avfilter: add hilbert source FIR filter

Signed-off-by: Paul B Mahol <onemda@gmail.com>

Changelog

@@ -32,6 +32,7 @@ version <next>:
   version is Windows Vista.
 - deconvolve video filter
 - entropy video filter
+- hilbert audio filter source
 
 
 version 3.4:

doc/filters.texi

@@ -926,6 +926,7 @@ afftfilt="1-clip((b/nb)*b,0,1)"
 @end example
 @end itemize
 
+@anchor{afir}
 @section afir
 
 Apply an arbitrary Frequency Impulse Response filter.
@@ -4873,6 +4874,33 @@ anoisesrc=d=60:c=pink:r=44100:a=0.5
 @end example
 @end itemize
 
+@section hilbert
+
+Generate odd-tap Hilbert transform FIR coefficients.
+
+The resulting stream can be used with @ref{afir} filter for phase-shifting
+the signal by 90 degrees.
+
+This is used in many matrix coding schemes and for analytic signal generation.
+The process is often written as a multiplication by i (or j), the imaginary unit.
+
+The filter accepts the following options:
+
+@table @option
+
+@item sample_rate, s
+Set sample rate, default is 44100.
+
+@item taps, t
+Set length of FIR filter, default is 22051.
+
+@item nb_samples, n
+Set number of samples per each frame.
+
+@item win_func, w
+Set window function to be used when generating FIR coefficients.
+@end table
+
 @section sine
 
 Generate an audio signal made of a sine wave with amplitude 1/8.

libavfilter/Makefile

@@ -126,6 +126,7 @@ OBJS-$(CONFIG_AEVALSRC_FILTER)               += aeval.o
 OBJS-$(CONFIG_ANOISESRC_FILTER)              += asrc_anoisesrc.o
 OBJS-$(CONFIG_ANULLSRC_FILTER)               += asrc_anullsrc.o
 OBJS-$(CONFIG_FLITE_FILTER)                  += asrc_flite.o
+OBJS-$(CONFIG_HILBERT_FILTER)                += asrc_hilbert.o
 OBJS-$(CONFIG_SINE_FILTER)                   += asrc_sine.o
 
 OBJS-$(CONFIG_ANULLSINK_FILTER)              += asink_anullsink.o

libavfilter/allfilters.c

@@ -137,6 +137,7 @@ static void register_all(void)
     REGISTER_FILTER(ANOISESRC,      anoisesrc,      asrc);
     REGISTER_FILTER(ANULLSRC,       anullsrc,       asrc);
     REGISTER_FILTER(FLITE,          flite,          asrc);
+    REGISTER_FILTER(HILBERT,        hilbert,        asrc);
     REGISTER_FILTER(SINE,           sine,           asrc);
 
     REGISTER_FILTER(ANULLSINK,      anullsink,      asink);

