avfilter: add drmeter audio filter

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

Changelog

@@ -45,6 +45,7 @@ version <next>:
 - Moved nvidia codec headers into an external repository.
   They can be found at http://git.videolan.org/?p=ffmpeg/nv-codec-headers.git
 - native SBC encoder and decoder
+- drmeter audio filter
 
 
 version 3.4:

doc/filters.texi

@@ -2538,6 +2538,21 @@ Optional. It should have a value much less than 1 (e.g. 0.05 or 0.02) and is
 used to prevent clipping.
 @end table
 
+@section drmeter
+Measure audio dynamic range.
+
+DR values of 14 and higher is found in very dynamic material. DR of 8 to 13
+is found in transition material. And anything less that 8 have very poor dynamics
+and is very compressed.
+
+The filter accepts the following options:
+
+@table @option
+@item length
+Set window length in seconds used to split audio into segments of equal length.
+Default is 3 seconds.
+@end table
+
 @section dynaudnorm
 Dynamic Audio Normalizer.
 

libavfilter/Makefile

@@ -87,6 +87,7 @@ OBJS-$(CONFIG_COMPENSATIONDELAY_FILTER)      += af_compensationdelay.o
 OBJS-$(CONFIG_CROSSFEED_FILTER)              += af_crossfeed.o
 OBJS-$(CONFIG_CRYSTALIZER_FILTER)            += af_crystalizer.o
 OBJS-$(CONFIG_DCSHIFT_FILTER)                += af_dcshift.o
+OBJS-$(CONFIG_DRMETER_FILTER)                += af_drmeter.o
 OBJS-$(CONFIG_DYNAUDNORM_FILTER)             += af_dynaudnorm.o
 OBJS-$(CONFIG_EARWAX_FILTER)                 += af_earwax.o
 OBJS-$(CONFIG_EBUR128_FILTER)                += f_ebur128.o

