/*
  * Copyright (c) 2016 Muhammad Faiz <mfcc64@gmail.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/opt.h"
 #include "libavutil/eval.h"
 #include "libavutil/avassert.h"
 #include "libavcodec/avfft.h"
 #include "avfilter.h"
 #include "internal.h"
 #include "audio.h"
 
 #define RDFT_BITS_MIN 4
 #define RDFT_BITS_MAX 16
 
 enum WindowFunc {

     WFUNC_RECTANGULAR,

     WFUNC_HANN,
     WFUNC_HAMMING,
     WFUNC_BLACKMAN,
     WFUNC_NUTTALL3,
     WFUNC_MNUTTALL3,
     WFUNC_NUTTALL,
     WFUNC_BNUTTALL,
     WFUNC_BHARRIS,

     WFUNC_TUKEY,

     NB_WFUNC

 };
 

 enum Scale {
     SCALE_LINLIN,
     SCALE_LINLOG,
     SCALE_LOGLIN,
     SCALE_LOGLOG,
     NB_SCALE
 };
 

 #define NB_GAIN_ENTRY_MAX 4096

 typedef struct GainEntry {

     double  freq;
     double  gain;
 } GainEntry;
 

 typedef struct OverlapIndex {

     int buf_idx;
     int overlap_idx;
 } OverlapIndex;
 

 typedef struct FIREqualizerContext {

     const AVClass *class;
 

     RDFTContext   *analysis_rdft;

     RDFTContext   *analysis_irdft;
     RDFTContext   *rdft;
     RDFTContext   *irdft;

     FFTContext    *fft_ctx;

     RDFTContext   *cepstrum_rdft;
     RDFTContext   *cepstrum_irdft;

     int           analysis_rdft_len;
     int           rdft_len;

     int           cepstrum_len;

 
     float         *analysis_buf;

     float         *dump_buf;

     float         *kernel_tmp_buf;
     float         *kernel_buf;

     float         *cepstrum_buf;

     float         *conv_buf;
     OverlapIndex  *conv_idx;
     int           fir_len;
     int           nsamples_max;
     int64_t       next_pts;
     int           frame_nsamples_max;
     int           remaining;
 
     char          *gain_cmd;
     char          *gain_entry_cmd;
     const char    *gain;
     const char    *gain_entry;
     double        delay;
     double        accuracy;
     int           wfunc;
     int           fixed;
     int           multi;

     int           zero_phase;

     int           scale;

     char          *dumpfile;
     int           dumpscale;

     int           fft2;

     int           min_phase;

 
     int           nb_gain_entry;
     int           gain_entry_err;
     GainEntry     gain_entry_tbl[NB_GAIN_ENTRY_MAX];
 } FIREqualizerContext;
 
 #define OFFSET(x) offsetof(FIREqualizerContext, x)
 #define FLAGS AV_OPT_FLAG_AUDIO_PARAM|AV_OPT_FLAG_FILTERING_PARAM
 
 static const AVOption firequalizer_options[] = {
     { "gain", "set gain curve", OFFSET(gain), AV_OPT_TYPE_STRING, { .str = "gain_interpolate(f)" }, 0, 0, FLAGS },
     { "gain_entry", "set gain entry", OFFSET(gain_entry), AV_OPT_TYPE_STRING, { .str = NULL }, 0, 0, FLAGS },
     { "delay", "set delay", OFFSET(delay), AV_OPT_TYPE_DOUBLE, { .dbl = 0.01 }, 0.0, 1e10, FLAGS },
     { "accuracy", "set accuracy", OFFSET(accuracy), AV_OPT_TYPE_DOUBLE, { .dbl = 5.0 }, 0.0, 1e10, FLAGS },

     { "wfunc", "set window function", OFFSET(wfunc), AV_OPT_TYPE_INT, { .i64 = WFUNC_HANN }, 0, NB_WFUNC-1, FLAGS, "wfunc" },

         { "rectangular", "rectangular window", 0, AV_OPT_TYPE_CONST, { .i64 = WFUNC_RECTANGULAR }, 0, 0, FLAGS, "wfunc" },
         { "hann", "hann window", 0, AV_OPT_TYPE_CONST, { .i64 = WFUNC_HANN }, 0, 0, FLAGS, "wfunc" },
         { "hamming", "hamming window", 0, AV_OPT_TYPE_CONST, { .i64 = WFUNC_HAMMING }, 0, 0, FLAGS, "wfunc" },
         { "blackman", "blackman window", 0, AV_OPT_TYPE_CONST, { .i64 = WFUNC_BLACKMAN }, 0, 0, FLAGS, "wfunc" },
         { "nuttall3", "3-term nuttall window", 0, AV_OPT_TYPE_CONST, { .i64 = WFUNC_NUTTALL3 }, 0, 0, FLAGS, "wfunc" },
         { "mnuttall3", "minimum 3-term nuttall window", 0, AV_OPT_TYPE_CONST, { .i64 = WFUNC_MNUTTALL3 }, 0, 0, FLAGS, "wfunc" },
         { "nuttall", "nuttall window", 0, AV_OPT_TYPE_CONST, { .i64 = WFUNC_NUTTALL }, 0, 0, FLAGS, "wfunc" },
         { "bnuttall", "blackman-nuttall window", 0, AV_OPT_TYPE_CONST, { .i64 = WFUNC_BNUTTALL }, 0, 0, FLAGS, "wfunc" },
         { "bharris", "blackman-harris window", 0, AV_OPT_TYPE_CONST, { .i64 = WFUNC_BHARRIS }, 0, 0, FLAGS, "wfunc" },

         { "tukey", "tukey window", 0, AV_OPT_TYPE_CONST, { .i64 = WFUNC_TUKEY }, 0, 0, FLAGS, "wfunc" },

