still working on getWordsLossless

[wavpack.git] / Codec / Audio / WavPack / Entropy.hs

diff --git a/Codec/Audio/WavPack/Entropy.hs b/Codec/Audio/WavPack/Entropy.hs
index 444fc17957b5b5b7f42fc1b50e4a4203ecb15a49..fc9b96d1709da9056a69172f8a4e8a56b887a146 100644 (file)
--- a/Codec/Audio/WavPack/Entropy.hs
+++ b/Codec/Audio/WavPack/Entropy.hs
@@ -4,18 +4,68 @@
 -- | FIXME
 module Codec.Audio.WavPack.Entropy
     ( EntropyData(..)
+
+    , clearMedians
+
+    , getMedian0
+    , getMedian1
+    , getMedian2
+
+    , incMedian0
+    , decMedian0
+    , incMedian1
+    , decMedian1
+    , incMedian2
+    , decMedian2
     )
     where
+import Control.Monad.ST
+import Control.Monad.Unicode
+import Data.Bits
+import Data.STRef
 import Data.Word
+import Prelude.Unicode
 
 -- | FIXME
-data EntropyData
+data EntropyData s
     = EntropyData {
         -- | Median log2 values for a channel.
-        edMedian     ∷ !(Word32, Word32, Word32)
+        edMedian0    ∷ !(STRef s Word32)
+      , edMedian1    ∷ !(STRef s Word32)
+      , edMedian2    ∷ !(STRef s Word32)
         -- | FIXME
-      , edSlowLevel  ∷ !Word32
+      , edSlowLevel  ∷ !(STRef s Word32)
         -- | FIXME
-      , edErrorLimit ∷ !Word32
+      , edErrorLimit ∷ !(STRef s Word32)
       }
-    deriving (Eq, Show)
+
+clearMedians ∷ EntropyData s → ST s ()
+clearMedians e
+    = writeSTRef (edMedian0 e) 0 ≫
+      writeSTRef (edMedian1 e) 0 ≫
+      writeSTRef (edMedian2 e) 0
+
+-- | The time constant of the 3 median level breakpoints
+div0, div1, div2 ∷ Word32
+div0 = 128 --  5/  7 of samples
+div1 =  64 -- 10/ 49 of samples
+div2 =  32 -- 20/343 of samples
+
+-- | Retrieve the specified median breakpoint (without frac; min = 1)
+getMedian0, getMedian1, getMedian2 ∷ EntropyData s → ST s Word32
+getMedian0 = fmap ((`shiftR` 4) ∘ (+ 1)) ∘ readSTRef ∘ edMedian0
+getMedian1 = fmap ((`shiftR` 4) ∘ (+ 1)) ∘ readSTRef ∘ edMedian1
+getMedian2 = fmap ((`shiftR` 4) ∘ (+ 1)) ∘ readSTRef ∘ edMedian2
+
+-- | Update the specified median breakpoints. Note that the median is
+-- incremented when the sample is higher than the median, else
+-- decremented.  They are designed so that the median will never drop
+-- below 1 and the value is essentially stationary if there are 2
+-- increments for every 5 decrements.
+incMedian0, decMedian0, incMedian1, decMedian1, incMedian2, decMedian2 ∷ EntropyData s → ST s ()
+incMedian0 = flip modifySTRef (\x → x + ((x +  div0   ) `div` div0) ⋅ 5) ∘ edMedian0
+decMedian0 = flip modifySTRef (\x → x - ((x + (div0-2)) `div` div0) ⋅ 2) ∘ edMedian0
+incMedian1 = flip modifySTRef (\x → x + ((x +  div1   ) `div` div1) ⋅ 5) ∘ edMedian1
+decMedian1 = flip modifySTRef (\x → x - ((x + (div1-2)) `div` div1) ⋅ 2) ∘ edMedian1
+incMedian2 = flip modifySTRef (\x → x + ((x +  div2   ) `div` div2) ⋅ 5) ∘ edMedian2
+decMedian2 = flip modifySTRef (\x → x - ((x + (div2-2)) `div` div2) ⋅ 2) ∘ edMedian2