/*
  * Copyright (c) 2017 Paul B Mahol
  *
  * 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/audio_fifo.h"
 #include "libavutil/channel_layout.h"
 #include "libavutil/opt.h"
 #include "libavcodec/avfft.h"
 #include "avfilter.h"
 #include "audio.h"
 #include "formats.h"
 
 typedef struct AudioSurroundContext {
     const AVClass *class;
 
     char *out_channel_layout_str;

     char *in_channel_layout_str;

     float level_in;
     float level_out;

     float fc_in;
     float fc_out;
     float lfe_in;
     float lfe_out;
 
     float *input_levels;
     float *output_levels;

     int output_lfe;
     int lowcutf;
     int highcutf;
 
     float lowcut;
     float highcut;
 
     uint64_t out_channel_layout;

     uint64_t in_channel_layout;

     int nb_in_channels;
     int nb_out_channels;
 
     AVFrame *input;
     AVFrame *output;
     AVFrame *overlap_buffer;
 
     int buf_size;
     int hop_size;
     AVAudioFifo *fifo;
     RDFTContext **rdft, **irdft;
     float *window_func_lut;
 
     int64_t pts;
 

     void (*filter)(AVFilterContext *ctx);
     void (*upmix_stereo)(AVFilterContext *ctx,
                          float l_phase,
                          float r_phase,
                          float c_phase,
                          float mag_total,
                          float x, float y,
                          int n);
     void (*upmix_2_1)(AVFilterContext *ctx,
                       float l_phase,
                       float r_phase,
                       float c_phase,
                       float mag_total,
                       float lfe_im,
                       float lfe_re,
                       float x, float y,
                       int n);
     void (*upmix_3_0)(AVFilterContext *ctx,
                       float l_phase,
                       float r_phase,
                       float c_mag,
                       float c_phase,
                       float mag_total,
                       float x, float y,
                       int n);

     void (*upmix_5_0)(AVFilterContext *ctx,
                       float c_re, float c_im,
                       float mag_totall, float mag_totalr,
                       float fl_phase, float fr_phase,
                       float bl_phase, float br_phase,
                       float sl_phase, float sr_phase,
                       float xl, float yl,
                       float xr, float yr,
                       int n);

     void (*upmix_5_1)(AVFilterContext *ctx,
                       float c_re, float c_im,
                       float lfe_re, float lfe_im,
                       float mag_totall, float mag_totalr,
                       float fl_phase, float fr_phase,
                       float bl_phase, float br_phase,
                       float sl_phase, float sr_phase,
                       float xl, float yl,
                       float xr, float yr,
                       int n);

 } AudioSurroundContext;
 
 static int query_formats(AVFilterContext *ctx)
 {
     AudioSurroundContext *s = ctx->priv;
     AVFilterFormats *formats = NULL;
     AVFilterChannelLayouts *layouts = NULL;
     int ret;
 
     ret = ff_add_format(&formats, AV_SAMPLE_FMT_FLTP);
     if (ret)
         return ret;
     ret = ff_set_common_formats(ctx, formats);
     if (ret)
         return ret;
 
     layouts = NULL;
     ret = ff_add_channel_layout(&layouts, s->out_channel_layout);
     if (ret)
         return ret;
 
     ret = ff_channel_layouts_ref(layouts, &ctx->outputs[0]->in_channel_layouts);
     if (ret)
         return ret;
 
     layouts = NULL;

     ret = ff_add_channel_layout(&layouts, s->in_channel_layout);

     if (ret)
         return ret;
 
     ret = ff_channel_layouts_ref(layouts, &ctx->inputs[0]->out_channel_layouts);
     if (ret)
         return ret;
 
     formats = ff_all_samplerates();
     if (!formats)
         return AVERROR(ENOMEM);
     return ff_set_common_samplerates(ctx, formats);
 }
 
 static int config_input(AVFilterLink *inlink)
 {
     AVFilterContext *ctx = inlink->dst;
     AudioSurroundContext *s = ctx->priv;
     int ch;
 
     s->rdft = av_calloc(inlink->channels, sizeof(*s->rdft));
     if (!s->rdft)
         return AVERROR(ENOMEM);
 
     for (ch = 0; ch < inlink->channels; ch++) {
         s->rdft[ch]  = av_rdft_init(ff_log2(s->buf_size), DFT_R2C);
         if (!s->rdft[ch])
             return AVERROR(ENOMEM);
     }
     s->nb_in_channels = inlink->channels;

     s->input_levels = av_malloc_array(s->nb_in_channels, sizeof(*s->input_levels));
     if (!s->input_levels)
         return AVERROR(ENOMEM);
     for (ch = 0;  ch < s->nb_in_channels; ch++)
         s->input_levels[ch] = s->level_in;
     ch = av_get_channel_layout_channel_index(inlink->channel_layout, AV_CH_FRONT_CENTER);
     if (ch >= 0)
         s->input_levels[ch] *= s->fc_in;
     ch = av_get_channel_layout_channel_index(inlink->channel_layout, AV_CH_LOW_FREQUENCY);
     if (ch >= 0)
         s->input_levels[ch] *= s->lfe_in;

 
     s->input = ff_get_audio_buffer(inlink, s->buf_size * 2);
     if (!s->input)
         return AVERROR(ENOMEM);
 
     s->fifo = av_audio_fifo_alloc(inlink->format, inlink->channels, s->buf_size);
     if (!s->fifo)
         return AVERROR(ENOMEM);
 
     s->lowcut = 1.f * s->lowcutf / (inlink->sample_rate * 0.5) * (s->buf_size / 2);
     s->highcut = 1.f * s->highcutf / (inlink->sample_rate * 0.5) * (s->buf_size / 2);
 
     return 0;
 }
 
 static int config_output(AVFilterLink *outlink)
 {
     AVFilterContext *ctx = outlink->src;
     AudioSurroundContext *s = ctx->priv;
     int ch;
 
     s->irdft = av_calloc(outlink->channels, sizeof(*s->irdft));
     if (!s->irdft)
         return AVERROR(ENOMEM);
 
     for (ch = 0; ch < outlink->channels; ch++) {
         s->irdft[ch] = av_rdft_init(ff_log2(s->buf_size), IDFT_C2R);
         if (!s->irdft[ch])
             return AVERROR(ENOMEM);
     }
     s->nb_out_channels = outlink->channels;

     s->output_levels = av_malloc_array(s->nb_out_channels, sizeof(*s->output_levels));
     if (!s->output_levels)
         return AVERROR(ENOMEM);
     for (ch = 0;  ch < s->nb_out_channels; ch++)
         s->output_levels[ch] = s->level_out;
     ch = av_get_channel_layout_channel_index(outlink->channel_layout, AV_CH_FRONT_CENTER);
     if (ch >= 0)
         s->output_levels[ch] *= s->fc_out;
     ch = av_get_channel_layout_channel_index(outlink->channel_layout, AV_CH_LOW_FREQUENCY);
     if (ch >= 0)
         s->output_levels[ch] *= s->lfe_out;

 
     s->output = ff_get_audio_buffer(outlink, s->buf_size * 2);
     s->overlap_buffer = ff_get_audio_buffer(outlink, s->buf_size * 2);
     if (!s->overlap_buffer || !s->output)
         return AVERROR(ENOMEM);
 
     return 0;
 }
 
 static void stereo_position(float a, float p, float *x, float *y)
 {
       *x = av_clipf(a+FFMAX(0, sinf(p-M_PI_2))*FFDIFFSIGN(a,0), -1, 1);
       *y = av_clipf(cosf(a*M_PI_2+M_PI)*cosf(M_PI_2-p/M_PI)*M_LN10+1, -1, 1);
 }
 
 static inline void get_lfe(int output_lfe, int n, float lowcut, float highcut,
                            float *lfe_mag, float *mag_total)
 {
     if (output_lfe && n < highcut) {
         *lfe_mag    = n < lowcut ? 1.f : .5f*(1.f+cosf(M_PI*(lowcut-n)/(lowcut-highcut)));
         *lfe_mag   *= *mag_total;
         *mag_total -= *lfe_mag;
     } else {
         *lfe_mag = 0.f;
     }
 }
 