     { "fixed", "set fixed frame samples", OFFSET(fixed), AV_OPT_TYPE_BOOL, { .i64 = 0 }, 0, 1, FLAGS },
     { "multi", "set multi channels mode", OFFSET(multi), AV_OPT_TYPE_BOOL, { .i64 = 0 }, 0, 1, FLAGS },

     { "zero_phase", "set zero phase mode", OFFSET(zero_phase), AV_OPT_TYPE_BOOL, { .i64 = 0 }, 0, 1, FLAGS },

     { "scale", "set gain scale", OFFSET(scale), AV_OPT_TYPE_INT, { .i64 = SCALE_LINLOG }, 0, NB_SCALE-1, FLAGS, "scale" },
         { "linlin", "linear-freq linear-gain", 0, AV_OPT_TYPE_CONST, { .i64 = SCALE_LINLIN }, 0, 0, FLAGS, "scale" },
         { "linlog", "linear-freq logarithmic-gain", 0, AV_OPT_TYPE_CONST, { .i64 = SCALE_LINLOG }, 0, 0, FLAGS, "scale" },
         { "loglin", "logarithmic-freq linear-gain", 0, AV_OPT_TYPE_CONST, { .i64 = SCALE_LOGLIN }, 0, 0, FLAGS, "scale" },
         { "loglog", "logarithmic-freq logarithmic-gain", 0, AV_OPT_TYPE_CONST, { .i64 = SCALE_LOGLOG }, 0, 0, FLAGS, "scale" },

     { "dumpfile", "set dump file", OFFSET(dumpfile), AV_OPT_TYPE_STRING, { .str = NULL }, 0, 0, FLAGS },
     { "dumpscale", "set dump scale", OFFSET(dumpscale), AV_OPT_TYPE_INT, { .i64 = SCALE_LINLOG }, 0, NB_SCALE-1, FLAGS, "scale" },

     { "fft2", "set 2-channels fft", OFFSET(fft2), AV_OPT_TYPE_BOOL, { .i64 = 0 }, 0, 1, FLAGS },

     { "min_phase", "set minimum phase mode", OFFSET(min_phase), AV_OPT_TYPE_BOOL, { .i64 = 0 }, 0, 1, FLAGS },

     { NULL }
 };
 
 AVFILTER_DEFINE_CLASS(firequalizer);
 
 static void common_uninit(FIREqualizerContext *s)
 {

     av_rdft_end(s->analysis_rdft);

     av_rdft_end(s->analysis_irdft);
     av_rdft_end(s->rdft);
     av_rdft_end(s->irdft);

     av_fft_end(s->fft_ctx);

     av_rdft_end(s->cepstrum_rdft);
     av_rdft_end(s->cepstrum_irdft);

     s->analysis_rdft = s->analysis_irdft = s->rdft = s->irdft = NULL;

     s->fft_ctx = NULL;

     s->cepstrum_rdft = NULL;
     s->cepstrum_irdft = NULL;

 
     av_freep(&s->analysis_buf);

     av_freep(&s->dump_buf);

     av_freep(&s->kernel_tmp_buf);
     av_freep(&s->kernel_buf);

     av_freep(&s->cepstrum_buf);

     av_freep(&s->conv_buf);
     av_freep(&s->conv_idx);
 }
 
 static av_cold void uninit(AVFilterContext *ctx)
 {
     FIREqualizerContext *s = ctx->priv;
 
     common_uninit(s);
     av_freep(&s->gain_cmd);
     av_freep(&s->gain_entry_cmd);
 }
 
 static int query_formats(AVFilterContext *ctx)
 {
     AVFilterChannelLayouts *layouts;
     AVFilterFormats *formats;
     static const enum AVSampleFormat sample_fmts[] = {
         AV_SAMPLE_FMT_FLTP,
         AV_SAMPLE_FMT_NONE
     };
     int ret;
 
     layouts = ff_all_channel_counts();
     if (!layouts)
         return AVERROR(ENOMEM);
     ret = ff_set_common_channel_layouts(ctx, layouts);
     if (ret < 0)
         return ret;
 
     formats = ff_make_format_list(sample_fmts);
     if (!formats)
         return AVERROR(ENOMEM);
     ret = ff_set_common_formats(ctx, formats);
     if (ret < 0)
         return ret;
 
     formats = ff_all_samplerates();
     if (!formats)
         return AVERROR(ENOMEM);
     return ff_set_common_samplerates(ctx, formats);
 }
 

 static void fast_convolute(FIREqualizerContext *av_restrict s, const float *av_restrict kernel_buf, float *av_restrict conv_buf,
                            OverlapIndex *av_restrict idx, float *av_restrict data, int nsamples)

 {
     if (nsamples <= s->nsamples_max) {
         float *buf = conv_buf + idx->buf_idx * s->rdft_len;
         float *obuf = conv_buf + !idx->buf_idx * s->rdft_len + idx->overlap_idx;

         int center = s->fir_len/2;

         int k;
 

         memset(buf, 0, center * sizeof(*data));
         memcpy(buf + center, data, nsamples * sizeof(*data));
         memset(buf + center + nsamples, 0, (s->rdft_len - nsamples - center) * sizeof(*data));

         av_rdft_calc(s->rdft, buf);
 
         buf[0] *= kernel_buf[0];

         buf[1] *= kernel_buf[s->rdft_len/2];
         for (k = 1; k < s->rdft_len/2; k++) {
             buf[2*k] *= kernel_buf[k];
             buf[2*k+1] *= kernel_buf[k];

