/*
  * Copyright (c) 2002 Anders Johansson <ajh@atri.curtin.edu.au>

  * Copyright (c) 2011 Clément Bœsch <u pkh me>

  * Copyright (c) 2011 Nicolas George <nicolas.george@normalesup.org>
  *
  * 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
  * Audio panning filter (channels mixing)
  * Original code written by Anders Johansson for MPlayer,
  * reimplemented for FFmpeg.
  */
 
 #include <stdio.h>
 #include "libavutil/avstring.h"

 #include "libavutil/channel_layout.h"

 #include "libavutil/opt.h"
 #include "libswresample/swresample.h"

 #include "audio.h"

 #include "avfilter.h"

 #include "formats.h"

 #include "internal.h"

 #define MAX_CHANNELS 64

 typedef struct PanContext {

     const AVClass *class;
     char *args;

     int64_t out_channel_layout;

     double gain[MAX_CHANNELS][MAX_CHANNELS];

     int64_t need_renorm;
     int need_renumber;
     int nb_output_channels;

 
     int pure_gains;
     /* channel mapping specific */

     int channel_map[MAX_CHANNELS];

     struct SwrContext *swr;

 } PanContext;
 

 static void skip_spaces(char **arg)
 {
     int len = 0;
 
     sscanf(*arg, " %n", &len);
     *arg += len;
 }
 

 static int parse_channel_name(char **arg, int *rchannel, int *rnamed)
 {
     char buf[8];

     int len, i, channel_id = 0;

     int64_t layout, layout0;
 

     skip_spaces(arg);

     /* try to parse a channel name, e.g. "FL" */

     if (sscanf(*arg, "%7[A-Z]%n", buf, &len)) {

         layout0 = layout = av_get_channel_layout(buf);

         /* channel_id <- first set bit in layout */

         for (i = 32; i > 0; i >>= 1) {
             if (layout >= (int64_t)1 << i) {
                 channel_id += i;
                 layout >>= i;
             }
         }

         /* reject layouts that are not a single channel */

         if (channel_id >= MAX_CHANNELS || layout0 != (int64_t)1 << channel_id)
             return AVERROR(EINVAL);
         *rchannel = channel_id;
         *rnamed = 1;
         *arg += len;
         return 0;
     }

     /* try to parse a channel number, e.g. "c2" */

     if (sscanf(*arg, "c%d%n", &channel_id, &len) &&

         channel_id >= 0 && channel_id < MAX_CHANNELS) {
         *rchannel = channel_id;
         *rnamed = 0;
         *arg += len;
         return 0;
     }
     return AVERROR(EINVAL);
 }
 

 static av_cold int init(AVFilterContext *ctx)

 {
     PanContext *const pan = ctx->priv;

     char *arg, *arg0, *tokenizer, *args = av_strdup(pan->args);

     int out_ch_id, in_ch_id, len, named, ret;

     int nb_in_channels[2] = { 0, 0 }; // number of unnamed and named input channels
     double gain;
 

     if (!pan->args) {

         av_log(ctx, AV_LOG_ERROR,
                "pan filter needs a channel layout and a set "

                "of channel definitions as parameter\n");

         return AVERROR(EINVAL);
     }

     if (!args)
         return AVERROR(ENOMEM);

     arg = av_strtok(args, "|", &tokenizer);

     ret = ff_parse_channel_layout(&pan->out_channel_layout,
                                   &pan->nb_output_channels, arg, ctx);

     if (ret < 0)

         goto fail;

 
     /* parse channel specifications */

     while ((arg = arg0 = av_strtok(NULL, "|", &tokenizer))) {

         /* channel name */
         if (parse_channel_name(&arg, &out_ch_id, &named)) {
             av_log(ctx, AV_LOG_ERROR,
                    "Expected out channel name, got \"%.8s\"\n", arg);

             ret = AVERROR(EINVAL);
             goto fail;

         }
         if (named) {
             if (!((pan->out_channel_layout >> out_ch_id) & 1)) {
                 av_log(ctx, AV_LOG_ERROR,
                        "Channel \"%.8s\" does not exist in the chosen layout\n", arg0);

                 ret = AVERROR(EINVAL);
                 goto fail;

             }
             /* get the channel number in the output channel layout:
              * out_channel_layout & ((1 << out_ch_id) - 1) are all the
              * channels that come before out_ch_id,
              * so their count is the index of out_ch_id */
             out_ch_id = av_get_channel_layout_nb_channels(pan->out_channel_layout & (((int64_t)1 << out_ch_id) - 1));
         }
         if (out_ch_id < 0 || out_ch_id >= pan->nb_output_channels) {
             av_log(ctx, AV_LOG_ERROR,
                    "Invalid out channel name \"%.8s\"\n", arg0);

             ret = AVERROR(EINVAL);
             goto fail;

