/*

  * Copyright (c) 2013-2014 Clément Bœsch

  *
  * This file is part of FFmpeg.
  *
  * FFmpeg is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
  * version 2.1 of the License, or (at your option) any later version.
  *
  * FFmpeg is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public
  * License along with FFmpeg; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
 /**

  * A simple, relatively efficient and slow DCT image denoiser.

  *

  * @see http://www.ipol.im/pub/art/2011/ys-dct/

  *
  * The DCT factorization used is based on "Fast and numerically stable
  * algorithms for discrete cosine transforms" from Gerlind Plonkaa & Manfred
  * Tasche (DOI: 10.1016/j.laa.2004.07.015).

  */
 

 #include "libavutil/avassert.h"

 #include "libavutil/eval.h"
 #include "libavutil/opt.h"
 #include "internal.h"
 
 static const char *const var_names[] = { "c", NULL };
 enum { VAR_C, VAR_VARS_NB };
 

 #define MAX_THREADS 8
 

 typedef struct DCTdnoizContext {

     const AVClass *class;
 
     /* coefficient factor expression */
     char *expr_str;

     AVExpr *expr[MAX_THREADS];
     double var_values[MAX_THREADS][VAR_VARS_NB];

     int nb_threads;

     int pr_width, pr_height;    // width and height to process
     float sigma;                // used when no expression are st
     float th;                   // threshold (3*sigma)
     float *cbuf[2][3];          // two planar rgb color buffers

     float *slices[MAX_THREADS]; // slices buffers (1 slice buffer per thread)

     float *weights;             // dct coeff are cumulated with overlapping; these values are used for averaging
     int p_linesize;             // line sizes for color and weights
     int overlap;                // number of block overlapping pixels

     int step;                   // block step increment (blocksize - overlap)
     int n;                      // 1<<n is the block size
     int bsize;                  // block size, 1<<n

     void (*filter_freq_func)(struct DCTdnoizContext *s,
                              const float *src, int src_linesize,

                              float *dst, int dst_linesize,
                              int thread_id);

     void (*color_decorrelation)(float **dst, int dst_linesize,

                                 const uint8_t **src, int src_linesize,

                                 int w, int h);

     void (*color_correlation)(uint8_t **dst, int dst_linesize,

                               float **src, int src_linesize,
                               int w, int h);

 } DCTdnoizContext;
 

 #define MIN_NBITS 3 /* blocksize = 1<<3 =  8 */
 #define MAX_NBITS 4 /* blocksize = 1<<4 = 16 */
 #define DEFAULT_NBITS 3
 

 #define OFFSET(x) offsetof(DCTdnoizContext, x)
 #define FLAGS AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_VIDEO_PARAM
 static const AVOption dctdnoiz_options[] = {
     { "sigma",   "set noise sigma constant",               OFFSET(sigma),    AV_OPT_TYPE_FLOAT,  {.dbl=0},            0, 999,          .flags = FLAGS },
     { "s",       "set noise sigma constant",               OFFSET(sigma),    AV_OPT_TYPE_FLOAT,  {.dbl=0},            0, 999,          .flags = FLAGS },

     { "overlap", "set number of block overlapping pixels", OFFSET(overlap),  AV_OPT_TYPE_INT,    {.i64=-1}, -1, (1<<MAX_NBITS)-1, .flags = FLAGS },

     { "expr",    "set coefficient factor expression",      OFFSET(expr_str), AV_OPT_TYPE_STRING, {.str=NULL},                          .flags = FLAGS },
     { "e",       "set coefficient factor expression",      OFFSET(expr_str), AV_OPT_TYPE_STRING, {.str=NULL},                          .flags = FLAGS },

     { "n",       "set the block size, expressed in bits",  OFFSET(n),        AV_OPT_TYPE_INT,    {.i64=DEFAULT_NBITS}, MIN_NBITS, MAX_NBITS, .flags = FLAGS },

     { NULL }
 };
 
 AVFILTER_DEFINE_CLASS(dctdnoiz);
 

 static void av_always_inline fdct8_1d(float *dst, const float *src,
                                       int dst_stridea, int dst_strideb,
                                       int src_stridea, int src_strideb)
 {
     int i;
 
     for (i = 0; i < 8; i++) {
         const float x00 = src[0*src_stridea] + src[7*src_stridea];
         const float x01 = src[1*src_stridea] + src[6*src_stridea];
         const float x02 = src[2*src_stridea] + src[5*src_stridea];
         const float x03 = src[3*src_stridea] + src[4*src_stridea];
         const float x04 = src[0*src_stridea] - src[7*src_stridea];
         const float x05 = src[1*src_stridea] - src[6*src_stridea];
         const float x06 = src[2*src_stridea] - src[5*src_stridea];
         const float x07 = src[3*src_stridea] - src[4*src_stridea];
         const float x08 = x00 + x03;
         const float x09 = x01 + x02;
         const float x0a = x00 - x03;
         const float x0b = x01 - x02;