 static void upmix_1_0(AVFilterContext *ctx,
                       float l_phase,
                       float r_phase,
                       float c_phase,
                       float mag_total,
                       float x, float y,
                       int n)
 {
     AudioSurroundContext *s = ctx->priv;
     float mag, *dst;
 
     dst = (float *)s->output->extended_data[0];
 
     mag = sqrtf(1.f - fabsf(x)) * ((y + 1.f) * .5f) * mag_total;
 
     dst[2 * n    ] = mag * cosf(c_phase);
     dst[2 * n + 1] = mag * sinf(c_phase);
 }
 
 static void upmix_stereo(AVFilterContext *ctx,
                          float l_phase,
                          float r_phase,
                          float c_phase,
                          float mag_total,
                          float x, float y,
                          int n)
 {
     AudioSurroundContext *s = ctx->priv;
     float l_mag, r_mag, *dstl, *dstr;
 
     dstl = (float *)s->output->extended_data[0];
     dstr = (float *)s->output->extended_data[1];
 
     l_mag = sqrtf(.5f * ( x + 1.f)) * ((y + 1.f) * .5f) * mag_total;
     r_mag = sqrtf(.5f * (-x + 1.f)) * ((y + 1.f) * .5f) * mag_total;
 
     dstl[2 * n    ] = l_mag * cosf(l_phase);
     dstl[2 * n + 1] = l_mag * sinf(l_phase);
 
     dstr[2 * n    ] = r_mag * cosf(r_phase);
     dstr[2 * n + 1] = r_mag * sinf(r_phase);
 }
 
 static void upmix_2_1(AVFilterContext *ctx,
                       float l_phase,
                       float r_phase,
                       float c_phase,
                       float mag_total,
                       float x, float y,
                       int n)
 {
     AudioSurroundContext *s = ctx->priv;
     float lfe_mag, l_mag, r_mag, *dstl, *dstr, *dstlfe;
 
     dstl = (float *)s->output->extended_data[0];
     dstr = (float *)s->output->extended_data[1];
     dstlfe = (float *)s->output->extended_data[2];
 
     get_lfe(s->output_lfe, n, s->lowcut, s->highcut, &lfe_mag, &mag_total);
 
     l_mag = sqrtf(.5f * ( x + 1.f)) * ((y + 1.f) * .5f) * mag_total;
     r_mag = sqrtf(.5f * (-x + 1.f)) * ((y + 1.f) * .5f) * mag_total;
 
     dstl[2 * n    ] = l_mag * cosf(l_phase);
     dstl[2 * n + 1] = l_mag * sinf(l_phase);
 
     dstr[2 * n    ] = r_mag * cosf(r_phase);
     dstr[2 * n + 1] = r_mag * sinf(r_phase);
 
     dstlfe[2 * n    ] = lfe_mag * cosf(c_phase);
     dstlfe[2 * n + 1] = lfe_mag * sinf(c_phase);
 }
 
 static void upmix_3_0(AVFilterContext *ctx,
                       float l_phase,
                       float r_phase,
                       float c_phase,
                       float mag_total,
                       float x, float y,
                       int n)
 {
     AudioSurroundContext *s = ctx->priv;
     float l_mag, r_mag, c_mag, *dstc, *dstl, *dstr;
 
     dstl = (float *)s->output->extended_data[0];
     dstr = (float *)s->output->extended_data[1];
     dstc = (float *)s->output->extended_data[2];
 
     c_mag = sqrtf(1.f - fabsf(x))   * ((y + 1.f) * .5f) * mag_total;
     l_mag = sqrtf(.5f * ( x + 1.f)) * ((y + 1.f) * .5f) * mag_total;
     r_mag = sqrtf(.5f * (-x + 1.f)) * ((y + 1.f) * .5f) * mag_total;
 
     dstl[2 * n    ] = l_mag * cosf(l_phase);
     dstl[2 * n + 1] = l_mag * sinf(l_phase);
 
     dstr[2 * n    ] = r_mag * cosf(r_phase);
     dstr[2 * n + 1] = r_mag * sinf(r_phase);
 
     dstc[2 * n    ] = c_mag * cosf(c_phase);
     dstc[2 * n + 1] = c_mag * sinf(c_phase);
 }
 
 static void upmix_3_1(AVFilterContext *ctx,
                       float l_phase,
                       float r_phase,
                       float c_phase,
                       float mag_total,
                       float x, float y,
                       int n)
 {
     AudioSurroundContext *s = ctx->priv;
     float lfe_mag, l_mag, r_mag, c_mag, *dstc, *dstl, *dstr, *dstlfe;
 
     dstl = (float *)s->output->extended_data[0];
     dstr = (float *)s->output->extended_data[1];
     dstc = (float *)s->output->extended_data[2];
     dstlfe = (float *)s->output->extended_data[3];
 
     get_lfe(s->output_lfe, n, s->lowcut, s->highcut, &lfe_mag, &mag_total);
 
     c_mag = sqrtf(1.f - fabsf(x))   * ((y + 1.f) * .5f) * mag_total;
     l_mag = sqrtf(.5f * ( x + 1.f)) * ((y + 1.f) * .5f) * mag_total;
     r_mag = sqrtf(.5f * (-x + 1.f)) * ((y + 1.f) * .5f) * mag_total;
 
     dstl[2 * n    ] = l_mag * cosf(l_phase);
     dstl[2 * n + 1] = l_mag * sinf(l_phase);
 
     dstr[2 * n    ] = r_mag * cosf(r_phase);
     dstr[2 * n + 1] = r_mag * sinf(r_phase);
 
     dstc[2 * n    ] = c_mag * cosf(c_phase);
     dstc[2 * n + 1] = c_mag * sinf(c_phase);
 
     dstlfe[2 * n    ] = lfe_mag * cosf(c_phase);
     dstlfe[2 * n + 1] = lfe_mag * sinf(c_phase);
 }
 

 static void upmix_3_1_surround(AVFilterContext *ctx,
                                float l_phase,
                                float r_phase,
                                float c_phase,
                                float c_mag,
                                float mag_total,
                                float x, float y,
                                int n)
 {
     AudioSurroundContext *s = ctx->priv;
     float lfe_mag, l_mag, r_mag, *dstc, *dstl, *dstr, *dstlfe;
 
     dstl = (float *)s->output->extended_data[0];
     dstr = (float *)s->output->extended_data[1];
     dstc = (float *)s->output->extended_data[2];
     dstlfe = (float *)s->output->extended_data[3];
 
     get_lfe(s->output_lfe, n, s->lowcut, s->highcut, &lfe_mag, &c_mag);
 
     l_mag = sqrtf(.5f * ( x + 1.f)) * ((y + 1.f) * .5f) * mag_total;
     r_mag = sqrtf(.5f * (-x + 1.f)) * ((y + 1.f) * .5f) * mag_total;
 
     dstl[2 * n    ] = l_mag * cosf(l_phase);
     dstl[2 * n + 1] = l_mag * sinf(l_phase);
 
     dstr[2 * n    ] = r_mag * cosf(r_phase);
     dstr[2 * n + 1] = r_mag * sinf(r_phase);
 
     dstc[2 * n    ] = c_mag * cosf(c_phase);
     dstc[2 * n + 1] = c_mag * sinf(c_phase);
 
     dstlfe[2 * n    ] = lfe_mag * cosf(c_phase);
     dstlfe[2 * n + 1] = lfe_mag * sinf(c_phase);
 }
 

 static void upmix_4_0(AVFilterContext *ctx,
                       float l_phase,
                       float r_phase,
                       float c_phase,
                       float mag_total,
                       float x, float y,
                       int n)
 {
     float b_mag, l_mag, r_mag, c_mag, *dstc, *dstl, *dstr, *dstb;
     AudioSurroundContext *s = ctx->priv;
 
     dstl = (float *)s->output->extended_data[0];
     dstr = (float *)s->output->extended_data[1];
     dstc = (float *)s->output->extended_data[2];
     dstb = (float *)s->output->extended_data[3];
 
