{-# 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 Data.Bits
import Data.Bitstream.Generic (Bitstream)
import qualified Data.Bitstream.Generic as B
+import Data.Int
+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
}
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'
+
+ 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
+-- | 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
projects / wavpack.git / blobdiff