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• Fix destination row striding in altivec_yuv2_bgr24.

  6 juillet 2012, par Pavel Koshevoy

  Fix destination row striding in altivec_yuv2_bgr24.

• How to find mp4 metadata with ffmpeg-light in haskell ?

  21 décembre 2015, par Noughtmare

  I’m using ffmpeg-light, JuicyPixels and gloss to display a video with Haskell. I want to find the metadata of videos I’m playing automatically, but I have not yet found a way to do so.

  I would like to access metadata like the resolution and the framerate of the video.

  Can you help me ?

  EDIT :

  I have tried your solution @CRDrost, but the video is now playing at 2x normal speed. I assume the function imageReaderTime is giving the wrong timestamps.

  EDIT 2 :

  The abnormal playing speed is a bug in the ffmpeg-light library. I’ve opened an issue at the github repository.

  My updated code :

  import Graphics.Gloss
  
  import Codec.FFmpeg
  
  import Codec.FFmpeg.Juicy
  
  import Codec.Picture
  
  import Control.Applicative
  
  import Data.Maybe
  
  import Graphics.Gloss.Juicy
  
  import Control.Monad
  
  -- import System.IO.Unsafe (unsafePerformIO)-- for debugging purposes
  
  
  
  resolution :: (Int,Int)
  
  resolution = (640, 360)
  
  
  
  frameCount :: Int
  
  frameCount = 100
  
  
  
  main :: IO ()
  
  main = do
  
      initFFmpeg
  
      (getFrame, cleanup) <- imageReaderTime "big_buck_bunny.mp4"
  
      frames <- replicateM frameCount $ nextFrame getFrame
  
      cleanup
  
      animate (InWindow "Nice Window" resolution (10,10)) white (frameAt frames)
  
  
  
  nextFrame :: IO (Maybe (Image PixelRGB8, Double)) -> IO (Picture, Float)
  
  nextFrame getFrame = mapSnd realToFrac . mapFst fromImageRGB8 . fromJust <$> getFrame
  
  
  
  frameAt :: [(Picture, Float)] -> Float -> Picture
  
  frameAt list time = fst . head . dropWhile ((< time) . snd) $ list
  
  
  
  mapFst :: (a -> c) -> (a, b) -> (c, b)
  
  mapFst f (a, b) = (f a, b) -- applies f to first element of a 2-tuple
  
  
  
  mapSnd :: (b -> c) -> (a, b) -> (a, c)
  
  mapSnd f (a, b) = (a, f b) -- applies f to the second element of a 2-tuple

• Mapping streams by language in FFmpeg

  8 décembre 2016, par ffmpeg123

  I have lots of files with multiple audio and subtitle languages, however the track numbers aren’t consistent (the English audio stream isn’t always the first) so using a command such as :

  ffmpeg -i "input.mkv" -map 0 -map -0:a:1 -c:v copy -c:a copy "output.mkv"

  doesn’t yield expected results. After searching around I discovered it was possible to map streams based on language with this command :

  ffmpeg -i "input.mkv" -map 0 -map -0:m:language:eng -c:v copy -c:a copy "output.mkv"

  However -map -0:m:language:eng will remove all tracks with the English language flag. To keep the subtitle tracks you can use -map 0:s this is a good solution however, I want to know if it’s possible to only map audio streams based on language.