     c_mag = sqrtf(1.f - fabsf(x))   * ((y + 1.f) * .5f) * mag_total;
     b_mag = sqrtf(1.f - fabsf(x))   * ((1.f - y) * .5f) * mag_total;
     l_mag = sqrtf(.5f * ( x + 1.f)) * ((y + 1.f) * .5f) * mag_total;
     r_mag = sqrtf(.5f * (-x + 1.f)) * ((y + 1.f) * .5f) * mag_total;
 
     dstl[2 * n    ] = l_mag * cosf(l_phase);
     dstl[2 * n + 1] = l_mag * sinf(l_phase);
 
     dstr[2 * n    ] = r_mag * cosf(r_phase);
     dstr[2 * n + 1] = r_mag * sinf(r_phase);
 
     dstc[2 * n    ] = c_mag * cosf(c_phase);
     dstc[2 * n + 1] = c_mag * sinf(c_phase);
 
     dstb[2 * n    ] = b_mag * cosf(c_phase);
     dstb[2 * n + 1] = b_mag * sinf(c_phase);
 }
 
 static void upmix_4_1(AVFilterContext *ctx,
                       float l_phase,
                       float r_phase,
                       float c_phase,
                       float mag_total,
                       float x, float y,
                       int n)
 {
     float lfe_mag, b_mag, l_mag, r_mag, c_mag, *dstc, *dstl, *dstr, *dstb, *dstlfe;
     AudioSurroundContext *s = ctx->priv;
 
     dstl = (float *)s->output->extended_data[0];
     dstr = (float *)s->output->extended_data[1];
     dstc = (float *)s->output->extended_data[2];
     dstlfe = (float *)s->output->extended_data[3];
     dstb = (float *)s->output->extended_data[4];
 
     get_lfe(s->output_lfe, n, s->lowcut, s->highcut, &lfe_mag, &mag_total);
 
     dstlfe[2 * n    ] = lfe_mag * cosf(c_phase);
     dstlfe[2 * n + 1] = lfe_mag * sinf(c_phase);
 
     c_mag = sqrtf(1.f - fabsf(x))   * ((y + 1.f) * .5f) * mag_total;
     b_mag = sqrtf(1.f - fabsf(x))   * ((1.f - y) * .5f) * mag_total;
     l_mag = sqrtf(.5f * ( x + 1.f)) * ((y + 1.f) * .5f) * mag_total;
     r_mag = sqrtf(.5f * (-x + 1.f)) * ((y + 1.f) * .5f) * mag_total;
 
     dstl[2 * n    ] = l_mag * cosf(l_phase);
     dstl[2 * n + 1] = l_mag * sinf(l_phase);
 
     dstr[2 * n    ] = r_mag * cosf(r_phase);
     dstr[2 * n + 1] = r_mag * sinf(r_phase);
 
     dstc[2 * n    ] = c_mag * cosf(c_phase);
     dstc[2 * n + 1] = c_mag * sinf(c_phase);
 
     dstb[2 * n    ] = b_mag * cosf(c_phase);
     dstb[2 * n + 1] = b_mag * sinf(c_phase);
 }
 
 static void upmix_5_0_back(AVFilterContext *ctx,
                            float l_phase,
                            float r_phase,
                            float c_phase,
                            float mag_total,
                            float x, float y,
                            int n)
 {
     float l_mag, r_mag, ls_mag, rs_mag, c_mag, *dstc, *dstl, *dstr, *dstls, *dstrs;
     AudioSurroundContext *s = ctx->priv;
 
     dstl  = (float *)s->output->extended_data[0];
     dstr  = (float *)s->output->extended_data[1];
     dstc  = (float *)s->output->extended_data[2];
     dstls = (float *)s->output->extended_data[3];
     dstrs = (float *)s->output->extended_data[4];
 
     c_mag  = sqrtf(1.f - fabsf(x))   * ((y + 1.f) * .5f) * mag_total;
     l_mag  = sqrtf(.5f * ( x + 1.f)) * ((y + 1.f) * .5f) * mag_total;
     r_mag  = sqrtf(.5f * (-x + 1.f)) * ((y + 1.f) * .5f) * mag_total;
     ls_mag = sqrtf(.5f * ( x + 1.f)) * (1.f - ((y + 1.f) * .5f)) * mag_total;
     rs_mag = sqrtf(.5f * (-x + 1.f)) * (1.f - ((y + 1.f) * .5f)) * mag_total;
 
     dstl[2 * n    ] = l_mag * cosf(l_phase);
     dstl[2 * n + 1] = l_mag * sinf(l_phase);
 
     dstr[2 * n    ] = r_mag * cosf(r_phase);
     dstr[2 * n + 1] = r_mag * sinf(r_phase);
 
     dstc[2 * n    ] = c_mag * cosf(c_phase);
     dstc[2 * n + 1] = c_mag * sinf(c_phase);
 
     dstls[2 * n    ] = ls_mag * cosf(l_phase);
     dstls[2 * n + 1] = ls_mag * sinf(l_phase);
 
     dstrs[2 * n    ] = rs_mag * cosf(r_phase);
     dstrs[2 * n + 1] = rs_mag * sinf(r_phase);
 }
 
 static void upmix_5_1_back(AVFilterContext *ctx,
                            float l_phase,
                            float r_phase,
                            float c_phase,
                            float mag_total,
                            float x, float y,
                            int n)
 {
     float lfe_mag, l_mag, r_mag, ls_mag, rs_mag, c_mag, *dstc, *dstl, *dstr, *dstls, *dstrs, *dstlfe;
     AudioSurroundContext *s = ctx->priv;
 
     dstl  = (float *)s->output->extended_data[0];
     dstr  = (float *)s->output->extended_data[1];
     dstc  = (float *)s->output->extended_data[2];
     dstlfe = (float *)s->output->extended_data[3];
     dstls = (float *)s->output->extended_data[4];
     dstrs = (float *)s->output->extended_data[5];
 
     get_lfe(s->output_lfe, n, s->lowcut, s->highcut, &lfe_mag, &mag_total);
 
     c_mag  = sqrtf(1.f - fabsf(x))   * ((y + 1.f) * .5f) * mag_total;
     l_mag  = sqrtf(.5f * ( x + 1.f)) * ((y + 1.f) * .5f) * mag_total;
     r_mag  = sqrtf(.5f * (-x + 1.f)) * ((y + 1.f) * .5f) * mag_total;
     ls_mag = sqrtf(.5f * ( x + 1.f)) * (1.f - ((y + 1.f) * .5f)) * mag_total;
     rs_mag = sqrtf(.5f * (-x + 1.f)) * (1.f - ((y + 1.f) * .5f)) * mag_total;
 
     dstl[2 * n    ] = l_mag * cosf(l_phase);
     dstl[2 * n + 1] = l_mag * sinf(l_phase);
 
     dstr[2 * n    ] = r_mag * cosf(r_phase);
     dstr[2 * n + 1] = r_mag * sinf(r_phase);
 
     dstc[2 * n    ] = c_mag * cosf(c_phase);
     dstc[2 * n + 1] = c_mag * sinf(c_phase);
 
     dstlfe[2 * n    ] = lfe_mag * cosf(c_phase);
     dstlfe[2 * n + 1] = lfe_mag * sinf(c_phase);
 
     dstls[2 * n    ] = ls_mag * cosf(l_phase);
     dstls[2 * n + 1] = ls_mag * sinf(l_phase);
 
     dstrs[2 * n    ] = rs_mag * cosf(r_phase);
     dstrs[2 * n + 1] = rs_mag * sinf(r_phase);
 }
 

 static void upmix_5_1_back_surround(AVFilterContext *ctx,
                                     float l_phase,
                                     float r_phase,
                                     float c_phase,
                                     float c_mag,
                                     float mag_total,
                                     float x, float y,
                                     int n)
 {
     AudioSurroundContext *s = ctx->priv;
     float lfe_mag, l_mag, r_mag, *dstc, *dstl, *dstr, *dstlfe;
     float ls_mag, rs_mag, *dstls, *dstrs;
 
     dstl = (float *)s->output->extended_data[0];
     dstr = (float *)s->output->extended_data[1];
     dstc = (float *)s->output->extended_data[2];
     dstlfe = (float *)s->output->extended_data[3];
     dstls = (float *)s->output->extended_data[4];
     dstrs = (float *)s->output->extended_data[5];
 
