/*
  * Copyright (c) 2013 Nicolas George
  *
  * 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 <float.h>
 

 #include "libavutil/avassert.h"
 #include "libavutil/channel_layout.h"
 #include "libavutil/opt.h"
 #include "audio.h"
 #include "avfilter.h"
 #include "internal.h"
 
 typedef struct {
     const AVClass *class;
     double frequency;
     double beep_factor;
     int samples_per_frame;
     int sample_rate;
     int64_t duration;
     int16_t *sin;
     int64_t pts;
     uint32_t phi;  ///< current phase of the sine (2pi = 1<<32)
     uint32_t dphi; ///< phase increment between two samples
     unsigned beep_period;
     unsigned beep_index;
     unsigned beep_length;
     uint32_t phi_beep;  ///< current phase of the beep
     uint32_t dphi_beep; ///< phase increment of the beep
 } SineContext;
 
 #define CONTEXT SineContext
 #define FLAGS AV_OPT_FLAG_AUDIO_PARAM|AV_OPT_FLAG_FILTERING_PARAM
 
 #define OPT_GENERIC(name, field, def, min, max, descr, type, deffield, ...) \
     { name, descr, offsetof(CONTEXT, field), AV_OPT_TYPE_ ## type,          \
       { .deffield = def }, min, max, FLAGS, __VA_ARGS__ }
 
 #define OPT_INT(name, field, def, min, max, descr, ...) \
     OPT_GENERIC(name, field, def, min, max, descr, INT, i64, __VA_ARGS__)
 
 #define OPT_DBL(name, field, def, min, max, descr, ...) \
     OPT_GENERIC(name, field, def, min, max, descr, DOUBLE, dbl, __VA_ARGS__)
 
 #define OPT_DUR(name, field, def, min, max, descr, ...) \
     OPT_GENERIC(name, field, def, min, max, descr, DURATION, str, __VA_ARGS__)
 
 static const AVOption sine_options[] = {

     OPT_DBL("frequency",         frequency,            440, 0, DBL_MAX,   "set the sine frequency"),
     OPT_DBL("f",                 frequency,            440, 0, DBL_MAX,   "set the sine frequency"),
     OPT_DBL("beep_factor",       beep_factor,            0, 0, DBL_MAX,   "set the beep fequency factor"),
     OPT_DBL("b",                 beep_factor,            0, 0, DBL_MAX,   "set the beep fequency factor"),

     OPT_INT("sample_rate",       sample_rate,        44100, 1, INT_MAX,   "set the sample rate"),
     OPT_INT("r",                 sample_rate,        44100, 1, INT_MAX,   "set the sample rate"),
     OPT_DUR("duration",          duration,               0, 0, INT64_MAX, "set the audio duration"),
     OPT_DUR("d",                 duration,               0, 0, INT64_MAX, "set the audio duration"),
     OPT_INT("samples_per_frame", samples_per_frame,   1024, 0, INT_MAX,   "set the number of samples per frame"),

     {NULL}

 };
 
 AVFILTER_DEFINE_CLASS(sine);
 
 #define LOG_PERIOD 15
 #define AMPLITUDE 4095
 #define AMPLITUDE_SHIFT 3
 
 static void make_sin_table(int16_t *sin)
 {
     unsigned half_pi = 1 << (LOG_PERIOD - 2);
     unsigned ampls = AMPLITUDE << AMPLITUDE_SHIFT;
     uint64_t unit2 = (uint64_t)(ampls * ampls) << 32;
     unsigned step, i, c, s, k, new_k, n2;
 
     /* Principle: if u = exp(i*a1) and v = exp(i*a2), then
        exp(i*(a1+a2)/2) = (u+v) / length(u+v) */
     sin[0] = 0;
     sin[half_pi] = ampls;
     for (step = half_pi; step > 1; step /= 2) {
         /* k = (1 << 16) * amplitude / length(u+v)
            In exact values, k is constant at a given step */
         k = 0x10000;
         for (i = 0; i < half_pi / 2; i += step) {
             s = sin[i] + sin[i + step];
             c = sin[half_pi - i] + sin[half_pi - i - step];
             n2 = s * s + c * c;
             /* Newton's method to solve n² * k² = unit² */
             while (1) {
                 new_k = (k + unit2 / ((uint64_t)k * n2) + 1) >> 1;
                 if (k == new_k)
                     break;
                 k = new_k;
             }
             sin[i + step / 2] = (k * s + 0x7FFF) >> 16;
             sin[half_pi - i - step / 2] = (k * c + 0x8000) >> 16;
         }
     }
     /* Unshift amplitude */
     for (i = 0; i <= half_pi; i++)
         sin[i] = (sin[i] + (1 << (AMPLITUDE_SHIFT - 1))) >> AMPLITUDE_SHIFT;
     /* Use symmetries to fill the other three quarters */
     for (i = 0; i < half_pi; i++)
         sin[half_pi * 2 - i] = sin[i];
     for (i = 0; i < 2 * half_pi; i++)
         sin[i + 2 * half_pi] = -sin[i];
 }
 