         const float x0c = 1.38703984532215f*x04 + 0.275899379282943f*x07;
         const float x0d = 1.17587560241936f*x05 + 0.785694958387102f*x06;
         const float x0e = -0.785694958387102f*x05 + 1.17587560241936f*x06;
         const float x0f = 0.275899379282943f*x04 - 1.38703984532215f*x07;
         const float x10 = 0.353553390593274f * (x0c - x0d);
         const float x11 = 0.353553390593274f * (x0e - x0f);
         dst[0*dst_stridea] = 0.353553390593274f * (x08 + x09);
         dst[1*dst_stridea] = 0.353553390593274f * (x0c + x0d);
         dst[2*dst_stridea] = 0.461939766255643f*x0a + 0.191341716182545f*x0b;
         dst[3*dst_stridea] = 0.707106781186547f * (x10 - x11);
         dst[4*dst_stridea] = 0.353553390593274f * (x08 - x09);
         dst[5*dst_stridea] = 0.707106781186547f * (x10 + x11);
         dst[6*dst_stridea] = 0.191341716182545f*x0a - 0.461939766255643f*x0b;
         dst[7*dst_stridea] = 0.353553390593274f * (x0e + x0f);

         dst += dst_strideb;
         src += src_strideb;
     }
 }
 
 static void av_always_inline idct8_1d(float *dst, const float *src,
                                       int dst_stridea, int dst_strideb,
                                       int src_stridea, int src_strideb,
                                       int add)
 {
     int i;
 
     for (i = 0; i < 8; i++) {

         const float x00 =  1.4142135623731f  *src[0*src_stridea];
         const float x01 =  1.38703984532215f *src[1*src_stridea] + 0.275899379282943f*src[7*src_stridea];
         const float x02 =  1.30656296487638f *src[2*src_stridea] + 0.541196100146197f*src[6*src_stridea];
         const float x03 =  1.17587560241936f *src[3*src_stridea] + 0.785694958387102f*src[5*src_stridea];
         const float x04 =  1.4142135623731f  *src[4*src_stridea];
         const float x05 = -0.785694958387102f*src[3*src_stridea] + 1.17587560241936f*src[5*src_stridea];
         const float x06 =  0.541196100146197f*src[2*src_stridea] - 1.30656296487638f*src[6*src_stridea];
         const float x07 = -0.275899379282943f*src[1*src_stridea] + 1.38703984532215f*src[7*src_stridea];

         const float x09 = x00 + x04;
         const float x0a = x01 + x03;

         const float x0b = 1.4142135623731f*x02;

         const float x0c = x00 - x04;
         const float x0d = x01 - x03;

         const float x0e = 0.353553390593274f * (x09 - x0b);
         const float x0f = 0.353553390593274f * (x0c + x0d);
         const float x10 = 0.353553390593274f * (x0c - x0d);
         const float x11 = 1.4142135623731f*x06;

         const float x12 = x05 + x07;
         const float x13 = x05 - x07;

         const float x14 = 0.353553390593274f * (x11 + x12);
         const float x15 = 0.353553390593274f * (x11 - x12);
         const float x16 = 0.5f*x13;
         dst[0*dst_stridea] = (add ? dst[ 0*dst_stridea] : 0) + 0.25f * (x09 + x0b) + 0.353553390593274f*x0a;

         dst[1*dst_stridea] = (add ? dst[ 1*dst_stridea] : 0) + 0.707106781186547f * (x0f + x15);
         dst[2*dst_stridea] = (add ? dst[ 2*dst_stridea] : 0) + 0.707106781186547f * (x0f - x15);

         dst[3*dst_stridea] = (add ? dst[ 3*dst_stridea] : 0) + 0.707106781186547f * (x0e + x16);
         dst[4*dst_stridea] = (add ? dst[ 4*dst_stridea] : 0) + 0.707106781186547f * (x0e - x16);
         dst[5*dst_stridea] = (add ? dst[ 5*dst_stridea] : 0) + 0.707106781186547f * (x10 - x14);
         dst[6*dst_stridea] = (add ? dst[ 6*dst_stridea] : 0) + 0.707106781186547f * (x10 + x14);
         dst[7*dst_stridea] = (add ? dst[ 7*dst_stridea] : 0) + 0.25f * (x09 + x0b) - 0.353553390593274f*x0a;

         dst += dst_strideb;
         src += src_strideb;
     }
 }
 
 

 static void av_always_inline fdct16_1d(float *dst, const float *src,
                                        int dst_stridea, int dst_strideb,
                                        int src_stridea, int src_strideb)

 {

     int i;

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

         const float x00 = src[ 0*src_stridea] + src[15*src_stridea];
         const float x01 = src[ 1*src_stridea] + src[14*src_stridea];
         const float x02 = src[ 2*src_stridea] + src[13*src_stridea];
         const float x03 = src[ 3*src_stridea] + src[12*src_stridea];
         const float x04 = src[ 4*src_stridea] + src[11*src_stridea];
         const float x05 = src[ 5*src_stridea] + src[10*src_stridea];
         const float x06 = src[ 6*src_stridea] + src[ 9*src_stridea];
         const float x07 = src[ 7*src_stridea] + src[ 8*src_stridea];
         const float x08 = src[ 0*src_stridea] - src[15*src_stridea];
         const float x09 = src[ 1*src_stridea] - src[14*src_stridea];
         const float x0a = src[ 2*src_stridea] - src[13*src_stridea];
         const float x0b = src[ 3*src_stridea] - src[12*src_stridea];
         const float x0c = src[ 4*src_stridea] - src[11*src_stridea];
         const float x0d = src[ 5*src_stridea] - src[10*src_stridea];
         const float x0e = src[ 6*src_stridea] - src[ 9*src_stridea];
         const float x0f = src[ 7*src_stridea] - src[ 8*src_stridea];
         const float x10 = x00 + x07;
         const float x11 = x01 + x06;
         const float x12 = x02 + x05;
         const float x13 = x03 + x04;
         const float x14 = x00 - x07;
         const float x15 = x01 - x06;
         const float x16 = x02 - x05;
         const float x17 = x03 - x04;
         const float x18 = x10 + x13;
         const float x19 = x11 + x12;
         const float x1a = x10 - x13;
         const float x1b = x11 - x12;

