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• Can't compile project with ffmpeg-light

  27 octobre 2016, par wowofbob

  Compilation of any project which uses openFile function from Codec.FFmpeg.Decode fails with error :

  Couldn't match type ‘GHC.IO.Exception.IOException’ with ‘[Char]’
           arising from a functional dependency between:
             constraint ‘mtl-2.2.1:Control.Monad.Error.Class.MonadError
                           String IO’
               arising from a use of ‘openFile’
             instance ‘mtl-2.2.1:Control.Monad.Error.Class.MonadError
                         GHC.IO.Exception.IOException IO’
               at <no location="location" info="info"></no>

  As an example, compilation of this fails :

  openVideoFile :: String -> IO ()
  
  openVideoFile filePath = do
  
  
  
    initFFmpeg
  
  
  
    avFmtCtx <- openFile filePath
  
  
  
    return ()

  I guess the reason is that there is no ready instance of MonadError String IO. But, when I add a dummy instance like this :

  instance MonadError String IO where
  
    throwError _   = undefined
  
    catchError _ _ = undefined

  I’m getting another error :

  Functional dependencies conflict between instance declarations:
 instance MonadError String IO
   -- Defined at src/Video/Play/Base.hs:20:10
 instance [safe] MonadError GHC.IO.Exception.IOException IO
   -- Defined in ‘Control.Monad.Error.Class’

  I don’t know how to force compiler to use MonadError String IO instace here.

  • Should I assure GHC that my instance is better ?
  • Do I have a wrong environment setup ? I’m using ffmpeg-light clone from here and resolver lts-7.2. Host OS is Ubuntu.
  • There is commit which replaces import of Control.Monad.Error.Class by Control.Monad.Except. But, Control.Monad.Error.Class is still used in Codec.FFmpeg.Common. First time I thought it caused a problem. But it turns out that Control.Monad.Except just re-exports MonadError class from Control.Monad.Error.Class. So, it’s not a problem.

• How do I get FFMPEG Progress in order to create a progress bar ?

  4 juillet 2022, par polandeer

  I'm trying to create a simple GUI for ffmpeg but am having problems getting the progress of a command. I'm using PySide as the GUI toolkit and I'm also using python3. I'm using QProcess to run the command and would just like to be able to create a progress bar.

  


  EDIT : Preferably I'd like to use QProgressDialog : http://www.pyside.org/docs/pyside/PySide/QtGui/QProgressDialog.html

  


• Create video vom rendered OpenGL frames

  10 mai 2012, par MrMuh

  i am searching for a way to create a video from a row of frames i have rendered with OpenGL and transfered to ram as int array using the glGetTexImage function. is it possible to achieve this directly in ram ( 10 secs video) or do i have to save each frame to the harddisk and encode the video afterwards ?

  i have found this sample http://cekirdek.pardus.org.tr/ ismail/ffmpeg-docs/api-example_8c-source.html in an other SO question but is this still the best way to do it ?