     get_lfe(s->output_lfe, n, s->lowcut, s->highcut, &lfe_mag, &c_mag);
 
     l_mag = sqrtf(.5f * ( x + 1.f)) * ((y + 1.f) * .5f) * mag_total;
     r_mag = sqrtf(.5f * (-x + 1.f)) * ((y + 1.f) * .5f) * mag_total;
     ls_mag = sqrtf(.5f * ( x + 1.f)) * (1.f - ((y + 1.f) * .5f)) * mag_total;
     rs_mag = sqrtf(.5f * (-x + 1.f)) * (1.f - ((y + 1.f) * .5f)) * mag_total;
 
     dstl[2 * n    ] = l_mag * cosf(l_phase);
     dstl[2 * n + 1] = l_mag * sinf(l_phase);
 
     dstr[2 * n    ] = r_mag * cosf(r_phase);
     dstr[2 * n + 1] = r_mag * sinf(r_phase);
 
     dstc[2 * n    ] = c_mag * cosf(c_phase);
     dstc[2 * n + 1] = c_mag * sinf(c_phase);
 
     dstlfe[2 * n    ] = lfe_mag * cosf(c_phase);
     dstlfe[2 * n + 1] = lfe_mag * sinf(c_phase);
 
     dstls[2 * n    ] = ls_mag * cosf(l_phase);
     dstls[2 * n + 1] = ls_mag * sinf(l_phase);
 
     dstrs[2 * n    ] = rs_mag * cosf(r_phase);
     dstrs[2 * n + 1] = rs_mag * sinf(r_phase);
 }
 
 static void upmix_5_1_back_2_1(AVFilterContext *ctx,
                                float l_phase,
                                float r_phase,
                                float c_phase,
                                float mag_total,
                                float lfe_re,
                                float lfe_im,
                                float x, float y,
                                int n)
 {
     AudioSurroundContext *s = ctx->priv;
     float c_mag, l_mag, r_mag, *dstc, *dstl, *dstr, *dstlfe;
     float ls_mag, rs_mag, *dstls, *dstrs;
 
     dstl = (float *)s->output->extended_data[0];
     dstr = (float *)s->output->extended_data[1];
     dstc = (float *)s->output->extended_data[2];
     dstlfe = (float *)s->output->extended_data[3];
     dstls = (float *)s->output->extended_data[4];
     dstrs = (float *)s->output->extended_data[5];
 
     c_mag  = sqrtf(1.f - fabsf(x))   * ((y + 1.f) * .5f) * mag_total;
     l_mag  = sqrtf(.5f * ( x + 1.f)) * ((y + 1.f) * .5f) * mag_total;
     r_mag  = sqrtf(.5f * (-x + 1.f)) * ((y + 1.f) * .5f) * mag_total;
     ls_mag = sqrtf(.5f * ( x + 1.f)) * (1.f - ((y + 1.f) * .5f)) * mag_total;
     rs_mag = sqrtf(.5f * (-x + 1.f)) * (1.f - ((y + 1.f) * .5f)) * mag_total;
 
     dstl[2 * n    ] = l_mag * cosf(l_phase);
     dstl[2 * n + 1] = l_mag * sinf(l_phase);
 
     dstr[2 * n    ] = r_mag * cosf(r_phase);
     dstr[2 * n + 1] = r_mag * sinf(r_phase);
 
     dstc[2 * n    ] = c_mag * cosf(c_phase);
     dstc[2 * n + 1] = c_mag * sinf(c_phase);
 
     dstlfe[2 * n    ] = lfe_re;
     dstlfe[2 * n + 1] = lfe_im;
 
     dstls[2 * n    ] = ls_mag * cosf(l_phase);
     dstls[2 * n + 1] = ls_mag * sinf(l_phase);
 
     dstrs[2 * n    ] = rs_mag * cosf(r_phase);
     dstrs[2 * n + 1] = rs_mag * sinf(r_phase);
 }
 

 static void upmix_7_0(AVFilterContext *ctx,
                       float l_phase,
                       float r_phase,
                       float c_phase,
                       float mag_total,
                       float x, float y,
                       int n)
 {
     float l_mag, r_mag, ls_mag, rs_mag, c_mag, lb_mag, rb_mag;
     float *dstc, *dstl, *dstr, *dstls, *dstrs, *dstlb, *dstrb;
     AudioSurroundContext *s = ctx->priv;
 
     dstl  = (float *)s->output->extended_data[0];
     dstr  = (float *)s->output->extended_data[1];
     dstc  = (float *)s->output->extended_data[2];
     dstlb = (float *)s->output->extended_data[3];
     dstrb = (float *)s->output->extended_data[4];
     dstls = (float *)s->output->extended_data[5];
     dstrs = (float *)s->output->extended_data[6];
 
     c_mag  = sqrtf(1.f - fabsf(x))   * ((y + 1.f) * .5f) * mag_total;
     l_mag  = sqrtf(.5f * ( x + 1.f)) * ((y + 1.f) * .5f) * mag_total;
     r_mag  = sqrtf(.5f * (-x + 1.f)) * ((y + 1.f) * .5f) * mag_total;
     lb_mag = sqrtf(.5f * ( x + 1.f)) * (1.f - ((y + 1.f) * .5f)) * mag_total;
     rb_mag = sqrtf(.5f * (-x + 1.f)) * (1.f - ((y + 1.f) * .5f)) * mag_total;
     ls_mag = sqrtf(.5f * ( x + 1.f)) * (1.f - fabsf(y)) * mag_total;
     rs_mag = sqrtf(.5f * (-x + 1.f)) * (1.f - fabsf(y)) * mag_total;
 
     dstl[2 * n    ] = l_mag * cosf(l_phase);
     dstl[2 * n + 1] = l_mag * sinf(l_phase);
 
     dstr[2 * n    ] = r_mag * cosf(r_phase);
     dstr[2 * n + 1] = r_mag * sinf(r_phase);
 
     dstc[2 * n    ] = c_mag * cosf(c_phase);
     dstc[2 * n + 1] = c_mag * sinf(c_phase);
 
     dstlb[2 * n    ] = lb_mag * cosf(l_phase);
     dstlb[2 * n + 1] = lb_mag * sinf(l_phase);
 
     dstrb[2 * n    ] = rb_mag * cosf(r_phase);
     dstrb[2 * n + 1] = rb_mag * sinf(r_phase);
 
     dstls[2 * n    ] = ls_mag * cosf(l_phase);
     dstls[2 * n + 1] = ls_mag * sinf(l_phase);
 
     dstrs[2 * n    ] = rs_mag * cosf(r_phase);
     dstrs[2 * n + 1] = rs_mag * sinf(r_phase);
 }
 
 static void upmix_7_1(AVFilterContext *ctx,
                       float l_phase,
                       float r_phase,
                       float c_phase,
                       float mag_total,
                       float x, float y,
                       int n)
 {
     float lfe_mag, l_mag, r_mag, ls_mag, rs_mag, c_mag, lb_mag, rb_mag;
     float *dstc, *dstl, *dstr, *dstls, *dstrs, *dstlb, *dstrb, *dstlfe;
     AudioSurroundContext *s = ctx->priv;
 
     dstl  = (float *)s->output->extended_data[0];
     dstr  = (float *)s->output->extended_data[1];
     dstc  = (float *)s->output->extended_data[2];
     dstlfe = (float *)s->output->extended_data[3];
     dstlb = (float *)s->output->extended_data[4];
     dstrb = (float *)s->output->extended_data[5];
     dstls = (float *)s->output->extended_data[6];
     dstrs = (float *)s->output->extended_data[7];
 
     get_lfe(s->output_lfe, n, s->lowcut, s->highcut, &lfe_mag, &mag_total);
 
     c_mag  = sqrtf(1.f - fabsf(x))   * ((y + 1.f) * .5f) * mag_total;
     l_mag  = sqrtf(.5f * ( x + 1.f)) * ((y + 1.f) * .5f) * mag_total;
     r_mag  = sqrtf(.5f * (-x + 1.f)) * ((y + 1.f) * .5f) * mag_total;
     lb_mag = sqrtf(.5f * ( x + 1.f)) * (1.f - ((y + 1.f) * .5f)) * mag_total;
     rb_mag = sqrtf(.5f * (-x + 1.f)) * (1.f - ((y + 1.f) * .5f)) * mag_total;
     ls_mag = sqrtf(.5f * ( x + 1.f)) * (1.f - fabsf(y)) * mag_total;
     rs_mag = sqrtf(.5f * (-x + 1.f)) * (1.f - fabsf(y)) * mag_total;
 