         }
 
         av_rdft_calc(s->irdft, buf);
         for (k = 0; k < s->rdft_len - idx->overlap_idx; k++)
             buf[k] += obuf[k];
         memcpy(data, buf, nsamples * sizeof(*data));
         idx->buf_idx = !idx->buf_idx;
         idx->overlap_idx = nsamples;
     } else {
         while (nsamples > s->nsamples_max * 2) {
             fast_convolute(s, kernel_buf, conv_buf, idx, data, s->nsamples_max);
             data += s->nsamples_max;
             nsamples -= s->nsamples_max;
         }
         fast_convolute(s, kernel_buf, conv_buf, idx, data, nsamples/2);
         fast_convolute(s, kernel_buf, conv_buf, idx, data + nsamples/2, nsamples - nsamples/2);
     }
 }
 

 static void fast_convolute_nonlinear(FIREqualizerContext *av_restrict s, const float *av_restrict kernel_buf,
                                      float *av_restrict conv_buf, OverlapIndex *av_restrict idx,
                                      float *av_restrict data, int nsamples)
 {
     if (nsamples <= s->nsamples_max) {
         float *buf = conv_buf + idx->buf_idx * s->rdft_len;
         float *obuf = conv_buf + !idx->buf_idx * s->rdft_len + idx->overlap_idx;
         int k;
 
         memcpy(buf, data, nsamples * sizeof(*data));
         memset(buf + nsamples, 0, (s->rdft_len - nsamples) * sizeof(*data));
         av_rdft_calc(s->rdft, buf);
 
         buf[0] *= kernel_buf[0];
         buf[1] *= kernel_buf[1];
         for (k = 2; k < s->rdft_len; k += 2) {
             float re, im;
             re = buf[k] * kernel_buf[k] - buf[k+1] * kernel_buf[k+1];
             im = buf[k] * kernel_buf[k+1] + buf[k+1] * kernel_buf[k];
             buf[k] = re;
             buf[k+1] = im;
         }
 
         av_rdft_calc(s->irdft, buf);
         for (k = 0; k < s->rdft_len - idx->overlap_idx; k++)
             buf[k] += obuf[k];
         memcpy(data, buf, nsamples * sizeof(*data));
         idx->buf_idx = !idx->buf_idx;
         idx->overlap_idx = nsamples;
     } else {
         while (nsamples > s->nsamples_max * 2) {
             fast_convolute_nonlinear(s, kernel_buf, conv_buf, idx, data, s->nsamples_max);
             data += s->nsamples_max;
             nsamples -= s->nsamples_max;
         }
         fast_convolute_nonlinear(s, kernel_buf, conv_buf, idx, data, nsamples/2);
         fast_convolute_nonlinear(s, kernel_buf, conv_buf, idx, data + nsamples/2, nsamples - nsamples/2);
     }
 }
 

 static void fast_convolute2(FIREqualizerContext *av_restrict s, const float *av_restrict kernel_buf, FFTComplex *av_restrict conv_buf,
                             OverlapIndex *av_restrict idx, float *av_restrict data0, float *av_restrict data1, int nsamples)

 {
     if (nsamples <= s->nsamples_max) {
         FFTComplex *buf = conv_buf + idx->buf_idx * s->rdft_len;
         FFTComplex *obuf = conv_buf + !idx->buf_idx * s->rdft_len + idx->overlap_idx;
         int center = s->fir_len/2;
         int k;
         float tmp;
 
         memset(buf, 0, center * sizeof(*buf));
         for (k = 0; k < nsamples; k++) {
             buf[center+k].re = data0[k];
             buf[center+k].im = data1[k];
         }
         memset(buf + center + nsamples, 0, (s->rdft_len - nsamples - center) * sizeof(*buf));
         av_fft_permute(s->fft_ctx, buf);
         av_fft_calc(s->fft_ctx, buf);
 
         /* swap re <-> im, do backward fft using forward fft_ctx */
         /* normalize with 0.5f */
         tmp = buf[0].re;
         buf[0].re = 0.5f * kernel_buf[0] * buf[0].im;
         buf[0].im = 0.5f * kernel_buf[0] * tmp;
         for (k = 1; k < s->rdft_len/2; k++) {
             int m = s->rdft_len - k;
             tmp = buf[k].re;
             buf[k].re = 0.5f * kernel_buf[k] * buf[k].im;
             buf[k].im = 0.5f * kernel_buf[k] * tmp;
             tmp = buf[m].re;
             buf[m].re = 0.5f * kernel_buf[k] * buf[m].im;
             buf[m].im = 0.5f * kernel_buf[k] * tmp;
         }
         tmp = buf[k].re;
         buf[k].re = 0.5f * kernel_buf[k] * buf[k].im;
         buf[k].im = 0.5f * kernel_buf[k] * tmp;
 
         av_fft_permute(s->fft_ctx, buf);
         av_fft_calc(s->fft_ctx, buf);
 
         for (k = 0; k < s->rdft_len - idx->overlap_idx; k++) {
             buf[k].re += obuf[k].re;
             buf[k].im += obuf[k].im;
         }
 
