X-Git-Url: http://git.cielonegro.org/gitweb.cgi?p=wavpack.git;a=blobdiff_plain;f=Codec%2FAudio%2FWavPack%2FWords.hs;h=6406d3e91f40b85ef29c7443c31a8d482cd64d89;hp=09235472ba308379a99659ffd0218a94e82ee3c9;hb=cef5d71977963aba55fc3a3d8ab313f497fb1acf;hpb=5f113a044d1a17a7313124802b58c91819bc54eb

diff --git a/Codec/Audio/WavPack/Words.hs b/Codec/Audio/WavPack/Words.hs
index 0923547..6406d3e 100644
--- a/Codec/Audio/WavPack/Words.hs
+++ b/Codec/Audio/WavPack/Words.hs
@@ -1,18 +1,43 @@
 {-# LANGUAGE
     BangPatterns
+  , FlexibleContexts
+  , ScopedTypeVariables
   , UnboxedTuples
   , UnicodeSyntax
   #-}
--- | FIXME
+{-| This module provides entropy word encoding and decoding functions
+using a variation on the Rice method.  This was introduced in wavpack
+3.93 because it allows splitting the data into a \"lossy\" stream and
+a \"correction\" stream in a very efficient manner and is therefore
+ideal for the "hybrid" mode.  For 4.0, the efficiency of this method
+was significantly improved by moving away from the normal Rice
+restriction of using powers of two for the modulus divisions and now
+the method can be used for both hybrid and pure lossless encoding.
+
+Samples are divided by median probabilities at 5\/7 (71.43%), 10\/49
+(20.41%), and 20\/343 (5.83%). Each zone has 3.5 times fewer samples
+than the previous. Using standard Rice coding on this data would
+result in 1.4 bits per sample average (not counting sign
+bit). However, there is a very simple encoding that is over 99%
+efficient with this data and results in about 1.22 bits per sample. -}
 module Codec.Audio.WavPack.Words
     ( WordsData(..)
+
+--    , getWordsLossless
     )
     where
 import Codec.Audio.WavPack.Entropy
 import Codec.Audio.WavPack.Internal
+import Control.Monad.ST
 import Data.Bits
 import Data.Bitstream.Generic (Bitstream)
 import qualified Data.Bitstream.Generic as B
+import Data.Int
+import Data.STRef
+import qualified Data.Vector.Generic as GV
+import qualified Data.Vector.Generic.Mutable as MV
+import Data.Vector.Generic.New (New)
+import qualified Data.Vector.Generic.New as New
 import Data.Word
 import Prelude.Unicode
 
@@ -30,33 +55,217 @@ data WordsData
       }
     deriving (Eq, Show)
 
--- This is an optimized version of 'getWord' that is used for lossless
--- only (error_limit ≡ 0). Also, rather than obtaining a single
--- sample, it can be used to obtain an entire buffer of either mono or
--- stereo samples.
---getWordsLossless ∷ 
+-- | This is an optimized version of 'getWord' that is used for
+-- lossless only ('edErrorLimit' ≡ 0). Also, rather than obtaining a
+-- single sample, it can be used to obtain an entire buffer of either
+-- mono or stereo samples.
+{-
+getWordsLossless ∷ ∀bs v. (Bitstream bs, GV.Vector v Int32)
+                 ⇒ Bool -- ^ Is the stream monaural?
+                 → WordsData
+                 → bs   -- ^ WV bitstream.
+                 → Int   -- ^ Number of samples to get.
