'''
The copyright in this software is being made available under the BSD
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and contributor rights, including patent rights, and no such rights are
granted under this license.

Copyright (c) 2022-2024, Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.
Copyright (c) 2024 Dolby International AB
All rights reserved.

Redistribution and use in source and binary forms, with or without modification,
are permitted (subject to the limitations in the disclaimer below) provided that
the following conditions are met:

  * Redistributions of source code must retain the above copyright notice,
  this list of conditions and the following disclaimer.

  * Redistributions in binary form must reproduce the above copyright
  notice, this list of conditions and the following disclaimer in the
  documentation and/or other materials provided with the distribution.

  * Neither the name of the copyright holder nor the names of its
  contributors may be used to endorse or promote products derived from this
  software without specific prior written permission.

NO EXPRESS OR IMPLIED LICENSES TO ANY PARTY'S PATENT RIGHTS ARE GRANTED BY
THIS LICENSE. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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POSSIBILITY OF SUCH DAMAGE.
'''




#!/usr/bin/python3

import math
import sys

assert sys.version_info >= (3, 6)

class BDRate():
  def __init__( self ):
    self._refDist = []
    self._refRate = []
    self._tgtDist = []
    self._tgtRate = []


  def getBDRate( self ):
    assert len( self._refRate ) > 0
    assert len( self._tgtRate ) > 0
    assert len( self._refDist ) == len( self._refRate )
    assert len( self._tgtDist ) == len( self._tgtRate )

    _minDist = max( min( self._refDist ), min( self._tgtDist ) )
    _maxDist = min( max( self._refDist ), max( self._tgtDist ) )

    _vA  = self.calcArea( self._refRate, self._refDist, _minDist, _maxDist )
    _vB  = self.calcArea( self._tgtRate, self._tgtDist, _minDist, _maxDist )
    _avg = ( _vB - _vA ) / ( _maxDist - _minDist )

    return ( ( 10.0 ** _avg ) - 1.0 ) * 100.0


  def calcArea( self, _rates, _dists, _minDist, _maxDist ):
    _numPts  = len( _rates )
    _logRate = [ 0.0 ] * _numPts
    _logDist = [ 0.0 ] * _numPts

    for i in range( _numPts ):
      _logRate[ i ] = math.log10( _rates[ _numPts - 1 - i ] )
      _logDist[ i ] = _dists[ _numPts - 1 - i ]

    _H     = [ 0.0 ] * ( _numPts - 1 )
    _delta = [ 0.0 ] * ( _numPts - 1 )

    for i in range( _numPts - 1 ):
      _H[ i ]     =   _logDist[ i + 1 ] - _logDist[ i ]
      _delta[ i ] = ( _logRate[ i + 1 ] - _logRate[ i ] ) / _H[ i ]

    _d      = [ 0.0 ] * _numPts
    _d[ 0 ] = self.pchipend( _H[ 0 ], _H[ 1 ], _delta[ 0 ], _delta[ 1 ] )

    for i in range( 1, _numPts - 1 ):
      _d[ i ] = ( 3 * _H[ i - 1 ] + 3 * _H[ i ] ) / ( ( 2 * _H[ i ] + _H[ i - 1 ] ) / _delta[ i - 1 ] + ( _H[ i ] + 2 * _H[ i - 1 ] ) / _delta[ i ] )

    _d[ _numPts - 1 ] = self.pchipend( _H[ 2 ], _H[ 1 ], _delta[ 2 ], _delta[ 1 ] )

    _c = [ 0.0 ] * ( _numPts - 1 )
    _b = [ 0.0 ] * ( _numPts - 1 )

    for i in range( _numPts - 1 ):
      _c[ i ] = ( 3 * _delta[ i ] - 2 * _d[ i ] - _d[ i + 1 ] ) / _H[ i ]
      _b[ i ] = ( _d[ i ] - 2 * _delta[ i ] + _d[ i + 1 ] ) / ( _H[ i ] * _H[ i ] )

    _s0     = 0.0
    _s1     = 0.0
    _result = 0.0

    for i in range( _numPts - 1 ):
      _s0 = _logDist[ i     ]
      _s1 = _logDist[ i + 1 ]
      # clip s0 to valid range
      _s0 = max( _s0, _minDist )
      _s0 = min( _s0, _maxDist )
      # clip s1 to valid range
      _s1 = max( _s1, _minDist )
      _s1 = min( _s1, _maxDist )
      _s0 = _s0 - _logDist[ i ]
      _s1 = _s1 - _logDist[ i ]

      if _s1 > _s0:
        _result = _result + ( _s1 - _s0 ) * _logRate[ i ]
        _result = _result + ( _s1 * _s1 - _s0 * _s0 ) * _d[ i ] / 2
        _result = _result + ( _s1 * _s1 * _s1 - _s0 * _s0 * _s0 ) * _c[ i ] / 3
        _result = _result + ( _s1 * _s1 * _s1 * _s1 - _s0 * _s0 * _s0 * _s0 ) * _b[ i ] / 4

    return _result


  def pchipend( self, _h1, _h2, _del1, _del2 ):
    _d = ( ( 2 * _h1 + _h2 ) * _del1 - _h1 * _del2 ) / ( _h1 + _h2 )

    if _d * _del1 < 0:
      _d = 0
    elif ( _del1 * _del2 < 0 ) and ( abs( _d ) > abs( 3 * _del1 ) ):
      _d = 3 * _del1

    return _d

'''
Below: Dummy example to calculate the BD-Rate
'''

if __name__ == "__main__":
    _bd = BDRate()
    _bd._refDist = [ 9.936, 9.026, 8.160, 7.255, 6.174, 5.370, 4.540, 3.835, 3.195, 2.680, 1.716, 1.236, 0.519 ]
    _bd._refRate = [ 0.175, 0.200, 0.237, 0.292, 0.376, 0.468, 0.602, 0.773, 1.014, 1.338, 2.203, 2.755, 3.255 ]
    _bd._tgtDist = [ 9.884, 9.021, 8.161, 7.259, 6.179, 5.373, 4.539, 3.834, 3.196, 2.680, 1.714, 1.238, 0.518 ]
    _bd._tgtRate = [ 0.176, 0.201, 0.237, 0.293, 0.375, 0.469, 0.602, 0.773, 1.013, 1.338, 2.205, 2.756, 3.259 ]
    bdrate = _bd.getBDRate()
    print( "The BD rate is: %.3f" % bdrate )