         const float x1c =   1.38703984532215f*x14 + 0.275899379282943f*x17;
         const float x1d =   1.17587560241936f*x15 + 0.785694958387102f*x16;
         const float x1e = -0.785694958387102f*x15 + 1.17587560241936f *x16;
         const float x1f =  0.275899379282943f*x14 - 1.38703984532215f *x17;
         const float x20 = 0.25f * (x1c - x1d);
         const float x21 = 0.25f * (x1e - x1f);
         const float x22 =  1.40740373752638f *x08 + 0.138617169199091f*x0f;
         const float x23 =  1.35331800117435f *x09 + 0.410524527522357f*x0e;
         const float x24 =  1.24722501298667f *x0a + 0.666655658477747f*x0d;
         const float x25 =  1.09320186700176f *x0b + 0.897167586342636f*x0c;
         const float x26 = -0.897167586342636f*x0b + 1.09320186700176f *x0c;
         const float x27 =  0.666655658477747f*x0a - 1.24722501298667f *x0d;
         const float x28 = -0.410524527522357f*x09 + 1.35331800117435f *x0e;
         const float x29 =  0.138617169199091f*x08 - 1.40740373752638f *x0f;

         const float x2a = x22 + x25;
         const float x2b = x23 + x24;
         const float x2c = x22 - x25;
         const float x2d = x23 - x24;

         const float x2e = 0.25f * (x2a - x2b);
         const float x2f = 0.326640741219094f*x2c + 0.135299025036549f*x2d;
         const float x30 = 0.135299025036549f*x2c - 0.326640741219094f*x2d;

         const float x31 = x26 + x29;
         const float x32 = x27 + x28;
         const float x33 = x26 - x29;
         const float x34 = x27 - x28;

         const float x35 = 0.25f * (x31 - x32);
         const float x36 = 0.326640741219094f*x33 + 0.135299025036549f*x34;
         const float x37 = 0.135299025036549f*x33 - 0.326640741219094f*x34;
         dst[ 0*dst_stridea] = 0.25f * (x18 + x19);
         dst[ 1*dst_stridea] = 0.25f * (x2a + x2b);
         dst[ 2*dst_stridea] = 0.25f * (x1c + x1d);
         dst[ 3*dst_stridea] = 0.707106781186547f * (x2f - x37);
         dst[ 4*dst_stridea] = 0.326640741219094f*x1a + 0.135299025036549f*x1b;
         dst[ 5*dst_stridea] = 0.707106781186547f * (x2f + x37);
         dst[ 6*dst_stridea] = 0.707106781186547f * (x20 - x21);
         dst[ 7*dst_stridea] = 0.707106781186547f * (x2e + x35);
         dst[ 8*dst_stridea] = 0.25f * (x18 - x19);
         dst[ 9*dst_stridea] = 0.707106781186547f * (x2e - x35);
         dst[10*dst_stridea] = 0.707106781186547f * (x20 + x21);
         dst[11*dst_stridea] = 0.707106781186547f * (x30 - x36);
         dst[12*dst_stridea] = 0.135299025036549f*x1a - 0.326640741219094f*x1b;
         dst[13*dst_stridea] = 0.707106781186547f * (x30 + x36);
         dst[14*dst_stridea] = 0.25f * (x1e + x1f);
         dst[15*dst_stridea] = 0.25f * (x31 + x32);

         dst += dst_strideb;
         src += src_strideb;

     }

 }
 
 static void av_always_inline idct16_1d(float *dst, const float *src,
                                        int dst_stridea, int dst_strideb,
                                        int src_stridea, int src_strideb,
                                        int add)
 {
     int i;

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

         const float x00 =  1.4142135623731f  *src[ 0*src_stridea];
         const float x01 =  1.40740373752638f *src[ 1*src_stridea] + 0.138617169199091f*src[15*src_stridea];
         const float x02 =  1.38703984532215f *src[ 2*src_stridea] + 0.275899379282943f*src[14*src_stridea];
         const float x03 =  1.35331800117435f *src[ 3*src_stridea] + 0.410524527522357f*src[13*src_stridea];
         const float x04 =  1.30656296487638f *src[ 4*src_stridea] + 0.541196100146197f*src[12*src_stridea];
         const float x05 =  1.24722501298667f *src[ 5*src_stridea] + 0.666655658477747f*src[11*src_stridea];
         const float x06 =  1.17587560241936f *src[ 6*src_stridea] + 0.785694958387102f*src[10*src_stridea];
         const float x07 =  1.09320186700176f *src[ 7*src_stridea] + 0.897167586342636f*src[ 9*src_stridea];
         const float x08 =  1.4142135623731f  *src[ 8*src_stridea];
         const float x09 = -0.897167586342636f*src[ 7*src_stridea] + 1.09320186700176f*src[ 9*src_stridea];
         const float x0a =  0.785694958387102f*src[ 6*src_stridea] - 1.17587560241936f*src[10*src_stridea];
         const float x0b = -0.666655658477747f*src[ 5*src_stridea] + 1.24722501298667f*src[11*src_stridea];
         const float x0c =  0.541196100146197f*src[ 4*src_stridea] - 1.30656296487638f*src[12*src_stridea];
         const float x0d = -0.410524527522357f*src[ 3*src_stridea] + 1.35331800117435f*src[13*src_stridea];
         const float x0e =  0.275899379282943f*src[ 2*src_stridea] - 1.38703984532215f*src[14*src_stridea];
         const float x0f = -0.138617169199091f*src[ 1*src_stridea] + 1.40740373752638f*src[15*src_stridea];

