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/* This file is based on VFGS, available on

 * https://github.com/InterDigitalInc/VersatileFilmGrain

 *

 * VFGS implements film grain synthesis as a hardware model: it simulates the

 * output of a cost-effective hardware implementation in a video display

 * pipeline. Also, the C code is split into "fw" (firmware) and "hw" (hardware)

 * parts, and as self-explanatory as possible. See VFGS github repository for

 * more details.

 *

 * The VFGS github repository also contains other tools to experiment with film

 * grain synthesis (e.g. a graphical display and tuning tool for FGC SEI

 * message).

 */

#include "FilmGrainImpl.h"

#include <cstring>   // memcpy

#include <algorithm>

#include <CommonDef.h>

namespace vvdec

{

/** Derive Y x/y offsets from (random) number

 *

 * Bit fields are designed to minimize overlaps across color channels, to

 * decorrelate them as much as possible.

 *

 * 10-bit for 12 or 13 bins makes a reasonably uniform distribution (1.2%

 * probability error).

 *

 * If 8-bit is requested to further simplify the multiplier, at the cost of less

 * uniform probability, the following bitfields can be considered:

 *

 * Y: sign = rnd[31], x = (rnd[7:0]*13 >> 8)*4,   y = (rnd[21:14]*12 >> 8)*4

 * U: sign = rnd[0],  x = (rnd[17:10]*13 >> 8)*2, y = (rnd[31:24]*12 >> 8)*2

 * V: sign = rnd[13], x = (rnd[27:20]*13 >> 8)*2, y = (rnd[11:4]*12 >> 8)*2

 *

 * Note: to fully support cross-component correlation within patterns, we would

 * need to align luma/chroma offsets.

 */

void FilmGrainImpl::get_offset_y( uint32_t val, int* s, uint8_t* x, uint8_t* y )

{

  uint32_t bf;   // bit field

  *s = ( ( val >> 31 ) & 1 ) ? -1 : 1;

  bf = ( val >> 0 ) & 0x3ff;

  *x = ( ( bf * 13 ) >> 10 ) * 4;   // 13 = 8 + 4 + 1 (two adders)

  bf = ( val >> 14 ) & 0x3ff;

  *y = ( ( bf * 12 ) >> 10 ) * 4;   // 12 = 8 + 4 (one adder)

                                    // Note: could shift 9 and * 2, to make a multiple of 2 and make use of all

                                    // pattern samples (when using overlap).

}

void FilmGrainImpl::get_offset_u( uint32_t val, int* s, uint8_t* x, uint8_t* y ) const

{

  uint32_t bf;   // bit field

  *s = ( ( val >> 2 ) & 1 ) ? -1 : 1;

  bf = ( val >> 10 ) & 0x3ff;

  *x = ( ( bf * 13 ) >> 10 ) * ( 4 / csubx );

  bf = ( ( val >> 24 ) & 0x0ff ) | ( ( val << 8 ) & 0x300 );

  *y = ( ( bf * 12 ) >> 10 ) * ( 4 / csuby );

}

void FilmGrainImpl::get_offset_v( uint32_t val, int* s, uint8_t* x, uint8_t* y ) const

{

  uint32_t bf;   // bit field

  *s = ( ( val >> 15 ) & 1 ) ? -1 : 1;

  bf = ( val >> 20 ) & 0x3ff;

  *x = ( ( bf * 13 ) >> 10 ) * ( 4 / csubx );

  bf = ( val >> 4 ) & 0x3ff;

  *y = ( ( bf * 12 ) >> 10 ) * ( 4 / csuby );

}

void FilmGrainImpl::add_grain_block( void* I, int c, int x, int y, int width, uint32_t rnd, uint32_t rnd_up, int16_t grain[3][32], uint8_t scale[3][32] ) const

{

  const int subx = c ? csubx : 1;

  const int suby = c ? csuby : 1;

  if( ( y & 1 ) && suby > 1 )

  {

    return;

  }

  CHECK( x & 15, "x not a multiple of 16" );

  CHECK( width <= 128, "wrong width" );

  CHECK( bs != 0 && bs != 2, "wrong bs" );

  CHECK( scale_shift + bs < 8 || scale_shift + bs > 13, "wrong scale_shift" );