         /* swapped re <-> im */
         for (k = 0; k < nsamples; k++) {
             data0[k] = buf[k].im;
             data1[k] = buf[k].re;
         }
         idx->buf_idx = !idx->buf_idx;
         idx->overlap_idx = nsamples;
     } else {
         while (nsamples > s->nsamples_max * 2) {
             fast_convolute2(s, kernel_buf, conv_buf, idx, data0, data1, s->nsamples_max);
             data0 += s->nsamples_max;
             data1 += s->nsamples_max;
             nsamples -= s->nsamples_max;
         }
         fast_convolute2(s, kernel_buf, conv_buf, idx, data0, data1, nsamples/2);
         fast_convolute2(s, kernel_buf, conv_buf, idx, data0 + nsamples/2, data1 + nsamples/2, nsamples - nsamples/2);
     }
 }
 

 static void dump_fir(AVFilterContext *ctx, FILE *fp, int ch)
 {
     FIREqualizerContext *s = ctx->priv;
     int rate = ctx->inputs[0]->sample_rate;
     int xlog = s->dumpscale == SCALE_LOGLIN || s->dumpscale == SCALE_LOGLOG;
     int ylog = s->dumpscale == SCALE_LINLOG || s->dumpscale == SCALE_LOGLOG;
     int x;
     int center = s->fir_len / 2;
     double delay = s->zero_phase ? 0.0 : (double) center / rate;
     double vx, ya, yb;
 

     if (!s->min_phase) {

         s->analysis_buf[0] *= s->rdft_len/2;
         for (x = 1; x <= center; x++) {
             s->analysis_buf[x] *= s->rdft_len/2;
             s->analysis_buf[s->analysis_rdft_len - x] *= s->rdft_len/2;
         }

     } else {
         for (x = 0; x < s->fir_len; x++)
             s->analysis_buf[x] *= s->rdft_len/2;
     }

 
     if (ch)
         fprintf(fp, "\n\n");
 
     fprintf(fp, "# time[%d] (time amplitude)\n", ch);
 

     if (!s->min_phase) {

     for (x = center; x > 0; x--)
         fprintf(fp, "%15.10f %15.10f\n", delay - (double) x / rate, (double) s->analysis_buf[s->analysis_rdft_len - x]);
 
     for (x = 0; x <= center; x++)
         fprintf(fp, "%15.10f %15.10f\n", delay + (double)x / rate , (double) s->analysis_buf[x]);

     } else {
         for (x = 0; x < s->fir_len; x++)
             fprintf(fp, "%15.10f %15.10f\n", (double)x / rate, (double) s->analysis_buf[x]);
     }

 
     av_rdft_calc(s->analysis_rdft, s->analysis_buf);
 
     fprintf(fp, "\n\n# freq[%d] (frequency desired_gain actual_gain)\n", ch);
 
     for (x = 0; x <= s->analysis_rdft_len/2; x++) {
         int i = (x == s->analysis_rdft_len/2) ? 1 : 2 * x;
         vx = (double)x * rate / s->analysis_rdft_len;
         if (xlog)
             vx = log2(0.05*vx);
         ya = s->dump_buf[i];

         yb = s->min_phase && (i > 1) ? hypotf(s->analysis_buf[i], s->analysis_buf[i+1]) : s->analysis_buf[i];
         if (s->min_phase)
             yb = fabs(yb);

         if (ylog) {
             ya = 20.0 * log10(fabs(ya));
             yb = 20.0 * log10(fabs(yb));
         }
         fprintf(fp, "%17.10f %17.10f %17.10f\n", vx, ya, yb);
     }
 }
 

 static double entry_func(void *p, double freq, double gain)
 {
     AVFilterContext *ctx = p;
     FIREqualizerContext *s = ctx->priv;
 
     if (s->nb_gain_entry >= NB_GAIN_ENTRY_MAX) {
         av_log(ctx, AV_LOG_ERROR, "entry table overflow.\n");
         s->gain_entry_err = AVERROR(EINVAL);
         return 0;
     }
 
     if (isnan(freq)) {
         av_log(ctx, AV_LOG_ERROR, "nan frequency (%g, %g).\n", freq, gain);
         s->gain_entry_err = AVERROR(EINVAL);
         return 0;
     }
 
     if (s->nb_gain_entry > 0 && freq <= s->gain_entry_tbl[s->nb_gain_entry - 1].freq) {
         av_log(ctx, AV_LOG_ERROR, "unsorted frequency (%g, %g).\n", freq, gain);
         s->gain_entry_err = AVERROR(EINVAL);
         return 0;
     }
 
     s->gain_entry_tbl[s->nb_gain_entry].freq = freq;
     s->gain_entry_tbl[s->nb_gain_entry].gain = gain;
     s->nb_gain_entry++;
     return 0;
 }
 
 static int gain_entry_compare(const void *key, const void *memb)
 {
     const double *freq = key;
     const GainEntry *entry = memb;
 
     if (*freq < entry[0].freq)
         return -1;
     if (*freq > entry[1].freq)
         return 1;
     return 0;
 }
 
 static double gain_interpolate_func(void *p, double freq)
 {
     AVFilterContext *ctx = p;
     FIREqualizerContext *s = ctx->priv;
     GainEntry *res;
     double d0, d1, d;
 
     if (isnan(freq))
         return freq;
 
     if (!s->nb_gain_entry)
         return 0;
 
     if (freq <= s->gain_entry_tbl[0].freq)
         return s->gain_entry_tbl[0].gain;
 
     if (freq >= s->gain_entry_tbl[s->nb_gain_entry-1].freq)
         return s->gain_entry_tbl[s->nb_gain_entry-1].gain;
 
     res = bsearch(&freq, &s->gain_entry_tbl, s->nb_gain_entry - 1, sizeof(*res), gain_entry_compare);
     av_assert0(res);
 
     d  = res[1].freq - res[0].freq;
     d0 = freq - res[0].freq;
     d1 = res[1].freq - freq;
 
     if (d0 && d1)
         return (d0 * res[1].gain + d1 * res[0].gain) / d;
 
     if (d0)
         return res[1].gain;
 
     return res[0].gain;
 }
 

 static double cubic_interpolate_func(void *p, double freq)
 {
     AVFilterContext *ctx = p;
     FIREqualizerContext *s = ctx->priv;
     GainEntry *res;
     double x, x2, x3;
     double a, b, c, d;
     double m0, m1, m2, msum, unit;
 
