[FFmpeg-devel] avfilter: add astretch filter

diff --git a/libavfilter/Makefile b/libavfilter/Makefile
index 79a89a1ab1..4a715915fc 100644
--- a/libavfilter/Makefile
+++ b/libavfilter/Makefile
@@ -81,6 +81,7 @@  OBJS-$(CONFIG_ASIDEDATA_FILTER)              += f_sidedata.o
 OBJS-$(CONFIG_ASPLIT_FILTER)                 += split.o
 OBJS-$(CONFIG_ASTATS_FILTER)                 += af_astats.o
 OBJS-$(CONFIG_ASTREAMSELECT_FILTER)          += f_streamselect.o framesync.o
+OBJS-$(CONFIG_ASTRETCH_FILTER)               += af_astretch.o
 OBJS-$(CONFIG_ATEMPO_FILTER)                 += af_atempo.o
 OBJS-$(CONFIG_ATRIM_FILTER)                  += trim.o
 OBJS-$(CONFIG_AZMQ_FILTER)                   += f_zmq.o
diff --git a/libavfilter/af_astretch.c b/libavfilter/af_astretch.c
new file mode 100644
index 0000000000..1e39ac3163
--- /dev/null
+++ b/libavfilter/af_astretch.c
@@ -0,0 +1,330 @@ 
+/*
+ * Copyright (c) 2018 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/avstring.h"
+#include "libavutil/lfg.h"
+#include "libavutil/random_seed.h"
+#include "libavfilter/internal.h"
+#include "libavutil/common.h"
+#include "libavutil/opt.h"
+#include "libavcodec/avfft.h"
+#include "audio.h"
+#include "filters.h"
+#include "window_func.h"
+
+typedef struct AStretchContext {
+    const AVClass *class;
+    double stretch;
+    double overlap;
+    int window_size;
+    int phase;
+    int win_func;
+    int64_t seed;
+
+    int fft_bits;
+    AVAudioFifo *fifo;
+    double start_pos;
+    double displace_pos;
+    int64_t pts;
+    AVFrame *buffer;
+    int start, end;
+    float win_scale;
+    float *window_func_lut;
+
+    AVLFG c;
+    FFTContext *fft;
+    FFTContext *ifft;
+    FFTComplex *fft_data;
+} AStretchContext;
+
+#define OFFSET(x) offsetof(AStretchContext, x)
+#define A AV_OPT_FLAG_AUDIO_PARAM|AV_OPT_FLAG_FILTERING_PARAM
+
+static const AVOption astretch_options[] = {
+    { "stretch", "set stretch factor",  OFFSET(stretch),     AV_OPT_TYPE_DOUBLE, {.dbl=1},   0.001,       1000, A },
+    { "overlap", "set overlap factor",  OFFSET(overlap),     AV_OPT_TYPE_DOUBLE, {.dbl=1},       0,          1, A },
+    { "winsize", "set window size",     OFFSET(window_size), AV_OPT_TYPE_INT,    {.i64=8192},   16,      65536, A },
+    { "phase",   "change phase",        OFFSET(phase),       AV_OPT_TYPE_BOOL,   {.i64=1},       0,          1, A },
+    { "winfunc", "set window function", OFFSET(win_func),    AV_OPT_TYPE_INT,    {.i64=WFUNC_SINE},     0, NB_WFUNC-1, A, "winfunc" },
+      { "rect",     "Rectangular",      0,                   AV_OPT_TYPE_CONST,  {.i64=WFUNC_RECT},     0, 0, A, "winfunc" },
+      { "bartlett", "Bartlett",         0,                   AV_OPT_TYPE_CONST,  {.i64=WFUNC_BARTLETT}, 0, 0, A, "winfunc" },
+      { "hann",     "Hann",             0,                   AV_OPT_TYPE_CONST,  {.i64=WFUNC_HANNING},  0, 0, A, "winfunc" },
+      { "hanning",  "Hanning",          0,                   AV_OPT_TYPE_CONST,  {.i64=WFUNC_HANNING},  0, 0, A, "winfunc" },
+      { "hamming",  "Hamming",          0,                   AV_OPT_TYPE_CONST,  {.i64=WFUNC_HAMMING},  0, 0, A, "winfunc" },
