text: /*
   * 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, sign = 1;
      int nb_in_channels[2] = { 0, 0 }; // number of unnamed and named input channels
      int used_out_ch[MAX_CHANNELS] = {0};
      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);
      if (!arg) {
          av_log(ctx, AV_LOG_ERROR, "Channel layout not specified\n");
          ret = AVERROR(EINVAL);
          goto fail;
      }
      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))) {
          int used_in_ch[MAX_CHANNELS] = {0};
          /* 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;
          }
          if (used_out_ch[out_ch_id]) {
              av_log(ctx, AV_LOG_ERROR,
                     "Can not reference out channel %d twice\n", out_ch_id);
              ret = AVERROR(EINVAL);
              goto fail;
          }
          used_out_ch[out_ch_id] = 1;
          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 */
          sign = 1;
          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;
              }
              if (used_in_ch[in_ch_id]) {
                  av_log(ctx, AV_LOG_ERROR,
                         "Can not reference in channel %d twice\n", in_ch_id);
                  ret = AVERROR(EINVAL);
                  goto fail;
              }
              used_in_ch[in_ch_id] = 1;
              pan->gain[out_ch_id][in_ch_id] = sign * gain;
              skip_spaces(&arg);
              if (!*arg)
                  break;
              if (*arg == '-') {
                  sign = -1;
              } else if (*arg != '+') {
                  av_log(ctx, AV_LOG_ERROR, "Syntax error near \"%.8s\"\n", arg);
                  ret = AVERROR(EINVAL);
                  goto fail;
              } else {
                  sign = 1;
              }
              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];
      AVFilterChannelLayouts *layouts;
      int ret;
  
      pan->pure_gains = are_gains_pure(pan);
      /* libswr supports any sample and packing formats */
      if ((ret = ff_set_common_formats(ctx, ff_all_formats(AVMEDIA_TYPE_AUDIO))) < 0)
          return ret;
  
      if ((ret = ff_set_common_all_samplerates(ctx)) < 0)
          return ret;
  
      // inlink supports any channel layout
      layouts = ff_all_channel_counts();
      if ((ret = ff_channel_layouts_ref(layouts, &inlink->outcfg.channel_layouts)) < 0)
          return ret;
  
      // outlink supports only requested output channel layout
      layouts = NULL;
      if ((ret = ff_add_channel_layout(&layouts,
                            pan->out_channel_layout ? pan->out_channel_layout :
                            FF_COUNT2LAYOUT(pan->nb_output_channels))) < 0)
          return ret;
      return ff_channel_layouts_ref(layouts, &outlink->incfg.channel_layouts);
  }
  
  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 += fabs(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) {
          av_frame_free(&insamples);
          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;
      outsamples->channels = 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 }, 0, 0, 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,
      },
  };
  
  static const AVFilterPad pan_outputs[] = {
      {
          .name = "default",
          .type = AVMEDIA_TYPE_AUDIO,
      },
  };
  
  const 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,
      FILTER_INPUTS(pan_inputs),
      FILTER_OUTPUTS(pan_outputs),
  };
  