RCMA/Translator/Jack.hs

   1 {-# LANGUAGE Arrows #-}
   2
   3 -- Contains all the information and functions necessary to run a Jack
   4 -- port and exchange information through reactive values and Yampa.
   5 module RCMA.Translator.Jack where
   6
   7 import qualified Control.Monad.Exception.Synchronous as Sync
   8 import qualified Control.Monad.Trans.Class           as Trans
   9 import qualified Data.EventList.Absolute.TimeBody    as EventListAbs
  10 import           Data.ReactiveValue
  11 import qualified Foreign.C.Error                     as E
  12 import           RCMA.Translator.Message
  13 import qualified Sound.JACK                          as Jack
  14 import qualified Sound.JACK.MIDI                     as JMIDI
  15
  16 rcmaName :: String
  17 rcmaName = "RCMA"
  18
  19 inPortName :: String
  20 inPortName = "input"
  21
  22 outPortName :: String
  23 outPortName = "output"
  24
  25 -- Starts a default client with an input and an output port. Doesn't
  26 -- do anything as such.
  27 jackSetup :: IO ()
  28 jackSetup = Jack.handleExceptions $
  29   Jack.withClientDefault rcmaName $ \client ->
  30   Jack.withPort client outPortName $ \output ->
  31   Jack.withPort client inPortName  $ \input ->
  32   jackRun client input output (jackCallBack client input output)
  33
  34 -- Loop that does nothing except setting up a callback function
  35 -- (called when Jack is ready to take new inputs).
  36 jackRun client input output callback =
  37   Jack.withProcess client callback $ do
  38   Trans.lift $ putStrLn $ "Started " ++ rcmaName
  39   Trans.lift $ Jack.waitForBreak
  40
  41 -- The callback function. It pumps value out of the input port, mix
  42 -- them with value coming from the machine itself and stuff them into
  43 -- the output port. When this function is not running, events are
  44 -- processed.
  45 jackCallBack client input output nframes@(Jack.NFrames nframesInt) = do
  46   -- This gets the sample rate of the client and the last frame number
  47   -- it processed. We then use it to calculate the current absolute time
  48   sr <- Trans.lift $ Jack.getSampleRate client
  49   (Jack.NFrames lframeInt) <- Trans.lift $ Jack.lastFrameTime client
  50   -- Read the events in the input buffer. /!\ This is in a weird
  51   -- structure that we dismount right after into a list.
  52   inBuffT <- JMIDI.readEventsFromPort input nframes
  53   let rateD = fromIntegral sr
  54       inBuff :: [(Frames, RawMessage)]
  55       inBuff = map (\(Jack.NFrames n,e) -> (fromIntegral n, e)) $
  56                EventListAbs.toPairList inBuffT
  57
  58   return ()