         }

         skip_spaces(&arg);

         if (*arg == '=') {
             arg++;
         } else if (*arg == '<') {
             pan->need_renorm |= (int64_t)1 << out_ch_id;
             arg++;
         } else {
             av_log(ctx, AV_LOG_ERROR,
                    "Syntax error after channel name in \"%.8s\"\n", arg0);

             ret = AVERROR(EINVAL);
             goto fail;

         }
         /* gains */
         while (1) {
             gain = 1;

             if (sscanf(arg, "%lf%n *%n", &gain, &len, &len))

                 arg += len;
             if (parse_channel_name(&arg, &in_ch_id, &named)){
                 av_log(ctx, AV_LOG_ERROR,
                        "Expected in channel name, got \"%.8s\"\n", arg);

                  ret = AVERROR(EINVAL);
                  goto fail;

             }
             nb_in_channels[named]++;
             if (nb_in_channels[!named]) {
                 av_log(ctx, AV_LOG_ERROR,
                        "Can not mix named and numbered channels\n");

                 ret = AVERROR(EINVAL);
                 goto fail;

             }

             pan->gain[out_ch_id][in_ch_id] = gain;

             skip_spaces(&arg);

             if (!*arg)
                 break;
             if (*arg != '+') {
                 av_log(ctx, AV_LOG_ERROR, "Syntax error near \"%.8s\"\n", arg);

                 ret = AVERROR(EINVAL);
                 goto fail;

             }
             arg++;
         }
     }
     pan->need_renumber = !!nb_in_channels[1];
 

     ret = 0;
 fail:

     av_free(args);

     return ret;

 }
 

 static int are_gains_pure(const PanContext *pan)
 {
     int i, j;
 
     for (i = 0; i < MAX_CHANNELS; i++) {
         int nb_gain = 0;
 
         for (j = 0; j < MAX_CHANNELS; j++) {

             double gain = pan->gain[i][j];

 
             /* channel mapping is effective only if 0% or 100% of a channel is
              * selected... */
             if (gain != 0. && gain != 1.)
                 return 0;
             /* ...and if the output channel is only composed of one input */
             if (gain && nb_gain++)
                 return 0;
         }
     }
     return 1;
 }
 

 static int query_formats(AVFilterContext *ctx)
 {
     PanContext *pan = ctx->priv;
     AVFilterLink *inlink  = ctx->inputs[0];
     AVFilterLink *outlink = ctx->outputs[0];

     AVFilterFormats *formats = NULL;

     AVFilterChannelLayouts *layouts;

 
     pan->pure_gains = are_gains_pure(pan);
     /* libswr supports any sample and packing formats */

     ff_set_common_formats(ctx, ff_all_formats(AVMEDIA_TYPE_AUDIO));

     formats = ff_all_samplerates();
     if (!formats)
         return AVERROR(ENOMEM);
     ff_set_common_samplerates(ctx, formats);
 

     // inlink supports any channel layout

     layouts = ff_all_channel_counts();

     ff_channel_layouts_ref(layouts, &inlink->out_channel_layouts);

 
     // outlink supports only requested output channel layout

     layouts = NULL;

     ff_add_channel_layout(&layouts,
                           pan->out_channel_layout ? pan->out_channel_layout :
                           FF_COUNT2LAYOUT(pan->nb_output_channels));

     ff_channel_layouts_ref(layouts, &outlink->in_channel_layouts);

     return 0;
 }
 

 static int config_props(AVFilterLink *link)
 {
     AVFilterContext *ctx = link->dst;
     PanContext *pan = ctx->priv;
     char buf[1024], *cur;
     int i, j, k, r;
     double t;
 
     if (pan->need_renumber) {
         // input channels were given by their name: renumber them
         for (i = j = 0; i < MAX_CHANNELS; i++) {
             if ((link->channel_layout >> i) & 1) {
                 for (k = 0; k < pan->nb_output_channels; k++)

                     pan->gain[k][j] = pan->gain[k][i];

                 j++;
             }
         }
     }

     // sanity check; can't be done in query_formats since the inlink
     // channel layout is unknown at that time

     if (link->channels > MAX_CHANNELS ||
         pan->nb_output_channels > MAX_CHANNELS) {

         av_log(ctx, AV_LOG_ERROR,

                "af_pan supports a maximum of %d channels. "

                "Feel free to ask for a higher limit.\n", MAX_CHANNELS);

         return AVERROR_PATCHWELCOME;
     }

     // init libswresample context
     pan->swr = swr_alloc_set_opts(pan->swr,
                                   pan->out_channel_layout, link->format, link->sample_rate,
                                   link->channel_layout,    link->format, link->sample_rate,
                                   0, ctx);
     if (!pan->swr)
         return AVERROR(ENOMEM);

     if (!link->channel_layout) {
         if (av_opt_set_int(pan->swr, "ich", link->channels, 0) < 0)
             return AVERROR(EINVAL);
     }
     if (!pan->out_channel_layout) {
         if (av_opt_set_int(pan->swr, "och", pan->nb_output_channels, 0) < 0)
             return AVERROR(EINVAL);
     }