+      { "blackman", "Blackman",         0,                   AV_OPT_TYPE_CONST,  {.i64=WFUNC_BLACKMAN}, 0, 0, A, "winfunc" },
+      { "welch",    "Welch",            0,                   AV_OPT_TYPE_CONST,  {.i64=WFUNC_WELCH},    0, 0, A, "winfunc" },
+      { "flattop",  "Flat-top",         0,                   AV_OPT_TYPE_CONST,  {.i64=WFUNC_FLATTOP},  0, 0, A, "winfunc" },
+      { "bharris",  "Blackman-Harris",  0,                   AV_OPT_TYPE_CONST,  {.i64=WFUNC_BHARRIS},  0, 0, A, "winfunc" },
+      { "bnuttall", "Blackman-Nuttall", 0,                   AV_OPT_TYPE_CONST,  {.i64=WFUNC_BNUTTALL}, 0, 0, A, "winfunc" },
+      { "bhann",    "Bartlett-Hann",    0,                   AV_OPT_TYPE_CONST,  {.i64=WFUNC_BHANN},    0, 0, A, "winfunc" },
+      { "sine",     "Sine",             0,                   AV_OPT_TYPE_CONST,  {.i64=WFUNC_SINE},     0, 0, A, "winfunc" },
+      { "nuttall",  "Nuttall",          0,                   AV_OPT_TYPE_CONST,  {.i64=WFUNC_NUTTALL},  0, 0, A, "winfunc" },
+      { "lanczos",  "Lanczos",          0,                   AV_OPT_TYPE_CONST,  {.i64=WFUNC_LANCZOS},  0, 0, A, "winfunc" },
+      { "gauss",    "Gauss",            0,                   AV_OPT_TYPE_CONST,  {.i64=WFUNC_GAUSS},    0, 0, A, "winfunc" },
+      { "tukey",    "Tukey",            0,                   AV_OPT_TYPE_CONST,  {.i64=WFUNC_TUKEY},    0, 0, A, "winfunc" },
+      { "dolph",    "Dolph-Chebyshev",  0,                   AV_OPT_TYPE_CONST,  {.i64=WFUNC_DOLPH},    0, 0, A, "winfunc" },
+      { "cauchy",   "Cauchy",           0,                   AV_OPT_TYPE_CONST,  {.i64=WFUNC_CAUCHY},   0, 0, A, "winfunc" },
+      { "parzen",   "Parzen",           0,                   AV_OPT_TYPE_CONST,  {.i64=WFUNC_PARZEN},   0, 0, A, "winfunc" },
+      { "poisson",  "Poisson",          0,                   AV_OPT_TYPE_CONST,  {.i64=WFUNC_POISSON},  0, 0, A, "winfunc" },
+      { "bohman",   "Bohman",           0,                   AV_OPT_TYPE_CONST,  {.i64=WFUNC_BOHMAN},   0, 0, A, "winfunc" },
+    { "seed",     "set random seed",    OFFSET(seed),        AV_OPT_TYPE_INT64,  {.i64 = -1},   -1, UINT_MAX, A },
+    { NULL },
+};
+
+AVFILTER_DEFINE_CLASS(astretch);
+
+static int config_input(AVFilterLink *inlink)
+{
+    AVFilterContext *ctx = inlink->dst;
+    AStretchContext *s = ctx->priv;
+    float overlap;
+
+    av_lfg_init(&s->c, s->seed);
+
+    s->fft_bits = av_log2(s->window_size);
+    if (s->phase)
+        s->window_size = 1 << s->fft_bits;
+
+    s->fft = av_fft_init(s->fft_bits, 0);
+    s->ifft = av_fft_init(s->fft_bits, 1);
+    if (!s->ifft || !s->fft)
+        return AVERROR(ENOMEM);
+
+    s->fft_data = av_calloc(s->window_size, sizeof(*s->fft_data));
+    if (!s->fft_data)
+        return AVERROR(ENOMEM);
+
+    s->fifo = av_audio_fifo_alloc(inlink->format, inlink->channels, s->window_size);
+    if (!s->fifo)
+        return AVERROR(ENOMEM);
+
+    s->window_func_lut = av_realloc_f(s->window_func_lut, s->window_size,
+                                      sizeof(*s->window_func_lut));
+    if (!s->window_func_lut)