     if (!s->nb_gain_entry)
         return 0;
 
     if (freq <= s->gain_entry_tbl[0].freq)
         return s->gain_entry_tbl[0].gain;
 
     if (freq >= s->gain_entry_tbl[s->nb_gain_entry-1].freq)
         return s->gain_entry_tbl[s->nb_gain_entry-1].gain;
 
     res = bsearch(&freq, &s->gain_entry_tbl, s->nb_gain_entry - 1, sizeof(*res), gain_entry_compare);
     av_assert0(res);
 
     unit = res[1].freq - res[0].freq;
     m0 = res != s->gain_entry_tbl ?
          unit * (res[0].gain - res[-1].gain) / (res[0].freq - res[-1].freq) : 0;
     m1 = res[1].gain - res[0].gain;
     m2 = res != s->gain_entry_tbl + s->nb_gain_entry - 2 ?
          unit * (res[2].gain - res[1].gain) / (res[2].freq - res[1].freq) : 0;
 
     msum = fabs(m0) + fabs(m1);
     m0 = msum > 0 ? (fabs(m0) * m1 + fabs(m1) * m0) / msum : 0;
     msum = fabs(m1) + fabs(m2);
     m1 = msum > 0 ? (fabs(m1) * m2 + fabs(m2) * m1) / msum : 0;
 
     d = res[0].gain;
     c = m0;
     b = 3 * res[1].gain - m1 - 2 * c - 3 * d;
     a = res[1].gain - b - c - d;
 
     x = (freq - res[0].freq) / unit;
     x2 = x * x;
     x3 = x2 * x;
 
     return a * x3 + b * x2 + c * x + d;
 }
 

 static const char *const var_names[] = {
     "f",
     "sr",
     "ch",
     "chid",
     "chs",
     "chlayout",
     NULL
 };
 
 enum VarOffset {
     VAR_F,
     VAR_SR,
     VAR_CH,
     VAR_CHID,
     VAR_CHS,
     VAR_CHLAYOUT,
     VAR_NB
 };
 

 static void generate_min_phase_kernel(FIREqualizerContext *s, float *rdft_buf)
 {
     int k, cepstrum_len = s->cepstrum_len, rdft_len = s->rdft_len;
     double norm = 2.0 / cepstrum_len;

     double minval = 1e-7 / rdft_len;

 
     memset(s->cepstrum_buf, 0, cepstrum_len * sizeof(*s->cepstrum_buf));
     memcpy(s->cepstrum_buf, rdft_buf, rdft_len/2 * sizeof(*rdft_buf));
     memcpy(s->cepstrum_buf + cepstrum_len - rdft_len/2, rdft_buf + rdft_len/2, rdft_len/2  * sizeof(*rdft_buf));
 
     av_rdft_calc(s->cepstrum_rdft, s->cepstrum_buf);
 

     s->cepstrum_buf[0] = log(FFMAX(s->cepstrum_buf[0], minval));
     s->cepstrum_buf[1] = log(FFMAX(s->cepstrum_buf[1], minval));

 
     for (k = 2; k < cepstrum_len; k += 2) {

         s->cepstrum_buf[k] = log(FFMAX(s->cepstrum_buf[k], minval));

         s->cepstrum_buf[k+1] = 0;
     }
 
     av_rdft_calc(s->cepstrum_irdft, s->cepstrum_buf);
 
     memset(s->cepstrum_buf + cepstrum_len/2 + 1, 0, (cepstrum_len/2 - 1) * sizeof(*s->cepstrum_buf));
     for (k = 1; k < cepstrum_len/2; k++)
         s->cepstrum_buf[k] *= 2;
 
     av_rdft_calc(s->cepstrum_rdft, s->cepstrum_buf);
 
     s->cepstrum_buf[0] = exp(s->cepstrum_buf[0] * norm) * norm;
     s->cepstrum_buf[1] = exp(s->cepstrum_buf[1] * norm) * norm;
     for (k = 2; k < cepstrum_len; k += 2) {
         double mag = exp(s->cepstrum_buf[k] * norm) * norm;
         double ph = s->cepstrum_buf[k+1] * norm;
         s->cepstrum_buf[k] = mag * cos(ph);
         s->cepstrum_buf[k+1] = mag * sin(ph);
     }
 
     av_rdft_calc(s->cepstrum_irdft, s->cepstrum_buf);
     memset(rdft_buf, 0, s->rdft_len * sizeof(*rdft_buf));
     memcpy(rdft_buf, s->cepstrum_buf, s->fir_len * sizeof(*rdft_buf));
 
     if (s->dumpfile) {
         memset(s->analysis_buf, 0, s->analysis_rdft_len * sizeof(*s->analysis_buf));
         memcpy(s->analysis_buf, s->cepstrum_buf, s->fir_len * sizeof(*s->analysis_buf));
     }
 
 }
 

 static int generate_kernel(AVFilterContext *ctx, const char *gain, const char *gain_entry)
 {
     FIREqualizerContext *s = ctx->priv;
     AVFilterLink *inlink = ctx->inputs[0];
     const char *gain_entry_func_names[] = { "entry", NULL };

     const char *gain_func_names[] = { "gain_interpolate", "cubic_interpolate", NULL };

     double (*gain_entry_funcs[])(void *, double, double) = { entry_func, NULL };

     double (*gain_funcs[])(void *, double) = { gain_interpolate_func, cubic_interpolate_func, NULL };

     double vars[VAR_NB];
     AVExpr *gain_expr;
     int ret, k, center, ch;

     int xlog = s->scale == SCALE_LOGLIN || s->scale == SCALE_LOGLOG;
     int ylog = s->scale == SCALE_LINLOG || s->scale == SCALE_LOGLOG;