libavfilter/af_drmeter.c

@@ -0,0 +1,233 @@
+/*
+ * 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 <float.h>
+
+#include "libavutil/ffmath.h"
+#include "libavutil/opt.h"
+#include "audio.h"
+#include "avfilter.h"
+#include "internal.h"
+
+typedef struct ChannelStats {
+    uint64_t nb_samples;
+    uint64_t blknum;
+    float peak;
+    float sum;
+    uint32_t peaks[10001];
+    uint32_t rms[10001];
+} ChannelStats;
+
+typedef struct DRMeterContext {
+    const AVClass *class;
+    ChannelStats *chstats;
+    int nb_channels;
+    uint64_t tc_samples;
+    double time_constant;
+} DRMeterContext;
+
+#define OFFSET(x) offsetof(DRMeterContext, x)
+#define FLAGS AV_OPT_FLAG_AUDIO_PARAM|AV_OPT_FLAG_FILTERING_PARAM
+
+static const AVOption drmeter_options[] = {
+    { "length", "set the window length", OFFSET(time_constant), AV_OPT_TYPE_DOUBLE, {.dbl=3}, .01, 10, FLAGS },
+    { NULL }
+};
+
+AVFILTER_DEFINE_CLASS(drmeter);
+
+static int query_formats(AVFilterContext *ctx)
+{
+    AVFilterFormats *formats;
+    AVFilterChannelLayouts *layouts;
+    static const enum AVSampleFormat sample_fmts[] = {
+        AV_SAMPLE_FMT_FLTP, AV_SAMPLE_FMT_FLT,
+        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 int config_output(AVFilterLink *outlink)
+{
+    DRMeterContext *s = outlink->src->priv;
+
+    s->chstats = av_calloc(sizeof(*s->chstats), outlink->channels);
+    if (!s->chstats)
+        return AVERROR(ENOMEM);
+    s->nb_channels = outlink->channels;
+    s->tc_samples = s->time_constant * outlink->sample_rate + .5;
+
+    return 0;
+}
+
+static void finish_block(ChannelStats *p)
+{
+    int peak_bin, rms_bin;
+    float peak, rms;
+
+    rms = sqrt(2 * p->sum / p->nb_samples);
+    peak = p->peak;
+    rms_bin = av_clip(rms * 10000, 0, 10000);
+    peak_bin = av_clip(peak * 10000, 0, 10000);
+    p->rms[rms_bin]++;
+    p->peaks[peak_bin]++;
+
+    p->peak = 0;
+    p->sum = 0;
+    p->nb_samples = 0;
+    p->blknum++;
+}
+
+static void update_stat(DRMeterContext *s, ChannelStats *p, float sample)
+{
+    if (p->nb_samples >= s->tc_samples) {
+        finish_block(p);
+    }
+
+    p->peak = FFMAX(FFABS(sample), p->peak);
+    p->sum += sample * sample;
+    p->nb_samples++;
+}
+
+static int filter_frame(AVFilterLink *inlink, AVFrame *buf)
+{
+    DRMeterContext *s = inlink->dst->priv;
+    const int channels = s->nb_channels;
+    int i, c;
+
+    switch (inlink->format) {
+    case AV_SAMPLE_FMT_FLTP:
+        for (c = 0; c < channels; c++) {
+            ChannelStats *p = &s->chstats[c];
+            const float *src = (const float *)buf->extended_data[c];
+
+            for (i = 0; i < buf->nb_samples; i++, src++)
+                update_stat(s, p, *src);
+        }
+        break;
+    case AV_SAMPLE_FMT_FLT: {
+        const float *src = (const float *)buf->extended_data[0];
+
+        for (i = 0; i < buf->nb_samples; i++) {
+            for (c = 0; c < channels; c++, src++)
+                update_stat(s, &s->chstats[c], *src);
+        }}
+        break;
+    }
+
+    return ff_filter_frame(inlink->dst->outputs[0], buf);
+}
+
+#define SQR(a) ((a)*(a))
+
+static void print_stats(AVFilterContext *ctx)
+{
+    DRMeterContext *s = ctx->priv;
+    float dr = 0;
+    int ch;
+
+    for (ch = 0; ch < s->nb_channels; ch++) {
+        ChannelStats *p = &s->chstats[ch];
+        float chdr, secondpeak, rmssum = 0;
+        int i, j, first = 0;
+
+        finish_block(p);
+
+        for (i = 0; i <= 10000; i++) {
+            if (p->peaks[10000 - i]) {
+                if (first)
+                    break;
+                first = 1;
+            }
+        }
+
+        secondpeak = (10000 - i) / 10000.;
+
+        for (i = 10000, j = 0; i >= 0 && j < 0.2 * p->blknum; i--) {
+            if (p->rms[i]) {
+                rmssum += SQR(i / 10000.) * p->rms[i];
+                j += p->rms[i];
+            }
+        }
+
+        chdr = 20 * log10(secondpeak / sqrt(rmssum / (0.2 * p->blknum)));
+        dr += chdr;
+        av_log(ctx, AV_LOG_INFO, "Channel %d: DR: %.1f\n", ch + 1, chdr);
+    }
+
+    av_log(ctx, AV_LOG_INFO, "Overall DR: %.1f\n", dr / s->nb_channels);
+}
+
+static av_cold void uninit(AVFilterContext *ctx)
+{
+    DRMeterContext *s = ctx->priv;
+
+    if (s->nb_channels)
+        print_stats(ctx);
+    av_freep(&s->chstats);
+}
+
+static const AVFilterPad drmeter_inputs[] = {
+    {
+        .name         = "default",
+        .type         = AVMEDIA_TYPE_AUDIO,
+        .filter_frame = filter_frame,
+    },
+    { NULL }
+};
+
+static const AVFilterPad drmeter_outputs[] = {
+    {
+        .name         = "default",
+        .type         = AVMEDIA_TYPE_AUDIO,
+        .config_props = config_output,
+    },
+    { NULL }
+};
+
+AVFilter ff_af_drmeter = {
+    .name          = "drmeter",
+    .description   = NULL_IF_CONFIG_SMALL("Measure audio dynamic range."),
+    .query_formats = query_formats,
+    .priv_size     = sizeof(DRMeterContext),
+    .priv_class    = &drmeter_class,
+    .uninit        = uninit,
+    .inputs        = drmeter_inputs,
+    .outputs       = drmeter_outputs,
+};

libavfilter/allfilters.c

@@ -98,6 +98,7 @@ static void register_all(void)
     REGISTER_FILTER(CROSSFEED,      crossfeed,      af);
     REGISTER_FILTER(CRYSTALIZER,    crystalizer,    af);
     REGISTER_FILTER(DCSHIFT,        dcshift,        af);
+    REGISTER_FILTER(DRMETER,        drmeter,        af);
     REGISTER_FILTER(DYNAUDNORM,     dynaudnorm,     af);
     REGISTER_FILTER(EARWAX,         earwax,         af);
     REGISTER_FILTER(EBUR128,        ebur128,        af);

libavfilter/version.h

@@ -30,7 +30,7 @@
 #include "libavutil/version.h"
 
 #define LIBAVFILTER_VERSION_MAJOR   7
-#define LIBAVFILTER_VERSION_MINOR  12
+#define LIBAVFILTER_VERSION_MINOR  13
 #define LIBAVFILTER_VERSION_MICRO 100
 
 #define LIBAVFILTER_VERSION_INT AV_VERSION_INT(LIBAVFILTER_VERSION_MAJOR, \