/*
  * Copyright (C) 2012 VLC authors and VideoLAN
  * Author : Sukrit Sangwan < sukritsangwan at gmail dot com >
  *
  * 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
  */
 
 #include "libavutil/channel_layout.h"
 #include "libavutil/opt.h"
 #include "avfilter.h"
 #include "audio.h"
 #include "formats.h"
 
 typedef struct StereoWidenContext {
     const AVClass *class;
 
     float delay;
     float feedback;
     float crossfeed;
     float drymix;
 
     float *buffer;

     float *cur;

     int length;
 } StereoWidenContext;
 
 #define OFFSET(x) offsetof(StereoWidenContext, x)
 #define A AV_OPT_FLAG_AUDIO_PARAM|AV_OPT_FLAG_FILTERING_PARAM
 
 static const AVOption stereowiden_options[] = {
     { "delay",     "set delay time",    OFFSET(delay),     AV_OPT_TYPE_FLOAT, {.dbl=20}, 1, 100, A },
     { "feedback",  "set feedback gain", OFFSET(feedback),  AV_OPT_TYPE_FLOAT, {.dbl=.3}, 0, 0.9, A },
     { "crossfeed", "set cross feed",    OFFSET(crossfeed), AV_OPT_TYPE_FLOAT, {.dbl=.3}, 0, 0.8, A },
     { "drymix",    "set dry-mix",       OFFSET(drymix),    AV_OPT_TYPE_FLOAT, {.dbl=.8}, 0, 1.0, A },
     { NULL }
 };
 
 AVFILTER_DEFINE_CLASS(stereowiden);
 
 static int query_formats(AVFilterContext *ctx)
 {
     AVFilterFormats *formats = NULL;
     AVFilterChannelLayouts *layout = NULL;

     int ret;

     if ((ret = ff_add_format                 (&formats, AV_SAMPLE_FMT_FLT  )) < 0 ||
         (ret = ff_set_common_formats         (ctx     , formats            )) < 0 ||
         (ret = ff_add_channel_layout         (&layout , AV_CH_LAYOUT_STEREO)) < 0 ||
         (ret = ff_set_common_channel_layouts (ctx     , layout             )) < 0)
         return ret;

 
     formats = ff_all_samplerates();
     return ff_set_common_samplerates(ctx, formats);
 }
 
 static int config_input(AVFilterLink *inlink)
 {
     AVFilterContext *ctx = inlink->dst;
     StereoWidenContext *s = ctx->priv;
 

     s->length = s->delay * inlink->sample_rate / 1000;
     s->length *= 2;

     s->buffer = av_calloc(s->length, sizeof(*s->buffer));

     if (!s->buffer)
         return AVERROR(ENOMEM);

     s->cur = s->buffer;

 
     return 0;
 }
 
 static int filter_frame(AVFilterLink *inlink, AVFrame *in)
 {
     AVFilterContext *ctx = inlink->dst;
     AVFilterLink *outlink = ctx->outputs[0];
     StereoWidenContext *s = ctx->priv;
     const float *src = (const float *)in->data[0];
     const float drymix = s->drymix;
     const float crossfeed = s->crossfeed;
     const float feedback = s->feedback;

     AVFrame *out;

     float *dst;
     int n;
 
     if (av_frame_is_writable(in)) {
         out = in;
     } else {

         out = ff_get_audio_buffer(inlink, in->nb_samples);

         if (!out) {
             av_frame_free(&in);
             return AVERROR(ENOMEM);
         }
         av_frame_copy_props(out, in);
     }
     dst = (float *)out->data[0];
 

     for (n = 0; n < in->nb_samples; n++, src += 2, dst += 2, s->cur += 2) {

         const float left = src[0], right = src[1];
 

         if (s->cur == s->buffer + s->length)
             s->cur = s->buffer;

         dst[0] = drymix * left - crossfeed * right - feedback * s->cur[1];
         dst[1] = drymix * right - crossfeed * left - feedback * s->cur[0];

         s->cur[0] = left;
         s->cur[1] = right;

     }
 
     if (out != in)
         av_frame_free(&in);
     return ff_filter_frame(outlink, out);
 }
 
 static av_cold void uninit(AVFilterContext *ctx)
 {
     StereoWidenContext *s = ctx->priv;
 
     av_freep(&s->buffer);
 }
 
 static const AVFilterPad inputs[] = {
     {
         .name         = "default",
         .type         = AVMEDIA_TYPE_AUDIO,
         .filter_frame = filter_frame,
         .config_props = config_input,
     },
     { NULL }
 };
 
 static const AVFilterPad outputs[] = {
     {
         .name = "default",
         .type = AVMEDIA_TYPE_AUDIO,
     },
     { NULL }
 };
 
 AVFilter ff_af_stereowiden = {
     .name           = "stereowiden",
     .description    = NULL_IF_CONFIG_SMALL("Apply stereo widening effect."),
     .query_formats  = query_formats,
     .priv_size      = sizeof(StereoWidenContext),
     .priv_class     = &stereowiden_class,
     .uninit         = uninit,
     .inputs         = inputs,
     .outputs        = outputs,
 };