     FILE *dump_fp = NULL;

 
     s->nb_gain_entry = 0;
     s->gain_entry_err = 0;
     if (gain_entry) {
         double result = 0.0;
         ret = av_expr_parse_and_eval(&result, gain_entry, NULL, NULL, NULL, NULL,
                                      gain_entry_func_names, gain_entry_funcs, ctx, 0, ctx);
         if (ret < 0)
             return ret;
         if (s->gain_entry_err < 0)
             return s->gain_entry_err;
     }
 
     av_log(ctx, AV_LOG_DEBUG, "nb_gain_entry = %d.\n", s->nb_gain_entry);
 
     ret = av_expr_parse(&gain_expr, gain, var_names,
                         gain_func_names, gain_funcs, NULL, NULL, 0, ctx);
     if (ret < 0)
         return ret;
 

     if (s->dumpfile && (!s->dump_buf || !s->analysis_rdft || !(dump_fp = fopen(s->dumpfile, "w"))))
         av_log(ctx, AV_LOG_WARNING, "dumping failed.\n");
 

     vars[VAR_CHS] = inlink->channels;
     vars[VAR_CHLAYOUT] = inlink->channel_layout;
     vars[VAR_SR] = inlink->sample_rate;
     for (ch = 0; ch < inlink->channels; ch++) {

         float *rdft_buf = s->kernel_tmp_buf + ch * s->rdft_len;

         double result;

         vars[VAR_CH] = ch;
         vars[VAR_CHID] = av_channel_layout_extract_channel(inlink->channel_layout, ch);
         vars[VAR_F] = 0.0;

         if (xlog)
             vars[VAR_F] = log2(0.05 * vars[VAR_F]);
         result = av_expr_eval(gain_expr, vars, ctx);
         s->analysis_buf[0] = ylog ? pow(10.0, 0.05 * result) : result;
 

         vars[VAR_F] = 0.5 * inlink->sample_rate;

         if (xlog)
             vars[VAR_F] = log2(0.05 * vars[VAR_F]);
         result = av_expr_eval(gain_expr, vars, ctx);
         s->analysis_buf[1] = ylog ? pow(10.0, 0.05 * result) : result;

 
         for (k = 1; k < s->analysis_rdft_len/2; k++) {
             vars[VAR_F] = k * ((double)inlink->sample_rate /(double)s->analysis_rdft_len);

             if (xlog)
                 vars[VAR_F] = log2(0.05 * vars[VAR_F]);
             result = av_expr_eval(gain_expr, vars, ctx);

             s->analysis_buf[2*k] = ylog ? pow(10.0, 0.05 * result) : s->min_phase ? fabs(result) : result;

             s->analysis_buf[2*k+1] = 0.0;
         }
 

         if (s->dump_buf)
             memcpy(s->dump_buf, s->analysis_buf, s->analysis_rdft_len * sizeof(*s->analysis_buf));
 

         av_rdft_calc(s->analysis_irdft, s->analysis_buf);
         center = s->fir_len / 2;
 
         for (k = 0; k <= center; k++) {
             double u = k * (M_PI/center);
             double win;
             switch (s->wfunc) {
             case WFUNC_RECTANGULAR:
                 win = 1.0;
                 break;
             case WFUNC_HANN:
                 win = 0.5 + 0.5 * cos(u);
                 break;
             case WFUNC_HAMMING:
                 win = 0.53836 + 0.46164 * cos(u);
                 break;
             case WFUNC_BLACKMAN:

                 win = 0.42 + 0.5 * cos(u) + 0.08 * cos(2*u);

                 break;
             case WFUNC_NUTTALL3:
                 win = 0.40897 + 0.5 * cos(u) + 0.09103 * cos(2*u);
                 break;
             case WFUNC_MNUTTALL3:
                 win = 0.4243801 + 0.4973406 * cos(u) + 0.0782793 * cos(2*u);
                 break;
             case WFUNC_NUTTALL:
                 win = 0.355768 + 0.487396 * cos(u) + 0.144232 * cos(2*u) + 0.012604 * cos(3*u);
                 break;
             case WFUNC_BNUTTALL:
                 win = 0.3635819 + 0.4891775 * cos(u) + 0.1365995 * cos(2*u) + 0.0106411 * cos(3*u);
                 break;
             case WFUNC_BHARRIS:
                 win = 0.35875 + 0.48829 * cos(u) + 0.14128 * cos(2*u) + 0.01168 * cos(3*u);
                 break;

             case WFUNC_TUKEY:
                 win = (u <= 0.5 * M_PI) ? 1.0 : (0.5 + 0.5 * cos(2*u - M_PI));
                 break;

             default:
                 av_assert0(0);
             }
             s->analysis_buf[k] *= (2.0/s->analysis_rdft_len) * (2.0/s->rdft_len) * win;

             if (k)
                 s->analysis_buf[s->analysis_rdft_len - k] = s->analysis_buf[k];

         }
 

         memset(s->analysis_buf + center + 1, 0, (s->analysis_rdft_len - s->fir_len) * sizeof(*s->analysis_buf));

         memcpy(rdft_buf, s->analysis_buf, s->rdft_len/2 * sizeof(*s->analysis_buf));
         memcpy(rdft_buf + s->rdft_len/2, s->analysis_buf + s->analysis_rdft_len - s->rdft_len/2, s->rdft_len/2 * sizeof(*s->analysis_buf));

         if (s->min_phase)
             generate_min_phase_kernel(s, rdft_buf);

         av_rdft_calc(s->rdft, rdft_buf);

 
         for (k = 0; k < s->rdft_len; k++) {

             if (isnan(rdft_buf[k]) || isinf(rdft_buf[k])) {

                 av_log(ctx, AV_LOG_ERROR, "filter kernel contains nan or infinity.\n");
                 av_expr_free(gain_expr);

                 if (dump_fp)
                     fclose(dump_fp);

                 return AVERROR(EINVAL);
             }
         }
 

         if (!s->min_phase) {

             rdft_buf[s->rdft_len-1] = rdft_buf[1];
             for (k = 0; k < s->rdft_len/2; k++)
                 rdft_buf[k] = rdft_buf[2*k];
             rdft_buf[s->rdft_len/2] = rdft_buf[s->rdft_len-1];