 static av_cold int init(AVFilterContext *ctx)

 {
     SineContext *sine = ctx->priv;
 
     if (!(sine->sin = av_malloc(sizeof(*sine->sin) << LOG_PERIOD)))
         return AVERROR(ENOMEM);
     sine->dphi = ldexp(sine->frequency, 32) / sine->sample_rate + 0.5;
     make_sin_table(sine->sin);
 
     if (sine->beep_factor) {
         sine->beep_period = sine->sample_rate;
         sine->beep_length = sine->beep_period / 25;
         sine->dphi_beep = ldexp(sine->beep_factor * sine->frequency, 32) /
                           sine->sample_rate + 0.5;
     }
 
     return 0;
 }
 
 static av_cold void uninit(AVFilterContext *ctx)
 {
     SineContext *sine = ctx->priv;
 
     av_freep(&sine->sin);
 }
 
 static av_cold int query_formats(AVFilterContext *ctx)
 {
     SineContext *sine = ctx->priv;
     static const int64_t chlayouts[] = { AV_CH_LAYOUT_MONO, -1 };
     int sample_rates[] = { sine->sample_rate, -1 };
     static const enum AVSampleFormat sample_fmts[] = { AV_SAMPLE_FMT_S16,
                                                        AV_SAMPLE_FMT_NONE };
 
     ff_set_common_formats (ctx, ff_make_format_list(sample_fmts));
     ff_set_common_channel_layouts(ctx, avfilter_make_format64_list(chlayouts));
     ff_set_common_samplerates(ctx, ff_make_format_list(sample_rates));
     return 0;
 }
 
 static av_cold int config_props(AVFilterLink *outlink)
 {
     SineContext *sine = outlink->src->priv;
     sine->duration = av_rescale(sine->duration, sine->sample_rate, AV_TIME_BASE);
     return 0;
 }
 
 static int request_frame(AVFilterLink *outlink)
 {
     SineContext *sine = outlink->src->priv;
     AVFrame *frame;
     int i, nb_samples = sine->samples_per_frame;
     int16_t *samples;
 
     if (sine->duration) {
         nb_samples = FFMIN(nb_samples, sine->duration - sine->pts);
         av_assert1(nb_samples >= 0);
         if (!nb_samples)
             return AVERROR_EOF;
     }
     if (!(frame = ff_get_audio_buffer(outlink, nb_samples)))
         return AVERROR(ENOMEM);
     samples = (int16_t *)frame->data[0];
 
     for (i = 0; i < nb_samples; i++) {
         samples[i] = sine->sin[sine->phi >> (32 - LOG_PERIOD)];
         sine->phi += sine->dphi;
         if (sine->beep_index < sine->beep_length) {
             samples[i] += sine->sin[sine->phi_beep >> (32 - LOG_PERIOD)] << 1;
             sine->phi_beep += sine->dphi_beep;
         }
         if (++sine->beep_index == sine->beep_period)
             sine->beep_index = 0;
     }
 
     frame->pts = sine->pts;
     sine->pts += nb_samples;
     return ff_filter_frame(outlink, frame);
 }
 
 static const AVFilterPad sine_outputs[] = {
     {
         .name          = "default",
         .type          = AVMEDIA_TYPE_AUDIO,
         .request_frame = request_frame,
         .config_props  = config_props,
     },
     { NULL }
 };
 

 AVFilter ff_asrc_sine = {

     .name          = "sine",
     .description   = NULL_IF_CONFIG_SMALL("Generate sine wave audio signal."),
     .query_formats = query_formats,
     .init          = init,
     .uninit        = uninit,
     .priv_size     = sizeof(SineContext),
     .inputs        = NULL,
     .outputs       = sine_outputs,
     .priv_class    = &sine_class,
 };