libavfilter/asrc_hilbert.c

+/*
+ * 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/opt.h"
+#include "audio.h"
+#include "avfilter.h"
+#include "internal.h"
+#include "window_func.h"
+
+typedef struct HilbertContext {
+    const AVClass *class;
+
+    int sample_rate;
+    int nb_taps;
+    int nb_samples;
+    int win_func;
+
+    float *taps;
+    int64_t pts;
+} HilbertContext;
+
+#define OFFSET(x) offsetof(HilbertContext, x)
+#define FLAGS AV_OPT_FLAG_AUDIO_PARAM|AV_OPT_FLAG_FILTERING_PARAM
+
+static const AVOption hilbert_options[] = {
+    { "sample_rate", "set sample rate",    OFFSET(sample_rate), AV_OPT_TYPE_INT, {.i64=44100},  1, INT_MAX,    FLAGS },
+    { "r",           "set sample rate",    OFFSET(sample_rate), AV_OPT_TYPE_INT, {.i64=44100},  1, INT_MAX,    FLAGS },
+    { "taps",        "set number of taps", OFFSET(nb_taps),     AV_OPT_TYPE_INT, {.i64=22051}, 11, UINT16_MAX, FLAGS },
+    { "t",           "set number of taps", OFFSET(nb_taps),     AV_OPT_TYPE_INT, {.i64=22051}, 11, UINT16_MAX, FLAGS },
+    { "nb_samples",  "set the number of samples per requested frame", OFFSET(nb_samples), AV_OPT_TYPE_INT, {.i64 = 1024}, 1, INT_MAX, FLAGS },
+    { "n",           "set the number of samples per requested frame", OFFSET(nb_samples), AV_OPT_TYPE_INT, {.i64 = 1024}, 1, INT_MAX, FLAGS },
+    { "win_func", "set window function", OFFSET(win_func), AV_OPT_TYPE_INT, {.i64=WFUNC_BLACKMAN}, 0, NB_WFUNC-1, FLAGS, "win_func" },
+    { "w",        "set window function", OFFSET(win_func), AV_OPT_TYPE_INT, {.i64=WFUNC_BLACKMAN}, 0, NB_WFUNC-1, FLAGS, "win_func" },
+        { "rect",     "Rectangular",      0, AV_OPT_TYPE_CONST, {.i64=WFUNC_RECT},     0, 0, FLAGS, "win_func" },
+        { "bartlett", "Bartlett",         0, AV_OPT_TYPE_CONST, {.i64=WFUNC_BARTLETT}, 0, 0, FLAGS, "win_func" },
+        { "hanning",  "Hanning",          0, AV_OPT_TYPE_CONST, {.i64=WFUNC_HANNING},  0, 0, FLAGS, "win_func" },
+        { "hamming",  "Hamming",          0, AV_OPT_TYPE_CONST, {.i64=WFUNC_HAMMING},  0, 0, FLAGS, "win_func" },
+        { "blackman", "Blackman",         0, AV_OPT_TYPE_CONST, {.i64=WFUNC_BLACKMAN}, 0, 0, FLAGS, "win_func" },
+        { "welch",    "Welch",            0, AV_OPT_TYPE_CONST, {.i64=WFUNC_WELCH},    0, 0, FLAGS, "win_func" },
+        { "flattop",  "Flat-top",         0, AV_OPT_TYPE_CONST, {.i64=WFUNC_FLATTOP},  0, 0, FLAGS, "win_func" },
+        { "bharris",  "Blackman-Harris",  0, AV_OPT_TYPE_CONST, {.i64=WFUNC_BHARRIS},  0, 0, FLAGS, "win_func" },
+        { "bnuttall", "Blackman-Nuttall", 0, AV_OPT_TYPE_CONST, {.i64=WFUNC_BNUTTALL}, 0, 0, FLAGS, "win_func" },
+        { "bhann",    "Bartlett-Hann",    0, AV_OPT_TYPE_CONST, {.i64=WFUNC_BHANN},    0, 0, FLAGS, "win_func" },
+        { "sine",     "Sine",             0, AV_OPT_TYPE_CONST, {.i64=WFUNC_SINE},     0, 0, FLAGS, "win_func" },
+        { "nuttall",  "Nuttall",          0, AV_OPT_TYPE_CONST, {.i64=WFUNC_NUTTALL},  0, 0, FLAGS, "win_func" },
+        { "lanczos",  "Lanczos",          0, AV_OPT_TYPE_CONST, {.i64=WFUNC_LANCZOS},  0, 0, FLAGS, "win_func" },
+        { "gauss",    "Gauss",            0, AV_OPT_TYPE_CONST, {.i64=WFUNC_GAUSS},    0, 0, FLAGS, "win_func" },
+        { "tukey",    "Tukey",            0, AV_OPT_TYPE_CONST, {.i64=WFUNC_TUKEY},    0, 0, FLAGS, "win_func" },
+        { "dolph",    "Dolph-Chebyshev",  0, AV_OPT_TYPE_CONST, {.i64=WFUNC_DOLPH},    0, 0, FLAGS, "win_func" },
+        { "cauchy",   "Cauchy",           0, AV_OPT_TYPE_CONST, {.i64=WFUNC_CAUCHY},   0, 0, FLAGS, "win_func" },
+        { "parzen",   "Parzen",           0, AV_OPT_TYPE_CONST, {.i64=WFUNC_PARZEN},   0, 0, FLAGS, "win_func" },