 
     // gains are pure, init the channel mapping
     if (pan->pure_gains) {
 

         // get channel map from the pure gains
         for (i = 0; i < pan->nb_output_channels; i++) {
             int ch_id = -1;

             for (j = 0; j < link->channels; j++) {

                 if (pan->gain[i][j]) {

                     ch_id = j;
                     break;
                 }
             }
             pan->channel_map[i] = ch_id;
         }
 
         av_opt_set_int(pan->swr, "icl", pan->out_channel_layout, 0);
         av_opt_set_int(pan->swr, "uch", pan->nb_output_channels, 0);
         swr_set_channel_mapping(pan->swr, pan->channel_map);
     } else {

         // renormalize
         for (i = 0; i < pan->nb_output_channels; i++) {
             if (!((pan->need_renorm >> i) & 1))
                 continue;
             t = 0;

             for (j = 0; j < link->channels; j++)

                 t += pan->gain[i][j];

             if (t > -1E-5 && t < 1E-5) {
                 // t is almost 0 but not exactly, this is probably a mistake
                 if (t)
                     av_log(ctx, AV_LOG_WARNING,
                            "Degenerate coefficients while renormalizing\n");
                 continue;
             }

             for (j = 0; j < link->channels; j++)

                 pan->gain[i][j] /= t;

         }

         av_opt_set_int(pan->swr, "icl", link->channel_layout, 0);
         av_opt_set_int(pan->swr, "ocl", pan->out_channel_layout, 0);

         swr_set_matrix(pan->swr, pan->gain[0], pan->gain[1] - pan->gain[0]);

     }

 
     r = swr_init(pan->swr);
     if (r < 0)
         return r;
 

     // summary
     for (i = 0; i < pan->nb_output_channels; i++) {
         cur = buf;

         for (j = 0; j < link->channels; j++) {

             r = snprintf(cur, buf + sizeof(buf) - cur, "%s%.3g i%d",

                          j ? " + " : "", pan->gain[i][j], j);

             cur += FFMIN(buf + sizeof(buf) - cur, r);
         }

         av_log(ctx, AV_LOG_VERBOSE, "o%d = %s\n", i, buf);

     }

     // add channel mapping summary if possible
     if (pan->pure_gains) {
         av_log(ctx, AV_LOG_INFO, "Pure channel mapping detected:");
         for (i = 0; i < pan->nb_output_channels; i++)
             if (pan->channel_map[i] < 0)
                 av_log(ctx, AV_LOG_INFO, " M");
             else
                 av_log(ctx, AV_LOG_INFO, " %d", pan->channel_map[i]);
         av_log(ctx, AV_LOG_INFO, "\n");
         return 0;
     }

     return 0;
 }
 

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

 {

     int ret;

     int n = insamples->nb_samples;

     AVFilterLink *const outlink = inlink->dst->outputs[0];

     AVFrame *outsamples = ff_get_audio_buffer(outlink, n);

     PanContext *pan = inlink->dst->priv;
 

     if (!outsamples)
         return AVERROR(ENOMEM);

     swr_convert(pan->swr, outsamples->extended_data, n,
                 (void *)insamples->extended_data, n);

     av_frame_copy_props(outsamples, insamples);
     outsamples->channel_layout = outlink->channel_layout;

     av_frame_set_channels(outsamples, outlink->channels);

     ret = ff_filter_frame(outlink, outsamples);

     av_frame_free(&insamples);

     return ret;

 }
 

 static av_cold void uninit(AVFilterContext *ctx)
 {
     PanContext *pan = ctx->priv;
     swr_free(&pan->swr);
 }
 

 #define OFFSET(x) offsetof(PanContext, x)
 
 static const AVOption pan_options[] = {
     { "args", NULL, OFFSET(args), AV_OPT_TYPE_STRING, { .str = NULL }, CHAR_MIN, CHAR_MAX, AV_OPT_FLAG_AUDIO_PARAM | AV_OPT_FLAG_FILTERING_PARAM },
     { NULL }
 };
 
 AVFILTER_DEFINE_CLASS(pan);
 

 static const AVFilterPad pan_inputs[] = {
     {
         .name         = "default",
         .type         = AVMEDIA_TYPE_AUDIO,
         .config_props = config_props,
         .filter_frame = filter_frame,
     },
     { NULL }
 };
 
 static const AVFilterPad pan_outputs[] = {
     {
         .name = "default",
         .type = AVMEDIA_TYPE_AUDIO,
     },
     { NULL }
 };
 

 AVFilter ff_af_pan = {

     .name          = "pan",

     .description   = NULL_IF_CONFIG_SMALL("Remix channels with coefficients (panning)."),

     .priv_size     = sizeof(PanContext),

     .priv_class    = &pan_class,

     .init          = init,

     .uninit        = uninit,

     .query_formats = query_formats,

     .inputs        = pan_inputs,
     .outputs       = pan_outputs,

 };