+                 → (# WordsData, bs, v Int32 #)
+{-# INLINEABLE getWordsLossless #-}
+getWordsLossless isMono w0 bs0 nSamples0
+    = let v0  = New.create $ MV.new nSamples
+          (# w1, bs1, n1, v1 #)
+              = go0 w0 bs0 0 v0
+          v2  = GV.new $ New.take n1 v1
+      in
+        (# w1, bs1, v2 #)
+    where
+      nSamples ∷ Int
+      nSamples = if isMono
+                 then nSamples0
+                 else nSamples0 ⋅ 2
+
+      go0 ∷ WordsData → bs → Int → New v Int32
+          → (# WordsData, bs, Int, New v Int32 #)
+      go0 w bs n v
+          | n ≥ nSamples
+              = (# w, bs, n, v #)
+          | edMedian0 (fst $ wdEntropyData w) < 2 ∧
+            wdHoldingZero w ≡ False               ∧
+            wdHoldingOne  w ≡ 0                   ∧
+            edMedian1 (fst $ wdEntropyData w) < 2
+              = if wdZeroesAcc w > 0 then
+                    let w' = w { wdZeroesAcc = wdZeroesAcc w - 1 }
+                    in
+                      if wdZeroesAcc w' > 0 then
+                          let (# n', v' #) = appendWord 0 n v
+                          in
+                            go0 w' bs n' v'
+                      else
+                          go1 w' bs n v
+                else
+                    let cBits = min 33 $ B.length (B.takeWhile id bs)
+                        bs'   = B.drop cBits bs
+                    in
+                      if cBits ≡ 33 then
+                          (# w, bs', n, v #)
+                      else
+                          let (# w', bs'' #) = go0' cBits w bs'
+                          in
+                            if wdZeroesAcc w' > 0 then
+                                let w'' = w' {
+                                            wdEntropyData =
+                                                ( clearMedian $ fst $ wdEntropyData w'
+                                                , clearMedian $ snd $ wdEntropyData w' )
+                                          }
+                                    (# n', v' #)
+                                        = appendWord 0 n v
+                                in
+                                  go0 w'' bs'' n' v'
+                            else
+                                go1 w' bs'' n v
+          | otherwise
+              = go1 w bs n v
+
+      go0' ∷ Word32 → WordsData → bs → (# WordsData, bs #)
+      go0' cBits w bs
+          | cBits < 2
+              = let w' = w { wdZeroesAcc = cBits }
+                in
+                  (# w', bs #)
+          | otherwise
+              = let w' = w { wdZeroesAcc = 0 }
+                in
+                  go0'' 1 cBits w' bs
+
+      go0'' ∷ Word32 → Word32 → WordsData → bs → (# WordsData, bs #)
+      go0'' mask cBits w bs
+          | cBits ≡ 1
+              = let w' = w { wdZeroesAcc = wdZeroesAcc w .|. mask }
+                in
+                  (# w', bs #)
+          | otherwise
+              = let cBits' = cBits - 1
+                    w'     = if B.head bs then
+                                 w { wdZeroesAcc = wdZeroesAcc w .|. mask }
+                             else
+                                 w
+                    mask'  = mask `shiftL` 1
+                    bs'    = B.tail bs
+                in
+                  go0'' mask' cBits' w' bs'
 
--- Read a single unsigned value from the specified bitstream with a
+      go1 ∷ WordsData → bs → Int → New v Int32
+          → (# WordsData, bs, Int, New v Int32 #)
+      go1 w bs n v
+          | wdHoldingZero w
+              = let w' = w { wdHoldingZero = False }
+                in
+                  go2 0 w' bs n v
+          | otherwise
+              = let next8 ∷ Word8
+                    next8 = B.toBits (B.take (8 ∷ Int) bs)
+                in
+                  if next8 ≡ 0xFF then
+                      error "FIXME"
+                  else
+                      error "FIXME"
+
+      go2 ∷ Word32 → WordsData → bs → Int → New v Int32
+          → (# WordsData, bs, Int, New v Int32 #)
+      go2 0 w bs n v
+          = let ent  = getEntropy n w
+                low  = 0
+                high = getMedian0 ent - 1
+                ent' = decMedian0 ent
+                w'   = setEntropy ent' n w
+            in
+              go3 low high w' bs n v
+      go2 1 w bs n v
