/*
  * 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/channel_layout.h"

 #include "avfilter.h"

 #include "audio.h"

 #include "formats.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)
 {

     static const int sample_rates[] = { 44100, -1 };

     AVFilterFormats *formats = NULL;

     AVFilterChannelLayouts *layout = NULL;
 

     ff_add_format(&formats, AV_SAMPLE_FMT_S16);
     ff_set_common_formats(ctx, formats);

     ff_add_channel_layout(&layout, AV_CH_LAYOUT_STEREO);
     ff_set_common_channel_layouts(ctx, layout);

     ff_set_common_samplerates(ctx, ff_make_format_list(sample_rates));

 
     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 = 0;

         for (j = 0; j < NUMTAPS; j++)
             sample += in[j] * filt[j];

         *out = av_clip_int16(sample >> 6);

         out++;
         in++;
     }
 
     return out;
 }
 

 static int filter_frame(AVFilterLink *inlink, AVFrame *insamples)

 {
     AVFilterLink *outlink = inlink->dst->outputs[0];
     int16_t *taps, *endin, *in, *out;

     AVFrame *outsamples = ff_get_audio_buffer(inlink, insamples->nb_samples);

     int len;

     if (!outsamples) {
         av_frame_free(&insamples);

         return AVERROR(ENOMEM);

     }
     av_frame_copy_props(outsamples, insamples);

     taps  = ((EarwaxContext *)inlink->dst->priv)->taps;
     out   = (int16_t *)outsamples->data[0];
     in    = (int16_t *)insamples ->data[0];
 

     len = FFMIN(NUMTAPS, 2*insamples->nb_samples);

     // copy part of new input and process with saved input

     memcpy(taps+NUMTAPS, in, len * sizeof(*taps));
     out   = scalarproduct(taps, taps + len, out);

 
     // process current input

     if (2*insamples->nb_samples >= NUMTAPS ){
         endin = in + insamples->nb_samples * 2 - NUMTAPS;
         scalarproduct(in, endin, out);
 
         // save part of input for next round
         memcpy(taps, endin, NUMTAPS * sizeof(*taps));
     } else
         memmove(taps, taps + 2*insamples->nb_samples, NUMTAPS * sizeof(*taps));

     av_frame_free(&insamples);

     return ff_filter_frame(outlink, outsamples);

 }
 

 static const AVFilterPad earwax_inputs[] = {
     {
         .name         = "default",
         .type         = AVMEDIA_TYPE_AUDIO,
         .filter_frame = filter_frame,
     },
     { NULL }
 };
 
 static const AVFilterPad earwax_outputs[] = {
     {
         .name = "default",
         .type = AVMEDIA_TYPE_AUDIO,
     },
     { NULL }
 };
 

 AVFilter avfilter_af_earwax = {
     .name           = "earwax",
     .description    = NULL_IF_CONFIG_SMALL("Widen the stereo image."),
     .query_formats  = query_formats,
     .priv_size      = sizeof(EarwaxContext),

     .inputs         = earwax_inputs,
     .outputs        = earwax_outputs,

 };