     dstl[2 * n    ] = l_mag * cosf(l_phase);
     dstl[2 * n + 1] = l_mag * sinf(l_phase);
 
     dstr[2 * n    ] = r_mag * cosf(r_phase);
     dstr[2 * n + 1] = r_mag * sinf(r_phase);
 
     dstc[2 * n    ] = c_mag * cosf(c_phase);
     dstc[2 * n + 1] = c_mag * sinf(c_phase);
 
     dstlfe[2 * n    ] = lfe_mag * cosf(c_phase);
     dstlfe[2 * n + 1] = lfe_mag * sinf(c_phase);
 
     dstlb[2 * n    ] = lb_mag * cosf(l_phase);
     dstlb[2 * n + 1] = lb_mag * sinf(l_phase);
 
     dstrb[2 * n    ] = rb_mag * cosf(r_phase);
     dstrb[2 * n + 1] = rb_mag * sinf(r_phase);
 
     dstls[2 * n    ] = ls_mag * cosf(l_phase);
     dstls[2 * n + 1] = ls_mag * sinf(l_phase);
 
     dstrs[2 * n    ] = rs_mag * cosf(r_phase);
     dstrs[2 * n + 1] = rs_mag * sinf(r_phase);
 }
 

 static void upmix_7_1_5_0_side(AVFilterContext *ctx,
                                float c_re, float c_im,
                                float mag_totall, float mag_totalr,
                                float fl_phase, float fr_phase,
                                float bl_phase, float br_phase,
                                float sl_phase, float sr_phase,
                                float xl, float yl,
                                float xr, float yr,
                                int n)
 {
     float fl_mag, fr_mag, ls_mag, rs_mag, lb_mag, rb_mag;
     float *dstc, *dstl, *dstr, *dstls, *dstrs, *dstlb, *dstrb, *dstlfe;
     float lfe_mag, c_phase, mag_total = (mag_totall + mag_totalr) * 0.5;
     AudioSurroundContext *s = ctx->priv;
 
     dstl  = (float *)s->output->extended_data[0];
     dstr  = (float *)s->output->extended_data[1];
     dstc  = (float *)s->output->extended_data[2];
     dstlfe = (float *)s->output->extended_data[3];
     dstlb = (float *)s->output->extended_data[4];
     dstrb = (float *)s->output->extended_data[5];
     dstls = (float *)s->output->extended_data[6];
     dstrs = (float *)s->output->extended_data[7];
 
     c_phase = atan2f(c_im, c_re);
 
     get_lfe(s->output_lfe, n, s->lowcut, s->highcut, &lfe_mag, &mag_total);
 
     fl_mag = sqrtf(.5f * (xl + 1.f)) * ((yl + 1.f) * .5f) * mag_totall;
     fr_mag = sqrtf(.5f * (xr + 1.f)) * ((yr + 1.f) * .5f) * mag_totalr;
     lb_mag = sqrtf(.5f * (-xl + 1.f)) * ((yl + 1.f) * .5f) * mag_totall;
     rb_mag = sqrtf(.5f * (-xr + 1.f)) * ((yr + 1.f) * .5f) * mag_totalr;
     ls_mag = sqrtf(1.f - fabsf(xl)) * ((yl + 1.f) * .5f) * mag_totall;
     rs_mag = sqrtf(1.f - fabsf(xr)) * ((yr + 1.f) * .5f) * mag_totalr;
 
     dstl[2 * n    ] = fl_mag * cosf(fl_phase);
     dstl[2 * n + 1] = fl_mag * sinf(fl_phase);
 
     dstr[2 * n    ] = fr_mag * cosf(fr_phase);
     dstr[2 * n + 1] = fr_mag * sinf(fr_phase);
 
     dstc[2 * n    ] = c_re;
     dstc[2 * n + 1] = c_im;
 
     dstlfe[2 * n    ] = lfe_mag * cosf(c_phase);
     dstlfe[2 * n + 1] = lfe_mag * sinf(c_phase);
 
     dstlb[2 * n    ] = lb_mag * cosf(bl_phase);
     dstlb[2 * n + 1] = lb_mag * sinf(bl_phase);
 
     dstrb[2 * n    ] = rb_mag * cosf(br_phase);
     dstrb[2 * n + 1] = rb_mag * sinf(br_phase);
 
     dstls[2 * n    ] = ls_mag * cosf(sl_phase);
     dstls[2 * n + 1] = ls_mag * sinf(sl_phase);
 
     dstrs[2 * n    ] = rs_mag * cosf(sr_phase);
     dstrs[2 * n + 1] = rs_mag * sinf(sr_phase);
 }
 

 static void upmix_7_1_5_1(AVFilterContext *ctx,
                           float c_re, float c_im,
                           float lfe_re, float lfe_im,
                           float mag_totall, float mag_totalr,
                           float fl_phase, float fr_phase,
                           float bl_phase, float br_phase,
                           float sl_phase, float sr_phase,
                           float xl, float yl,
                           float xr, float yr,
                           int n)
 {
     float fl_mag, fr_mag, ls_mag, rs_mag, lb_mag, rb_mag;
     float *dstc, *dstl, *dstr, *dstls, *dstrs, *dstlb, *dstrb, *dstlfe;
     AudioSurroundContext *s = ctx->priv;
 
     dstl  = (float *)s->output->extended_data[0];
     dstr  = (float *)s->output->extended_data[1];
     dstc  = (float *)s->output->extended_data[2];
     dstlfe = (float *)s->output->extended_data[3];
     dstlb = (float *)s->output->extended_data[4];
     dstrb = (float *)s->output->extended_data[5];
     dstls = (float *)s->output->extended_data[6];
     dstrs = (float *)s->output->extended_data[7];
 
     fl_mag = sqrtf(.5f * (xl + 1.f)) * ((yl + 1.f) * .5f) * mag_totall;
     fr_mag = sqrtf(.5f * (xr + 1.f)) * ((yr + 1.f) * .5f) * mag_totalr;
     lb_mag = sqrtf(.5f * (-xl + 1.f)) * ((yl + 1.f) * .5f) * mag_totall;
     rb_mag = sqrtf(.5f * (-xr + 1.f)) * ((yr + 1.f) * .5f) * mag_totalr;
     ls_mag = sqrtf(1.f - fabsf(xl)) * ((yl + 1.f) * .5f) * mag_totall;
     rs_mag = sqrtf(1.f - fabsf(xr)) * ((yr + 1.f) * .5f) * mag_totalr;
 
     dstl[2 * n    ] = fl_mag * cosf(fl_phase);
     dstl[2 * n + 1] = fl_mag * sinf(fl_phase);
 
     dstr[2 * n    ] = fr_mag * cosf(fr_phase);
     dstr[2 * n + 1] = fr_mag * sinf(fr_phase);
 
     dstc[2 * n    ] = c_re;
     dstc[2 * n + 1] = c_im;
 
     dstlfe[2 * n    ] = lfe_re;
     dstlfe[2 * n + 1] = lfe_im;
 
     dstlb[2 * n    ] = lb_mag * cosf(bl_phase);
     dstlb[2 * n + 1] = lb_mag * sinf(bl_phase);
 
     dstrb[2 * n    ] = rb_mag * cosf(br_phase);
     dstrb[2 * n + 1] = rb_mag * sinf(br_phase);
 
     dstls[2 * n    ] = ls_mag * cosf(sl_phase);
     dstls[2 * n + 1] = ls_mag * sinf(sl_phase);
 
     dstrs[2 * n    ] = rs_mag * cosf(sr_phase);
     dstrs[2 * n + 1] = rs_mag * sinf(sr_phase);
 }
 
 static void filter_stereo(AVFilterContext *ctx)
 {
     AudioSurroundContext *s = ctx->priv;
     float *srcl, *srcr;
     int n;
 