+        return AVERROR(ENOMEM);
+    generate_window_func(s->window_func_lut, s->window_size, s->win_func, &overlap);
+    if (s->overlap == 1)
+        s->overlap = overlap;
+
+    s->buffer = ff_get_audio_buffer(inlink, 2 * s->window_size);
+    if (!s->buffer)
+        return AVERROR(ENOMEM);
+
+    s->start_pos = 0.;
+    s->displace_pos = (s->window_size * (1. - s->overlap)) / s->stretch;
+    s->pts = AV_NOPTS_VALUE;
+
+    return 0;
+}
+
+static int activate(AVFilterContext *ctx)
+{
+    AVFilterLink *inlink = ctx->inputs[0];
+    AVFilterLink *outlink = ctx->outputs[0];
+    AStretchContext *s = ctx->priv;
+    AVFrame *frame = NULL;
+    int ret = 0;
+
+    FF_FILTER_FORWARD_STATUS_BACK(outlink, inlink);
+
+    if (av_audio_fifo_size(s->fifo) < s->window_size) {
+        ret = ff_inlink_consume_frame(inlink, &frame);
+        if (ret < 0)
+            return ret;
+    }
+
+    if (ret > 0) {
+        if (s->pts == AV_NOPTS_VALUE)
+            s->pts = frame->pts;
+
+        ret = av_audio_fifo_write(s->fifo, (void **)frame->extended_data, frame->nb_samples);
+        av_frame_free(&frame);
+        if (ret < 0)
+            return ret;
+    }
+
+    if (av_audio_fifo_size(s->fifo) >= s->window_size) {
+        int istart_pos, hwin = s->window_size * (1. - s->overlap);
+        AVFrame *in = ff_get_audio_buffer(outlink, s->window_size);
+        AVFrame *out = ff_get_audio_buffer(outlink, hwin);
+
+        if (!out || !in) {
+            av_frame_free(&in);
+            av_frame_free(&out);
+            return AVERROR(ENOMEM);
+        }
+
+        ret = av_audio_fifo_peek(s->fifo, (void **)in->extended_data, s->window_size);
+        if (ret < 0) {
+            av_frame_free(&in);
+            av_frame_free(&out);
+            return ret;
+        }
+
+        if (s->phase) {
+            for (int ch = 0; ch < outlink->channels; ch++) {
+                const float *src = (float *)in->extended_data[ch];
+                const float *w = s->window_func_lut;
+                float *ptr = (float *)s->buffer->extended_data[ch];
+                FFTComplex *dst = s->fft_data;
+                float magnitude, phase;
+
+                for (int n = 0; n < s->window_size; n++) {
+                    dst[n].re = src[n] * w[n];
+                    dst[n].im = 0;
+                }
+
+                av_fft_permute(s->fft, s->fft_data);
+                av_fft_calc(s->fft, s->fft_data);
+
+                for (int n = 0; n < s->window_size; n++) {
+                    magnitude = hypotf(dst[n].re, dst[n].im);
+                    phase = M_PI * (((2. * av_lfg_get(&s->c)) / (UINT_MAX + 1.0)) - 1.);
+                    dst[n].re = magnitude * cos(phase);
+                    dst[n].im = magnitude * sin(phase);
+                }
+
+                av_fft_permute(s->ifft, s->fft_data);
+                av_fft_calc(s->ifft, s->fft_data);
+
+                for (int n = 0; n < s->window_size; n++) {
+                    const float *w = s->window_func_lut;
+
+                    ptr[n] += (dst[n].re / s->window_size) * w[n];
+                }
+            }
