--- /dev/null
+/*
+ * 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,
+};
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