         const float x12 = x00 + x08;
         const float x13 = x01 + x07;
         const float x14 = x02 + x06;
         const float x15 = x03 + x05;

         const float x16 = 1.4142135623731f*x04;

         const float x17 = x00 - x08;
         const float x18 = x01 - x07;
         const float x19 = x02 - x06;
         const float x1a = x03 - x05;
         const float x1d = x12 + x16;
         const float x1e = x13 + x15;

         const float x1f = 1.4142135623731f*x14;

         const float x20 = x12 - x16;
         const float x21 = x13 - x15;

         const float x22 = 0.25f * (x1d - x1f);
         const float x23 = 0.25f * (x20 + x21);
         const float x24 = 0.25f * (x20 - x21);
         const float x25 = 1.4142135623731f*x17;
         const float x26 = 1.30656296487638f*x18 + 0.541196100146197f*x1a;
         const float x27 = 1.4142135623731f*x19;
         const float x28 = -0.541196100146197f*x18 + 1.30656296487638f*x1a;
         const float x29 = 0.176776695296637f * (x25 + x27) + 0.25f*x26;
         const float x2a = 0.25f * (x25 - x27);
         const float x2b = 0.176776695296637f * (x25 + x27) - 0.25f*x26;
         const float x2c = 0.353553390593274f*x28;
         const float x1b = 0.707106781186547f * (x2a - x2c);
         const float x1c = 0.707106781186547f * (x2a + x2c);
         const float x2d = 1.4142135623731f*x0c;

         const float x2e = x0b + x0d;
         const float x2f = x0a + x0e;
         const float x30 = x09 + x0f;
         const float x31 = x09 - x0f;
         const float x32 = x0a - x0e;
         const float x33 = x0b - x0d;

         const float x37 = 1.4142135623731f*x2d;
         const float x38 = 1.30656296487638f*x2e + 0.541196100146197f*x30;
         const float x39 = 1.4142135623731f*x2f;
         const float x3a = -0.541196100146197f*x2e + 1.30656296487638f*x30;
         const float x3b = 0.176776695296637f * (x37 + x39) + 0.25f*x38;
         const float x3c = 0.25f * (x37 - x39);
         const float x3d = 0.176776695296637f * (x37 + x39) - 0.25f*x38;
         const float x3e = 0.353553390593274f*x3a;
         const float x34 = 0.707106781186547f * (x3c - x3e);
         const float x35 = 0.707106781186547f * (x3c + x3e);
         const float x3f = 1.4142135623731f*x32;

         const float x40 = x31 + x33;
         const float x41 = x31 - x33;

         const float x42 = 0.25f * (x3f + x40);
         const float x43 = 0.25f * (x3f - x40);
         const float x44 = 0.353553390593274f*x41;
         dst[ 0*dst_stridea] = (add ? dst[ 0*dst_stridea] : 0) + 0.176776695296637f * (x1d + x1f) + 0.25f*x1e;

         dst[ 1*dst_stridea] = (add ? dst[ 1*dst_stridea] : 0) + 0.707106781186547f * (x29 + x3d);
         dst[ 2*dst_stridea] = (add ? dst[ 2*dst_stridea] : 0) + 0.707106781186547f * (x29 - x3d);
         dst[ 3*dst_stridea] = (add ? dst[ 3*dst_stridea] : 0) + 0.707106781186547f * (x23 - x43);
         dst[ 4*dst_stridea] = (add ? dst[ 4*dst_stridea] : 0) + 0.707106781186547f * (x23 + x43);

         dst[ 5*dst_stridea] = (add ? dst[ 5*dst_stridea] : 0) + 0.707106781186547f * (x1b - x35);
         dst[ 6*dst_stridea] = (add ? dst[ 6*dst_stridea] : 0) + 0.707106781186547f * (x1b + x35);
         dst[ 7*dst_stridea] = (add ? dst[ 7*dst_stridea] : 0) + 0.707106781186547f * (x22 + x44);
         dst[ 8*dst_stridea] = (add ? dst[ 8*dst_stridea] : 0) + 0.707106781186547f * (x22 - x44);

         dst[ 9*dst_stridea] = (add ? dst[ 9*dst_stridea] : 0) + 0.707106781186547f * (x1c + x34);
         dst[10*dst_stridea] = (add ? dst[10*dst_stridea] : 0) + 0.707106781186547f * (x1c - x34);

         dst[11*dst_stridea] = (add ? dst[11*dst_stridea] : 0) + 0.707106781186547f * (x24 + x42);
         dst[12*dst_stridea] = (add ? dst[12*dst_stridea] : 0) + 0.707106781186547f * (x24 - x42);
         dst[13*dst_stridea] = (add ? dst[13*dst_stridea] : 0) + 0.707106781186547f * (x2b - x3b);
         dst[14*dst_stridea] = (add ? dst[14*dst_stridea] : 0) + 0.707106781186547f * (x2b + x3b);
         dst[15*dst_stridea] = (add ? dst[15*dst_stridea] : 0) + 0.176776695296637f * (x1d + x1f) - 0.25f*x1e;

         dst += dst_strideb;
         src += src_strideb;