         }

         if (dump_fp)
             dump_fir(ctx, dump_fp, ch);
 

         if (!s->multi)
             break;
     }
 
     memcpy(s->kernel_buf, s->kernel_tmp_buf, (s->multi ? inlink->channels : 1) * s->rdft_len * sizeof(*s->kernel_buf));
     av_expr_free(gain_expr);

     if (dump_fp)
         fclose(dump_fp);

     return 0;
 }
 

 #define SELECT_GAIN(s) (s->gain_cmd ? s->gain_cmd : s->gain)
 #define SELECT_GAIN_ENTRY(s) (s->gain_entry_cmd ? s->gain_entry_cmd : s->gain_entry)
 

 static int config_input(AVFilterLink *inlink)
 {
     AVFilterContext *ctx = inlink->dst;
     FIREqualizerContext *s = ctx->priv;
     int rdft_bits;
 
     common_uninit(s);
 
     s->next_pts = 0;
     s->frame_nsamples_max = 0;
 
     s->fir_len = FFMAX(2 * (int)(inlink->sample_rate * s->delay) + 1, 3);
     s->remaining = s->fir_len - 1;
 
     for (rdft_bits = RDFT_BITS_MIN; rdft_bits <= RDFT_BITS_MAX; rdft_bits++) {
         s->rdft_len = 1 << rdft_bits;
         s->nsamples_max = s->rdft_len - s->fir_len + 1;
         if (s->nsamples_max * 2 >= s->fir_len)
             break;
     }
 
     if (rdft_bits > RDFT_BITS_MAX) {
         av_log(ctx, AV_LOG_ERROR, "too large delay, please decrease it.\n");
         return AVERROR(EINVAL);
     }
 
     if (!(s->rdft = av_rdft_init(rdft_bits, DFT_R2C)) || !(s->irdft = av_rdft_init(rdft_bits, IDFT_C2R)))
         return AVERROR(ENOMEM);
 

     if (s->fft2 && !s->multi && inlink->channels > 1 && !(s->fft_ctx = av_fft_init(rdft_bits, 0)))
         return AVERROR(ENOMEM);
 

     if (s->min_phase) {
         int cepstrum_bits = rdft_bits + 2;
         if (cepstrum_bits > RDFT_BITS_MAX) {
             av_log(ctx, AV_LOG_ERROR, "too large delay, please decrease it.\n");
             return AVERROR(EINVAL);
         }
 
         cepstrum_bits = FFMIN(RDFT_BITS_MAX, cepstrum_bits + 1);
         s->cepstrum_rdft = av_rdft_init(cepstrum_bits, DFT_R2C);
         s->cepstrum_irdft = av_rdft_init(cepstrum_bits, IDFT_C2R);
         if (!s->cepstrum_rdft || !s->cepstrum_irdft)
             return AVERROR(ENOMEM);
 
         s->cepstrum_len = 1 << cepstrum_bits;
         s->cepstrum_buf = av_malloc_array(s->cepstrum_len, sizeof(*s->cepstrum_buf));
         if (!s->cepstrum_buf)
             return AVERROR(ENOMEM);
     }
 

     for ( ; rdft_bits <= RDFT_BITS_MAX; rdft_bits++) {
         s->analysis_rdft_len = 1 << rdft_bits;
         if (inlink->sample_rate <= s->accuracy * s->analysis_rdft_len)
             break;
     }
 
     if (rdft_bits > RDFT_BITS_MAX) {
         av_log(ctx, AV_LOG_ERROR, "too small accuracy, please increase it.\n");
         return AVERROR(EINVAL);
     }
 
     if (!(s->analysis_irdft = av_rdft_init(rdft_bits, IDFT_C2R)))
         return AVERROR(ENOMEM);
 

     if (s->dumpfile) {
         s->analysis_rdft = av_rdft_init(rdft_bits, DFT_R2C);
         s->dump_buf = av_malloc_array(s->analysis_rdft_len, sizeof(*s->dump_buf));
     }
 

     s->analysis_buf = av_malloc_array(s->analysis_rdft_len, sizeof(*s->analysis_buf));
     s->kernel_tmp_buf = av_malloc_array(s->rdft_len * (s->multi ? inlink->channels : 1), sizeof(*s->kernel_tmp_buf));
     s->kernel_buf = av_malloc_array(s->rdft_len * (s->multi ? inlink->channels : 1), sizeof(*s->kernel_buf));
     s->conv_buf   = av_calloc(2 * s->rdft_len * inlink->channels, sizeof(*s->conv_buf));
     s->conv_idx   = av_calloc(inlink->channels, sizeof(*s->conv_idx));
     if (!s->analysis_buf || !s->kernel_tmp_buf || !s->kernel_buf || !s->conv_buf || !s->conv_idx)
         return AVERROR(ENOMEM);
 
     av_log(ctx, AV_LOG_DEBUG, "sample_rate = %d, channels = %d, analysis_rdft_len = %d, rdft_len = %d, fir_len = %d, nsamples_max = %d.\n",
            inlink->sample_rate, inlink->channels, s->analysis_rdft_len, s->rdft_len, s->fir_len, s->nsamples_max);
 
     if (s->fixed)
         inlink->min_samples = inlink->max_samples = inlink->partial_buf_size = s->nsamples_max;
 

     return generate_kernel(ctx, SELECT_GAIN(s), SELECT_GAIN_ENTRY(s));

