diff --git a/demo/Transcode.hs b/demo/Transcode.hs
new file mode 100644
--- /dev/null
+++ b/demo/Transcode.hs
@@ -0,0 +1,53 @@
+module Main where
+
+import System.Environment (getArgs)
+import qualified Codec.FFmpeg as FF
+import qualified Codec.FFmpeg.Encode as FF
+import Codec.Picture
+
+type Frame = Image PixelRGB8
+
+usage :: String
+usage =
+  unlines [ "Usage: transcode inputFile outputFile [outputFormat] [outputWidth] [outputHeight]"
+          , "  Example: transcode rtmp://localhost/app/one rtmp://localhost/app/two flv 640 480"
+          , ""
+          , "  Copies the content from inputFile to outputFile using H264."
+          , "  Defaults:"
+          , "  outputFormat=flv"
+          , "  outputWidth=640"
+          , "  outputHeight=480"
+          ]
+
+main :: IO ()
+main = do
+  args <- getArgs
+  FF.initFFmpeg
+  FF.setLogLevel FF.avLogDebug
+  case args of
+    [from, to] -> copy from to "flv" 640 480
+    [from, to, format, w, h] -> copy from to format (read w) (read h)
+    _ -> error usage
+
+copy :: FilePath -> FilePath -> String -> Int -> Int -> IO ()
+copy from to format w h = let ep = (FF.defaultH264 (fromIntegral w) (fromIntegral h))
+                                   { FF.epFormatName = Just format } in do
+  (getFrame, cleanup) <- FF.imageReader (FF.File from)
+  putFrame <- FF.imageWriter ep to
+  loop getFrame cleanup putFrame (\x -> return x)
+
+loop :: IO (Maybe Frame)
+     -> IO cleanup
+     -> (Maybe Frame -> IO ())
+     -> (Frame -> IO Frame)
+     -> IO cleanup
+loop getFrame finishReading putFrame editFrame = do
+  maybeFrame <- getFrame
+  case maybeFrame of
+    Nothing -> do
+      putFrame Nothing
+      finishReading
+    Just x -> do
+      x' <- editFrame x
+      putFrame (Just x')
+      loop getFrame finishReading putFrame editFrame
diff --git a/ffmpeg-light.cabal b/ffmpeg-light.cabal
--- a/ffmpeg-light.cabal
+++ b/ffmpeg-light.cabal
@@ -1,5 +1,5 @@
 name:                ffmpeg-light
-version:             0.12.0
+version:             0.12.0.1
 synopsis:            Minimal bindings to the FFmpeg library.
 
 description:         Stream frames from an encoded video, or stream frames to
@@ -48,6 +48,11 @@
   default:     False
   manual:      True
 
+flag BuildTranscodeDemo
+  description: Build transcode demo executable
+  default:     False
+  manual:      True
+
 library
   exposed-modules:     Codec.FFmpeg,
                        Codec.FFmpeg.Common,
@@ -61,7 +66,7 @@
                        Codec.FFmpeg.Internal.Debug,
                        Codec.FFmpeg.Internal.Linear
   build-tools:         hsc2hs
-  build-depends:       base >=4.6 && < 4.10,
+  build-depends:       base >=4.6 && < 4.11,
                        either,
                        exceptions,
                        vector >= 0.10.9 && < 0.13,
@@ -108,3 +113,14 @@
   main-is:           VPlay.hs
   default-language:  Haskell2010
   ghc-options:      -Wall -O2
+
+executable transcode
+  if !flag(BuildTranscodeDemo)
+    buildable:      False
+  build-depends:    base < 5, JuicyPixels
+  if flag(BuildTranscodeDemo)
+    build-depends:  ffmpeg-light
+  hs-source-dirs:   demo
+  main-is:          Transcode.hs
+  default-language: Haskell2010
+  ghc-options:      -Wall
diff --git a/src/Codec/FFmpeg/Encode.hs b/src/Codec/FFmpeg/Encode.hs
--- a/src/Codec/FFmpeg/Encode.hs
+++ b/src/Codec/FFmpeg/Encode.hs
@@ -60,8 +60,8 @@
   av_guess_format :: CString -> CString -> CString -> IO AVOutputFormat
 
 foreign import ccall "avformat_alloc_output_context2"
-  avformat_alloc_output_context :: Ptr AVFormatContext -> AVOutputFormat
-                                -> CString -> CString -> IO CInt
+  avformat_alloc_output_context2 :: Ptr AVFormatContext -> AVOutputFormat
+                                 -> CString -> CString -> IO CInt
 
 foreign import ccall "avformat_new_stream"
   avformat_new_stream :: AVFormatContext -> AVCodec -> IO AVStream
@@ -117,17 +117,21 @@
                  -- during the palettization process. This will
                  -- improve image quality, but result in a larger
                  -- file.
+                 , epFormatName :: Maybe String
+                 -- ^ FFmpeg muxer format name. If 'Nothing', tries to infer
+                 -- from the output file name. If 'Just', the string value
+                 -- should be the one available in @ffmpeg -formats@.
                  }
 
 -- | Use default parameters for a video of the given width and
 -- height, forcing the choice of the h264 encoder.
 defaultH264 :: CInt -> CInt -> EncodingParams
-defaultH264 w h = EncodingParams w h 30 (Just avCodecIdH264) Nothing "medium"
+defaultH264 w h = EncodingParams w h 30 (Just avCodecIdH264) Nothing "medium" Nothing
 
 -- | Use default parameters for a video of the given width and
 -- height. The output format is determined by the output file name.
 defaultParams :: CInt -> CInt -> EncodingParams
-defaultParams w h = EncodingParams w h 30 Nothing Nothing ""
+defaultParams w h = EncodingParams w h 30 Nothing Nothing "" Nothing
 
 -- | Determine if the bitwise intersection of two values is non-zero.
 checkFlag :: Bits a => a -> a -> Bool
@@ -203,13 +207,19 @@
 
 -- | Allocate an output context inferring the codec from the given
 -- file name.
-allocOutputContext :: FilePath -> IO AVFormatContext
-allocOutputContext fname = do
+allocOutputContext :: Maybe String -> FilePath -> IO AVFormatContext
+allocOutputContext outputFormat fname =
+  let
+    withFormat = case outputFormat of
+      Just f -> withCString f
+      Nothing -> (\f -> f nullPtr)
+  in do
   oc <- alloca $ \ocTmp -> do
           r <- withCString fname $ \fname' ->
-                 avformat_alloc_output_context
-                   ocTmp (AVOutputFormat nullPtr)
-                   nullPtr fname'
+                 withFormat $ \format ->
+                   avformat_alloc_output_context2
+                     ocTmp (AVOutputFormat nullPtr)
+                     format fname'
           when (r < 0)
                (error "Couldn't allocate output format context")
           peek ocTmp
@@ -305,7 +315,7 @@
 frameWriter :: EncodingParams -> FilePath
             -> IO (Maybe (AVPixelFormat, V2 CInt, Vector CUChar) -> IO ())
 frameWriter ep fname = do
-  oc <- allocOutputContext fname
+  oc <- allocOutputContext (epFormatName ep) fname
   (st,ctx) <- initStream ep oc
 
   dstFmt <- getPixelFormat ctx