Rice coding: Difference between revisions

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do -- Rice encoding - ~~translated~~ ~~from~~ the Julia sample

do -- Rice encoding - translation of the Julia sample

-- Golomb-Rice encoding helper function

local function do_rice_encode( q, r, k )

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~~local~~ result = {}

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for i = 1, q do result[ #result + 1 ] = "1" end

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result[ #result + 1 ] = "0"

local dPos, digits, v = #result + 1, 0, r

while v > 0 do

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~~digits~~ = ~~digits~~ + 1

local d = v % 2

v = math.floor( v / 2 )

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~~table.insert(~~ result, ~~dPos,~~ d ~= 0 and "1" or "0" )

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end

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~~for~~ ~~pad = digits + 1, k do~~ table.~~insert~~( result~~, dPos~~, "0" ) ~~end~~

return table.concat( result, "" )

end

-- Golomb-Rice encoding of a positive number to a bit vector (string of 0s and 1s) using M of 2^k

local function rice_encode( n, k )

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k = k or 2

local m = math.floor( 2^k )

local q, r = math.floor( n / m ), n % m

local result, q, r = {}, math.floor( n / m ), n % m

~~return~~ ~~do_rice_encode(~~ ~~q, r,~~ k )

while r > 0 do

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result[ #result + 1 ] = r % 2 == 0 and "0" or "1"

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r = math.floor( r / 2 )

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end

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while #result < k do result[ #result + 1 ] = "0" end

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result[ #result + 1 ] = "0"

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for i = 1, q do result[ #result + 1 ] = "1" end

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return string.reverse( table.concat( result, "" ) )

end

-- see wikipedia.org/wiki/Golomb_coding#Use_with_signed_integers

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local function extended_rice_decode( a, k )

k =k or 2

k = k or 2

local i = rice_decode( a, k )

return math.floor( i % 2 == 1 and - ( ( i + 1 ) / 2 ) or i / 2 )