     }

 }

 #define DEF_FILTER_FREQ_FUNCS(bsize)                                                        \
 static av_always_inline void filter_freq_##bsize(const float *src, int src_linesize,        \
                                                  float *dst, int dst_linesize,              \
                                                  AVExpr *expr, double *var_values,          \
                                                  int sigma_th)                              \
 {                                                                                           \
     unsigned i;                                                                             \
     DECLARE_ALIGNED(32, float, tmp_block1)[bsize * bsize];                                  \
     DECLARE_ALIGNED(32, float, tmp_block2)[bsize * bsize];                                  \
                                                                                             \
     /* forward DCT */                                                                       \
     fdct##bsize##_1d(tmp_block1, src, 1, bsize, 1, src_linesize);                           \
     fdct##bsize##_1d(tmp_block2, tmp_block1, bsize, 1, bsize, 1);                           \
                                                                                             \
     for (i = 0; i < bsize*bsize; i++) {                                                     \
         float *b = &tmp_block2[i];                                                          \
         /* frequency filtering */                                                           \
         if (expr) {                                                                         \

             var_values[VAR_C] = fabsf(*b);                                                  \

             *b *= av_expr_eval(expr, var_values, NULL);                                     \
         } else {                                                                            \

             if (fabsf(*b) < sigma_th)                                                       \

                 *b = 0;                                                                     \
         }                                                                                   \
     }                                                                                       \
                                                                                             \
     /* inverse DCT */                                                                       \
     idct##bsize##_1d(tmp_block1, tmp_block2, 1, bsize, 1, bsize, 0);                        \
     idct##bsize##_1d(dst, tmp_block1, dst_linesize, 1, bsize, 1, 1);                        \
 }                                                                                           \
                                                                                             \
 static void filter_freq_sigma_##bsize(DCTdnoizContext *s,                                   \
                                       const float *src, int src_linesize,                   \

                                       float *dst, int dst_linesize, int thread_id)          \

 {                                                                                           \
     filter_freq_##bsize(src, src_linesize, dst, dst_linesize, NULL, NULL, s->th);           \
 }                                                                                           \
                                                                                             \
 static void filter_freq_expr_##bsize(DCTdnoizContext *s,                                    \
                                      const float *src, int src_linesize,                    \

                                      float *dst, int dst_linesize, int thread_id)           \

 {                                                                                           \

     filter_freq_##bsize(src, src_linesize, dst, dst_linesize,                               \
                         s->expr[thread_id], s->var_values[thread_id], 0);                   \

 }
 

 DEF_FILTER_FREQ_FUNCS(8)
 DEF_FILTER_FREQ_FUNCS(16)

 #define DCT3X3_0_0  0.5773502691896258f /*  1/sqrt(3) */
 #define DCT3X3_0_1  0.5773502691896258f /*  1/sqrt(3) */
 #define DCT3X3_0_2  0.5773502691896258f /*  1/sqrt(3) */
 #define DCT3X3_1_0  0.7071067811865475f /*  1/sqrt(2) */
 #define DCT3X3_1_2 -0.7071067811865475f /* -1/sqrt(2) */
 #define DCT3X3_2_0  0.4082482904638631f /*  1/sqrt(6) */
 #define DCT3X3_2_1 -0.8164965809277261f /* -2/sqrt(6) */
 #define DCT3X3_2_2  0.4082482904638631f /*  1/sqrt(6) */
 
 static av_always_inline void color_decorrelation(float **dst, int dst_linesize,

                                                  const uint8_t **src, int src_linesize,

                                                  int w, int h,
                                                  int r, int g, int b)
 {
     int x, y;
     float *dstp_r = dst[0];
     float *dstp_g = dst[1];
     float *dstp_b = dst[2];

     const uint8_t *srcp = src[0];

 
     for (y = 0; y < h; y++) {
         for (x = 0; x < w; x++) {
             dstp_r[x] = srcp[r] * DCT3X3_0_0 + srcp[g] * DCT3X3_0_1 + srcp[b] * DCT3X3_0_2;
             dstp_g[x] = srcp[r] * DCT3X3_1_0 +                        srcp[b] * DCT3X3_1_2;
             dstp_b[x] = srcp[r] * DCT3X3_2_0 + srcp[g] * DCT3X3_2_1 + srcp[b] * DCT3X3_2_2;
             srcp += 3;
         }

         srcp   += src_linesize - w * 3;

         dstp_r += dst_linesize;
         dstp_g += dst_linesize;
         dstp_b += dst_linesize;
     }
 }
 

 static av_always_inline void color_correlation(uint8_t **dst, int dst_linesize,

                                                float **src, int src_linesize,
                                                int w, int h,
                                                int r, int g, int b)
 {
     int x, y;
     const float *src_r = src[0];
     const float *src_g = src[1];
     const float *src_b = src[2];

     uint8_t *dstp = dst[0];

 
     for (y = 0; y < h; y++) {
         for (x = 0; x < w; x++) {
             dstp[r] = av_clip_uint8(src_r[x] * DCT3X3_0_0 + src_g[x] * DCT3X3_1_0 + src_b[x] * DCT3X3_2_0);
             dstp[g] = av_clip_uint8(src_r[x] * DCT3X3_0_1 +                         src_b[x] * DCT3X3_2_1);
             dstp[b] = av_clip_uint8(src_r[x] * DCT3X3_0_2 + src_g[x] * DCT3X3_1_2 + src_b[x] * DCT3X3_2_2);
             dstp += 3;
         }

         dstp  += dst_linesize - w * 3;

         src_r += src_linesize;
         src_g += src_linesize;
         src_b += src_linesize;
     }
 }
 
