/*
  * Copyright (c) 2011 Mina Nagy Zaki
  * Copyright (c) 2000 Edward Beingessner And Sundry Contributors.
  * This source code is freely redistributable and may be used for any purpose.
  * This copyright notice must be maintained.  Edward Beingessner And Sundry
  * Contributors are not responsible for the consequences of using this
  * software.
  *
  * 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
  */
 
 /**
  * @file
  * Stereo Widening Effect. Adds audio cues to move stereo image in
  * front of the listener. Adapted from the libsox earwax effect.
  */
 
 #include "libavutil/audioconvert.h"
 #include "avfilter.h"
 
 #define NUMTAPS 64
 
 static const int8_t filt[NUMTAPS] = {
 /* 30°  330° */
     4,   -6,     /* 32 tap stereo FIR filter. */
     4,  -11,     /* One side filters as if the */
    -1,   -5,     /* signal was from 30 degrees */
     3,    3,     /* from the ear, the other as */
    -2,    5,     /* if 330 degrees. */
    -5,    0,
     9,    1,
     6,    3,     /*                         Input                         */
    -4,   -1,     /*                   Left         Right                  */
    -5,   -3,     /*                __________   __________                */
    -2,   -5,     /*               |          | |          |               */
    -7,    1,     /*           .---|  Hh,0(f) | |  Hh,0(f) |---.           */
     6,   -7,     /*          /    |__________| |__________|    \          */
    30,  -29,     /*         /                \ /                \         */
    12,   -3,     /*        /                  X                  \        */
   -11,    4,     /*       /                  / \                  \       */
    -3,    7,     /*  ____V_____   __________V   V__________   _____V____  */
   -20,   23,     /* |          | |          |   |          | |          | */
     2,    0,     /* | Hh,30(f) | | Hh,330(f)|   | Hh,330(f)| | Hh,30(f) | */
     1,   -6,     /* |__________| |__________|   |__________| |__________| */
   -14,   -5,     /*      \     ___      /           \      ___     /      */
    15,  -18,     /*       \   /   \    /    _____    \    /   \   /       */
     6,    7,     /*        `->| + |<--'    /     \    `-->| + |<-'        */
    15,  -10,     /*           \___/      _/       \_      \___/           */
   -14,   22,     /*               \     / \       / \     /               */
    -7,   -2,     /*                `--->| |       | |<---'                */
    -4,    9,     /*                     \_/       \_/                     */
     6,  -12,     /*                                                       */
     6,   -6,     /*                       Headphones                      */
     0,  -11,
     0,   -5,
     4,    0};
 
 typedef struct {
     int16_t taps[NUMTAPS * 2];
 } EarwaxContext;
 
 static int query_formats(AVFilterContext *ctx)
 {
     AVFilterFormats *formats = NULL;
     avfilter_add_format(&formats, AV_SAMPLE_FMT_S16);
     avfilter_set_common_sample_formats(ctx, formats);
     formats = NULL;
     avfilter_add_format(&formats, AV_CH_LAYOUT_STEREO);
     avfilter_set_common_channel_layouts(ctx, formats);
     formats = NULL;
     avfilter_add_format(&formats, AVFILTER_PACKED);
     avfilter_set_common_packing_formats(ctx, formats);
 
     return 0;
 }
 
 static int config_input(AVFilterLink *inlink)
 {
     if (inlink->sample_rate != 44100) {
         av_log(inlink->dst, AV_LOG_ERROR,
                "The earwax filter only works for 44.1kHz audio. Insert "
                "a resample filter before this\n");
         return AVERROR(EINVAL);
     }
     return 0;
 }
 
 //FIXME: replace with DSPContext.scalarproduct_int16
 static inline int16_t *scalarproduct(const int16_t *in, const int16_t *endin, int16_t *out)
 {
     int32_t sample;
     int16_t j;
 
     while (in < endin) {
         sample = 32;
         for (j = 0; j < NUMTAPS; j++)
             sample += in[j] * filt[j];
         *out = sample >> 6;
         out++;
         in++;
     }
 
     return out;
 }
 
 static void filter_samples(AVFilterLink *inlink, AVFilterBufferRef *insamples)
 {
     AVFilterLink *outlink = inlink->dst->outputs[0];
     int16_t *taps, *endin, *in, *out;
     AVFilterBufferRef *outsamples =
         avfilter_get_audio_buffer(inlink, AV_PERM_WRITE,
                                   insamples->audio->nb_samples);

     avfilter_copy_buffer_ref_props(outsamples, insamples);
 

     taps  = ((EarwaxContext *)inlink->dst->priv)->taps;
     out   = (int16_t *)outsamples->data[0];
     in    = (int16_t *)insamples ->data[0];
 
     // copy part of new input and process with saved input
     memcpy(taps+NUMTAPS, in, NUMTAPS * sizeof(*taps));
     out   = scalarproduct(taps, taps + NUMTAPS, out);
 
     // process current input
     endin = in + insamples->audio->nb_samples * 2 - NUMTAPS;
     out   = scalarproduct(in, endin, out);
 
     // save part of input for next round
     memcpy(taps, endin, NUMTAPS * sizeof(*taps));
 
     avfilter_filter_samples(outlink, outsamples);
     avfilter_unref_buffer(insamples);
 }
 
 AVFilter avfilter_af_earwax = {
     .name           = "earwax",
     .description    = NULL_IF_CONFIG_SMALL("Widen the stereo image."),
     .query_formats  = query_formats,
     .priv_size      = sizeof(EarwaxContext),

     .inputs  = (const AVFilterPad[])  {{  .name     = "default",

                                     .type           = AVMEDIA_TYPE_AUDIO,
                                     .filter_samples = filter_samples,
                                     .config_props   = config_input,
                                     .min_perms      = AV_PERM_READ, },
                                  {  .name = NULL}},
 

     .outputs = (const AVFilterPad[])  {{  .name     = "default",

                                     .type           = AVMEDIA_TYPE_AUDIO, },
                                  {  .name = NULL}},
 };