg' is not recognized as an internal or external command, operable program or batch file.

  


  I have tried calling FFMPEG from the dockerfile to test if it has installed but it just returns this :

  


  Step 5/17 : RUN powershell.exe   powershell choco install chocolatey-compatibility.extension -y --force;   powershell choco install chocolatey-core.extension -y --force;   powershell choco install ffmpeg-full -y --force;   ffmpeg;   exit 0;
 ---> Using cache
 ---> 83b2941d03e6


  


• How can I change the fps of video without restarting the video stream, which is being played by ffmpeg command ?

  7 juin 2018, par Mehta Naisargi Rajeshbhai

  I am playing the video (.mp4) in VLC by this below command in terminal :

  ffmpeg -i input_file.mp4 -crf 18 -c:a copy -r 60 http://localhost:1234/feed1.ffm

  Currently it is 60 fps.

  Now I want to change the fps during the playback of video file, so is it possible to change the fps during runtime without restarting/breaking the video using FFmpeg ? And if it is possible then please guide me.

• 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 ?