+        { "poisson",  "Poisson",          0, AV_OPT_TYPE_CONST, {.i64=WFUNC_POISSON},  0, 0, FLAGS, "win_func" },
+    {NULL}
+};
+
+AVFILTER_DEFINE_CLASS(hilbert);
+
+static av_cold int init(AVFilterContext *ctx)
+{
+    HilbertContext *s = ctx->priv;
+
+    if (!(s->nb_taps & 1)) {
+        av_log(s, AV_LOG_ERROR, "Number of taps %d must be odd length.\n", s->nb_taps);
+        return AVERROR(EINVAL);
+    }
+
+    return 0;
+}
+
+static av_cold void uninit(AVFilterContext *ctx)
+{
+    HilbertContext *s = ctx->priv;
+
+    av_freep(&s->taps);
+}
+
+static av_cold int query_formats(AVFilterContext *ctx)
+{
+    HilbertContext *s = ctx->priv;
+    static const int64_t chlayouts[] = { AV_CH_LAYOUT_MONO, -1 };
+    int sample_rates[] = { s->sample_rate, -1 };
+    static const enum AVSampleFormat sample_fmts[] = {
+        AV_SAMPLE_FMT_FLT,
+        AV_SAMPLE_FMT_NONE
+    };
+
+    AVFilterFormats *formats;
+    AVFilterChannelLayouts *layouts;
+    int 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;
+
+    layouts = avfilter_make_format64_list(chlayouts);
+    if (!layouts)
+        return AVERROR(ENOMEM);
+    ret = ff_set_common_channel_layouts(ctx, layouts);
+    if (ret < 0)
+        return ret;
+
+    formats = ff_make_format_list(sample_rates);
+    if (!formats)
+        return AVERROR(ENOMEM);
+    return ff_set_common_samplerates(ctx, formats);
+}
+
+static av_cold int config_props(AVFilterLink *outlink)
+{
+    AVFilterContext *ctx = outlink->src;
+    HilbertContext *s = ctx->priv;
+    float overlap;
+    int i;
+
+    s->taps = av_malloc_array(s->nb_taps, sizeof(*s->taps));
+    if (!s->taps)
+        return AVERROR(ENOMEM);
+
+    generate_window_func(s->taps, s->nb_taps, s->win_func, &overlap);
+
+    for (i = 0; i < s->nb_taps; i++) {
+        int k = -(s->nb_taps / 2) + i;
+
+        if (k & 1) {
+            float pk = M_PI * k;
+
+            s->taps[i] *= (1.f - cosf(pk)) / pk;
+        } else {
+            s->taps[i] = 0.f;
+        }
+    }
+
+    s->pts = 0;
+
+    return 0;
+}
+
+static int request_frame(AVFilterLink *outlink)
+{
+    AVFilterContext *ctx = outlink->src;
+    HilbertContext *s = ctx->priv;
+    AVFrame *frame;
+    int nb_samples;
+
+    nb_samples = FFMIN(s->nb_samples, s->nb_taps - s->pts);
+    if (!nb_samples)
+        return AVERROR_EOF;
+
+    if (!(frame = ff_get_audio_buffer(outlink, nb_samples)))
+        return AVERROR(ENOMEM);
+
+    memcpy(frame->data[0], s->taps + s->pts, nb_samples * sizeof(float));
+
+    frame->pts = s->pts;
+    s->pts    += nb_samples;
+    return ff_filter_frame(outlink, frame);
+}
+
+static const AVFilterPad hilbert_outputs[] = {
+    {
+        .name          = "default",
+        .type          = AVMEDIA_TYPE_AUDIO,
+        .request_frame = request_frame,
+        .config_props  = config_props,
+    },
+    { NULL }
+};
+
+AVFilter ff_asrc_hilbert = {
+    .name          = "hilbert",
+    .description   = NULL_IF_CONFIG_SMALL("Generate a Hilbert transform FIR coefficients."),
+    .query_formats = query_formats,
+    .init          = init,
+    .uninit        = uninit,
+    .priv_size     = sizeof(HilbertContext),
+    .inputs        = NULL,
+    .outputs       = hilbert_outputs,
+    .priv_class    = &hilbert_class,
+};

libavfilter/version.h

@@ -30,7 +30,7 @@
 #include "libavutil/version.h"
 
 #define LIBAVFILTER_VERSION_MAJOR   7
-#define LIBAVFILTER_VERSION_MINOR   9
+#define LIBAVFILTER_VERSION_MINOR  10
 #define LIBAVFILTER_VERSION_MICRO 100
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \