Initial control for logging verbosity

This doesn't do anything fancy; it just allows Haskell code to control
the log level.

Related to Issue #19

CHANGELOG.md

@@ -1,6 +1,8 @@
 # 0.11.0
 
 * Query stream duration (Matthias Treydte)
+* Initial support for verbosity control; defaults to quiet
+   * Can be changed with the new `setLogLevel` function
 
 # 0.10. 0
 

demo/Main.hs

@@ -66,7 +66,8 @@ loopFor time m =
 
 testCamera :: IO ()
 testCamera =
-  do initFFmpeg
+  do initFFmpeg -- Defaults to quiet (minimal) logging
+     -- setLogLevel avLogInfo -- Restore standard ffmpeg logging
      (getFrame, cleanup) <- imageReader (Camera "0:0" defaultCameraConfig)
      frame1 <- getFrame
      case frame1 of

src/Codec/FFmpeg.hs

@@ -2,7 +2,7 @@
 -- | Interface to initialize FFmpeg, decode video files, encode video
 -- files, and convert decoded image frames to JuicyPixels images.
 module Codec.FFmpeg (-- * Initialization
-                     initFFmpeg, 
+                     initFFmpeg, setLogLevel,
                      -- * Decoding
                      imageReader, imageReaderTime,
                      imageReaderT, imageReaderTimeT,
@@ -16,14 +16,22 @@ import Codec.FFmpeg.Encode
 import Codec.FFmpeg.Enums
 import Codec.FFmpeg.Juicy
 import Codec.FFmpeg.Types
+import Foreign.C.Types (CInt(..))
 
 foreign import ccall "av_register_all" av_register_all :: IO ()
 foreign import ccall "avdevice_register_all" avdevice_register_all :: IO ()
 
--- foreign import ccall "avcodec_register_all" avcodec_register_all :: IO ()
+-- foreign import ccall "avcodec_register_all" avcodec_register_all :: IO (
 
--- | Initialize FFmpeg by registering all known codecs. This /must/
--- be called before using other FFmpeg functions.
-initFFmpeg :: IO ()
-initFFmpeg = av_register_all >> avdevice_register_all
+foreign import ccall "av_log_set_level" av_log_set_level :: CInt -> IO ()
+
+-- | Log output is sent to stderr.
+setLogLevel :: LogLevel -> IO ()
+setLogLevel (LogLevel l) = av_log_set_level l
 
+-- | Initialize FFmpeg by registering all known codecs. This /must/ be
+-- called before using other FFmpeg functions. The debug level is
+-- initially set to @quiet@. If you would like the standard ffmpeg
+-- debug level, call @setLogLevel avLogInfo@ after @initFFmpeg@.
+initFFmpeg :: IO ()
+initFFmpeg = av_register_all >> avdevice_register_all >> setLogLevel avLogQuiet

src/Codec/FFmpeg/Enums.hsc

@@ -212,3 +212,16 @@ newtype PacketFlag = PacketFlag CInt deriving (Eq, Bits, Storable)
 #enum PacketFlag, PacketFlag \
  , AV_PKT_FLAG_KEY\
  , AV_PKT_FLAG_CORRUPT
+
+newtype LogLevel = LogLevel CInt deriving (Eq, Bits, Storable)
+#enum LogLevel, LogLevel \
+ , AV_LOG_QUIET\
+ , AV_LOG_PANIC\
+ , AV_LOG_FATAL\
+ , AV_LOG_ERROR\
+ , AV_LOG_WARNING\
+ , AV_LOG_INFO\
+ , AV_LOG_VERBOSE\
+ , AV_LOG_DEBUG\
+ , AV_LOG_TRACE\
+ , AV_LOG_MAX_OFFSET