     srcl = (float *)s->input->extended_data[0];
     srcr = (float *)s->input->extended_data[1];
 
     for (n = 0; n < s->buf_size; n++) {
         float l_re = srcl[2 * n], r_re = srcr[2 * n];
         float l_im = srcl[2 * n + 1], r_im = srcr[2 * n + 1];
         float c_phase = atan2f(l_im + r_im, l_re + r_re);
         float l_mag = hypotf(l_re, l_im);
         float r_mag = hypotf(r_re, r_im);
         float l_phase = atan2f(l_im, l_re);
         float r_phase = atan2f(r_im, r_re);
         float phase_dif = fabsf(l_phase - r_phase);
         float mag_dif = (l_mag - r_mag) / (l_mag + r_mag);
         float mag_total = hypotf(l_mag, r_mag);
         float x, y;
 
         if (phase_dif > M_PI)
             phase_dif = 2 * M_PI - phase_dif;
 
         stereo_position(mag_dif, phase_dif, &x, &y);
 
         s->upmix_stereo(ctx, l_phase, r_phase, c_phase, mag_total, x, y, n);
     }
 }
 
 static void filter_surround(AVFilterContext *ctx)
 {
     AudioSurroundContext *s = ctx->priv;
     float *srcl, *srcr, *srcc;
     int n;
 
     srcl = (float *)s->input->extended_data[0];
     srcr = (float *)s->input->extended_data[1];
     srcc = (float *)s->input->extended_data[2];
 
     for (n = 0; n < s->buf_size; n++) {
         float l_re = srcl[2 * n], r_re = srcr[2 * n];
         float l_im = srcl[2 * n + 1], r_im = srcr[2 * n + 1];
         float c_re = srcc[2 * n], c_im = srcc[2 * n + 1];
         float c_mag = hypotf(c_re, c_im);
         float c_phase = atan2f(c_im, c_re);
         float l_mag = hypotf(l_re, l_im);
         float r_mag = hypotf(r_re, r_im);
         float l_phase = atan2f(l_im, l_re);
         float r_phase = atan2f(r_im, r_re);
         float phase_dif = fabsf(l_phase - r_phase);
         float mag_dif = (l_mag - r_mag) / (l_mag + r_mag);
         float mag_total = hypotf(l_mag, r_mag);
         float x, y;
 
         if (phase_dif > M_PI)
             phase_dif = 2 * M_PI - phase_dif;
 
         stereo_position(mag_dif, phase_dif, &x, &y);
 
         s->upmix_3_0(ctx, l_phase, r_phase, c_phase, c_mag, mag_total, x, y, n);
     }
 }
 
 static void filter_2_1(AVFilterContext *ctx)
 {
     AudioSurroundContext *s = ctx->priv;
     float *srcl, *srcr, *srclfe;
     int n;
 
     srcl = (float *)s->input->extended_data[0];
     srcr = (float *)s->input->extended_data[1];
     srclfe = (float *)s->input->extended_data[2];
 
     for (n = 0; n < s->buf_size; n++) {
         float l_re = srcl[2 * n], r_re = srcr[2 * n];
         float l_im = srcl[2 * n + 1], r_im = srcr[2 * n + 1];
         float lfe_re = srclfe[2 * n], lfe_im = srclfe[2 * n + 1];
         float c_phase = atan2f(l_im + r_im, l_re + r_re);
         float l_mag = hypotf(l_re, l_im);
         float r_mag = hypotf(r_re, r_im);
         float l_phase = atan2f(l_im, l_re);
         float r_phase = atan2f(r_im, r_re);
         float phase_dif = fabsf(l_phase - r_phase);
         float mag_dif = (l_mag - r_mag) / (l_mag + r_mag);
         float mag_total = hypotf(l_mag, r_mag);
         float x, y;
 
         if (phase_dif > M_PI)
             phase_dif = 2 * M_PI - phase_dif;
 
         stereo_position(mag_dif, phase_dif, &x, &y);
 
         s->upmix_2_1(ctx, l_phase, r_phase, c_phase, mag_total, lfe_re, lfe_im, x, y, n);
     }
 }
 

 static void filter_5_0_side(AVFilterContext *ctx)
 {
     AudioSurroundContext *s = ctx->priv;
     float *srcl, *srcr, *srcc, *srcsl, *srcsr;
     int n;
 
     srcl = (float *)s->input->extended_data[0];
     srcr = (float *)s->input->extended_data[1];
     srcc = (float *)s->input->extended_data[2];
     srcsl = (float *)s->input->extended_data[3];
     srcsr = (float *)s->input->extended_data[4];
 
     for (n = 0; n < s->buf_size; n++) {
         float fl_re = srcl[2 * n], fr_re = srcr[2 * n];
         float fl_im = srcl[2 * n + 1], fr_im = srcr[2 * n + 1];
         float c_re = srcc[2 * n], c_im = srcc[2 * n + 1];
         float sl_re = srcsl[2 * n], sl_im = srcsl[2 * n + 1];
         float sr_re = srcsr[2 * n], sr_im = srcsr[2 * n + 1];
         float fl_mag = hypotf(fl_re, fl_im);
         float fr_mag = hypotf(fr_re, fr_im);
         float fl_phase = atan2f(fl_im, fl_re);
         float fr_phase = atan2f(fr_im, fr_re);
         float sl_mag = hypotf(sl_re, sl_im);
         float sr_mag = hypotf(sr_re, sr_im);
         float sl_phase = atan2f(sl_im, sl_re);
         float sr_phase = atan2f(sr_im, sr_re);
         float phase_difl = fabsf(fl_phase - sl_phase);
         float phase_difr = fabsf(fr_phase - sr_phase);
         float mag_difl = (fl_mag - sl_mag) / (fl_mag + sl_mag);
         float mag_difr = (fr_mag - sr_mag) / (fr_mag + sr_mag);
         float mag_totall = hypotf(fl_mag, sl_mag);
         float mag_totalr = hypotf(fr_mag, sr_mag);
         float bl_phase = atan2f(fl_im + sl_im, fl_re + sl_re);
         float br_phase = atan2f(fr_im + sr_im, fr_re + sr_re);
         float xl, yl;
         float xr, yr;
 
         if (phase_difl > M_PI)
             phase_difl = 2 * M_PI - phase_difl;
 
         if (phase_difr > M_PI)
             phase_difr = 2 * M_PI - phase_difr;
 
         stereo_position(mag_difl, phase_difl, &xl, &yl);
         stereo_position(mag_difr, phase_difr, &xr, &yr);
 
         s->upmix_5_0(ctx, c_re, c_im,
                      mag_totall, mag_totalr,
                      fl_phase, fr_phase,
                      bl_phase, br_phase,
                      sl_phase, sr_phase,
                      xl, yl, xr, yr, n);
     }
 }
 
 static void filter_5_1_side(AVFilterContext *ctx)
 {
     AudioSurroundContext *s = ctx->priv;
     float *srcl, *srcr, *srcc, *srclfe, *srcsl, *srcsr;
     int n;
 
     srcl = (float *)s->input->extended_data[0];
     srcr = (float *)s->input->extended_data[1];
     srcc = (float *)s->input->extended_data[2];
     srclfe = (float *)s->input->extended_data[3];
     srcsl = (float *)s->input->extended_data[4];
     srcsr = (float *)s->input->extended_data[5];
 