+          = let ent  = getEntropy n w
+                low  = getMedian0 ent
+                high = low + getMedian1 ent - 1
+                ent' = (incMedian0 ∘ decMedian1) ent
+                w'   = setEntropy ent' n w
+            in
+              go3 low high w' bs n v
+      go2 2 w bs n v
+          = let ent   = getEntropy n w
+                low   = getMedian0 ent + getMedian1 ent
+                high  = low + getMedian2 ent - 1
+                ent'  = (incMedian0 ∘ incMedian1 ∘ decMedian2) ent
+                w'    = setEntropy ent' n w
+            in
+              go3 low high w' bs n v
+      go2 onesCount w bs n v
+          = let ent   = getEntropy n w
+                low   = getMedian0 ent + getMedian1 ent + (onesCount-2) ⋅ getMedian2 ent
+                high  = low + getMedian2 ent - 1
+                ent'  = (incMedian0 ∘ incMedian1 ∘ incMedian2) ent
+                w'    = setEntropy ent' n w
+            in
+              go3 low high w' bs n v
+
+      go3 ∷ Word32 → Word32 → WordsData → bs → Int → New v Int32
+          → (# WordsData, bs, Int, New v Int32 #)
+      go3 low high w bs n v
+          = let (# code, bs' #)
+                     = readCode bs (high - low)
+                low' = low + code
+                word = if B.head bs' then
+                           fromIntegral $ complement low'
+                       else
+                           fromIntegral low'
+                bs'' = B.tail bs'
+                (# n', v' #)
+                     = appendWord word n v
+            in
+              go0 w bs'' n' v'
+
+      appendWord ∷ Int32 → Int → New v Int32 → (# Int, New v Int32 #)
+      appendWord word n v
+          = let v' = New.modify (\mv → MV.unsafeWrite mv n word) v
+                n' = n + 1
+            in
+              (# n', v' #)
+
+      getEntropy ∷ Int → WordsData → EntropyData
+      getEntropy n w
+          | isMono        = fst $ wdEntropyData w
+          | n `testBit` 0 = fst $ wdEntropyData w
+          | otherwise     = snd $ wdEntropyData w
+
+      setEntropy ∷ EntropyData → Int → WordsData → WordsData
+      setEntropy e n w
+          | isMono        = w { wdEntropyData = (e, snd $ wdEntropyData w) }
+          | n `testBit` 0 = w { wdEntropyData = (e, snd $ wdEntropyData w) }
+          | otherwise     = w { wdEntropyData = (fst $ wdEntropyData w, e) }
+-}
+
+-- | Read a single unsigned value from the specified bitstream with a
 -- value from 0 to maxCode. If there are exactly a power of two number
 -- of possible codes then this will read a fixed number of bits;
 -- otherwise it reads the minimum number of bits and then determines
 -- whether another bit is needed to define the code.
-readCode ∷ Bitstream bs ⇒ bs → Word32 → (# Word32, bs #)
+readCode ∷ Bitstream bs ⇒ STRef s bs → Word32 → ST s Word32
 {-# INLINEABLE readCode #-}
-readCode bs 0       = (# 0, bs #)
-readCode bs 1       = (# b2n (B.head bs), B.tail bs #)
+readCode bs 0       = return 0
+readCode bs 1       = fmap b2n $ takeHead bs
 readCode bs maxCode
-    = let !bitCount = countBits maxCode
-          !extras   = bit bitCount - maxCode - 1
-          !code     = B.toBits (B.take (bitCount - 1) bs)
-          (# code', bitCount' #)
-                    = if code ≥ extras then
-                          (# (code `shiftL` 1)
-                             - extras
-                             + b2n (bs B.!! bitCount)
-                           , bitCount #)
-                      else
-                          (# code, bitCount - 1 #)
-          !bs'      = B.drop bitCount' bs
-      in
-        (# code', bs' #)
+    = do let bitCount = countBits maxCode
+             extras   = bit bitCount - maxCode - 1
+         code ← takeBits bs (bitCount - 1)
+         if code ≥ extras then
+             do nextBit ← takeHead bs
+                return $ (code `shiftL` 1) - extras + b2n nextBit
+           else
+             return code
+
+takeHead ∷ Bitstream bs ⇒ STRef s bs → ST s Bool
+{-# INLINEABLE takeHead #-}
+takeHead bsr
+    = do bs ← readSTRef bsr
+         writeSTRef bsr (B.tail bs)
+         return (B.head bs)
+
+takeBits ∷ (Integral n, Bitstream bs, Bits a) ⇒ STRef s bs → n → ST s a
+{-# INLINEABLE takeBits #-}
+takeBits bsr n
+    = do bs ← readSTRef bsr
+         writeSTRef bsr (B.drop n bs)
+         return (B.toBits (B.take n bs))