 #define DECLARE_COLOR_FUNCS(name, r, g, b)                                          \
 static void color_decorrelation_##name(float **dst, int dst_linesize,               \

                                        const uint8_t **src, int src_linesize,       \

                                        int w, int h)                                \
 {                                                                                   \
     color_decorrelation(dst, dst_linesize, src, src_linesize, w, h, r, g, b);       \
 }                                                                                   \
                                                                                     \

 static void color_correlation_##name(uint8_t **dst, int dst_linesize,               \

                                      float **src, int src_linesize,                 \
                                      int w, int h)                                  \
 {                                                                                   \
     color_correlation(dst, dst_linesize, src, src_linesize, w, h, r, g, b);         \
 }
 
 DECLARE_COLOR_FUNCS(rgb, 0, 1, 2)
 DECLARE_COLOR_FUNCS(bgr, 2, 1, 0)

 static av_always_inline void color_decorrelation_gbrp(float **dst, int dst_linesize,
                                                       const uint8_t **src, int src_linesize,
                                                       int w, int h)
 {
     int x, y;
     float *dstp_r = dst[0];
     float *dstp_g = dst[1];
     float *dstp_b = dst[2];
     const uint8_t *srcp_r = src[2];
     const uint8_t *srcp_g = src[0];
     const uint8_t *srcp_b = src[1];
 
     for (y = 0; y < h; y++) {
         for (x = 0; x < w; x++) {
             dstp_r[x] = srcp_r[x] * DCT3X3_0_0 + srcp_g[x] * DCT3X3_0_1 + srcp_b[x] * DCT3X3_0_2;
             dstp_g[x] = srcp_r[x] * DCT3X3_1_0 +                          srcp_b[x] * DCT3X3_1_2;
             dstp_b[x] = srcp_r[x] * DCT3X3_2_0 + srcp_g[x] * DCT3X3_2_1 + srcp_b[x] * DCT3X3_2_2;
         }
         srcp_r += src_linesize;
         srcp_g += src_linesize;
         srcp_b += src_linesize;
         dstp_r += dst_linesize;
         dstp_g += dst_linesize;
         dstp_b += dst_linesize;
     }
 }
 
 static av_always_inline void color_correlation_gbrp(uint8_t **dst, int dst_linesize,
                                                     float **src, int src_linesize,
                                                     int w, int h)
 {
     int x, y;
     const float *src_r = src[0];
     const float *src_g = src[1];
     const float *src_b = src[2];
     uint8_t *dstp_r = dst[2];
     uint8_t *dstp_g = dst[0];
     uint8_t *dstp_b = dst[1];
 
     for (y = 0; y < h; y++) {
         for (x = 0; x < w; x++) {
             dstp_r[x] = av_clip_uint8(src_r[x] * DCT3X3_0_0 + src_g[x] * DCT3X3_1_0 + src_b[x] * DCT3X3_2_0);
             dstp_g[x] = av_clip_uint8(src_r[x] * DCT3X3_0_1 +                         src_b[x] * DCT3X3_2_1);
             dstp_b[x] = av_clip_uint8(src_r[x] * DCT3X3_0_2 + src_g[x] * DCT3X3_1_2 + src_b[x] * DCT3X3_2_2);
         }
         dstp_r += dst_linesize;
         dstp_g += dst_linesize;
         dstp_b += dst_linesize;
         src_r += src_linesize;
         src_g += src_linesize;
         src_b += src_linesize;
     }
 }
 

 static int config_input(AVFilterLink *inlink)
 {
     AVFilterContext *ctx = inlink->dst;
     DCTdnoizContext *s = ctx->priv;

     int i, x, y, bx, by, linesize, *iweights, max_slice_h, slice_h;

     const int bsize = 1 << s->n;

     switch (inlink->format) {
     case AV_PIX_FMT_BGR24:
         s->color_decorrelation = color_decorrelation_bgr;
         s->color_correlation   = color_correlation_bgr;
         break;
     case AV_PIX_FMT_RGB24:
         s->color_decorrelation = color_decorrelation_rgb;
         s->color_correlation   = color_correlation_rgb;
         break;

     case AV_PIX_FMT_GBRP:
         s->color_decorrelation = color_decorrelation_gbrp;
         s->color_correlation   = color_correlation_gbrp;
         break;

     default:
         av_assert0(0);
     }

     s->pr_width  = inlink->w - (inlink->w - bsize) % s->step;
     s->pr_height = inlink->h - (inlink->h - bsize) % s->step;

     if (s->pr_width != inlink->w)
         av_log(ctx, AV_LOG_WARNING, "The last %d horizontal pixels won't be denoised\n",
                inlink->w - s->pr_width);
     if (s->pr_height != inlink->h)
         av_log(ctx, AV_LOG_WARNING, "The last %d vertical pixels won't be denoised\n",
                inlink->h - s->pr_height);
 

