/*
  * Copyright (C) 2012 Michael Niedermayer (michaelni@gmx.at)
  *
  * This file is part of libswresample
  *
  * libswresample 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.
  *
  * libswresample 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 libswresample; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
 #include "libavutil/avassert.h"
 #include "swresample_internal.h"
 

 void swri_get_dither(SwrContext *s, void *dst, int len, unsigned seed, enum AVSampleFormat out_fmt, enum AVSampleFormat in_fmt) {

     double scale = 0;

 #define TMP_EXTRA 2
     double *tmp = av_malloc((len + TMP_EXTRA) * sizeof(double));

     int i;
 

     out_fmt = av_get_packed_sample_fmt(out_fmt);
     in_fmt  = av_get_packed_sample_fmt( in_fmt);
 

     if(in_fmt == AV_SAMPLE_FMT_FLT || in_fmt == AV_SAMPLE_FMT_DBL){
         if(out_fmt == AV_SAMPLE_FMT_S32) scale = 1.0/(1L<<31);
         if(out_fmt == AV_SAMPLE_FMT_S16) scale = 1.0/(1L<<15);
         if(out_fmt == AV_SAMPLE_FMT_U8 ) scale = 1.0/(1L<< 7);
     }
     if(in_fmt == AV_SAMPLE_FMT_S32 && out_fmt == AV_SAMPLE_FMT_S16) scale = 1L<<16;
     if(in_fmt == AV_SAMPLE_FMT_S32 && out_fmt == AV_SAMPLE_FMT_U8 ) scale = 1L<<24;
     if(in_fmt == AV_SAMPLE_FMT_S16 && out_fmt == AV_SAMPLE_FMT_U8 ) scale = 1L<<8;
 

     scale *= s->dither_scale;
 

     for(i=0; i<len + TMP_EXTRA; i++){

         double v;
         seed = seed* 1664525 + 1013904223;
 

         switch(s->dither_method){

             case SWR_DITHER_RECTANGULAR: v= ((double)seed) / UINT_MAX - 0.5; break;

             case SWR_DITHER_TRIANGULAR :

             case SWR_DITHER_TRIANGULAR_HIGHPASS :

                 v = ((double)seed) / UINT_MAX;
                 seed = seed*1664525 + 1013904223;
                 v-= ((double)seed) / UINT_MAX;
                 break;

             default: av_assert0(0);
         }

         tmp[i] = v;
     }
 
     for(i=0; i<len; i++){
         double v;
 

         switch(s->dither_method){

             case SWR_DITHER_RECTANGULAR:
             case SWR_DITHER_TRIANGULAR :
                 v = tmp[i];
                 break;
             case SWR_DITHER_TRIANGULAR_HIGHPASS :
                 v = (- tmp[i] + 2*tmp[i+1] - tmp[i+2]) / sqrt(6);
                 break;
             default: av_assert0(0);
         }

 
         v*= scale;
 
         switch(in_fmt){
             case AV_SAMPLE_FMT_S16: ((int16_t*)dst)[i] = v; break;
             case AV_SAMPLE_FMT_S32: ((int32_t*)dst)[i] = v; break;
             case AV_SAMPLE_FMT_FLT: ((float  *)dst)[i] = v; break;
             case AV_SAMPLE_FMT_DBL: ((double *)dst)[i] = v; break;
             default: av_assert0(0);
         }
     }

 
     av_free(tmp);

 }