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• Haskell - Converting multiple images into a video file - ffmpeg-lights' frameWriter-function fails

  26 octobre 2017, par oRole

  Situation
  Currently I am working on an application for image-processing that uses ffmpeg-light to fetch all the frames of a given video-file so that the program afterwards can apply grayscaling, as well as edge detection alogrithms to each of the frames.

  With the help of friendly stackoverflowers I was able to set up a method capable of converting several images into one video file using ffmpeg-lights’ frameWriter function.

  Problem
  The application runs fine to the moment it hits the frameWriterfunction and I don’t really know why as there are no errors or exception-messages thrown. (OS : Win 10 64bit)

  What did I try ?
  I tried..
  
   different versions of ffmpeg (from 3.2 to 3.4).
  
   ffmpeg.exe using the command line to test if there are any codecs missing, but any conversion I tried worked.
  
   different EncodingParams-combinations : like.. EncodingParams width height fps (Nothing) (Nothing) "medium"
  

  Question
  Unfortunately, none of above worked and the web lacks on information to that specific case. Maybe I missed something essential (like ghc flags or something) or made a bigger mistake within my code. That is why I have to ask you : Do you have any suggestions/advice for me ?

  Haskell Packages
  
   ffmpeg-light-0.12.0
  
   JuicyPixels-3.2.8.3
  

  Code
  

  {--------------------------------------------------------------------------------------------
  
   Applies "juicyToFFmpeg'" and "getFPS" to a list of images and saves the output-video
  
   to a user defined location.
  
  ---------------------------------------------------------------------------------------------}     
  
  saveVideo :: String -> [Image PixelYA8] -> Int -> IO ()
  
  saveVideo path imgs fps = do
  
           -- program stops after hitting next line --
  
           frame <- frameWriter ep path
  
           ------------------------------------------------
  
           Prelude.mapM_ (frame . Just) ffmpegImgs 
  
           frame Nothing
  
           where ep = EncodingParams width height fps (Just avCodecIdMpeg4) (Just avPixFmtGray8a) "medium"
  
                 width      = toCInt $ imageWidth  $ head imgs
  
                 height     = toCInt $ imageHeight $ head imgs
  
                 ffmpegImgs = juicyToFFmpeg' imgs
  
                 toCInt x   = fromIntegral x :: CInt
  
  
  
  {--------------------------------------------------------------------------------------------
  
   Converts a single image from JuicyPixel-format to ffmpeg-light-format. 
  
  ---------------------------------------------------------------------------------------------}      
  
  juicyToFFmpeg :: Image PixelYA8 -> (AVPixelFormat, V2 CInt, Vector CUChar)
  
  juicyToFFmpeg img = (avPixFmtGray8a, V2 (toCInt width) (toCInt height), ffmpegData)
  
                    where toCInt   x   = fromIntegral x :: CInt
  
                          toCUChar x   = fromIntegral x :: CUChar
  
                          width        = imageWidth img
  
                          height       = imageHeight img
  
                          ffmpegData   = VS.map toCUChar (imageData img)
  
  
  
  {--------------------------------------------------------------------------------------------
  
   Converts a list of images from JuicyPixel-format to ffmpeg-light-format. 
  
  ---------------------------------------------------------------------------------------------}                        
  
  juicyToFFmpeg' :: [Image PixelYA8] -> [(AVPixelFormat, V2 CInt, Vector CUChar)]
  
  juicyToFFmpeg' imgs = Prelude.foldr (\i acc -> acc++[juicyToFFmpeg i]) [] imgs
  
  
  
  {--------------------------------------------------------------------------------------------
  
   Simply calculates the FPS for image-to-video conversion.
  
   -> frame :: (Double, DynamicImage) where Double is a timestamp of when it got extracted 
  
  ---------------------------------------------------------------------------------------------}
  
  getFPS :: [(Double, DynamicImage)] -> Int
  
  getFPS frames = div (ceiling $ lastTimestamp - firstTimestamp) frameCount :: Int
  
                where firstTimestamp = fst $ head frames
  
                      lastTimestamp  = fst $ last frames
  
                      frameCount     = length frames

• Alternative to sws_scale

  19 décembre 2012, par Hrishikesh_Pardeshi

  I am performing encoding of the captured windows screen with x264 using libavcodec. Since, the input is RGB, i am converting it to YUV to make it compatible with x264. I am using the sws_scale function for the same.
  My question is if there is any alternate for this function since i don't need any scaling to be done in my case. Also, it would be useful if someone could throw light on the workflow of this function.

  P.S : I am assuming x264 operates only in YUV color space. If this assumption is incorrect, please inform me on the same.

  Thanks in advance.

• Live Photos on android implementation ?

  18 novembre 2016, par mohit gupta

  I have come up with a project which implements LIVE Photos capturing on android and I will hopefully make it open sourced,Spoiler : it takes a 1.5 second shot before and after you click the pic and combines them and make the video , While i tried it I was unable to do it with MediaRecorder in android , I even experimented with FFMPEG it just does not works . Anyone has any idea or a little light so i can follow and implement this.My min Api support is 16