avfilter: add fractional delay IR source filter

Changelog

@@ -28,6 +28,7 @@ version <next>:
 - showcwt multimedia filter
 - corr video filter
 - adrc audio filter
+- afdelaysrc audio filter
 
 
 version 5.1:

doc/filters.texi

@@ -7519,6 +7519,33 @@ aevalsrc="0.1*sin(2*PI*(360-2.5/2)*t) | 0.1*sin(2*PI*(360+2.5/2)*t)"
 
 @end itemize
 
+@section afdelaysrc
+
+Generate a fractional delay FIR coefficients.
+
+The resulting stream can be used with @ref{afir} filter for filtering the audio signal.
+
+The filter accepts the following options:
+
+@table @option
+@item delay, d
+Set the fractional delay. Default is 0.
+
+@item sample_rate, r
+Set the sample rate, default is 44100.
+
+@item nb_samples, n
+Set the number of samples per each frame. Default is 1024.
+
+@item taps, t
+Set the number of filter coefficents in output audio stream.
+Default value is 0.
+
+@item channel_layout, c
+Specifies the channel layout, and can be a string representing a channel layout.
+The default value of @var{channel_layout} is "stereo".
+@end table
+
 @section afirsrc
 
 Generate a FIR coefficients using frequency sampling method.

libavfilter/Makefile

@@ -171,6 +171,7 @@ OBJS-$(CONFIG_VOLUME_FILTER)                 += af_volume.o
 OBJS-$(CONFIG_VOLUMEDETECT_FILTER)           += af_volumedetect.o
 
 OBJS-$(CONFIG_AEVALSRC_FILTER)               += aeval.o
+OBJS-$(CONFIG_AFDELAYSRC_FILTER)             += asrc_afdelaysrc.o
 OBJS-$(CONFIG_AFIRSRC_FILTER)                += asrc_afirsrc.o
 OBJS-$(CONFIG_ANOISESRC_FILTER)              += asrc_anoisesrc.o
 OBJS-$(CONFIG_ANULLSRC_FILTER)               += asrc_anullsrc.o

libavfilter/allfilters.c

@@ -159,6 +159,7 @@ extern const AVFilter ff_af_volume;
 extern const AVFilter ff_af_volumedetect;
 
 extern const AVFilter ff_asrc_aevalsrc;
+extern const AVFilter ff_asrc_afdelaysrc;
 extern const AVFilter ff_asrc_afirsrc;
 extern const AVFilter ff_asrc_anoisesrc;
 extern const AVFilter ff_asrc_anullsrc;