+        } else {
+            for (int ch = 0; ch < outlink->channels; ch++) {
+                const float *src = (float *)in->extended_data[ch];
+                float *dst = (float *)s->buffer->extended_data[ch];
+
+                for (int n = 0; n < s->window_size; n++) {
+                    dst[n] += src[n];
+                }
+            }
+        }
+
+
+        s->start_pos += s->displace_pos;
+        istart_pos = lrint(floor(s->start_pos));
+        if (istart_pos > 0) {
+            av_audio_fifo_drain(s->fifo, istart_pos);
+            s->start_pos -= istart_pos;
+        }
+        out->pts = s->pts;
+        s->pts += out->nb_samples;
+
+        av_samples_copy(out->extended_data, s->buffer->extended_data,
+                        0, 0, hwin, s->buffer->channels, s->buffer->format);
+
+        for (int ch = 0; ch < outlink->channels; ch++) {
+            float *buf = (float *)s->buffer->extended_data[ch];
+            memmove(buf, buf + hwin, (s->window_size * 2 - hwin) * sizeof(*buf));
+        }
+
+        for (int ch = 0; ch < outlink->channels; ch++) {
+            float *buf = (float *)s->buffer->extended_data[ch];
+            memset(buf + s->window_size * 2 - hwin, 0, hwin * sizeof(*buf));
+        }
+
+        av_frame_free(&in);
+        return ff_filter_frame(outlink, out);
+    }
+
+    FF_FILTER_FORWARD_STATUS(inlink, outlink);
+    FF_FILTER_FORWARD_WANTED(outlink, inlink);
+
+    return FFERROR_NOT_READY;
+}
+
+static int query_formats(AVFilterContext *ctx)
+{
+    AVFilterFormats *formats;
+    AVFilterChannelLayouts *layouts;
+    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 av_cold void uninit(AVFilterContext *ctx)
+{
+    AStretchContext *s = ctx->priv;
+
+    av_frame_free(&s->buffer);
+    av_freep(&s->window_func_lut);
+    av_freep(&s->fft_data);
+    av_fft_end(s->fft);
+    s->fft = NULL;
+    av_fft_end(s->ifft);
+    s->ifft = NULL;
+
+    av_audio_fifo_free(s->fifo);
+}
+
+static const AVFilterPad inputs[] = {
+    {
+        .name         = "default",
+        .type         = AVMEDIA_TYPE_AUDIO,
+        .config_props = config_input,
+    },
+    { NULL }
+};
+
+static const AVFilterPad outputs[] = {
+    {
+        .name = "default",
+        .type = AVMEDIA_TYPE_AUDIO,
+    },
+    { NULL }
+};
+
+AVFilter ff_af_astretch = {
+    .name            = "astretch",
+    .description     = NULL_IF_CONFIG_SMALL("Apply stretch."),
+    .priv_size       = sizeof(AStretchContext),
+    .priv_class      = &astretch_class,
+    .inputs          = inputs,
+    .outputs         = outputs,
+    .activate        = activate,
+    .query_formats   = query_formats,
+    .uninit          = uninit,
+};
diff --git a/libavfilter/allfilters.c b/libavfilter/allfilters.c
index 484b080dea..a43376abc7 100644
--- a/libavfilter/allfilters.c
+++ b/libavfilter/allfilters.c
@@ -74,6 +74,7 @@  extern AVFilter ff_af_asidedata;
 extern AVFilter ff_af_asplit;
 extern AVFilter ff_af_astats;
 extern AVFilter ff_af_astreamselect;
+extern AVFilter ff_af_astretch;
 extern AVFilter ff_af_atempo;
 extern AVFilter ff_af_atrim;
 extern AVFilter ff_af_azmq;