  // TODO: assert subx, suby, Y/C min/max, max pLUT values, etc

  const int j = y & 0xf;

  uint8_t oc1, oc2;                 // overlapping coefficients

  if( y > 15 && j == 0 )            // first line of overlap

  {

    oc1 = ( suby > 1 ) ? 20 : 12;   // current

    oc2 = ( suby > 1 ) ? 20 : 24;   // upper

  }

  else if( y > 15 && j == 1 )       // second line of overlap

  {

    oc1 = 24;

    oc2 = 12;

  }

  else

  {

    oc1 = oc2 = 0;

  }

  // Derive block offsets + sign

  int     s;        // random sign flip (current)

  uint8_t ox, oy;   // random offset (current)

  if( c == 0 )

  {

    get_offset_y( rnd, &s, &ox, &oy );

  }

  else if( c == 1 )

  {

    get_offset_u( rnd, &s, &ox, &oy );

  }

  else

  {

    get_offset_v( rnd, &s, &ox, &oy );

  }

  oy += j / suby;

  // Same for upper block (overlap)

  int     s_up;           // random sign flip (upper row)

  uint8_t ox_up, oy_up;   // random offset (upper row)

  if( c == 0 )

  {

    get_offset_y( rnd_up, &s_up, &ox_up, &oy_up );

  }

  else if( c == 1 )

  {

    get_offset_u( rnd_up, &s_up, &ox_up, &oy_up );

  }

  else

  {

    get_offset_v( rnd_up, &s_up, &ox_up, &oy_up );

  }

  oy_up += ( 16 + j ) / suby;

  // Make grain pattern

  make_grain_pattern( I, c, x, subx, oc1, oc2, ox, ox_up, oy, oy_up, s, s_up, grain, scale );

  // Scale & output

  scale_and_output( I, c, x, subx, width, grain, scale );

}

void FilmGrainImpl::make_grain_pattern( const void* I,

                                        int         c,

                                        int         x,

                                        int         subx,

                                        uint8_t     oc1,

                                        uint8_t     oc2,

                                        uint8_t     ox,

                                        uint8_t     ox_up,

                                        uint8_t     oy,

                                        uint8_t     oy_up,

                                        int         s,

                                        int         s_up,

                                        int16_t     grain[3][32],

                                        uint8_t     scale[3][32] ) const

{

  const uint8_t*  I8  = (const uint8_t*) I;

  const uint16_t* I16 = (const uint16_t*) I;

  {

    for( int i = 0; i < 16 / subx; i++ )

    {

      uint8_t intensity = bs ? I16[x / subx + i] >> bs : I8[x / subx + i];

      uint8_t pi        = pLUT[c][intensity] >> 4;                  // pattern index (integer part)

      int     P         = pattern[c ? 1 : 0][pi][oy][ox + i] * s;   // Pattern sample (from current pattern index)

                                                                    // We could consider just XORing the sign bit

#if PATTERN_INTERPOLATION

      uint8_t pf = pLUT[c][intensity] & 15;           // pattern index fractional part (interpolate with next) -- could restrict to less bits (e.g. 2)

      int     Pn =

        pattern[c ? 1 : 0][pi + 1][oy][ox + i] * s;   // Next-pattern sample (from pattern index+1)

                                                      // But there are equivalent hw tricks, e.g. storing values as sign + amplitude instead of two's complement

#endif

      if( oc1 )   // overlap

      {

        P = round( P * oc1 + pattern[c ? 1 : 0][pi][oy_up][ox_up + i] * oc2 * s_up, 5 );

#if PATTERN_INTERPOLATION

        Pn = round( Pn * oc1 + pattern[c ? 1 : 0][pi + 1][oy_up][ox_up + i] * oc2 * s_up, 5 );

#endif

      }

#if PATTERN_INTERPOLATION

      // Pattern interpolation: P is current, Pn is next, pf is interpolation coefficient

      grain[c][16 / subx + i] = round( P * ( 16 - pf ) + Pn * pf, 4 );

#else

      grain[c][16 / subx + i] = P;

#endif

      // Scale sign already integrated above because of overlap

      scale[c][16 / subx + i] = sLUT[c][intensity];

    }

  }

}

void FilmGrainImpl::scale_and_output( void* I, int c, int x, int subx, int width, int16_t grain[3][32], uint8_t scale[3][32] ) const