libavfilter/asrc_afdelaysrc.c

@@ -0,0 +1,173 @@
+/*
+ * Copyright (c) 2023 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/avassert.h"
+#include "libavutil/channel_layout.h"
+#include "libavutil/opt.h"
+
+#include "audio.h"
+#include "avfilter.h"
+#include "filters.h"
+#include "internal.h"
+
+typedef struct AFDelaySrcContext {
+    const AVClass *class;
+
+    double delay;
+    int sample_rate;
+    int nb_samples;
+    int nb_taps;
+    AVChannelLayout chlayout;
+    char *chlayout_str;
+
+    int64_t pts;
+} AFDelaySrcContext;
+
+static av_cold int init(AVFilterContext *ctx)
+{
+    AFDelaySrcContext *s = ctx->priv;
+    int ret;
+
+    ret = ff_parse_channel_layout(&s->chlayout, NULL, s->chlayout_str, ctx);
+    if (ret < 0)
+        return ret;
+
+    return 0;
+}
+
+static float sincf(float x)
+{
+    if (x == 0.f)
+        return 1.f;
+    return sinf(M_PI * x) / (M_PI * x);
+}
+
+static int activate(AVFilterContext *ctx)
+{
+    AVFilterLink *outlink = ctx->outputs[0];
+    AFDelaySrcContext *s = ctx->priv;
+    AVFrame *frame = NULL;
+    int nb_samples;
+    float *dst;
+
+    if (!ff_outlink_frame_wanted(outlink))
+        return FFERROR_NOT_READY;
+
+    nb_samples = FFMIN(s->nb_samples, s->nb_taps - s->pts);
+    if (nb_samples <= 0) {
+        ff_outlink_set_status(outlink, AVERROR_EOF, s->pts);
+        return 0;
+    }
+
+    if (!(frame = ff_get_audio_buffer(outlink, nb_samples)))
+        return AVERROR(ENOMEM);
+
+    dst = (float *)frame->extended_data[0];
+    for (int n = 0; n < nb_samples; n++) {
+        float x = s->pts + n;
+        dst[n] = sincf(x - s->delay) * cosf(M_PI * (x - s->delay) / s->nb_taps) / sincf((x - s->delay) / s->nb_taps);
+    }
+
+    for (int ch = 1; ch < frame->ch_layout.nb_channels; ch++)
+        memcpy(frame->extended_data[ch], dst, sizeof(*dst) * nb_samples);
+
+    frame->pts = s->pts;
+    s->pts    += nb_samples;
+
+    return ff_filter_frame(outlink, frame);
+}
+
+static int query_formats(AVFilterContext *ctx)
+{
+    AFDelaySrcContext *s = ctx->priv;
+    AVChannelLayout chlayouts[] = { s->chlayout, { 0 } };
+    int sample_rates[] = { s->sample_rate, -1 };
+    static const enum AVSampleFormat sample_fmts[] = { AV_SAMPLE_FMT_FLTP,
+                                                       AV_SAMPLE_FMT_NONE };
+    int ret = ff_set_common_formats_from_list(ctx, sample_fmts);
+    if (ret < 0)
+        return ret;
+
+    ret = ff_set_common_channel_layouts_from_list(ctx, chlayouts);
+    if (ret < 0)
+        return ret;
+
+    return ff_set_common_samplerates_from_list(ctx, sample_rates);
+}
+
+static int config_output(AVFilterLink *outlink)
+{
+    AVFilterContext *ctx = outlink->src;
+    AFDelaySrcContext *s = ctx->priv;
+
+    outlink->sample_rate = s->sample_rate;
+    s->pts = 0;
+    if (s->nb_taps <= 0)
+        s->nb_taps = s->delay * 8 + 1;
+
+    return 0;
+}
+
+static const AVFilterPad afdelaysrc_outputs[] = {
+    {
+        .name          = "default",
+        .type          = AVMEDIA_TYPE_AUDIO,
+        .config_props  = config_output,
+    },
+};
+
+static av_cold void uninit(AVFilterContext *ctx)
+{
+    AFDelaySrcContext *s = ctx->priv;
+
+    av_channel_layout_uninit(&s->chlayout);
+}
+
+#define AF AV_OPT_FLAG_AUDIO_PARAM|AV_OPT_FLAG_FILTERING_PARAM
+#define OFFSET(x) offsetof(AFDelaySrcContext, x)
+
+static const AVOption afdelaysrc_options[] = {
+    { "delay",       "set fractional delay",                          OFFSET(delay),       AV_OPT_TYPE_DOUBLE,{.dbl=0},      0, INT16_MAX, AF },
+    { "d",           "set fractional delay",                          OFFSET(delay),       AV_OPT_TYPE_DOUBLE,{.dbl=0},      0, INT16_MAX, AF },
+    { "sample_rate", "set sample rate",                               OFFSET(sample_rate), AV_OPT_TYPE_INT,   {.i64=44100},  1, INT_MAX,   AF },
+    { "r",           "set sample rate",                               OFFSET(sample_rate), AV_OPT_TYPE_INT,   {.i64=44100},  1, INT_MAX,   AF },
+    { "nb_samples",  "set the number of samples per requested frame", OFFSET(nb_samples),  AV_OPT_TYPE_INT,   {.i64=1024},   1, INT_MAX,   AF },
+    { "n",           "set the number of samples per requested frame", OFFSET(nb_samples),  AV_OPT_TYPE_INT,   {.i64=1024},   1, INT_MAX,   AF },
+    { "taps",        "set number of taps for delay filter",           OFFSET(nb_taps),     AV_OPT_TYPE_INT,   {.i64=0},      0,   32768,   AF },
+    { "t",           "set number of taps for delay filter",           OFFSET(nb_taps),     AV_OPT_TYPE_INT,   {.i64=0},      0,   32768,   AF },
+    { "channel_layout", "set channel layout",                         OFFSET(chlayout_str),AV_OPT_TYPE_STRING,{.str="stereo"},0,      0,   AF },
+    { "c",              "set channel layout",                         OFFSET(chlayout_str),AV_OPT_TYPE_STRING,{.str="stereo"},0,      0,   AF },
+    { NULL }
+};
+
+AVFILTER_DEFINE_CLASS(afdelaysrc);
+
+const AVFilter ff_asrc_afdelaysrc = {
+    .name          = "afdelaysrc",
+    .description   = NULL_IF_CONFIG_SMALL("Generate a Fractional delay FIR coefficients."),
+    .priv_size     = sizeof(AFDelaySrcContext),
+    .priv_class    = &afdelaysrc_class,
+    .init          = init,
+    .activate      = activate,
+    .uninit        = uninit,
+    .inputs        = NULL,
+    FILTER_OUTPUTS(afdelaysrc_outputs),
+    FILTER_QUERY_FUNC(query_formats),
+};

libavfilter/version.h

@@ -31,7 +31,7 @@
 
 #include "version_major.h"
 
-#define LIBAVFILTER_VERSION_MINOR  53
+#define LIBAVFILTER_VERSION_MINOR  54
 #define LIBAVFILTER_VERSION_MICRO 100