     max_slice_h = s->pr_height / ((s->bsize - 1) * 2);

     s->nb_threads = FFMIN3(MAX_THREADS, ff_filter_get_nb_threads(ctx), max_slice_h);

     av_log(ctx, AV_LOG_DEBUG, "threads: [max=%d hmax=%d user=%d] => %d\n",

            MAX_THREADS, max_slice_h, ff_filter_get_nb_threads(ctx), s->nb_threads);

     s->p_linesize = linesize = FFALIGN(s->pr_width, 32);
     for (i = 0; i < 2; i++) {

         s->cbuf[i][0] = av_malloc_array(linesize * s->pr_height, sizeof(*s->cbuf[i][0]));
         s->cbuf[i][1] = av_malloc_array(linesize * s->pr_height, sizeof(*s->cbuf[i][1]));
         s->cbuf[i][2] = av_malloc_array(linesize * s->pr_height, sizeof(*s->cbuf[i][2]));

         if (!s->cbuf[i][0] || !s->cbuf[i][1] || !s->cbuf[i][2])
             return AVERROR(ENOMEM);
     }
 

     /* eval expressions are probably not thread safe when the eval internal
      * state can be changed (typically through load & store operations) */
     if (s->expr_str) {
         for (i = 0; i < s->nb_threads; i++) {
             int ret = av_expr_parse(&s->expr[i], s->expr_str, var_names,
                                     NULL, NULL, NULL, NULL, 0, ctx);
             if (ret < 0)
                 return ret;
         }
     }
 
     /* each slice will need to (pre & re)process the top and bottom block of
      * the previous one in in addition to its processing area. This is because
      * each pixel is averaged by all the surrounding blocks */

     slice_h = (int)ceilf(s->pr_height / (float)s->nb_threads) + (s->bsize - 1) * 2;

     for (i = 0; i < s->nb_threads; i++) {
         s->slices[i] = av_malloc_array(linesize, slice_h * sizeof(*s->slices[i]));
         if (!s->slices[i])
             return AVERROR(ENOMEM);
     }
 

     s->weights = av_malloc(s->pr_height * linesize * sizeof(*s->weights));
     if (!s->weights)
         return AVERROR(ENOMEM);
     iweights = av_calloc(s->pr_height, linesize * sizeof(*iweights));
     if (!iweights)
         return AVERROR(ENOMEM);

     for (y = 0; y < s->pr_height - bsize + 1; y += s->step)
         for (x = 0; x < s->pr_width - bsize + 1; x += s->step)
             for (by = 0; by < bsize; by++)
                 for (bx = 0; bx < bsize; bx++)

                     iweights[(y + by)*linesize + x + bx]++;
     for (y = 0; y < s->pr_height; y++)
         for (x = 0; x < s->pr_width; x++)
             s->weights[y*linesize + x] = 1. / iweights[y*linesize + x];
     av_free(iweights);
 
     return 0;
 }
 
 static av_cold int init(AVFilterContext *ctx)
 {
     DCTdnoizContext *s = ctx->priv;
 

     s->bsize = 1 << s->n;
     if (s->overlap == -1)
         s->overlap = s->bsize - 1;
 
     if (s->overlap > s->bsize - 1) {
         av_log(s, AV_LOG_ERROR, "Overlap value can not except %d "
                "with a block size of %dx%d\n",
                s->bsize - 1, s->bsize, s->bsize);
         return AVERROR(EINVAL);
     }
 

     if (s->expr_str) {

         switch (s->n) {
         case 3: s->filter_freq_func = filter_freq_expr_8;  break;
         case 4: s->filter_freq_func = filter_freq_expr_16; break;
         default: av_assert0(0);
         }

     } else {

         switch (s->n) {
         case 3: s->filter_freq_func = filter_freq_sigma_8;  break;
         case 4: s->filter_freq_func = filter_freq_sigma_16; break;
         default: av_assert0(0);
         }

     }
 
     s->th   = s->sigma * 3.;

     s->step = s->bsize - s->overlap;

     return 0;
 }
 
 static int query_formats(AVFilterContext *ctx)
 {
     static const enum AVPixelFormat pix_fmts[] = {
         AV_PIX_FMT_BGR24, AV_PIX_FMT_RGB24,

         AV_PIX_FMT_GBRP,

         AV_PIX_FMT_NONE
     };

     AVFilterFormats *fmts_list = ff_make_format_list(pix_fmts);
     if (!fmts_list)
         return AVERROR(ENOMEM);
     return ff_set_common_formats(ctx, fmts_list);

 }
 

 typedef struct ThreadData {
     float *src, *dst;
 } ThreadData;
 
 static int filter_slice(AVFilterContext *ctx,
                         void *arg, int jobnr, int nb_jobs)

 {

     int x, y;

     DCTdnoizContext *s = ctx->priv;

     const ThreadData *td = arg;
     const int w = s->pr_width;
     const int h = s->pr_height;
     const int slice_start = (h *  jobnr   ) / nb_jobs;
     const int slice_end   = (h * (jobnr+1)) / nb_jobs;
     const int slice_start_ctx = FFMAX(slice_start - s->bsize + 1, 0);
     const int slice_end_ctx   = FFMIN(slice_end, h - s->bsize + 1);
     const int slice_h = slice_end_ctx - slice_start_ctx;
     const int src_linesize   = s->p_linesize;
     const int dst_linesize   = s->p_linesize;
     const int slice_linesize = s->p_linesize;
     float *dst;
     const float *src = td->src + slice_start_ctx * src_linesize;
     const float *weights = s->weights + slice_start * dst_linesize;
     float *slice = s->slices[jobnr];