{

  uint8_t*  I8  = (uint8_t*) I;

  uint16_t* I16 = (uint16_t*) I;

  const uint8_t I_min = c ? C_min : Y_min;

  const uint8_t I_max = c ? C_max : Y_max;

  int flush = 0;

  do

  {

    if( x > 0 )

    {

      if( !flush )

      {

        // Horizontal deblock (across previous block)

        int16_t l1, l0, r0, r1;

        l1 = grain[c][16 / subx - 2];

        l0 = grain[c][16 / subx - 1];

        r0 = grain[c][16 / subx + 0];

        r1 = grain[c][16 / subx + 1];

        grain[c][16 / subx - 1] = round( l1 + 3 * l0 + r0, 2 );

        grain[c][16 / subx + 0] = round( l0 + 3 * r0 + r1, 2 );

      }

      {

        for( int i = 0; i < 16 / subx; i++ )

        {

          // Output previous block (or flush current)

          int32_t g = round( scale[c][i] * (int16_t) grain[c][i], scale_shift );

          if( bs )

          {

            I16[( x - 16 ) / subx + i] = std::max<int32_t>( I_min << bs, std::min<int32_t>( I_max << bs, I16[( x - 16 ) / subx + i] + g ) );

          }

          else

          {

            I8[( x - 16 ) / subx + i] = std::max<int32_t>( I_min, std::min<int32_t>( I_max, I8[( x - 16 ) / subx + i] + g ) );

          }

        }

      }

    }

    // Shift pipeline

    if( !flush )

    {

      if( c == 0 )

      {

        for( int i = 0; i < 16; i++ )

        {

          grain[0][i] = grain[0][i + 16];

          scale[0][i] = scale[0][i + 16];

        }

      }

      else

      {

        for( int i = 0; i < 8; i++ )

        {

          grain[c][i] = grain[c][i + 8];

          scale[c][i] = scale[c][i + 8];

        }

      }

    }

    if( x + 16 >= width )

    {

      flush++;

      x += 16;

    }

  } while( flush == 1 );

}

/* Public interface ***********************************************************/

void FilmGrainImpl::set_luma_pattern( int index, int8_t* P )

{

  CHECK( index < 0 || index >= 8, "luma pattern index out of bounds" );

  memcpy( pattern[0][index], P, 64 * 64 );

}

void FilmGrainImpl::set_chroma_pattern( int index, int8_t* P )

{

  CHECK( index < 0 || index >= 8, "chroma pattern index out of bounds" );

  for( int i = 0; i < 64 / csuby; i++ )

  {

    memcpy( pattern[1][index][i], P + ( 64 / csuby ) * i, 64 / csubx );

  }

}

void FilmGrainImpl::set_scale_lut( int c, uint8_t lut[] )

{

  CHECK( c < 0 || c >= 3, "scale lut idx out of bounds" );

  memcpy( sLUT[c], lut, 256 );

}

void FilmGrainImpl::set_pattern_lut( int c, uint8_t lut[], bool all0 )

{

  CHECK( c < 0 || c >= 3, "pattern lut idx out of bounds" );

  allZero[c] = all0;

  memcpy( pLUT[c], lut, 256 );

}

void FilmGrainImpl::set_scale_shift( int shift )

{

  CHECK( shift < 2 || shift >= 8, "scale shift out of range" );

  scale_shift = shift + 6 - bs;

}

void FilmGrainImpl::set_depth( int depth )

{

  CHECK( depth != 8 && depth != 10, "only bit depth 8 and 10 supported." )

  if( bs == 0 && depth > 8 )

  {

    scale_shift -= 2;

  }

  if( bs == 2 && depth == 8 )

  {

    scale_shift += 2;

  }

  bs = depth - 8;

}

void FilmGrainImpl::set_chroma_subsampling( int subx, int suby )

{

  CHECK( subx != 1 && subx != 2, "chroma subsampling should be 1 or 2" );

  CHECK( suby != 1 && suby != 2, "chroma subsampling should be 1 or 2" );

  csubx = subx;

  csuby = suby;

}

FilmGrainImpl::FilmGrainImpl()

{

  memset( pattern, 0, sizeof( pattern ) );

  memset( sLUT,    0, sizeof( sLUT ) );

  memset( pLUT,    0, sizeof( pLUT ) );

}

}   // namespace vvdec