 }
 
 static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
 {
     AVFilterContext *ctx = inlink->dst;
     FIREqualizerContext *s = ctx->priv;
     int ch;
 

     if (!s->min_phase) {

         for (ch = 0; ch + 1 < inlink->channels && s->fft_ctx; ch += 2) {
             fast_convolute2(s, s->kernel_buf, (FFTComplex *)(s->conv_buf + 2 * ch * s->rdft_len),
                             s->conv_idx + ch, (float *) frame->extended_data[ch],
                             (float *) frame->extended_data[ch+1], frame->nb_samples);
         }

         for ( ; ch < inlink->channels; ch++) {
             fast_convolute(s, s->kernel_buf + (s->multi ? ch * s->rdft_len : 0),
                         s->conv_buf + 2 * ch * s->rdft_len, s->conv_idx + ch,
                         (float *) frame->extended_data[ch], frame->nb_samples);
         }

     } else {
         for (ch = 0; ch < inlink->channels; ch++) {
             fast_convolute_nonlinear(s, s->kernel_buf + (s->multi ? ch * s->rdft_len : 0),
                                      s->conv_buf + 2 * ch * s->rdft_len, s->conv_idx + ch,
                                      (float *) frame->extended_data[ch], frame->nb_samples);
         }
     }

     s->next_pts = AV_NOPTS_VALUE;
     if (frame->pts != AV_NOPTS_VALUE) {
         s->next_pts = frame->pts + av_rescale_q(frame->nb_samples, av_make_q(1, inlink->sample_rate), inlink->time_base);

         if (s->zero_phase && !s->min_phase)

             frame->pts -= av_rescale_q(s->fir_len/2, av_make_q(1, inlink->sample_rate), inlink->time_base);
     }

     s->frame_nsamples_max = FFMAX(s->frame_nsamples_max, frame->nb_samples);
     return ff_filter_frame(ctx->outputs[0], frame);
 }
 
 static int request_frame(AVFilterLink *outlink)
 {
     AVFilterContext *ctx = outlink->src;
     FIREqualizerContext *s= ctx->priv;
     int ret;
 
     ret = ff_request_frame(ctx->inputs[0]);
     if (ret == AVERROR_EOF && s->remaining > 0 && s->frame_nsamples_max > 0) {
         AVFrame *frame = ff_get_audio_buffer(outlink, FFMIN(s->remaining, s->frame_nsamples_max));
 
         if (!frame)
             return AVERROR(ENOMEM);
 
         av_samples_set_silence(frame->extended_data, 0, frame->nb_samples, outlink->channels, frame->format);
         frame->pts = s->next_pts;
         s->remaining -= frame->nb_samples;
         ret = filter_frame(ctx->inputs[0], frame);
     }
 
     return ret;
 }
 
 static int process_command(AVFilterContext *ctx, const char *cmd, const char *args,
                            char *res, int res_len, int flags)
 {
     FIREqualizerContext *s = ctx->priv;
     int ret = AVERROR(ENOSYS);
 
     if (!strcmp(cmd, "gain")) {
         char *gain_cmd;
 

         if (SELECT_GAIN(s) && !strcmp(SELECT_GAIN(s), args)) {
             av_log(ctx, AV_LOG_DEBUG, "equal gain, do not rebuild.\n");
             return 0;
         }
 

         gain_cmd = av_strdup(args);
         if (!gain_cmd)
             return AVERROR(ENOMEM);
 

         ret = generate_kernel(ctx, gain_cmd, SELECT_GAIN_ENTRY(s));

         if (ret >= 0) {
             av_freep(&s->gain_cmd);
             s->gain_cmd = gain_cmd;
         } else {
             av_freep(&gain_cmd);
         }
     } else if (!strcmp(cmd, "gain_entry")) {
         char *gain_entry_cmd;
 

         if (SELECT_GAIN_ENTRY(s) && !strcmp(SELECT_GAIN_ENTRY(s), args)) {
             av_log(ctx, AV_LOG_DEBUG, "equal gain_entry, do not rebuild.\n");
             return 0;
         }
 

         gain_entry_cmd = av_strdup(args);
         if (!gain_entry_cmd)
             return AVERROR(ENOMEM);
 

         ret = generate_kernel(ctx, SELECT_GAIN(s), gain_entry_cmd);

         if (ret >= 0) {
             av_freep(&s->gain_entry_cmd);
             s->gain_entry_cmd = gain_entry_cmd;
         } else {
             av_freep(&gain_entry_cmd);
         }
     }
 
     return ret;
 }
 
 static const AVFilterPad firequalizer_inputs[] = {
     {
         .name           = "default",
         .config_props   = config_input,
         .filter_frame   = filter_frame,
         .type           = AVMEDIA_TYPE_AUDIO,
         .needs_writable = 1,
     },
     { NULL }
 };
 
 static const AVFilterPad firequalizer_outputs[] = {
     {
         .name           = "default",
         .request_frame  = request_frame,
         .type           = AVMEDIA_TYPE_AUDIO,
     },
     { NULL }
 };
 
 AVFilter ff_af_firequalizer = {
     .name               = "firequalizer",

     .description        = NULL_IF_CONFIG_SMALL("Finite Impulse Response Equalizer."),

     .uninit             = uninit,
     .query_formats      = query_formats,
     .process_command    = process_command,
     .priv_size          = sizeof(FIREqualizerContext),
     .inputs             = firequalizer_inputs,
     .outputs            = firequalizer_outputs,
     .priv_class         = &firequalizer_class,
 };