     for (n = 0; n < s->buf_size; n++) {
         float fl_re = srcl[2 * n], fr_re = srcr[2 * n];
         float fl_im = srcl[2 * n + 1], fr_im = srcr[2 * n + 1];
         float c_re = srcc[2 * n], c_im = srcc[2 * n + 1];
         float lfe_re = srclfe[2 * n], lfe_im = srclfe[2 * n + 1];
         float sl_re = srcsl[2 * n], sl_im = srcsl[2 * n + 1];
         float sr_re = srcsr[2 * n], sr_im = srcsr[2 * n + 1];
         float fl_mag = hypotf(fl_re, fl_im);
         float fr_mag = hypotf(fr_re, fr_im);
         float fl_phase = atan2f(fl_im, fl_re);
         float fr_phase = atan2f(fr_im, fr_re);
         float sl_mag = hypotf(sl_re, sl_im);
         float sr_mag = hypotf(sr_re, sr_im);
         float sl_phase = atan2f(sl_im, sl_re);
         float sr_phase = atan2f(sr_im, sr_re);
         float phase_difl = fabsf(fl_phase - sl_phase);
         float phase_difr = fabsf(fr_phase - sr_phase);
         float mag_difl = (fl_mag - sl_mag) / (fl_mag + sl_mag);
         float mag_difr = (fr_mag - sr_mag) / (fr_mag + sr_mag);
         float mag_totall = hypotf(fl_mag, sl_mag);
         float mag_totalr = hypotf(fr_mag, sr_mag);
         float bl_phase = atan2f(fl_im + sl_im, fl_re + sl_re);
         float br_phase = atan2f(fr_im + sr_im, fr_re + sr_re);
         float xl, yl;
         float xr, yr;
 
         if (phase_difl > M_PI)
             phase_difl = 2 * M_PI - phase_difl;
 
         if (phase_difr > M_PI)
             phase_difr = 2 * M_PI - phase_difr;
 
         stereo_position(mag_difl, phase_difl, &xl, &yl);
         stereo_position(mag_difr, phase_difr, &xr, &yr);
 
         s->upmix_5_1(ctx, c_re, c_im, lfe_re, lfe_im,
                      mag_totall, mag_totalr,
                      fl_phase, fr_phase,
                      bl_phase, br_phase,
                      sl_phase, sr_phase,
                      xl, yl, xr, yr, n);
     }
 }
 

 static void filter_5_1_back(AVFilterContext *ctx)
 {
     AudioSurroundContext *s = ctx->priv;
     float *srcl, *srcr, *srcc, *srclfe, *srcbl, *srcbr;
     int n;
 
     srcl = (float *)s->input->extended_data[0];
     srcr = (float *)s->input->extended_data[1];
     srcc = (float *)s->input->extended_data[2];
     srclfe = (float *)s->input->extended_data[3];
     srcbl = (float *)s->input->extended_data[4];
     srcbr = (float *)s->input->extended_data[5];
 
     for (n = 0; n < s->buf_size; n++) {
         float fl_re = srcl[2 * n], fr_re = srcr[2 * n];
         float fl_im = srcl[2 * n + 1], fr_im = srcr[2 * n + 1];
         float c_re = srcc[2 * n], c_im = srcc[2 * n + 1];
         float lfe_re = srclfe[2 * n], lfe_im = srclfe[2 * n + 1];
         float bl_re = srcbl[2 * n], bl_im = srcbl[2 * n + 1];
         float br_re = srcbr[2 * n], br_im = srcbr[2 * n + 1];
         float fl_mag = hypotf(fl_re, fl_im);
         float fr_mag = hypotf(fr_re, fr_im);
         float fl_phase = atan2f(fl_im, fl_re);
         float fr_phase = atan2f(fr_im, fr_re);
         float bl_mag = hypotf(bl_re, bl_im);
         float br_mag = hypotf(br_re, br_im);
         float bl_phase = atan2f(bl_im, bl_re);
         float br_phase = atan2f(br_im, br_re);
         float phase_difl = fabsf(fl_phase - bl_phase);
         float phase_difr = fabsf(fr_phase - br_phase);
         float mag_difl = (fl_mag - bl_mag) / (fl_mag + bl_mag);
         float mag_difr = (fr_mag - br_mag) / (fr_mag + br_mag);
         float mag_totall = hypotf(fl_mag, bl_mag);
         float mag_totalr = hypotf(fr_mag, br_mag);
         float sl_phase = atan2f(fl_im + bl_im, fl_re + bl_re);
         float sr_phase = atan2f(fr_im + br_im, fr_re + br_re);
         float xl, yl;
         float xr, yr;
 
         if (phase_difl > M_PI)
             phase_difl = 2 * M_PI - phase_difl;
 
         if (phase_difr > M_PI)
             phase_difr = 2 * M_PI - phase_difr;
 
         stereo_position(mag_difl, phase_difl, &xl, &yl);
         stereo_position(mag_difr, phase_difr, &xr, &yr);
 
         s->upmix_5_1(ctx, c_re, c_im, lfe_re, lfe_im,
                      mag_totall, mag_totalr,
                      fl_phase, fr_phase,
                      bl_phase, br_phase,
                      sl_phase, sr_phase,
                      xl, yl, xr, yr, n);
     }
 }
 

 static int init(AVFilterContext *ctx)
 {
     AudioSurroundContext *s = ctx->priv;
     float overlap;
     int i;
 
     if (!(s->out_channel_layout = av_get_channel_layout(s->out_channel_layout_str))) {

         av_log(ctx, AV_LOG_ERROR, "Error parsing output channel layout '%s'.\n",

                s->out_channel_layout_str);
         return AVERROR(EINVAL);
     }
 

     if (!(s->in_channel_layout = av_get_channel_layout(s->in_channel_layout_str))) {
         av_log(ctx, AV_LOG_ERROR, "Error parsing input channel layout '%s'.\n",
                s->in_channel_layout_str);
         return AVERROR(EINVAL);
     }
 

     if (s->lowcutf >= s->highcutf) {
         av_log(ctx, AV_LOG_ERROR, "Low cut-off '%d' should be less than high cut-off '%d'.\n",
                s->lowcutf, s->highcutf);
         return AVERROR(EINVAL);
     }
 

     switch (s->in_channel_layout) {

     case AV_CH_LAYOUT_STEREO:

         s->filter = filter_stereo;
         switch (s->out_channel_layout) {
         case AV_CH_LAYOUT_MONO:
             s->upmix_stereo = upmix_1_0;
             break;
         case AV_CH_LAYOUT_STEREO:
             s->upmix_stereo = upmix_stereo;
             break;
         case AV_CH_LAYOUT_2POINT1:
             s->upmix_stereo = upmix_2_1;
             break;
         case AV_CH_LAYOUT_SURROUND:
             s->upmix_stereo = upmix_3_0;
             break;
         case AV_CH_LAYOUT_3POINT1:
             s->upmix_stereo = upmix_3_1;
             break;
         case AV_CH_LAYOUT_4POINT0:
             s->upmix_stereo = upmix_4_0;
             break;
         case AV_CH_LAYOUT_4POINT1:
             s->upmix_stereo = upmix_4_1;
             break;
         case AV_CH_LAYOUT_5POINT0_BACK:
             s->upmix_stereo = upmix_5_0_back;
             break;
         case AV_CH_LAYOUT_5POINT1_BACK:
             s->upmix_stereo = upmix_5_1_back;
             break;
         case AV_CH_LAYOUT_7POINT0:
             s->upmix_stereo = upmix_7_0;
             break;
         case AV_CH_LAYOUT_7POINT1:
             s->upmix_stereo = upmix_7_1;
             break;
         default:
             goto fail;
         }

         break;
     case AV_CH_LAYOUT_2POINT1:

         s->filter = filter_2_1;
         switch (s->out_channel_layout) {
         case AV_CH_LAYOUT_5POINT1_BACK:
             s->upmix_2_1 = upmix_5_1_back_2_1;
             break;
         default:
             goto fail;
         }

         break;
     case AV_CH_LAYOUT_SURROUND:

         s->filter = filter_surround;
         switch (s->out_channel_layout) {
         case AV_CH_LAYOUT_3POINT1:
             s->upmix_3_0 = upmix_3_1_surround;
             break;
         case AV_CH_LAYOUT_5POINT1_BACK:
             s->upmix_3_0 = upmix_5_1_back_surround;
             break;
         default:
             goto fail;
         }

         break;

     case AV_CH_LAYOUT_5POINT0:
         s->filter = filter_5_0_side;
         switch (s->out_channel_layout) {
         case AV_CH_LAYOUT_7POINT1:
             s->upmix_5_0 = upmix_7_1_5_0_side;
             break;
         default:
             goto fail;
         }
         break;
     case AV_CH_LAYOUT_5POINT1:
         s->filter = filter_5_1_side;
         switch (s->out_channel_layout) {
         case AV_CH_LAYOUT_7POINT1:
             s->upmix_5_1 = upmix_7_1_5_1;
             break;
         default:
             goto fail;
         }
         break;

