Jan Ehrhardt in gmane.comp.video.ffmpeg.devel (Mon, 15 Jul 2013 06:47:48 +0200):
Would it be possible to insert the momentary value for volumedetect in the metadata and use that as input in af_volume.c? One pass normalization based on volumedetect should be faster than what we have now.
To answer my own question: Yes, that is possible. Since Nicolas problably does not want to tamper with volumedetect, I created a clone called af_volumeinject.c. See below. Just like I now use volume=metadata=lavfi.r128.I this volumeinject allows me to use volume=metadata=lavfi.mean_volume. It is only a tiny bit slower than something like volume=-3dB, but faster than a two pass volumedetect + volume=-xx.xdB. One thing came while testing volumeinject. I am really a novice in loudness and would have expected that volumedetect and ebur128 would report more or less the same value. They do not. They were 3-4 dB apart in my testfiles, with ebur128 reporting a louder value. Jan af_volumeinject.c: /* * Copyright (c) 2012 Nicolas George * * This file is (not yet) 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/channel_layout.h" #include "libavutil/avassert.h" #include "audio.h" #include "avfilter.h" #include "internal.h" typedef struct { /** * Number of samples at each PCM value. * histogram[0x8000 + i] is the number of samples at value i. * The extra element is there for symmetry. */ uint64_t histogram[0x10001]; uint64_t nb_tot_samples; uint64_t power; } VolInjectContext; static int query_formats(AVFilterContext *ctx) { static const enum AVSampleFormat sample_fmts[] = { AV_SAMPLE_FMT_S16, AV_SAMPLE_FMT_S16P, AV_SAMPLE_FMT_NONE }; AVFilterFormats *formats; if (!(formats = ff_make_format_list(sample_fmts))) return AVERROR(ENOMEM); ff_set_common_formats(ctx, formats); return 0; } #define MAX_DB 91 static inline double logdb(uint64_t v) { double d = v / (double)(0x8000 * 0x8000); if (!v) return MAX_DB; return log(d) * -4.3429448190325182765112891891660508229; /* -10/log(10) */ } static int filter_frame(AVFilterLink *inlink, AVFrame *samples) { AVFilterContext *ctx = inlink->dst; VolInjectContext *vd = ctx->priv; int64_t layout = samples->channel_layout; int nb_samples = samples->nb_samples; int nb_channels = av_get_channel_layout_nb_channels(layout); int nb_planes = nb_channels; int plane, i; int16_t *pcm; uint64_t mean_power = 0; double mean_volume; char metabuf[128]; if (!av_sample_fmt_is_planar(samples->format)) { nb_samples *= nb_channels; nb_planes = 1; } for (plane = 0; plane < nb_planes; plane++) { pcm = (int16_t *)samples->extended_data[plane]; for (i = 0; i < nb_samples; i++) { vd->histogram[pcm[i] + 0x8000]++; vd->nb_tot_samples++; vd->power += pcm[i] * pcm[i]; } } av_log(ctx, AV_LOG_VERBOSE, "tot_samples: %"PRId64"\n", vd->nb_tot_samples); if (vd->nb_tot_samples) { mean_power = (vd->power + vd->nb_tot_samples / 2) / vd->nb_tot_samples; mean_volume = -logdb(mean_power); #define SET_META(name, var) do { \ snprintf(metabuf, sizeof(metabuf), "%.3f", var); \ av_dict_set(&samples->metadata, "lavfi." name, metabuf, 0); \ } while (0) SET_META("mean_volume", mean_volume); av_log(ctx, AV_LOG_VERBOSE, "mean_volume: %.1f dB\n", mean_volume); } return ff_filter_frame(inlink->dst->outputs[0], samples); } static void print_stats(AVFilterContext *ctx) { VolInjectContext *vd = ctx->priv; int i, max_volume, shift; uint64_t nb_samples = 0, power = 0, nb_samples_shift = 0, sum = 0; uint64_t histdb[MAX_DB + 1] = { 0 }; for (i = 0; i < 0x10000; i++) nb_samples += vd->histogram[i]; av_log(ctx, AV_LOG_INFO, "n_samples: %"PRId64"\n", nb_samples); if (!nb_samples) return; /* If nb_samples > 1<<34, there is a risk of overflow in the multiplication or the sum: shift all histogram values to avoid that. The total number of samples must be recomputed to avoid rounding errors. */ shift = av_log2(nb_samples >> 33); for (i = 0; i < 0x10000; i++) { nb_samples_shift += vd->histogram[i] >> shift; power += (i - 0x8000) * (i - 0x8000) * (vd->histogram[i] >> shift); } if (!nb_samples_shift) return; power = (power + nb_samples_shift / 2) / nb_samples_shift; av_assert0(power <= 0x8000 * 0x8000); av_log(ctx, AV_LOG_INFO, "mean_volume: %.1f dB\n", -logdb(power)); max_volume = 0x8000; while (max_volume > 0 && !vd->histogram[0x8000 + max_volume] && !vd->histogram[0x8000 - max_volume]) max_volume--; av_log(ctx, AV_LOG_INFO, "max_volume: %.1f dB\n", -logdb(max_volume * max_volume)); for (i = 0; i < 0x10000; i++) histdb[(int)logdb((i - 0x8000) * (i - 0x8000))] += vd->histogram[i]; for (i = 0; i <= MAX_DB && !histdb[i]; i++); for (; i <= MAX_DB && sum < nb_samples / 1000; i++) { av_log(ctx, AV_LOG_INFO, "histogram_%ddb: %"PRId64"\n", i, histdb[i]); sum += histdb[i]; } } static av_cold void uninit(AVFilterContext *ctx) { print_stats(ctx); } static const AVFilterPad volumeinject_inputs[] = { { .name = "default", .type = AVMEDIA_TYPE_AUDIO, .get_audio_buffer = ff_null_get_audio_buffer, .filter_frame = filter_frame, }, { NULL } }; static const AVFilterPad volumeinject_outputs[] = { { .name = "default", .type = AVMEDIA_TYPE_AUDIO, }, { NULL } }; AVFilter avfilter_af_volumeinject = { .name = "volumeinject", .description = NULL_IF_CONFIG_SMALL("inject audio volume."), .priv_size = sizeof(VolInjectContext), .query_formats = query_formats, .uninit = uninit, .inputs = volumeinject_inputs, .outputs = volumeinject_outputs, };