 
     // reset block sums

     memset(slice, 0, (slice_h + s->bsize - 1) * dst_linesize * sizeof(*slice));

 
     // block dct sums

     for (y = 0; y < slice_h; y += s->step) {

         for (x = 0; x < w - s->bsize + 1; x += s->step)

             s->filter_freq_func(s, src + x, src_linesize,

                                 slice + x, slice_linesize,
                                 jobnr);

         src += s->step * src_linesize;

         slice += s->step * slice_linesize;

     }
 
     // average blocks

     slice = s->slices[jobnr] + (slice_start - slice_start_ctx) * slice_linesize;
     dst = td->dst + slice_start * dst_linesize;
     for (y = slice_start; y < slice_end; y++) {

         for (x = 0; x < w; x++)

             dst[x] = slice[x] * weights[x];
         slice += slice_linesize;

         dst += dst_linesize;
         weights += dst_linesize;
     }

 
     return 0;

 }
 
 static int filter_frame(AVFilterLink *inlink, AVFrame *in)
 {
     AVFilterContext *ctx = inlink->dst;
     DCTdnoizContext *s = ctx->priv;
     AVFilterLink *outlink = inlink->dst->outputs[0];
     int direct, plane;
     AVFrame *out;
 
     if (av_frame_is_writable(in)) {
         direct = 1;
         out = in;
     } else {
         direct = 0;
         out = ff_get_video_buffer(outlink, outlink->w, outlink->h);
         if (!out) {
             av_frame_free(&in);
             return AVERROR(ENOMEM);
         }
         av_frame_copy_props(out, in);
     }
 

     s->color_decorrelation(s->cbuf[0], s->p_linesize,

                            (const uint8_t **)in->data, in->linesize[0],

                            s->pr_width, s->pr_height);

     for (plane = 0; plane < 3; plane++) {
         ThreadData td = {
             .src = s->cbuf[0][plane],
             .dst = s->cbuf[1][plane],
         };
         ctx->internal->execute(ctx, filter_slice, &td, NULL, s->nb_threads);
     }

     s->color_correlation(out->data, out->linesize[0],

                          s->cbuf[1], s->p_linesize,
                          s->pr_width, s->pr_height);

 
     if (!direct) {
         int y;
         uint8_t *dst = out->data[0];
         const uint8_t *src = in->data[0];
         const int dst_linesize = out->linesize[0];
         const int src_linesize = in->linesize[0];
         const int hpad = (inlink->w - s->pr_width) * 3;
         const int vpad = (inlink->h - s->pr_height);
 
         if (hpad) {
             uint8_t       *dstp = dst + s->pr_width * 3;
             const uint8_t *srcp = src + s->pr_width * 3;
 
             for (y = 0; y < s->pr_height; y++) {
                 memcpy(dstp, srcp, hpad);
                 dstp += dst_linesize;
                 srcp += src_linesize;
             }
         }
         if (vpad) {
             uint8_t       *dstp = dst + s->pr_height * dst_linesize;
             const uint8_t *srcp = src + s->pr_height * src_linesize;
 
             for (y = 0; y < vpad; y++) {
                 memcpy(dstp, srcp, inlink->w * 3);
                 dstp += dst_linesize;
                 srcp += src_linesize;
             }
         }
 
         av_frame_free(&in);
     }
 
     return ff_filter_frame(outlink, out);
 }
 
 static av_cold void uninit(AVFilterContext *ctx)
 {
     int i;
     DCTdnoizContext *s = ctx->priv;
 

     av_freep(&s->weights);

     for (i = 0; i < 2; i++) {

         av_freep(&s->cbuf[i][0]);
         av_freep(&s->cbuf[i][1]);
         av_freep(&s->cbuf[i][2]);

     }

     for (i = 0; i < s->nb_threads; i++) {

         av_freep(&s->slices[i]);

         av_expr_free(s->expr[i]);
     }

 }
 
 static const AVFilterPad dctdnoiz_inputs[] = {
     {
         .name         = "default",
         .type         = AVMEDIA_TYPE_VIDEO,
         .filter_frame = filter_frame,
         .config_props = config_input,
     },
     { NULL }
 };
 
 static const AVFilterPad dctdnoiz_outputs[] = {
     {
         .name = "default",
         .type = AVMEDIA_TYPE_VIDEO,
     },
     { NULL }
 };
 

 AVFilter ff_vf_dctdnoiz = {

     .name          = "dctdnoiz",
     .description   = NULL_IF_CONFIG_SMALL("Denoise frames using 2D DCT."),
     .priv_size     = sizeof(DCTdnoizContext),
     .init          = init,
     .uninit        = uninit,
     .query_formats = query_formats,
     .inputs        = dctdnoiz_inputs,
     .outputs       = dctdnoiz_outputs,
     .priv_class    = &dctdnoiz_class,

     .flags         = AVFILTER_FLAG_SUPPORT_TIMELINE_GENERIC | AVFILTER_FLAG_SLICE_THREADS,

 };