     case AV_CH_LAYOUT_5POINT1_BACK:

         s->filter = filter_5_1_back;
         switch (s->out_channel_layout) {
         case AV_CH_LAYOUT_7POINT1:
             s->upmix_5_1 = upmix_7_1_5_1;
             break;
         default:
             goto fail;
         }

         break;
     default:

 fail:
         av_log(ctx, AV_LOG_ERROR, "Unsupported upmix: '%s' -> '%s'.\n",
                s->in_channel_layout_str, s->out_channel_layout_str);

         return AVERROR(EINVAL);
     }
 
     s->buf_size = 4096;
     s->pts = AV_NOPTS_VALUE;
 
     s->window_func_lut = av_calloc(s->buf_size, sizeof(*s->window_func_lut));
     if (!s->window_func_lut)
         return AVERROR(ENOMEM);
 
     for (i = 0; i < s->buf_size; i++)
         s->window_func_lut[i] = sqrtf(0.5 * (1 - cosf(2 * M_PI * i / s->buf_size)) / s->buf_size);
     overlap = .5;
     s->hop_size = s->buf_size * (1. - overlap);
 
     return 0;
 }
 
 static int fft_channel(AVFilterContext *ctx, void *arg, int ch, int nb_jobs)
 {
     AudioSurroundContext *s = ctx->priv;

     const float level_in = s->input_levels[ch];

     float *dst;
     int n;
 
     memset(s->input->extended_data[ch] + s->buf_size * sizeof(float), 0, s->buf_size * sizeof(float));
 
     dst = (float *)s->input->extended_data[ch];
     for (n = 0; n < s->buf_size; n++) {
         dst[n] *= s->window_func_lut[n] * level_in;
     }
 
     av_rdft_calc(s->rdft[ch], (float *)s->input->extended_data[ch]);
 
     return 0;
 }
 
 static int ifft_channel(AVFilterContext *ctx, void *arg, int ch, int nb_jobs)
 {
     AudioSurroundContext *s = ctx->priv;

     const float level_out = s->output_levels[ch];

     AVFrame *out = arg;
     float *dst, *ptr;
     int n;
 
     av_rdft_calc(s->irdft[ch], (float *)s->output->extended_data[ch]);
 
     dst = (float *)s->output->extended_data[ch];
     ptr = (float *)s->overlap_buffer->extended_data[ch];
 
     memmove(s->overlap_buffer->extended_data[ch],
             s->overlap_buffer->extended_data[ch] + s->hop_size * sizeof(float),
             s->buf_size * sizeof(float));
     memset(s->overlap_buffer->extended_data[ch] + s->buf_size * sizeof(float),
            0, s->hop_size * sizeof(float));
 
     for (n = 0; n < s->buf_size; n++) {
         ptr[n] += dst[n] * s->window_func_lut[n] * level_out;
     }
 
     ptr = (float *)s->overlap_buffer->extended_data[ch];
     dst = (float *)out->extended_data[ch];
     memcpy(dst, ptr, s->hop_size * sizeof(float));
 
     return 0;
 }
 
 static int filter_frame(AVFilterLink *inlink, AVFrame *in)
 {
     AVFilterContext *ctx = inlink->dst;
     AVFilterLink *outlink = ctx->outputs[0];
     AudioSurroundContext *s = ctx->priv;

     int ret;

     ret = av_audio_fifo_write(s->fifo, (void **)in->extended_data,
                               in->nb_samples);
     if (ret >= 0 && s->pts == AV_NOPTS_VALUE)

         s->pts = in->pts;
 
     av_frame_free(&in);

     if (ret < 0)
         return ret;

 
     while (av_audio_fifo_size(s->fifo) >= s->buf_size) {
         AVFrame *out;
 
         ret = av_audio_fifo_peek(s->fifo, (void **)s->input->extended_data, s->buf_size);
         if (ret < 0)
             return ret;
 
         ctx->internal->execute(ctx, fft_channel, NULL, NULL, inlink->channels);
 

         s->filter(ctx);

 
         out = ff_get_audio_buffer(outlink, s->hop_size);
         if (!out)
             return AVERROR(ENOMEM);
 
         ctx->internal->execute(ctx, ifft_channel, out, NULL, outlink->channels);
 
         out->pts = s->pts;
         if (s->pts != AV_NOPTS_VALUE)
             s->pts += av_rescale_q(out->nb_samples, (AVRational){1, outlink->sample_rate}, outlink->time_base);
         av_audio_fifo_drain(s->fifo, s->hop_size);
         ret = ff_filter_frame(outlink, out);
         if (ret < 0)
             return ret;
     }
 
     return 0;
 }
 
 static av_cold void uninit(AVFilterContext *ctx)
 {
     AudioSurroundContext *s = ctx->priv;
     int ch;
 
     av_frame_free(&s->input);
     av_frame_free(&s->output);
     av_frame_free(&s->overlap_buffer);
 
     for (ch = 0; ch < s->nb_in_channels; ch++) {
         av_rdft_end(s->rdft[ch]);
     }
     for (ch = 0; ch < s->nb_out_channels; ch++) {
         av_rdft_end(s->irdft[ch]);
     }

     av_freep(&s->input_levels);
     av_freep(&s->output_levels);

     av_freep(&s->rdft);
     av_freep(&s->irdft);
     av_audio_fifo_free(s->fifo);
     av_freep(&s->window_func_lut);
 }
 
 #define OFFSET(x) offsetof(AudioSurroundContext, x)
 #define FLAGS AV_OPT_FLAG_AUDIO_PARAM|AV_OPT_FLAG_FILTERING_PARAM
 
 static const AVOption surround_options[] = {
     { "chl_out",   "set output channel layout", OFFSET(out_channel_layout_str), AV_OPT_TYPE_STRING, {.str="5.1"}, 0,   0, FLAGS },

     { "chl_in",    "set input channel layout",  OFFSET(in_channel_layout_str),  AV_OPT_TYPE_STRING, {.str="stereo"},0, 0, FLAGS },

     { "level_in",  "set input level",           OFFSET(level_in),               AV_OPT_TYPE_FLOAT,  {.dbl=1},     0,  10, FLAGS },
     { "level_out", "set output level",          OFFSET(level_out),              AV_OPT_TYPE_FLOAT,  {.dbl=1},     0,  10, FLAGS },
     { "lfe",       "output LFE",                OFFSET(output_lfe),             AV_OPT_TYPE_BOOL,   {.i64=1},     0,   1, FLAGS },
     { "lfe_low",   "LFE low cut off",           OFFSET(lowcutf),                AV_OPT_TYPE_INT,    {.i64=128},   0, 256, FLAGS },
     { "lfe_high",  "LFE high cut off",          OFFSET(highcutf),               AV_OPT_TYPE_INT,    {.i64=256},   0, 512, FLAGS },

     { "fc_in",     "set front center channel input level",  OFFSET(fc_in),      AV_OPT_TYPE_FLOAT,  {.dbl=1},     0,  10, FLAGS },
     { "fc_out",    "set front center channel output level", OFFSET(fc_out),     AV_OPT_TYPE_FLOAT,  {.dbl=1},     0,  10, FLAGS },
     { "lfe_in",    "set lfe channel input level",  OFFSET(lfe_in),              AV_OPT_TYPE_FLOAT,  {.dbl=1},     0,  10, FLAGS },
     { "lfe_out",   "set lfe channel output level", OFFSET(lfe_out),             AV_OPT_TYPE_FLOAT,  {.dbl=1},     0,  10, FLAGS },

     { NULL }
 };
 
 AVFILTER_DEFINE_CLASS(surround);
 
 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,
         .config_props = config_output,
     },
     { NULL }
 };
 
 AVFilter ff_af_surround = {
     .name           = "surround",
     .description    = NULL_IF_CONFIG_SMALL("Apply audio surround upmix filter."),
     .query_formats  = query_formats,
     .priv_size      = sizeof(AudioSurroundContext),
     .priv_class     = &surround_class,
     .init           = init,
     .uninit         = uninit,
     .inputs         = inputs,
     .outputs        = outputs,
     .flags          = AVFILTER_FLAG_SLICE_THREADS,
 };